Startseite Photochemical Transformation of some 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4Hchromen-4-ones: A Remote Substituent Effect
Artikel Open Access

Photochemical Transformation of some 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4Hchromen-4-ones: A Remote Substituent Effect

  • Aarti Dalal , Radhika Khanna und Ramesh C. Kamboj EMAIL logo
Veröffentlicht/Copyright: 21. Februar 2018
Artikel downloaden (PDF)
Open Chemistry
Aus der Zeitschrift Open Chemistry Band 16 Heft 1

Abstract

The effect on photochemical transformations of the substituents present remotely from the reaction site in 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones has been determined. The structure(s) of the substrates and photoproducts were established by spectroscopic techniques (UV, IR, and NMR). The substituents had profound effects on product yield and distribution. Electron withdrawing groups (EWGs) on the benzenoid moiety of the chromenone nucleus increased the yield of the photoproducts whereas electron donating groups (EDGs) decreased the yield. These results may be attributed to “state switching” of the substituents during excitation.

Graphical Abstract

Keywords: photocyclization; substituent effect; 1,4-biradical; angular pentacyclics; chromenones; benzothiophene; photoirradiation

1 Introduction

Norrish Type II reactions, which involve an intramolecular H-abstraction initiated by a photo-excited carbonyl compound, have found several synthetic applications [1,2,3,4,5,6,7,8]. Various examples in the literature revealed a profound effect of the substituent upon the outcome of Norrish type II reactions [9,10,11,12,13]. Encouraged by the interesting Norrish Type II photochemical properties of the chromones [14], in our previous study, we tested the photochemical behavior of a methanolic solution of 3-alkoxy-6-chloro-2-(benzo[b] thiophen-2-yl)-4H-chromen-4-ones having different alkoxy groups (benzyloxy, allyloxy, ethoxy and methoxy) on the benzenoid moiety, and the various photoproducts, including the cyclised and cyclodehydrogenated ones [15,16,17], were determined. In the present communication, we intend to expand the scope of this work. The photolysis of 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones bearing electron-withdrawing and electron-donating groups on the benzenoid moiety has been carried out. The purpose of this study is to determine the effects of remote substituents (i.e. substituents present far away from the reaction centre) [18] on the formation and distribution of the photoproducts.

2 Experimental

2.1 General

1H NMR (300 and 400 MHz) and proton-decoupled 13C NMR (75.4 and 100.6 MHz) spectra were taken on a Bruker spectrometer using TMS as an internal standard. The infrared (IR) spectra were recorded in KBr pellets on a MB3000 FT-IRwith HORIZON MB™ FTIR software from ABB Bomen. Melting points were determined in open capillaries and are uncorrected. The photo-irradiation of the solution of substrates was carried out under nitrogen atmosphere from a 125 W (medium pressure) Hg-vapor lamp using a Pyrex filter. The columns for chromatographic separation were packed in petroleum ether with silica gel and were eluted with a mixture of pet ether and ethyl acetate (99:1). The X-ray crystallographic structure was collected on a Bruker Kappa APEX II diffractometer equipped with a CCDC detector and sealed-tube monochromated MoKα radiation using the program APEX2.

2.2 Synthesis of 3-(benzo[b]thiophen-2-yl)-1-(2-hydroxy-phenyl)prop-2-en-1-ones 3(a-d)

1(a-d) and benzothiphene-2-carbaldehyde 2 were added to a well-stirred suspension of powdered NaOH (0.8 g, 0.02 mol) in EtOH (100 ml) at 0°C. The reaction mixture was stirred further overnight. Thereafter, it was poured over ice and neutralized with dilute HCl to obtain acrylophenone, which was crystallized from EtOH to give the yellowish-orange needles of 3(a-d).

2.2.1 3-(Benzo[b]thiophen-2-yl)-1-(5-chloro-2-hydroxy-4-methyl-phenyl)prop-2-en-1-one 3a

Yield 78%, orange solid; mp 161-163°C; IR νmax (cm-1): 3390 (-OH), 1640 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 12.72 (1H, s, OH), 8.12 (1H, d, J2,3 = 15.2 Hz, H-3), 7.88 (1H, s, H-6’), 7.70 (2H, m, H-3” & H-7”), 7.59 (1H, d, J3,2 = 15.2 Hz, H-2), 7.47 (3H, m, H-4”, H-5” & H-6”), 6.93 (1H, s, H-3’), 2.41 (3H, s, CH3); 13C NMR [CDCl3, δ (ppm)]: 192.39, 162.01, 146.02, 145.64, 134.44, 131.14, 129.22, 128.95, 128.80, 127.50, 126.74, 126.30, 124.22, 122.99, 120.61, 120.22, 118.99 and 20.85.

2.2.2 3-(Benzo[b]thiophene-2-yl)-1-(2-hydroxyphenyl)prop-2-en-1-one 3b

Yield 78%, orange solid; mp 154-156°C; IR νmax (cm-1): 3390 (-OH), 1645 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 12.82 (1H, s, OH), 8.02 (1H, dd, Jo = 8.4 Hz, Jm = 1.6 Hz, H-6’), 7.84 (1H, s, H-6”), 7.76 (1H, d, J3,2 = 15.2 Hz, H-3), 7.64 (1H, dd, Jo = 7.6 Hz, Jm = 2.0 Hz, H-2”), 7.54 (1H, d, J2,3 = 15.6 Hz, H-2), 7.52 (1H, dd, Jo = 8.4 Hz, Jm = 2.4 Hz, H-5”), 7.43 (1H, ddd, Jo = 7.2 Hz, Jm = 1.6 Hz, H-4’), 7.29 (1H, ddd, Jo = 8.4 Hz and 7.2 Hz, Jm = 1.2 Hz, H-5’), 7.09 (1H, ddd, Jo = 8.4 Hz, Jm = 2.0, H-4”), 7.05 (1H, ddd, Jo = 8.4 Hz, Jm = 2.4 Hz, H-3”), 6.99 (1H, dd, Jo = 7.2 Hz, Jm = 1.2 H-3’); 13C NMR [CDCl3, δ (ppm)]: 179.7, 159.8, 144.1, 138.8, 137.1, 135.3, 136.5, 131.4, 129.8, 127.6, 127.1, 124.6, 123.5, 121.1, 119.8, 116.8 and 111.4.

2.2.3 3-(Benzo[b]thiophene-2-yl)-1-(5-methyl-2-hydroxyphenyl)prop-2-en-1-one 3c

Yield 75%, yellowish-Orange solid; mp 166-168°C; IR νmax (cm-1): 3340 (-OH), 1644 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 12.64 (1H, s, OH), 8.15 (1H, d, J3,2 = 14.2 Hz, H-3), 7.96 (1H, d, Jm = 1.6 Hz, H-6’), 7.84 (2H, dd, Jo = 8.0 Hz, Jm = 1.6 Hz, H-4’ & H-7”), 7.70 (3H, ddd, Jo = 7.2 Hz, Jm = 1.6 Hz, H-4”, H-5” & H-6”), 7.50 (1H, d, J2,3 = 14.2 Hz, H-2), 7.28 (1H, s, H-3”), 6.28 (1H, d, Jo = 8.0 Hz, H-3’), 2.40 (3H, s, CH3); 13C NMR [CDCl3, δ (ppm)]: 192.85, 161.58, 140.45, 140.07, 139.68, 138.11, 137.69, 130.46, 128.28, 128.05, 126.71, 125.07, 124.72, 122.54, 121.38, 119.57, 118.41 and 20.66.

2.2.4 3-(Benzo[b]thiophene-2-yl)-1-(2-hydroxy-5-methoxyphenyl)prop-2-en-1-one 3d

Yield 74%, yellowish-orange solid; mp 159-161°C; IR νmax (cm-1): 3360 (-OH), 1642 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 12.39 (1H, s, -OH), 8.13 (1H, d, J3,2= 15.2 Hz, H-3), 7.91 (1H, d, Jm= 1.2 Hz, H-6’), 7.64 (1H, s, 3”), 7.44 (1H, d, J2,3 = 15.2 Hz, H-2), 7.35 (2H, d, Jo = 8.4 Hz, Jm = 1.6 Hz, H-4”& H-7”), 7.28 (1H, d, Jo = 7.2 Hz, Jm = 1.2 Hz, H-4’), 7.18 (2H, dd, Jo = 8.8 Hz, Jm = 2.8 Hz, H-5” & H-6”), 7.02 (1H, d, Jo = 7.2 Hz, H-3’), 3.39 (3H, s, OCH3); 13C NMR [CDCl3, δ (ppm)]: 192.60, 158.01, 151.77, 140.48, 139.95, 139.65, 138.47, 130.67, 126.79, 125.10, 124.76, 124.06, 122.56, 121.21, 119.41, 112.87, 107.37 and 56.18.

2.3 Synthesis of 2-(benzo[b]thiophen-2-yl)-3-hydroxy-4H-chromen-4-ones 4(a-d)

To a well stirred suspension of compound 3(a-d) in MeOH was added aqueous KOH (10.0 ml, 20%). This mixture was cooled to 0°C. H2O2 (50%) was added to this dark red solution drop-wise until the colour changed to yellow, and the stirring was continued for 4h. The reaction mixture was neutralized with ice-cold HCl to yield light yellow precipitates, which crystallized to a light yellow solid 4(a-d).

2.3.1 2-(Benzo[b]thiophen-2-yl)-3-hydroxy-6-methyl-4H-chromen-4-one 4a

Yield 81%, creamish solid; mp 108-110°C; IR νmax (cm-1): 3215 (-OH), 1628 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.20 (1H, s, H-5), 7.87 (1H, s, H-3’), 7.477.57 (3H, m, H-4’, H-5’ and H-6’), 7.28 (1H, m, H-7’), 6.95 (1H, s, H-8), 4.62 (1H, s, OH), 2.43 (3H, s, CH3). 13C NMR [CDCl3, δ (ppm)]: 193.08, 153.65, 142.99, 131.39, 130.89, 130.27, 129.48, 128.89, 128.72, 128.61, 127.75, 127.55, 126.85, 126.14, 124.90, 120.18, 119.94 and 20.95.

2.3.2 2-(Benzo[b]thiophen-2-yl)-3-hydroxy-6-methyl-4H-chromen-4-one 4b

Yield 71%, creamish solid; mp 108-110°C; IR νmax (cm-1): 3215 (-OH), 1620 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.28 (1H, dd, Jo = 8.0 Hz, Jm = 1.6 Hz, H-5), 7.94 (1H, ddd, Jo = 7.6 Hz, Jm = 2.0 Hz, H-7), 7.73 (1H, s, H-7’), 7.70 (1H, ddd, Jo = 8.0 Hz, Jm = 2.0 Hz, H-6), 7.64 (1H, ddd, Jo = 8.4 Hz, Jm = 2.0 Hz, H-3’), 7.55 (2H, m, H-4’ and 5”), 7.15 (1H, ddd, Jo = 8.4 Hz, Jm = 2.4 Hz, H-6’), 7.02 (1H, dd, Jo = 7.6 Hz, Jm = 2.0 Hz, H-8); 13C NMR [CDCl3, δ (ppm)]: 173.9, 155.3, 154.7, 145.6, 140.4, 139.7, 138.7, 135.8, 134.5, 128.9, 127.4, 125.1, 124.5, 122.5, 121.5, 119.9, 118.7.

2.3.3 2-(Benzo[b]thiophen-2-yl)-3-hydroxy-6-methyl-4H-chromen-4-one 4c

Yield 69%, creamish-white solid, mp 103-105°C; IR νmax (cm-1): 3200 (-OH), 1618 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.20 (1H, d, Jo = 2.0 Hz, H-5, 7.84 (2H, complicated dd, Jo = 6.8 Hz, Jm = 1.2 Hz, H-5’ and H-6’),7.38-7.36 (2H, m, H-4’ and 5”), 7.28 (1H, s, H-3’), 7.01 (1H, dd, Jo = 7.6 Hz, Jm = 2.0 Hz, H-7), 6.82 (1H, d, Jo = 8.0 Hz, H-8), 2.33 (3H, s, CH3); 13C NMR [CDCl3, δ (ppm)]: 175.86, 160.65, 160.63, 159.22, 153.41, 153.37, 148.42, 137.45, 130.07, 126.60, 124.63, 124.59, 124.20, 122.45, 119.37, 118.06, 117.72 and 20.43.

2.3.4 2-(Benzo[b]thiophen-2-yl)-3-hydroxy-6-mehoxy-4H-chromen-4-one 4d

Yield 72%, pale yellow solid; mp 114-116°C; IR νmax (cm-1): 3212 (-OH), 1620 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.28 (1H, s, H-3’), 7.92 (1H, d, Jm = 2.8 Hz, H-5), 7.78 (1H, d, Jo = 7.2 Hz, Jm = 2.8 Hz, H-7), 7.66 (1H, d, Jo = 7.6 Hz, H-8), 7.53 (2H, m, H-5’ and H-6’), 7.34 (1H, dd, Jo = 6.4 Hz, Jm = 2.4 Hz, H-4’), 7.28 (1H, dd, Jo = 6.4 Hz, Jm = 2.8 Hz, H-7’), 4.51 (1H, s, -OH), 3.98 (3H, s, OCH3); 13C NMR [CDCl3, δ (ppm)]: 177.42, 150.81, 143.30, 140.11, 139.62, 134.06, 132.88, 127.68, 126.58, 125.62, 124.89, 124.28, 123.67, 123.01, 122.25, 122.12, 119.43 and 55.96.

2.4 Synthesis of 2-(benzo[b]thiophen-2-yl)-3-(benzyloxy)-4H-chromen-4-ones 5(a-d)

2.4.1 2-(Benzo[b]thiophen-2-yl)-3-(benzyloxy)-6-chloro-7-methyl-4H-chromen-4-one 5a

Yield 76%, white solid; mp 110-112°C; IR νmax (cm-1): 1644 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 7.91 (1H, s, H-3’), 7.87 (1H, s, H-5), 7.76 (2H, complicated ddd, Jo = 7.6 Hz, Jm = 1.6 Hz, H-5’ and 6’), 7.33-7.42 (5H, m, H-2”, H-3”, H-4”, H-5” and H-6”), 7.48 (2H, dd, Jo = 7.6 Hz, Jm = 2.0 Hz, H-7’ and H-4’), 6.97 (1H, s, H-8), 5.18 (2H, s, H-1”), 2.44 (3H, s, CH3); 13C NMR [CDCl3, δ (ppm)]: 197.89, 176.62, 158.45, 154.25, 147.88, 139.66, 138.82, 138.49, 129.11, 128.76, 128.32, 128.25, 127.59, 126.33, 124.38, 124.06, 123.18, 122.27, 119.95, 115.29, 107.63, 71.08 and 20.47.

2.4.2 2-(Benzo[b]thiophen-2-yl)-3-(benzyloxy)-4H-chromen-4-one 5b

Yield 75%, White solid; mp 109-111°C; IR νmax (cm-1): 1632 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.29 (1H, dd, Jo = 8.0 Hz, Jm = 1.6 Hz, H-5), 8.21 (1H, s, H-7’), 7.87 (2H, m, H-3’and H-6’), 7.71 (1H, ddd, Jo = 7.2 Hz, Jm = 1.6 Hz, H-7), 7.65 (2H, m, H-4’ and H-5’), 7.59 (1H, ddd, Jo = 8.4 Hz, Jm = 1.6 Hz, H-6), 7.44 (5H, m, H-2”, H-3”, H-4”, H-5” and H-6”), 7.36 (1H, dd, Jo = 7.2 Hz, Jm = 1.6 Hz, H-8), 5.40 (2H, s, H-1”); 13C NMR [CDCl3, δ (ppm)]: 171.9, 155.8, 155.3, 143.8, 140.4, 139.7, 138.4, 134.5, 132.1, 131.2, 128.4, 127.09, 126.2, 125.1, 124.9, 122.5, 121.9, 119.6, 118.4, 117.8, 111.2, 74.9.

2.4.3 2-(Benzo[b]thiophen-2-yl)-3-(benzyloxy)-6-methyl-4H-chromen-4-one 5c

White solid in 72% yield, mp 117-119°C; IR νmax (cm-1): 1622 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.19 (1H, s, H-3’), 8.07 (1H, d, Jm = 2.0 Hz, H-5), 7.88 (2H, complicated ddd, Jo = 7.6 Hz, Jm = 2.4 Hz, H-5’ and 6’), 7.66 (2H, dd, Jo = 8.0 Hz, Jm = 1.6 Hz, H-4’ and H-7’), 7.52 (1H, dd, Jo = 8.4 Hz, Jm = 2.0 Hz, H-7), 7.46 (1H, d, Jo = 8.8 Hz, H-8), 7.36-7.44 (5H, m, H-2”, H-3xyd, H-4”, H-5” and H-6”), 5.41 (2H, s, -OCH2-), 2.49 (3H, s, -CH3); 13C NMR [CDCl3, δ (ppm)]: 174.24, 153.25, 151.42, 142.02, 138.67, 136.65, 134.93, 134.77, 132.13, 129.17, 128.42, 128.36, 127.50, 126.74, 126.07, 125.04, 124.82, 124.69, 123.95, 122.25, 117.63, 73.91 and 20.83.

2.4.4 2-(Benzo[b]thiophen-2-yl)-3-(benzyloxy)-6-methoxy-4H-chromen-4-one 5d

White solid in 68% yield, mp 119-121°C; νmax (cm-1): 1632 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.17 (1H, s, H-3’), 7.88 (3H, m, H-5, H-7’ and H-4’), 7.67 (3H, m, H-7, H-5’ and H-6’), 7.34-7.50 (5H, m, H-2”, H-3”, H-4”, H-5” and H-6”), 7.30 (1H, d, Jo = 9.6 Hz, H-8), 5.41 (2H, s, H-1”), 3.93 (3H, s, OCH3). 13C NMR [CDCl3, δ (ppm): 173.95, 156.71, 149.82, 141.99, 138.70, 136.69, 132.08, 129.17, 128.45, 127.66, 126.71, 126.08, 125.04, 124.84, 124.70, 123.88, 122.25, 121.33, 119.32, 105.11, 104.61, 73.90 and 55.93.

2.5 Photo-irradiation of chromenones 5(a-d)

2.5.1 Photolysis of compound (5a)

A dry methanolic solution (100.0 ml) of chromenone 5a (500 mg) was photo-irradiated with light from a 125 W Hg vapor-lamp in a Photo reactor under an inert nitrogen atmosphere for 30 min. The removal of solvent left a gummy solid, which was chromatographed to yield 6a.

Compound (6a)

Yield 40%, shining white crystalline solid; mp 198-200°C; IR νmax (cm-1): 1628 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.08 (1H, s, H-9), 7.33-7.39 (3H, m, H-2, H-2’, H-6’), 7.23-7.28 (3H, m, H-3’, H-4’, H-5’), 7.16 (1H, ddd, Jo = 8.0 Hz, Jo = 7.6 Hz, Jm = 1.2 Hz, H-3), 7.14 (1H, s, H-12), 6.81 (1H, ddd, Jo = 7.6 Hz, Jo = 7.2 Hz, Jm = 1.2 Hz, H-4), 6.16 (1H, d, Jo = 7.6 Hz, H-5), 5.28 (1H, d, J13b,5b = 6.8 Hz, H-13b), 5.08 (1H, d, J6,5b = 10.0 Hz, H-6), 3.91 (1H, dd, J5b,13b = 6.8 Hz, J5b,6 = 10.0 Hz, H-5b), 2.47 (3H, s, CH3); 13C NMR [CDCl3, δ (ppm)]: 198.24, 156.57, 145.21, 142.22, 140.12, 139.36, 135.64, 130.89, 128.81, 128.48, 127.89, 126.75, 126.70, 124.02, 123.46, 122.75, 122.04, 120.64, 115.37, 71.26 (C-13b), 45.13 (C-6), 25.25 (C-5b) and 20.76 (-CH3).

2.5.2 Photolysis of compound (5b)

A dry methanolic solution of 5b (500 mg) on photolysis for 30 min furnished 6b and processed as above.

Compound (6b)

Yield 54%, white solid; mp 208-210°C; IR νmax (cm-1): 1645 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.29 (1H, dd, Jo = 8.0 Hz, Jm = 1.6 Hz, H-9), 7.68 (1H, ddd, Jo = 8.0 Hz and 7.2 Hz, Jm = 1.6 Hz, H-11), 7.54 (1H, ddd, Jo = 8.0 Hz, Jm = 2.0 Hz, H-10), 7.38 (1H, dd, Jo = 8.0 Hz, Jm = 1.6 Hz, H-12), 7.33 (3H, m, H-2, H-2” and H-6”), 7.23 (3H, m, H-3”, H-4” and H-5”), 7.17 (1H, ddd, Jo = 8.4 Hz and 8.0 Hz, Jm = 1.2 Hz, H-3), 6.79 (1H, ddd, Jo = 8.0 Hz and 7.6 Hz, Jm = 1.2 Hz, H-4), 6.13 (1H, d, Jo = 7.6 Hz, Jm = 1.6 Hz, H-5), 5.28 (1H, d, J = 6.8 Hz, H-13b), 5.06 (1H, d, J = 10.4 Hz, H-6), 3.91 (1H, dd, J = 10.4 Hz and 6.8 Hz, H-5a); 13C NMR [CDCl3, δ (ppm)]: 191.1, 182.3, 172.3, 155.6, 147.9, 138.4, 136.6, 133.5, 131.4, 129.6, 128.9, 128.3, 127.5, 127.0, 126.2, 125.1, 124.5, 124.3, 121.8, 121.4, 118.7, 117.9, 51.9, 47.1.

2.5.3 Photolysis of compound (5c)

A dry methanolic solution of 5c (500 mg) on photolysis for 30 min furnished 6c and processed as above.

Compound (6c)

Yield 36%, shinning white crystal; mp 207-209°C; IR νmax (cm-1): 1632 (C=O) 1H NMR [CDCl3, δ (ppm), 400 MHz]: 8.09 (1H, d, Jm = 1.2 Hz, H-9), 7.48 (1H, dd, Jo = 8.4 Hz, Jm = 1.2 Hz, H-11), 7.33-7.39 (5H, m, H-2’, H-3’, H-4’, H-5’ and H-6’), 7.26 (2H, ddd, Jo = 8.4 Hz, Jo = 8.0Hz, Jm = 1.2 Hz, H-3 and H-4), 7.18 (1H, dt, Jo = 7.6Hz, Jm = 1.2 Hz, H-2), 6.80 (1H, ddd, Jo = 7.6 Hz, Jm = 1.6 Hz, H-5), 6.16 (1H, d, Jo = 7.6 Hz, H-12), 5.26 (1H, d, J13b,5b = 6.8 Hz, H-13b), 5.06 (1H, d, J6,5b = 10.0 Hz, H-6), 3.90 (1H, dd, J5b,13b = 6.8 Hz, J5b,6 = 10.0 Hz, H-5b), 3.18 (3H, s, CH3); 13C NMR [CDCl3, δ (ppm)]: 171.73, 153.56, 147.82, 139.82, 138.99, 136.70, 136.56, 134.84, 134.48, 132.23, 128.86, 128.41, 128.28, 127.09, 125.41, 124.32, 123.45, 122.25, 117.63, 114.12, 51.96, 47.23 and 29.76.

2.5.4 Photolysis of compound (5d)

A dry methanolic solution of 5d (500 mg) on photolysis for 30 min furnished 6d and processed as above.

Compound (6d)

Yield 28%, white solid; mp 195-197°C; IR νmax (cm-1): 1638 (C=O); 1H NMR [CDCl3, δ (ppm), 400 MHz]: 7.93 (1H, d, Jm = 1.2 Hz, H-9), 7.84-7.87 (3H, m, H-2, H-2’, H-6’), 7.67 (1H, ddd, Jo = 7.2 Hz, Jo = 6.8 Hz, Jm = 1.2 Hz, H-4), 7.53 (1H, d, Jo = 7.6 Hz, H-5), 7.41-7.47 (3H, m, H-3’, H-4’, H-5’), 7.34 (1H, dd, Jo = 7.6 Hz, Jm = 1.6Hz, H-11), 7.31 (1H, ddd, Jo = 7.6 Hz, Jo = 7.2 Hz, Jm = 2.0 Hz, H-3), 7.14 (1H, d, H-12), 5.43 (1H, d, J13b,5b = 6.8 Hz, H-13b), 5.09 (1H, d, J6,5b = 10.2 Hz, H-6), 3.98 (1H, dd, J5b,13b = 6.8 Hz, J5b,6 = 10.2 Hz, H-5b), 3.45 (3H, s, OCH3); 13C NMR [CDCl3, δ (ppm)]: 166.36, 140.24, 139.44, 138.18, 135.92, 129.71, 128.85, 128.64, 128.35, 127.06, 126.29, 125.58, 124.88, 124.47, 123.59, 122.48, 119.83, 119.09, 112.38, 70.24, 67.15, 31.96 and 29.73.

Ethical approval: The conducted research is not related to the use of either humans or animals.

3 Results and Discussion

In our recent studies [15,16,17] the 3-alkoxy-6-chloro-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones yielded both dihydrogenated and dehydrogenated products along with a migrated photoproduct following photochemical irradiation. These studies mainly included substrates with different substituents at the C-3 position. In the present study, 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones with different substituents (-Cl & CH3, -H, -CH3 and -OCH3) attached to the benzenoid moiety have been synthesized and photolysed to observe the effects of substituents on photoproduct distribution and formation.

The targets 5(a-d) were synthesized by (i) condensing the 2-hydroxyacetophenones 1(a-d) with benzothiophene-2-carbaldehyde in the presence of NaOH/EtOH [19] followed by (ii) the cyclisation of chalcones 3(a-d) to 3-hydroxychromenones 4(a-d) under Algar–Flynn–Oyamada conditions [20,21,22] and (iii) subsequent alkylation of the latter with benzyl chloride, in the presence of dry acetone, freshly dried K2CO3 and tetra n-butyl ammonium iodide (Scheme 1). The structure of the compounds 6(a-d) were found to be consistent with their spectral parameters (IR, 1H/13C NMR vide experimental). The yields of all these compounds were in the range of 74-82%.

Scheme 1 Synthesis of Chromenones 5(a-d).
Scheme 1

Synthesis of Chromenones 5(a-d).

Scheme 2 Photolysis of Chromenones 5(a-d).
Scheme 2

Photolysis of Chromenones 5(a-d).

These chromenones 5(a-d) (absorption maxima (λmax) between 352 and 364 nm in MeOH) were irradiated with Pyrex filtered UV-light. The photolysis of a dry methanolic solution of 5(a-d) with a 125 W medium pressure Hg-vapor lamp under nitrogen produced photoproducts 6(a-d), and structures of these photoproducts were established by their spectral data(IR, 1H/13C-NMR).Methanol was used as solvent because better yields of photoproducts 6(a-d) were obtained in polar protic solvents (ethanol and methanol) than in polar aprotic solvents (benzene, C6H12, DMF and CH3CN), a result that was in agreement with previous observations [23]. The photoproducts [15] similar to aromatic benzothiophene fused xanthenone, benzyl migrated product and substituted epoxide could not be isolated from the photolysate of these chromenones 5(a-d). These photoproducts were produced in minute quantities, as observed by TLC analysis and NMR spectra of the photolysates (data not shown) but they could not be isolated despite our best efforts.

The IR spectrum of crystals of compound 6a displays a C=O stretch at 1659 cm-1. In the 1H NMR, benzenoid protons H-9 and H-12 appeared as singlets at: δ 8.08 and δ 7.14. The benzothienyl protons were seen at δ 7.16 (1H, ddd, H-3), δ 6.81 (1H, ddd, H-4) and δ 6.16 (1H, d, H-5). A comparison of the 1HNMR spectra of 5a and 6a exhibited that the resonances at δ 5.18 (-OCH2) and δ 7.91 (H-3’) present in the 5a were missing in the 6a, thereby pronouncing the involvement of these protons in the photo-conversion. Regarding the rest of the spectrum, the bridgehead protons H-13b and H-5b (Figure 1) were found to be placed at δ 5.28 (d, J13b,5b = 6.8 Hz) and δ 3.91 (dd, J5b 13b = 6.8 Hz, J5b,6 = 10.0 Hz). The other proton, H-6 was seen at δ 5.08 (d, J6,5b = 10.0 Hz). At the extreme right appeared a singlet δ 2.47 due to –CH3 group. The 13C NMR spectrum of this photoproduct also corroborated the structure proposed, as C-13b and C-5b, the ring junction carbons, resonated at 45.13 and 20.76 ppm respectively. The structures of other photoproducts 6(b-d) were established similarly (vide experimental).

Figure 1 400MHz 1H spectrum of Photoproduct 6a.
Figure 1

400MHz 1H spectrum of Photoproduct 6a.

The MM2 energy minimizations programme [24,25,26] (Figure 2) was applied to elucidate the stereochemical features of the dihydrogenated photoproduct 6. The various dihedral angles (Φ) and the expected J† values along with the torsional energies of configurations 6(a-d) are tabulated in Table 1. The observed 3J values found for 6(a-d) are in accordance with the J† values for the energy minimized (MM2) configuration I as in our earlier observations [15] where protons H-5b and H-6 are in trans orientation relative to each other (as opposed to configuration II where the protons H-5b and H-6 are in cis). Such outcomes have been reported previously from our laboratory [27] as well as for the naturally occurring pterocarpans [28,29,30,31].

Figure 2 Energy minimized MM2 structures of 6.
Figure 2

Energy minimized MM2 structures of 6.

Table 1

Expected coupling constants for the two configurations of 6(a-d).

Coupling protons H-5b and H-6 in PhotoproductConfiguration IConfiguration IIObserved J
ΦJ† (Hz)E (Kcal/mol)ΦJ† (Hz)E (Kcal/mol)
6a14411.519.144-66.274.1020.31210.0Hz
6b1459.618.486-59.252.3023.76110.2Hz
6c14311.518.747-68.794.1121.16610.0Hz
6d14411.520.529-65.434.0821.71110.2Hz

  1. J†Expected value

Table 2

Yield/Percentage of photoproducts 6(a-d).

PhotoproductPhotoproducts yield (%)
-Cl [15]Cl, CH3H, HCH3OCH3
Dihydro4240383628
photoproduct

A closer look on the effects of different substituents at benzenoid moiety in the present chromones suggests that an increase in electron density by the electron releasing group on the chromenone ring decreases the yield of the dihydro photoproduct (6a, R = Cl and R’= CH3 yield 40%; 6b, R = H and R’= H, yield 38%; 6c, R = CH3 and R’= H, yield 36%; 6d, R = -OCH3 and R’ = H, yield 28%). In our earlier studies, the benzothienyl containing chromones with electron withdrawing groups [15] (R = Cl and R’= H) resulted in a 42% yield of aromatic, 1,5-migrated and dealkoxylated photoproducts. This behavior may be attributed due to the fact that electron donating substituents may cause state switching [32,33,34] from n→π* to π→π* that may reduce the hydrogen abstraction capacity of the carbonyl group of pyrones [18].

The photo-transformations of target photochemical substrates 5(a-d) and formation of the angular pentacyclic dihydrogenated photoproduct described above, i.e. 5a→6a, 5b→6b, 5c→6c, 5d→6d, can be envisagedto occur simply through an initial H-abstraction from an –OCH2-group by the excited C=O group of the pyrone moiety to produce a 1,4-biradical [15] generated through the Norrish type-II process. The ease of H-obstraction may be the result of a possible six-membered transition state in the substrates. The photoproducts have been projected to be formed through bond formation between a – CH – radical and the C-3’-position of the thiophene ring followed by the concerted sigmatropic 1,5-H shift as reported in our earlier studies [15,16,17] yielding 6(a-d).

4 Conclusion

It may be concluded from the above studies that the electron withdrawing groups (EWG) on the benzenoid moiety of the chromenone favour the formation of dihydrophotoproducts in higher yield than do the electron releasing groups (ERG) due to “state switching”. These substituents also had a profound effect on the distribution of photoproduct(s) as the aromatic 1,5-migrated and dealkoxylated photoproducts were not isolated or realised.

Acknowledgements

Two of the authors wish to express their gratitude to the University Grants commission (UGC), New Delhi (Aarti Dalal, SRF) and the Department of Science and Technology, New Delhi (Radhika Khanna, SRF) for financial support of this work.

  1. Conflict of interest: Authors state no conflict of interest.

References

[1] Norrish R.G.W., Primary photochemical reactions. Part VII. Photochemical decomposition of isovaleraldehyde and di-n-propyl ketone, Trans. Faraday Soc., 1935, 1504-1511.10.1039/jr9350001504Suche in Google Scholar

[2] “IUPAC Gold Book - Norrish Type II photoreaction” 10.1351/goldbook.N0428.Suche in Google Scholar

[3] Kamboj R.C., Berar, U., Berar, S., Thakur, M., Arora, R., Gupta, S.C., Photochemistry of 3-alkoxychromones I — Photocyclisation of 6-chloro-3-alkoxy-2-(furan-3-yl)-4H-chromen-4-ones, Can. J. Chem., 2009, 87, 422-429.10.1139/V08-177Suche in Google Scholar

[4] Kamboj R.C., Arora R., Berar S., Thakur M., Berar U., Gupta S.C., A photochemical synthesis of some novel spiropyrans, Indian J. Heterocyclic chem., 2009, 18, 271-274.Suche in Google Scholar

[5] Alvarez-Dorta D., Leon E.I., Kennedy A.R., Riesco-Fagundo C., Suárez E., Sequential Norrish Type II Photoelimination and Intramolecular Aldol Cyclization of 1,2-Diketones in Carbohydrate Systems: Stereoselective Synthesis of Cyclopentitols, Angew. Chem. Int. Ed., 2008, 47, 8917-8919.10.1002/anie.200803696Suche in Google Scholar

[6] Thakur M., Berar S., Berar U., Gupta S.C., Kamboj R.C., Phototransformations of 6-chloro-3-propargyloxy-2-aryl-4-oxo-4H-1-benzopyran: 1,4-hydrogen abstraction in propargylethers, Tetrahedron, 2008, 64, 5168-5173.10.1016/j.tet.2008.03.040Suche in Google Scholar

[7a)] Gupta S.C., Yusuf M., Sharma S., Arora S., Photoisomerization of allyl ethers: syntheses of vinyl ethers, Tetrahedron Lett., 2002, 43, 6875-6877;10.1016/S0040-4039(02)01366-7Suche in Google Scholar

[7b)] Gupta S.C., Sharma S., Yusuf M., Arora S., Saini A., Kamboj R.C., Dhawan S.N., Photocyclisation of 3-alkoxythiochromones: activation for H-abstraction, J. Chem. Res. (S), 2002, 165-167.10.3184/030823402103171744Suche in Google Scholar

[8a)] Iki S.M., Abdel-Latif F.M., Nakayama T., Hamanous K., Photochemical reaction of [6]-l, 4-cyclophaneanthraquinone, J Chem. Sci., 1993, 105, 797-80210.1007/BF03040850Suche in Google Scholar

[8b)] Waiss A.C., Lundin R.E., Lee A., Corse J., Anthony C., et al. Photochemistry of quercetin pentamethyl ether, J. Am. Chem. Soc., 1967, 89, 6213-6218.10.1021/ja01000a039Suche in Google Scholar

[9a)] Yang N.C., Yang D.H., Photochemical reactions of ketones in solution, J. Am. Chem. Soc., 1958, 80, 2913-291410.1021/ja01544a092Suche in Google Scholar

[9b)] Henery-logan K.R., Chen C.G., Synthesis of oxygen analogs of the penicillins. I. Photocyclization of 2-oxoamides to 3-carbomethoxy-6-hydroxypenams, Tetrahedron lett. 1973, 14, 1103-110410.1016/S0040-4039(01)95915-5Suche in Google Scholar

[9c)] Arnould J.C., Pete J.P., Photolyse D’ α alcoxycyclohexanones, Tetrahedron Lett., 1972, 13, 2415-241810.1016/S0040-4039(01)84835-8Suche in Google Scholar

[10] Dalal A., Khanna R., Kumar D., Jindal P., Chaudhary A., Kamboj R.C., Photochemical Intramolecular H-Abstractions: A Brief Account on their Synthetic Utility, Current Organic Chemistry, 2015, 19, 2156-2195.10.2174/1385272819666150730215450Suche in Google Scholar

[11] Givens R.S., Stensrud K., Conrad P.G., Yousef A.L., Perera C., Senadheera S.N., Heger D., Wirz J., p-Hydroxyphenacyl photoremovable protecting groups—Robust photochemistry despite substituent diversity, Can. J. Chem., 2011, 89, 364-384.10.1139/V10-143Suche in Google Scholar PubMed PubMed Central

[12] Cai X., Cygon P., Goldfuss B., Griesbeck A.G., Heckroth H., Fujitsuka M., Majima T., α-Carbonyl Substituent Effect on the Lifetimes of Triplet 1, 4-Biradicals from Norrish-Type-II Reactions, Chemistry European Journal, 2006, 12, 4662-4667.10.1002/chem.200600011Suche in Google Scholar PubMed

[13] Kamboj R.C., Sharma G., Kumar D., Arora R., Photocyclisation of 3-alkoxy-6-chloro-2-(3-methylthiophen-2-yl)-4H-chromen-4-ones, C. R. Chimie, 2012, 15, 311-316.10.1016/j.crci.2011.11.005Suche in Google Scholar

[14] Kamboj R.C., Arora R., Kumar D., Sharma G., Photoreorganization of 3-alkoxy-6-chloro-2-(thiophen-3-yl)-4H-chromen-4-ones: Regioselective cyclization via Y-hydrogen abstraction, J. Photochem. Photobiol., A, 2011, 220, 124-133.10.1016/j.jphotochem.2011.04.002Suche in Google Scholar

[15] Dalal A., Khanna R., Kumar P., Kamboj R.C., Photoreorganization of 3-alkoxy-6-chloro-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones: a green and convenient synthesis of angular pentacyclics, Photochem. Photobiol. Sci., 2017, 16, 672-682.10.1039/C6PP00476HSuche in Google Scholar

[16a)] a) Gupta S.C., Shrama S., Saini A., Dhawan S.N., Photochemistry of chromones: photoreorganisation of 3-alkoxy-2-thienyl-4-oxo-4 H-1-benzopyrans, J. Chem. Soc., Perkin Trans. 1999, 1, 2391-239510.1039/a901090dSuche in Google Scholar

[16b)] Kumar R., Yusuf M., Photolysis of some 3-alkoxy-2-thienylchromones, Arkivoc, 2007, 16, 227-237.10.3998/ark.5550190.0008.g22Suche in Google Scholar

[17] M. Yusuf, Ph.D. Thesis, K.U. Kurukshetra, 2002.Suche in Google Scholar

[18a)] Dalal A., Khanna R., Berar U., Kamboj R.C., Photochemistry of aroyloxiranes: Substituent effect on oxepinones and hydroxyalkenones formation, J. Photochem. Photobiol. A: Chemistry, 2016, 329, 238-24510.1016/j.jphotochem.2016.07.008Suche in Google Scholar

[18b)] Khanna R., Dalal A., Kumar R., Kamboj R.C., Phototransformation of 3-alkoxychromenones: Regioselective photocyclisation and Dealkoxylation, Photochem. Photobiol. Sci., 2015, 14, 2195–2202.10.1039/C5PP00318KSuche in Google Scholar

[19a)] Simpson T.H., Whalley B., 2’-Hydroxy and 2’-Methoxy Flavazones, J. Chem. Soc., 1955, 166-16910.1039/JR9550000166Suche in Google Scholar

[19b)] Joshi K.C., Jauhar A.K., Studies in fluorochalkones, part I: Synthesis of chalkones from fluorohydroxyacetophenones, J. Indian Chem. Soc., 1962, 39, 463-468.Suche in Google Scholar

[20] Dean F.M., Podimuang V., The Course of the Algar-Flynn-Oyamada (A.F.O.) Reaction, J. Chem. Soc., 1965, 3978-3987.10.1039/JR9650003978Suche in Google Scholar

[21] Oyamada T., A new general method for the synthesis of the derivatives of flavonol, J. Chem. Soc. Jpn., 1934, 55, 1256-1260.10.1246/bcsj.10.182Suche in Google Scholar

[22] Algar J., Flynn J.P., New synthesis of flavonols, J. P. Proc. Roy. Irish. Acad., 1934, 42B, 1-8.Suche in Google Scholar

[23] Avila D.V., Brown C.E., Ingold K.U., Lusztyk J., Solvent effects on the competitive beta.-scission and hydrogen atom abstraction reactions of the cumyloxyl radical. Resolution of a longstanding problem, J. Am. Chem. Soc., 1993, 115, 466-470.10.1021/ja00055a015Suche in Google Scholar

[24a)] Karplus M., Grant D.M., A criterion for orbital hybridization and charge distribution in chemical bonds, Proc. Nat. Acad. Sci., USA, 1959, 45, 1269-127310.1073/pnas.45.8.1269Suche in Google Scholar

[24b)] Haasnoot C.A.G.,. de leeuw F.A.A.M, Altona C., The relationship between proton-proton NMR coupling constants and substituent electronegativities—I: an empirical generalization of the Karplus equation, tetrahedron, 1980, 36, 2783-2792.10.1016/0040-4020(80)80155-4Suche in Google Scholar

[25] Jackman L.M., Sternhell S., Applications of NMR spectroscopy in organic chemistry 2nd ed.; Pergamon Press: NewYork, 1969, 91-207.10.1016/B978-0-08-012542-8.50029-3Suche in Google Scholar

[26] Minimize Energy to Minimum RMS Gradient of 0.100 by MM2 incorporated in Chem office 7.0 Chem 3D ultra 7.0.Suche in Google Scholar

[27] Gupta S.C., Saini A., Kumar D., Yadav N.S., Chand K., Mor S., Dhawan S.N., On the mechanism for the phototransformation of 3-alkoxy-2-(2’-furyl)-4-oxo-4H-1-benzopyrans, J. Chem. Soc. Perkin Trans I, 1995, 177-181.10.1039/P19950000177Suche in Google Scholar

[28] Pachler K.G.R., Underwood W.G.E., A proton magnetic resonance study of some pterocarpan derivatives: The conformation of the 6a, 11a-dihydro-6H-benzofuro [3, 2-c][1] benzopyran ring system, Tetrahedron, 1967, 23, 1817-1826.10.1016/S0040-4020(01)82581-3Suche in Google Scholar

[29] Harper S.H., Kemp A.D., Underwood W.G.E., Isoflavonoid Constituents of the Heartwood of Cordyla Africana, J. Chem. Soc., Chem. Commun., 1965, 14, 309.10.1039/c19650000309Suche in Google Scholar

[30] Shibata S., Nishikawa Y., Studies on the Constituents of Japanese and Chinese Crude Drugs. VII. On the Constituents of the Roots of Sophora subprostrata CHUN et T. CHEN,(2), and Sophora japonica L.(1), Chem. Pharm Bull., 1963, 11, 167-177.10.1248/cpb.11.167Suche in Google Scholar

[31] Perrin D.R., The structure of phaseolin, Tetrahedron Lett., 1964, 5, 29-35.10.1016/S0040-4039(01)89318-7Suche in Google Scholar

[32] Kumar C.V., Ramaiah D., Das P.K., George M.V., Photochemistry of aromatic alpha, beta.-epoxy ketones. Substituent effects on oxirane ring-opening and related ylide behavior, J. Org. Chem., 1985, 50, 2818-2825.10.1021/jo00216a003Suche in Google Scholar

[33] Grabowsky S., Schirmeister T., Paulmann C., Pfeuffer T., Luger P., Effect of electron-withdrawing substituents on the epoxide ring: an experimental and theoretical electron density analysis of a series of epoxide derivatives, J Org Chem., 2011, 76, 1305-1318.10.1021/jo102125nSuche in Google Scholar

[34] Gupta S.C., Yadav N.S., Dhawan S.N., Photoirradiation Of Some 3-Benzyloxy-2 Phenyl-4-Oxo-4h-1-Benzopyrans, J. Ind. Chem. Soc., 1990, 67, 770-772.Suche in Google Scholar

Received: 2017-08-11
Accepted: 2017-11-21
Published Online: 2018-02-21

© 2018 Aarti Dalal et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Artikel in diesem Heft

  1. Regular Articles
  2. The effect of CuO modification for a TiO2 nanotube confined CeO2 catalyst on the catalytic combustion of butane
  3. The preparation and antibacterial activity of cellulose/ZnO composite: a review
  4. Linde Type A and nano magnetite/NaA zeolites: cytotoxicity and doxorubicin loading efficiency
  5. Performance and thermal decomposition analysis of foaming agent NPL-10 for use in heavy oil recovery by steam injection
  6. Spectroscopic (FT-IR, FT-Raman, UV, 1H and 13C NMR) insights, electronic profiling and DFT computations on ({(E)-[3-(1H-imidazol-1-yl)-1-phenylpropylidene] amino}oxy)(4-nitrophenyl)methanone, an imidazole-bearing anti-Candida agent
  7. A Simplistic Preliminary Assessment of Ginstling-Brounstein Model for Solid Spherical Particles in the Context of a Diffusion-Controlled Synthesis
  8. M-Polynomials And Topological Indices Of Zigzag And Rhombic Benzenoid Systems
  9. Photochemical Transformation of some 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4Hchromen-4-ones: A Remote Substituent Effect
  10. Dynamic Changes of Secondary Metabolites and Antioxidant Activity of Ligustrum lucidum During Fruit Growth
  11. Studies on the flammability of polypropylene/ammonium polyphosphate and montmorillonite by using the cone calorimeter test
  12. DSC, FT-IR, NIR, NIR-PCA and NIR-ANOVA for determination of chemical stability of diuretic drugs: impact of excipients
  13. Antioxidant and Hepatoprotective Effects of Methanolic Extracts of Zilla spinosa and Hammada elegans Against Carbon Tetrachlorideinduced Hepatotoxicity in Rats
  14. Prunus cerasifera Ehrh. fabricated ZnO nano falcates and its photocatalytic and dose dependent in vitro bio-activity
  15. Organic biocides hosted in layered double hydroxides: enhancing antimicrobial activity
  16. Experimental study on the regulation of the cholinergic pathway in renal macrophages by microRNA-132 to alleviate inflammatory response
  17. Synthesis, characterization, in-vitro antimicrobial properties, molecular docking and DFT studies of 3-{(E)-[(4,6-dimethylpyrimidin-2-yl)imino]methyl} naphthalen-2-ol and Heteroleptic Mn(II), Co(II), Ni(II) and Zn(II) complexes
  18. M-Polynomials and Topological Indices of Dominating David Derived Networks
  19. Human Health Risk Assessment of Trace Metals in Surface Water Due to Leachate from the Municipal Dumpsite by Pollution Index: A Case Study from Ndawuse River, Abuja, Nigeria
  20. Analysis of Bowel Diseases from Blood Serum by Autofluorescence and Atomic Force Microscopy Techniques
  21. Hydrographic parameters and distribution of dissolved Cu, Ni, Zn and nutrients near Jeddah desalination plant
  22. Relationships between diatoms and environmental variables in industrial water biotopes of Trzuskawica S.A. (Poland)
  23. Optimum Conversion of Major Ginsenoside Rb1 to Minor Ginsenoside Rg3(S) by Pulsed Electric Field-Assisted Acid Hydrolysis Treatment
  24. Antioxidant, Anti-microbial Properties and Chemical Composition of Cumin Essential Oils Extracted by Three Methods
  25. Regulatory mechanism of ulinastatin on autophagy of macrophages and renal tubular epithelial cells
  26. Investigation of the sustained-release mechanism of hydroxypropyl methyl cellulose skeleton type Acipimox tablets
  27. Bio-accumulation of Polycyclic Aromatic Hydrocarbons in the Grey Mangrove (Avicennia marina) along Arabian Gulf, Saudi Coast
  28. Dynamic Change of Secondary Metabolites and spectrum-effect relationship of Malus halliana Koehne flowers during blooming
  29. Lipids constituents from Gardenia aqualla Stapf & Hutch
  30. Effect of using microwaves for catalysts preparation on the catalytic acetalization of glycerol with furfural to obtain fuel additives
  31. Effect of Humic Acid on the Degradation of Methylene Blue by Peroxymonosulfate
  32. Serum containing drugs of Gua Lou Xie Bai decoction (GLXB-D) can inhibit TGF-β1-Induced Epithelial to Mesenchymal Transition (EMT) in A549 Cells
  33. Antiulcer Activity of Different Extracts of Anvillea garcinii and Isolation of Two New Secondary Metabolites
  34. Analysis of Metabolites in Cabernet Sauvignon and Shiraz Dry Red Wines from Shanxi by 1H NMR Spectroscopy Combined with Pattern Recognition Analysis
  35. Can water temperature impact litter decomposition under pollution of copper and zinc mixture
  36. Released from ZrO2/SiO2 coating resveratrol inhibits senescence and oxidative stress of human adipose-derived stem cells (ASC)
  37. Validated thin-layer chromatographic method for alternative and simultaneous determination of two anti-gout agents in their fixed dose combinations
  38. Fast removal of pollutants from vehicle emissions during cold-start stage
  39. Review Article
  40. Catalytic activities of heterogeneous catalysts obtained by copolymerization of metal-containing 2-(acetoacetoxy)ethyl methacrylate
  41. Antibiotic Residue in the Aquatic Environment: Status in Africa
  42. Regular Articles
  43. Mercury fractionation in gypsum using temperature desorption and mass spectrometric detection
  44. Phytosynthetic Ag doped ZnO nanoparticles: Semiconducting green remediators
  45. Epithelial–Mesenchymal Transition Induced by SMAD4 Activation in Invasive Growth Hormone-Secreting Adenomas
  46. Physicochemical properties of stabilized sewage sludge admixtures by modified steel slag
  47. In Vitro Cytotoxic and Antiproliferative Activity of Cydonia oblonga flower petals, leaf and fruit pellet ethanolic extracts. Docking simulation of the active flavonoids on anti-apoptotic protein Bcl-2
  48. Synthesis and Characterization of Pd exchanged MMT Clay for Mizoroki-Heck Reaction
  49. A new selective, and sensitive method for the determination of lixivaptan, a vasopressin 2 (V2)-receptor antagonist, in mouse plasma and its application in a pharmacokinetic study
  50. Anti-EGFL7 antibodies inhibit rat prolactinoma MMQ cells proliferation and PRL secretion
  51. Density functional theory calculations, vibration spectral analysis and molecular docking of the antimicrobial agent 6-(1,3-benzodioxol-5-ylmethyl)-5-ethyl-2-{[2-(morpholin-4-yl)ethyl] sulfanyl}pyrimidin-4(3H)-one
  52. Effect of Nano Zeolite on the Transformation of Cadmium Speciation and Its Uptake by Tobacco in Cadmium-contaminated Soil
  53. Effects and Mechanisms of Jinniu Capsule on Methamphetamine-Induced Conditioned Place Preference in Rats
  54. Calculating the Degree-based Topological Indices of Dendrimers
  55. Efficient optimization and mineralization of UV absorbers: A comparative investigation with Fenton and UV/H2O2
  56. Metabolites of Tryptophane and Phenylalanine as Markers of Small Bowel Ischemia-Reperfusion Injury
  57. Adsorption and determination of polycyclic aromatic hydrocarbons in water through the aggregation of graphene oxide
  58. The role of NR2C2 in the prolactinomas
  59. Chromium removal from industrial wastewater using Phyllostachys pubescens biomass loaded Cu-S nanospheres
  60. Hydrotalcite Anchored Ruthenium Catalyst for CO2 Hydrogenation Reaction
  61. Preparation of Calcium Fluoride using Phosphogypsum by Orthogonal Experiment
  62. The mechanism of antibacterial activity of corylifolinin against three clinical bacteria from Psoralen corylifolia L
  63. 2-formyl-3,6-bis(hydroxymethyl)phenyl benzoate in Electrochemical Dry Cell
  64. Electro-photocatalytic degradation of amoxicillin using calcium titanate
  65. Effect of Malus halliana Koehne Polysaccharides on Functional Constipation
  66. Structural Properties and Nonlinear Optical Responses of Halogenated Compounds: A DFT Investigation on Molecular Modelling
  67. DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones and their derivatives: in-vitro antifungal, antibacterial and antioxidant evaluations
  68. Production of Methanol as a Fuel Energy from CO2 Present in Polluted Seawater - A Photocatalytic Outlook
  69. Study of different extraction methods on finger print and fatty acid of raw beef fat using fourier transform infrared and gas chromatography-mass spectrometry
  70. Determination of trace fluoroquinolones in water solutions and in medicinal preparations by conventional and synchronous fluorescence spectrometry
  71. Extraction and determination of flavonoids in Carthamus tinctorius
  72. Therapeutic Application of Zinc and Vanadium Complexes against Diabetes Mellitus a Coronary Disease: A review
  73. Study of calcined eggshell as potential catalyst for biodiesel formation using used cooking oil
  74. Manganese oxalates - structure-based Insights
  75. Topological Indices of H-Naphtalenic Nanosheet
  76. Long-Term Dissolution of Glass Fibers in Water Described by Dissolving Cylinder Zero-Order Kinetic Model: Mass Loss and Radius Reduction
  77. Topological study of the para-line graphs of certain pentacene via topological indices
  78. A brief insight into the prediction of water vapor transmissibility in highly impermeable hybrid nanocomposites based on bromobutyl/epichlorohydrin rubber blends
  79. Comparative sulfite assay by voltammetry using Pt electrodes, photometry and titrimetry: Application to cider, vinegar and sugar analysis
  80. MicroRNA delivery mediated by PEGylated polyethylenimine for prostate cancer therapy
  81. Reversible Fluorescent Turn-on Sensors for Fe3+ based on a Receptor Composed of Tri-oxygen Atoms of Amide Groups in Water
  82. Sonocatalytic degradation of methyl orange in aqueous solution using Fe-doped TiO2 nanoparticles under mechanical agitation
  83. Hydrotalcite Anchored Ruthenium Catalyst for CO2 Hydrogenation Reaction
  84. Production and Analysis of Recycled Ammonium Perrhenate from CMSX-4 superalloys
  85. Topical Issue on Agriculture
  86. New phosphorus biofertilizers from renewable raw materials in the aspect of cadmium and lead contents in soil and plants
  87. Survey of content of cadmium, calcium, chromium, copper, iron, lead, magnesium, manganese, mercury, sodium and zinc in chamomile and green tea leaves by electrothermal or flame atomizer atomic absorption spectrometry
  88. Biogas digestate – benefits and risks for soil fertility and crop quality – an evaluation of grain maize response
  89. A numerical analysis of heat transfer in a cross-current heat exchanger with controlled and newly designed air flows
  90. Freshwater green macroalgae as a biosorbent of Cr(III) ions
  91. The main influencing factors of soil mechanical characteristics of the gravity erosion environment in the dry-hot valley of Jinsha river
  92. Free amino acids in Viola tricolor in relation to different habitat conditions
  93. The influence of filler amount on selected properties of new experimental resin dental composite
  94. Effect of poultry wastewater irrigation on nitrogen, phosphorus and carbon contents in farmland soil
  95. Response of spring wheat to NPK and S fertilization. The content and uptake of macronutrients and the value of ionic ratios
  96. The Effect of Macroalgal Extracts and Near Infrared Radiation on Germination of Soybean Seedlings: Preliminary Research Results
  97. Content of Zn, Cd and Pb in purple moor-grass in soils heavily contaminated with heavy metals around a zinc and lead ore tailing landfill
  98. Topical Issue on Research for Natural Bioactive Products
  99. Synthesis of (±)-3,4-dimethoxybenzyl-4-methyloctanoate as a novel internal standard for capsinoid determination by HPLC-ESI-MS/MS(QTOF)
  100. Repellent activity of monoterpenoid esters with neurotransmitter amino acids against yellow fever mosquito, Aedes aegypti
  101. Effect of Flammulina velutipes (golden needle mushroom, eno-kitake) polysaccharides on constipation
  102. Bioassay-directed fractionation of a blood coagulation factor Xa inhibitor, betulinic acid from Lycopus lucidus
  103. Antifungal and repellent activities of the essential oils from three aromatic herbs from western Himalaya
  104. Chemical composition and microbiological evaluation of essential oil from Hyssopus officinalis L. with white and pink flowers
  105. Bioassay-guided isolation and identification of Aedes aegypti larvicidal and biting deterrent compounds from Veratrum lobelianum
  106. α-Terpineol, a natural monoterpene: A review of its biological properties
  107. Utility of essential oils for development of host-based lures for Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), vector of laurel wilt
  108. Phenolic composition and antioxidant potential of different organs of Kazakh Crataegus almaatensis Pojark: A comparison with the European Crataegus oxyacantha L. flowers
  109. Isolation of eudesmane type sesquiterpene ketone from Prangos heyniae H.Duman & M.F.Watson essential oil and mosquitocidal activity of the essential oils
  110. Comparative analysis of the polyphenols profiles and the antioxidant and cytotoxicity properties of various blue honeysuckle varieties
  111. Special Issue on ICCESEN 2017
  112. Modelling world energy security data from multinomial distribution by generalized linear model under different cumulative link functions
  113. Pine Cone and Boron Compounds Effect as Reinforcement on Mechanical and Flammability Properties of Polyester Composites
  114. Artificial Neural Network Modelling for Prediction of SNR Effected by Probe Properties on Ultrasonic Inspection of Austenitic Stainless Steel Weldments
  115. Calculation and 3D analyses of ERR in the band crack front contained in a rectangular plate made of multilayered material
  116. Improvement of fuel properties of biodiesel with bioadditive ethyl levulinate
  117. Properties of AlSi9Cu3 metal matrix micro and nano composites produced via stir casting
  118. Investigation of Antibacterial Properties of Ag Doped TiO2 Nanofibers Prepared by Electrospinning Process
  119. Modeling of Total Phenolic contents in Various Tea samples by Experimental Design Methods
  120. Nickel doping effect on the structural and optical properties of indium sulfide thin films by SILAR
  121. The effect mechanism of Ginnalin A as a homeopathic agent on various cancer cell lines
  122. Excitation functions of proton induced reactions of some radioisotopes used in medicine
  123. Oxide ionic conductivity and microstructures of Pr and Sm co-doped CeO2-based systems
  124. Rapid Synthesis of Metallic Reinforced in Situ Intermetallic Composites in Ti-Al-Nb System via Resistive Sintering
  125. Oxidation Behavior of NiCr/YSZ Thermal Barrier Coatings (TBCs)
  126. Clustering Analysis of Normal Strength Concretes Produced with Different Aggregate Types
  127. Magnetic Nano-Sized Solid Acid Catalyst Bearing Sulfonic Acid Groups for Biodiesel Synthesis
  128. The biological activities of Arabis alpina L. subsp. brevifolia (DC.) Cullen against food pathogens
  129. Humidity properties of Schiff base polymers
  130. Free Vibration Analysis of Fiber Metal Laminated Straight Beam
  131. Comparative study of in vitro antioxidant, acetylcholinesterase and butyrylcholinesterase activity of alfalfa (Medicago sativa L.) collected during different growth stages
  132. Isothermal Oxidation Behavior of Gadolinium Zirconate (Gd2Zr2O7) Thermal Barrier Coatings (TBCs) produced by Electron Beam Physical Vapor Deposition (EB-PVD) technique
  133. Optimization of Adsorption Parameters for Ultra-Fine Calcite Using a Box-Behnken Experimental Design
  134. The Microstructural Investigation of Vermiculite-Infiltrated Electron Beam Physical Vapor Deposition Thermal Barrier Coatings
  135. Modelling Porosity Permeability of Ceramic Tiles using Fuzzy Taguchi Method
  136. Experimental and theoretical study of a novel naphthoquinone Schiff base
  137. Physicochemical properties of heat treated sille stone for ceramic industry
  138. Sand Dune Characterization for Preparing Metallurgical Grade Silicon
  139. Catalytic Applications of Large Pore Sulfonic Acid-Functionalized SBA-15 Mesoporous Silica for Esterification
  140. One-photon Absorption Characterizations, Dipole Polarizabilities and Second Hyperpolarizabilities of Chlorophyll a and Crocin
  141. The Optical and Crystallite Characterization of Bilayer TiO2 Films Coated on Different ITO layers
  142. Topical Issue on Bond Activation
  143. Metal-mediated reactions towards the synthesis of a novel deaminolysed bisurea, dicarbamolyamine
  144. The structure of ortho-(trifluoromethyl)phenol in comparison to its homologues – A combined experimental and theoretical study
  145. Heterogeneous catalysis with encapsulated haem and other synthetic porphyrins: Harnessing the power of porphyrins for oxidation reactions
  146. Recent Advances on Mechanistic Studies on C–H Activation Catalyzed by Base Metals
  147. Reactions of the organoplatinum complex [Pt(cod) (neoSi)Cl] (neoSi = trimethylsilylmethyl) with the non-coordinating anions SbF6– and BPh4–
  148. Erratum
  149. Investigation on Two Compounds of O, O’-dithiophosphate Derivatives as Corrosion Inhibitors for Q235 Steel in Hydrochloric Acid Solution
https://doi.org/10.1515/chem-2018-0009
Schlagwörter für diesen Artikel
photocyclization; substituent effect; 1,4-biradical; angular pentacyclics; chromenones; benzothiophene; photoirradiation
Creative Commons
BY-NC-ND 4.0

Artikel in diesem Heft

  1. Regular Articles
  2. The effect of CuO modification for a TiO2 nanotube confined CeO2 catalyst on the catalytic combustion of butane
  3. The preparation and antibacterial activity of cellulose/ZnO composite: a review
  4. Linde Type A and nano magnetite/NaA zeolites: cytotoxicity and doxorubicin loading efficiency
  5. Performance and thermal decomposition analysis of foaming agent NPL-10 for use in heavy oil recovery by steam injection
  6. Spectroscopic (FT-IR, FT-Raman, UV, 1H and 13C NMR) insights, electronic profiling and DFT computations on ({(E)-[3-(1H-imidazol-1-yl)-1-phenylpropylidene] amino}oxy)(4-nitrophenyl)methanone, an imidazole-bearing anti-Candida agent
  7. A Simplistic Preliminary Assessment of Ginstling-Brounstein Model for Solid Spherical Particles in the Context of a Diffusion-Controlled Synthesis
  8. M-Polynomials And Topological Indices Of Zigzag And Rhombic Benzenoid Systems
  9. Photochemical Transformation of some 3-benzyloxy-2-(benzo[b]thiophen-2-yl)-4Hchromen-4-ones: A Remote Substituent Effect
  10. Dynamic Changes of Secondary Metabolites and Antioxidant Activity of Ligustrum lucidum During Fruit Growth
  11. Studies on the flammability of polypropylene/ammonium polyphosphate and montmorillonite by using the cone calorimeter test
  12. DSC, FT-IR, NIR, NIR-PCA and NIR-ANOVA for determination of chemical stability of diuretic drugs: impact of excipients
  13. Antioxidant and Hepatoprotective Effects of Methanolic Extracts of Zilla spinosa and Hammada elegans Against Carbon Tetrachlorideinduced Hepatotoxicity in Rats
  14. Prunus cerasifera Ehrh. fabricated ZnO nano falcates and its photocatalytic and dose dependent in vitro bio-activity
  15. Organic biocides hosted in layered double hydroxides: enhancing antimicrobial activity
  16. Experimental study on the regulation of the cholinergic pathway in renal macrophages by microRNA-132 to alleviate inflammatory response
  17. Synthesis, characterization, in-vitro antimicrobial properties, molecular docking and DFT studies of 3-{(E)-[(4,6-dimethylpyrimidin-2-yl)imino]methyl} naphthalen-2-ol and Heteroleptic Mn(II), Co(II), Ni(II) and Zn(II) complexes
  18. M-Polynomials and Topological Indices of Dominating David Derived Networks
  19. Human Health Risk Assessment of Trace Metals in Surface Water Due to Leachate from the Municipal Dumpsite by Pollution Index: A Case Study from Ndawuse River, Abuja, Nigeria
  20. Analysis of Bowel Diseases from Blood Serum by Autofluorescence and Atomic Force Microscopy Techniques
  21. Hydrographic parameters and distribution of dissolved Cu, Ni, Zn and nutrients near Jeddah desalination plant
  22. Relationships between diatoms and environmental variables in industrial water biotopes of Trzuskawica S.A. (Poland)
  23. Optimum Conversion of Major Ginsenoside Rb1 to Minor Ginsenoside Rg3(S) by Pulsed Electric Field-Assisted Acid Hydrolysis Treatment
  24. Antioxidant, Anti-microbial Properties and Chemical Composition of Cumin Essential Oils Extracted by Three Methods
  25. Regulatory mechanism of ulinastatin on autophagy of macrophages and renal tubular epithelial cells
  26. Investigation of the sustained-release mechanism of hydroxypropyl methyl cellulose skeleton type Acipimox tablets
  27. Bio-accumulation of Polycyclic Aromatic Hydrocarbons in the Grey Mangrove (Avicennia marina) along Arabian Gulf, Saudi Coast
  28. Dynamic Change of Secondary Metabolites and spectrum-effect relationship of Malus halliana Koehne flowers during blooming
  29. Lipids constituents from Gardenia aqualla Stapf & Hutch
  30. Effect of using microwaves for catalysts preparation on the catalytic acetalization of glycerol with furfural to obtain fuel additives
  31. Effect of Humic Acid on the Degradation of Methylene Blue by Peroxymonosulfate
  32. Serum containing drugs of Gua Lou Xie Bai decoction (GLXB-D) can inhibit TGF-β1-Induced Epithelial to Mesenchymal Transition (EMT) in A549 Cells
  33. Antiulcer Activity of Different Extracts of Anvillea garcinii and Isolation of Two New Secondary Metabolites
  34. Analysis of Metabolites in Cabernet Sauvignon and Shiraz Dry Red Wines from Shanxi by 1H NMR Spectroscopy Combined with Pattern Recognition Analysis
  35. Can water temperature impact litter decomposition under pollution of copper and zinc mixture
  36. Released from ZrO2/SiO2 coating resveratrol inhibits senescence and oxidative stress of human adipose-derived stem cells (ASC)
  37. Validated thin-layer chromatographic method for alternative and simultaneous determination of two anti-gout agents in their fixed dose combinations
  38. Fast removal of pollutants from vehicle emissions during cold-start stage
  39. Review Article
  40. Catalytic activities of heterogeneous catalysts obtained by copolymerization of metal-containing 2-(acetoacetoxy)ethyl methacrylate
  41. Antibiotic Residue in the Aquatic Environment: Status in Africa
  42. Regular Articles
  43. Mercury fractionation in gypsum using temperature desorption and mass spectrometric detection
  44. Phytosynthetic Ag doped ZnO nanoparticles: Semiconducting green remediators
  45. Epithelial–Mesenchymal Transition Induced by SMAD4 Activation in Invasive Growth Hormone-Secreting Adenomas
  46. Physicochemical properties of stabilized sewage sludge admixtures by modified steel slag
  47. In Vitro Cytotoxic and Antiproliferative Activity of Cydonia oblonga flower petals, leaf and fruit pellet ethanolic extracts. Docking simulation of the active flavonoids on anti-apoptotic protein Bcl-2
  48. Synthesis and Characterization of Pd exchanged MMT Clay for Mizoroki-Heck Reaction
  49. A new selective, and sensitive method for the determination of lixivaptan, a vasopressin 2 (V2)-receptor antagonist, in mouse plasma and its application in a pharmacokinetic study
  50. Anti-EGFL7 antibodies inhibit rat prolactinoma MMQ cells proliferation and PRL secretion
  51. Density functional theory calculations, vibration spectral analysis and molecular docking of the antimicrobial agent 6-(1,3-benzodioxol-5-ylmethyl)-5-ethyl-2-{[2-(morpholin-4-yl)ethyl] sulfanyl}pyrimidin-4(3H)-one
  52. Effect of Nano Zeolite on the Transformation of Cadmium Speciation and Its Uptake by Tobacco in Cadmium-contaminated Soil
  53. Effects and Mechanisms of Jinniu Capsule on Methamphetamine-Induced Conditioned Place Preference in Rats
  54. Calculating the Degree-based Topological Indices of Dendrimers
  55. Efficient optimization and mineralization of UV absorbers: A comparative investigation with Fenton and UV/H2O2
  56. Metabolites of Tryptophane and Phenylalanine as Markers of Small Bowel Ischemia-Reperfusion Injury
  57. Adsorption and determination of polycyclic aromatic hydrocarbons in water through the aggregation of graphene oxide
  58. The role of NR2C2 in the prolactinomas
  59. Chromium removal from industrial wastewater using Phyllostachys pubescens biomass loaded Cu-S nanospheres
  60. Hydrotalcite Anchored Ruthenium Catalyst for CO2 Hydrogenation Reaction
  61. Preparation of Calcium Fluoride using Phosphogypsum by Orthogonal Experiment
  62. The mechanism of antibacterial activity of corylifolinin against three clinical bacteria from Psoralen corylifolia L
  63. 2-formyl-3,6-bis(hydroxymethyl)phenyl benzoate in Electrochemical Dry Cell
  64. Electro-photocatalytic degradation of amoxicillin using calcium titanate
  65. Effect of Malus halliana Koehne Polysaccharides on Functional Constipation
  66. Structural Properties and Nonlinear Optical Responses of Halogenated Compounds: A DFT Investigation on Molecular Modelling
  67. DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones and their derivatives: in-vitro antifungal, antibacterial and antioxidant evaluations
  68. Production of Methanol as a Fuel Energy from CO2 Present in Polluted Seawater - A Photocatalytic Outlook
  69. Study of different extraction methods on finger print and fatty acid of raw beef fat using fourier transform infrared and gas chromatography-mass spectrometry
  70. Determination of trace fluoroquinolones in water solutions and in medicinal preparations by conventional and synchronous fluorescence spectrometry
  71. Extraction and determination of flavonoids in Carthamus tinctorius
  72. Therapeutic Application of Zinc and Vanadium Complexes against Diabetes Mellitus a Coronary Disease: A review
  73. Study of calcined eggshell as potential catalyst for biodiesel formation using used cooking oil
  74. Manganese oxalates - structure-based Insights
  75. Topological Indices of H-Naphtalenic Nanosheet
  76. Long-Term Dissolution of Glass Fibers in Water Described by Dissolving Cylinder Zero-Order Kinetic Model: Mass Loss and Radius Reduction
  77. Topological study of the para-line graphs of certain pentacene via topological indices
  78. A brief insight into the prediction of water vapor transmissibility in highly impermeable hybrid nanocomposites based on bromobutyl/epichlorohydrin rubber blends
  79. Comparative sulfite assay by voltammetry using Pt electrodes, photometry and titrimetry: Application to cider, vinegar and sugar analysis
  80. MicroRNA delivery mediated by PEGylated polyethylenimine for prostate cancer therapy
  81. Reversible Fluorescent Turn-on Sensors for Fe3+ based on a Receptor Composed of Tri-oxygen Atoms of Amide Groups in Water
  82. Sonocatalytic degradation of methyl orange in aqueous solution using Fe-doped TiO2 nanoparticles under mechanical agitation
  83. Hydrotalcite Anchored Ruthenium Catalyst for CO2 Hydrogenation Reaction
  84. Production and Analysis of Recycled Ammonium Perrhenate from CMSX-4 superalloys
  85. Topical Issue on Agriculture
  86. New phosphorus biofertilizers from renewable raw materials in the aspect of cadmium and lead contents in soil and plants
  87. Survey of content of cadmium, calcium, chromium, copper, iron, lead, magnesium, manganese, mercury, sodium and zinc in chamomile and green tea leaves by electrothermal or flame atomizer atomic absorption spectrometry
  88. Biogas digestate – benefits and risks for soil fertility and crop quality – an evaluation of grain maize response
  89. A numerical analysis of heat transfer in a cross-current heat exchanger with controlled and newly designed air flows
  90. Freshwater green macroalgae as a biosorbent of Cr(III) ions
  91. The main influencing factors of soil mechanical characteristics of the gravity erosion environment in the dry-hot valley of Jinsha river
  92. Free amino acids in Viola tricolor in relation to different habitat conditions
  93. The influence of filler amount on selected properties of new experimental resin dental composite
  94. Effect of poultry wastewater irrigation on nitrogen, phosphorus and carbon contents in farmland soil
  95. Response of spring wheat to NPK and S fertilization. The content and uptake of macronutrients and the value of ionic ratios
  96. The Effect of Macroalgal Extracts and Near Infrared Radiation on Germination of Soybean Seedlings: Preliminary Research Results
  97. Content of Zn, Cd and Pb in purple moor-grass in soils heavily contaminated with heavy metals around a zinc and lead ore tailing landfill
  98. Topical Issue on Research for Natural Bioactive Products
  99. Synthesis of (±)-3,4-dimethoxybenzyl-4-methyloctanoate as a novel internal standard for capsinoid determination by HPLC-ESI-MS/MS(QTOF)
  100. Repellent activity of monoterpenoid esters with neurotransmitter amino acids against yellow fever mosquito, Aedes aegypti
  101. Effect of Flammulina velutipes (golden needle mushroom, eno-kitake) polysaccharides on constipation
  102. Bioassay-directed fractionation of a blood coagulation factor Xa inhibitor, betulinic acid from Lycopus lucidus
  103. Antifungal and repellent activities of the essential oils from three aromatic herbs from western Himalaya
  104. Chemical composition and microbiological evaluation of essential oil from Hyssopus officinalis L. with white and pink flowers
  105. Bioassay-guided isolation and identification of Aedes aegypti larvicidal and biting deterrent compounds from Veratrum lobelianum
  106. α-Terpineol, a natural monoterpene: A review of its biological properties
  107. Utility of essential oils for development of host-based lures for Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), vector of laurel wilt
  108. Phenolic composition and antioxidant potential of different organs of Kazakh Crataegus almaatensis Pojark: A comparison with the European Crataegus oxyacantha L. flowers
  109. Isolation of eudesmane type sesquiterpene ketone from Prangos heyniae H.Duman & M.F.Watson essential oil and mosquitocidal activity of the essential oils
  110. Comparative analysis of the polyphenols profiles and the antioxidant and cytotoxicity properties of various blue honeysuckle varieties
  111. Special Issue on ICCESEN 2017
  112. Modelling world energy security data from multinomial distribution by generalized linear model under different cumulative link functions
  113. Pine Cone and Boron Compounds Effect as Reinforcement on Mechanical and Flammability Properties of Polyester Composites
  114. Artificial Neural Network Modelling for Prediction of SNR Effected by Probe Properties on Ultrasonic Inspection of Austenitic Stainless Steel Weldments
  115. Calculation and 3D analyses of ERR in the band crack front contained in a rectangular plate made of multilayered material
  116. Improvement of fuel properties of biodiesel with bioadditive ethyl levulinate
  117. Properties of AlSi9Cu3 metal matrix micro and nano composites produced via stir casting
  118. Investigation of Antibacterial Properties of Ag Doped TiO2 Nanofibers Prepared by Electrospinning Process
  119. Modeling of Total Phenolic contents in Various Tea samples by Experimental Design Methods
  120. Nickel doping effect on the structural and optical properties of indium sulfide thin films by SILAR
  121. The effect mechanism of Ginnalin A as a homeopathic agent on various cancer cell lines
  122. Excitation functions of proton induced reactions of some radioisotopes used in medicine
  123. Oxide ionic conductivity and microstructures of Pr and Sm co-doped CeO2-based systems
  124. Rapid Synthesis of Metallic Reinforced in Situ Intermetallic Composites in Ti-Al-Nb System via Resistive Sintering
  125. Oxidation Behavior of NiCr/YSZ Thermal Barrier Coatings (TBCs)
  126. Clustering Analysis of Normal Strength Concretes Produced with Different Aggregate Types
  127. Magnetic Nano-Sized Solid Acid Catalyst Bearing Sulfonic Acid Groups for Biodiesel Synthesis
  128. The biological activities of Arabis alpina L. subsp. brevifolia (DC.) Cullen against food pathogens
  129. Humidity properties of Schiff base polymers
  130. Free Vibration Analysis of Fiber Metal Laminated Straight Beam
  131. Comparative study of in vitro antioxidant, acetylcholinesterase and butyrylcholinesterase activity of alfalfa (Medicago sativa L.) collected during different growth stages
  132. Isothermal Oxidation Behavior of Gadolinium Zirconate (Gd2Zr2O7) Thermal Barrier Coatings (TBCs) produced by Electron Beam Physical Vapor Deposition (EB-PVD) technique
  133. Optimization of Adsorption Parameters for Ultra-Fine Calcite Using a Box-Behnken Experimental Design
  134. The Microstructural Investigation of Vermiculite-Infiltrated Electron Beam Physical Vapor Deposition Thermal Barrier Coatings
  135. Modelling Porosity Permeability of Ceramic Tiles using Fuzzy Taguchi Method
  136. Experimental and theoretical study of a novel naphthoquinone Schiff base
  137. Physicochemical properties of heat treated sille stone for ceramic industry
  138. Sand Dune Characterization for Preparing Metallurgical Grade Silicon
  139. Catalytic Applications of Large Pore Sulfonic Acid-Functionalized SBA-15 Mesoporous Silica for Esterification
  140. One-photon Absorption Characterizations, Dipole Polarizabilities and Second Hyperpolarizabilities of Chlorophyll a and Crocin
  141. The Optical and Crystallite Characterization of Bilayer TiO2 Films Coated on Different ITO layers
  142. Topical Issue on Bond Activation
  143. Metal-mediated reactions towards the synthesis of a novel deaminolysed bisurea, dicarbamolyamine
  144. The structure of ortho-(trifluoromethyl)phenol in comparison to its homologues – A combined experimental and theoretical study
  145. Heterogeneous catalysis with encapsulated haem and other synthetic porphyrins: Harnessing the power of porphyrins for oxidation reactions
  146. Recent Advances on Mechanistic Studies on C–H Activation Catalyzed by Base Metals
  147. Reactions of the organoplatinum complex [Pt(cod) (neoSi)Cl] (neoSi = trimethylsilylmethyl) with the non-coordinating anions SbF6– and BPh4–
  148. Erratum
  149. Investigation on Two Compounds of O, O’-dithiophosphate Derivatives as Corrosion Inhibitors for Q235 Steel in Hydrochloric Acid Solution
Jetzt anmelden und 20% sparen
Institutioneller Zugang
Wie funktioniert Authentifizierung?
Haben Sie eine Idee, wie wir unsere Website verbessern können?
Bitte schreiben Sie uns.
© 2025 De Gruyter Brill
Heruntergeladen am 7.9.2025 von https://www.degruyterbrill.com/document/doi/10.1515/chem-2018-0009/html
Button zum nach oben scrollen