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Novel 5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine derivatives

  • Xixi Hou , Jianxue Yang , Linlin Mao , Caoxuan Lou EMAIL logo and Longfei Mao
Published/Copyright: October 4, 2016
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Heterocyclic Communications
From the journal Heterocyclic Communications Volume 22 Issue 5

Abstract

Starting with 4-piperidone, new 5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo [5,4-c]pyridines were synthesized. Structures of these compounds were confirmed by 1H NMR, 13C NMR, MS and elemental analysis.

Keywords: 4-piperidone; 5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo [5,4-c]pyridine; synthesis

Introduction

Piperidine (hexahydropyridine) and imidazole are important nitrogen-containing heterocyclic compounds. Piperidine has good water solubility due to its basic group. The piperidine ring structure is often introduced into drug molecules, which can improve bioavailability and efficacy of the drugs [1]. Imidazole is widely present in natural products, and a variety of its derivatives have been developed to treat bacterial infection, cancer, inflammatory disease and low blood sugar among other things [2]. There are reports [3], [4] that tetrahydropyridine derivatives alter the Hedgehog signaling pathway and thus significantly inhibit the growth of prostate cancer, pancreatic cancer, breast cancer and some blood cancers. There are also reports [5], [6], [7], [8] that imidazole compounds inhibit Met receptor tyrosine kinase, which indicates the potential therapeutical benefits of such compounds. Several new compounds containing tetrahydropyridine and imidazole, 4 and 5, were synthesized as part of this work (Scheme 1).

Scheme 1
Scheme 1

Results and discussion

The amino group of 4-piperidone (1) was first protected with a Boc group to give compound 2 which then was allowed to react with elemental sulfur and cyanamide in the presence of p-toluenesulfonic acid to form N-Boc-2-amino-4,5,6,7-tetrahydrothiazolo[5,4-c]pyridine (3). Compound 3 was allowed to react with a variety of 3-bromoacetyl-bearing compounds to form cyclic products 4a–k. These compounds were then deprotected to give compounds 5a–k. The molecular structures of 5a–k were analyzed using 1H NMR, 13C NMR, and elemental analysis. The presence of water in the reaction mixture leading to 3 greatly reduces the yield of compound 3. Due to the fact that the catalyst p-toluenesulfonic acid is a monohydrate and water is also produced in the course of the reaction, the water must be constantly removed using a Dean-Stark apparatus. The yield of compound 3 increases with increasing temperature up to 90°C. A further increase in temperature lowers the yield due to formation of by-products. A catalyst is not required for the subsequent synthesis of 4a. The reactions conducted in solvents of low polarity including 1,4-dioxane, benzene and toluene furnish higher yields of 4a (76–82%) compared to the polar solvents such as methanol (34%), ethanol (51%) and acetonitrile (59%). The use of dichloromethane as a solvent gives product 4a in a low yield of 23%, which indicates, as already mentioned, that low temperature is an adverse factor. Overall, 1,4-dioxane is a preferred solvent when compared with highly toxic benzene and toluene with high boiling point that makes it difficult to remove.

Conclusion

The reported synthesis of 5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridines (5a–k) is experimentally simple and highly efficient.

Experimental

Melting points were determined on a YUHUA X-3 melting point apparatus and are uncorrected. The 1H NMR (400 MHz) and 13C (100 MHz) spectra were recorded in CDCl3 on a Bruker Avance 400 spectrometer. The electrospray ionization mass spectra (ESI-MS) were recorded on a Bruker Esquire 3000 instrument. Elemental analyses were conducted using an ELTRA analyzer. All reagents were obtained from commercial sources and used without further purification. All reactions were monitored by thin-layer chromatography (TLC). Compound 2 was synthesized by using previously published procedure [9], [10].

Synthesis of tert-butyl 2-amino-4,5,6,7-tetrahydrothiazolo[5,4-c]pyridine-5-carboxylate (3)

To a solution of compound 2 (30 g, 150 mmol) in cyclohexane (100 mL) were added pyrrolidine (13.2 mL, 158 mmol) and TsOH·H2O (1.43 g, 7.53 mmol) and the mixture was heated under reflux for 3 h with constant removal of water using a Dean-Stark apparatus. After cooling to room temperature, the mixture was filtered and the filtrate was concentrated. The residue was dissolved in dry methanol (130 mL), and the solution was treated with elemental sulfur (S8, 4.8 g, 151 mmol) followed by addition of a solution of cyanamide (6.34 g, 151 mmol) in dry methanol (20 mL) dropwise at 0°C. The mixture was stirred for 2 h at 90°C. After concentration, the residue was purified by column chromatography on silica gel eluting with petroleum ether/ethyl acetate, 1:2, to give 22.8 g (59%) of compound 3 as a pale yellow solid; 1H NMR: δ 4.26 (s, 2 H), 3.56 (t, J=5.7 Hz, 2 H), 2.42 (m, 2 H), 1.36 (s, 9 H); MS: m/z 256.3, [M+H]+.

General procedure for the preparation of 4a–k

To a solution of compound 3 (50.3 g, 197 mmol) in 1,4-dioxane (1000 mL) was added R-C(O)CH2Br (217 mmol, see Scheme 1 for R) in one portion. After stirring at room temperature for 1 h, the mixture was heated under reflux overnight. After concentration, the residue was purified by column chromatography on silica gel eluting with petroleum ether/ethyl acetate, 2:1, to give compound 4a–k as a pale yellow solid; yield 80%.

tert-Butyl 2-(4-cyanophenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4a)

Yield 80%; 1H NMR: δ 7.89 (d, J=8.8 Hz, 2 H), 7.65 (m, 2 H), 7.37 (s, 1 H), 4.54 (s, 2 H), 3.86 (t, J=5.6 Hz, 2 H), 2.79–2.76 (m, 2 H), 1.49 (s, 9 H); MS: m/z 380.9, [M+H]+. Anal. Calcd for C20H20N4OS: C, 63.14; H, 5.30; N, 14.73. Found: C, 63.17; H, 5.34; N, 14.75.

tert-Butyl 2-(tert-butyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4b)

Yield 75%; 1H NMR: δ 7.02 (s, 1 H), 4.49 (s, 2 H), 3.81 (t, J=5.2 Hz, 2 H), 2.71 (t, J=5.2 Hz, 2 H), 1.48 (s, 9 H), 1.33 (s, 9 H); MS: m/z 335.8, [M+H]+. Anal. Calcd for C17H25N3O2S: C, 60.87; H, 7.51; N, 12.53. Found: C, 60.79; H, 7.54; N, 12.55.

tert-Butyl 2-phenyl-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4c)

Yield 72%; 1H NMR: δ 7.94 (s, 1 H), 7.79 (d, J=7.6 Hz, 2 H), 7.40 (t, J=7.2 Hz, 2 H), 7.30 (t, J=7.2 Hz, 1 H), 4.58 (s, 2 H), 3.87 (t, J=6.0 Hz, 2 H), 2.85–2.82 (m, 2 H), 1.54 (s, 9 H); MS: m/z 356.2, [M+H]+. Anal. Calcd for C19H21N3O2S: C, 64.20; H, 5.95; N, 11.82. Found: C, 64.27; H, 5.94; N, 11.76.

tert-Butyl 2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4d)

Yield 70%; 1H NMR: δ 7.63 (s, 1 H), 4.56 (s, 2 H), 3.86 (t, J=5.6 Hz, 2 H), 2.79 (m, 2 H), 1.48 (s, 9 H); MS: m/z 347.8, [M+H]+. Anal. Calcd for C14H16F3N3O2S: C, 48.41; H, 4.64; N, 12.10. Found: C, 48.45; H, 4.65; N, 12.17.

tert-Butyl 2-(4-chlorophenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4e)

Yield 61%; 1H NMR: δ 7.74 (d, J=8.4 Hz, 2 H), 7.56 (s, 1 H), 7.35 (d, J=8.4 Hz, 2 H), 4.53 (m, 2 H), 3.86 (m, 2 H), 2.77 (m, 2 H), 1.49 (s, 9 H); MS: m/z 390.1, [M+H]+. Anal. Calcd for C19H20ClN3O2S: C, 58.53; H, 5.17; N, 10.78. Found: C, 58.51; H, 5.14; N, 10.72.

tert-Butyl 2-(3-methoxyphenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4f)

Yield 67%; 1H NMR: δ 7.57 (s, 1 H), 7.42 (s, 1 H), 7.33 (d, J=7.6 Hz, 1 H), 7.27 (t, J=8.0 Hz, 1 H), 6.83 (d, J=8.0 Hz, 1 H), 4.54 (m, 2 H), 3.81 (m, 5 H), 2.77 (m, 2 H), 1.50 (s, 9 H); MS: m/z 386.2, [M+H]+. Anal. Calcd for C20H23N3O3S: C, 62.32; H, 6.01; N, 10.90. Found: C, 62.30; H, 6.05; N, 10.87.

tert-Butyl 2-(4-fluorophenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4g)

Yield 64%; 1H NMR: δ 7.68 (d, J=8.4 Hz, 2 H), 7.55 (s, 1 H), 7.39 (d, J=8.4 Hz, 2 H), 4.41 (m, 2 H), 3.87 (m, 2 H), 2.74 (m, 2 H), 1.47 (s, 9 H); MS: m/z 374.5, [M+H]+. Anal. Calcd for C19H20FN3O2S: C, 61.11; H, 5.40; N, 11.25. Found: C, 61.17; H, 5.45; N, 11.21.

tert-Butyl 2-methyl-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4h)

Yield 76%; 1H NMR: δ 7.79 (s, 1 H), 4.71 (s, 2 H), 3.69 (t, J=5.6 Hz, 2 H), 2.87 (m, 2 H), 2.36 (s, 3 H), 1.45 (s, 9 H); MS: m/z 294.4, [M+H]+. Anal. Calcd for C14H19N3O2S: C, 57.31; H, 6.53; N, 14.32. Found: C, 57.36; H, 6.61; N, 14.33.

tert-Butyl 2-isopropyl-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4i)

Yield 73%; 1H NMR: δ 7.56 (s, 1 H), 4.93 (s, 2 H), 3.66 (t, J=5.6 Hz, 2 H), 3.17 (d, J=8.0 Hz, 1 H), 2.60 (m, 2 H), 1.65 (s, 9 H), 1.38 (s, 6 H); MS: m/z 322.5, [M+H]+. Anal. Calcd for C16H23N3O2S: C, 59.78; H, 7.21; N, 13.07. Found: C, 59.76; H, 7.19; N, 13.03.

tert-Butyl 2-(4-nitrophenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4j)

Yield 59%; 1H NMR: δ 7.97 (d, J=8.4 Hz, 2 H), 7.65 (s, 1 H), 7.48 (d, J=8.4 Hz, 2 H), 4.93 (m, 2 H), 3.76 (d, J=8.4 Hz, 2 H), 2.83 (m, 2 H), 1.43 (s, 9 H); MS: m/z 401.4, [M+H]+. Anal. Calcd for C19H20N4O4S: C, 56.99; H, 5.03; N, 13.99. Found: C, 56.96; H, 5.01; N, 13.93.

tert-Butyl 2-(p-tolyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-7-carboxylate (4k)

Yield 54%; 1H NMR: δ 7.76 (d, J=8.4 Hz, 2 H), 7.67 (s, 1 H), 7.39 (d, J=8.4 Hz, 2 H), 4.81 (m, 2 H), 3.65 (d, J=8.4 Hz, 2 H), 2.75 (m, 2 H), 2.17 (s, 3 H), 1.43 (s, 9 H); MS: m/z 370.5, [M+H]+. Anal. Calcd for C20H23N3O2S: C, 65.01; H, 6.27; N, 11.37. Found: C, 65.06; H, 6.32; N, 11.33.

General procedure for the preparation of 5a–k

To a solution of compound 4a–k (84.5 mmol) in methanol (350 mL) was added dropwise a solution of 4 m HCl in MeOH (300 mL) at 0°C. The mixture was stirred at room temperature for 0.5 h and then concentrated to afford compound 5a–k.

4-{(5,6,7,8-Tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine-2-yl}benzonitrile hydrochloride (5a)

Yellow solid; yield 98%; mp 199–201°C; 1H NMR: δ 10.26 (s, 1 H), 8.52 (s, 1 H), 8.00 (d, J=8.4 Hz, 2 H), 7.86 (d, J=8.4 Hz, 2 H), 4.52 (s, 2 H), 3.78 (t, J=6.0 Hz, 2 H), 3.28 (m, 2 H); 13C NMR: δ 165.2, 153.1, 139.4, 138.6, 131.8, 127.9, 122.2, 107.1, 101.5, 59.8, 56.3, 47.3, 42.1; MS: m/z 281.2, [M+H]+. Anal. Calcd for C15H13ClN4S: C, 56.87; H, 4.14; N, 17.68. Found: C, 56.89; H, 4.09; N, 17.65.

2-(tert-Butyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5b)

Yellow solid, yield 98%; mp 142–144°C; 1H NMR: δ 10.14 (s, 1 H), 8.12 (s, 1 H), 4.67 (s, 2 H), 3.88 (t, J=6.0 Hz, 2 H), 3.41 (t, J=6.0 Hz, 2 H), 1.58 (s, 9 H); 13C NMR: δ 159.2, 131.4, 126.5, 122.3, 101.8, 59.1, 51.5, 42.3, 28.1, 23.6; MS: m/z 236.1, [M+H]+. Anal. Calcd for C12H18ClN3S: C, 53.03; H, 6.77; N, 15.46. Found: C, 53.09; H, 6.74; N, 15.49.

2-Phenyl-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5c)

White solid; yield 95%; mp 207–209°C; 1H NMR: δ 10.23 (s, 1 H), 8.19 (s, 1 H), 7.69 (m, 2 H), 7.54 (m, 3 H), 4.56 (s, 2 H), 3.76 (t, J=5.6 Hz, 2 H), 3.25 (t, J=6.0 Hz, 2 H); 13C NMR: δ 165.2, 153.3, 139.3, 138.6, 131.8, 127.9, 122.1, 101.5, 59.8, 56.3, 47.3, 41.9; MS: m/z 256.3, [M+H]+. Anal. Calcd for C14H14ClN3S: C, 57.63; H, 4.84; N, 14.40. Found: C, 57.57; H, 4.89; N, 14.45.

2-(Trifluoromethyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5d)

White solid; yield 91%; mp 191–193°C; 1H NMR: δ 10.12 (s, 1 H), 8.16 (s, 1 H), 3.95 (s, 2 H), 3.25 (t, J=6.0 Hz, 2 H), 2.81 (m, 2 H); 13C NMR: δ 161.4, 129.5, 122.5, 119.7, 101.4, 59.7, 52.1, 42.3, 27.3; MS: m/z 248.2, [M+H]+. Anal. Calcd for C9H9ClF3N3S: C, 38.10; H, 3.20; N, 14.81. Found: C, 38.16; H, 3.14; N, 14.85.

2-(4-Chlorophenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5e)

Yellow solid; yield 94%; mp 271–274°C; 1H NMR: δ 10.16 (s, 1 H), 8.51 (s, 1 H), 7.87 (d, J=8.8 Hz, 2 H), 7.52 (d, J=8.8 Hz, 2 H), 4.32 (m, 2 H), 3.54 (m, 2 H), 3.11 (m, 2 H); 13C NMR: δ 165.2, 153.3, 139.3, 138.6, 131.8, 129.3, 124.7, 104.1, 59.8, 56.3, 47.3, 41.9; MS: m/z 289.7, [M+H]+. Anal. Calcd for C14H13Cl2N3S: C, 51.54; H, 4.02; N, 12.88. Found: C, 51.49; H, 4.04; N, 12.85.

2-(3-Methoxyphenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5f)

Yellow solid; yield 96%; mp 174–177°C; 1H NMR: δ 10.13 (s, 1 H), 8.58 (s, 1 H), 7.44 (m, 2 H), 7.36 (t, J=8.0 Hz, 1 H), 6.91 (d, J=8.0 Hz, 1 H), 4.33 (m, 2 H), 3.81 (s, 3 H), 3.54 (m, 2 H), 3.10 (m, 2 H); 13C NMR: δ 165.3, 152.9, 139.4, 138.6, 131.8, 127.9, 122.2, 107.1, 101.5, 59.8, 52.9, 44.2, 39.5; MS: m/z 286.3, [M+H]+. Anal. Calcd for C15H16ClN3OS: C, 55.98; H, 5.01; N, 13.06. Found: C, 55.92; H, 5.04; N, 13.05.

2-(4-Fluorophenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5g)

Yellow solid; yield 89%; mp 217–219°C; 1H NMR: δ 10.21 (s, 1 H), 8.57 (s, 1 H), 7.69 (d, J=8.8 Hz, 2 H), 7.46 (d, J=8.8 Hz, 2 H), 4.27 (m, 2 H), 3.53 (m, 2 H), 3.08 (m, 2 H); 13C NMR: δ 164.7, 154.1, 139.3, 138.7, 132.2, 129.6, 124.5, 104.3, 59.8, 56.3, 47.5, 42.3; MS: m/z 274.4, [M+H]+. Anal. Calcd for C14H13ClFN3S: C, 54.28; H, 4.23; N, 13.56. Found: C, 54.19; H, 4.34; N, 13.55.

2-Methyl-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5h)

White solid; yield 97%; mp 167–169°C; 1H NMR: δ 10.17 (s, 1 H), 7.97 (s, 1 H), 4.11 (s, 2 H), 3.62 (t, J=6.0 Hz, 2 H), 2.83 (d, J=6.0 Hz, 2 H), 2.21 (s, 3 H); 13C NMR: δ 159.6, 131.4, 130.1, 117.6, 98.9, 59.3, 53.2, 44.6, 21.7; MS: m/z 248.2, [M+H]+. Anal. Calcd for C9H12ClN3S: C, 47.05; H, 5.27; N, 18.29. Found: C, 46.97; H, 5.34; N, 18.17.

2-Isopropyl-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5i)

White solid; yield 94%; mp 203–205°C; 1H NMR: δ 10.11 (s, 1 H), 8.37 (s, 1 H), 4.33 (s, 2 H), 3.59 (t, J=5.6 Hz, 2 H), 3.21 (d, J=8.0 Hz, 1 H), 2.45 (m, 2 H), 1.25 (s, 6 H); 13C NMR: δ 160.4, 132.7, 128.9, 116.3, 100.6, 61.1, 54.8, 45.6, 32.6, 22.9; MS: m/z 222.3, [M+H]+. Anal. Calcd for C11H16ClN3S: C, 51.25; H, 6.26; N, 16.30. Found: C, 51.31; H, 6.23; N, 16.37.

2-(4-Nitrophenyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5j)

Yellow solid; yield 87%; mp 241–243°C; 1H NMR: δ 10.37 (s, 1 H), 8.49 (s, 1 H), 8.17 (d, J=8.8 Hz, 2 H), 7.97 (d, J=8.8 Hz, 2 H), 4.32 (m, 2 H), 3.36 (m, 2 H), 2.93 (m, 2 H); 13C NMR: δ 165.9, 156.4, 136.7, 131.5, 129.6, 127.7, 121.5, 102.6, 62.3, 55.4, 42.8, 41.3; MS: m/z 301.4, [M+H]+. Anal. Calcd for C14H13ClN4O2S: C, 49.93; H, 3.89; N, 16.64. Found: C, 49.99; H, 3.84; N, 16.65.

2-(p-Tolyl)-5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine hydrochloride (5k)

White solid; yield 92%; mp 252–254°C; 1H NMR: δ 10.25 (s, 1 H), 8.81 (s, 1 H), 7.84 (d, J=8.8 Hz, 2 H), 7.47 (d, J=8.8 Hz, 2 H), 4.60 (m, 2 H), 3.32 (d, J=8.0 Hz, 2 H), 2.74 (m, 2 H), 2.21 (s, 3 H); 13C NMR: δ 160.3, 155.8, 136.7, 129.4, 127.6, 124.9, 118.1, 101.7, 65.3, 54.5, 42.2, 42.5, 27.6; MS: m/z 270.4, [M+H]+. Anal. Calcd for C15H16ClN3S: C, 58.91; H, 5.27; N, 13.74. Found: C, 58.97; H, 5.24; N, 13.69.

Funding: Key Scientific and Technological Project of He’nan province, (Grant/Award Number: ‘no. 15210221 0285’).

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Received: 2016-7-20
Accepted: 2016-8-27
Published Online: 2016-10-4
Published in Print: 2016-10-1

©2016 Walter de Gruyter GmbH, Berlin/Boston

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  9. Polymeric (anion-π)n interactions in crystals of 2-(2,4,6-trioxo-[1,3,5]triazinan-1-yl)ethylammonium iodide
  10. 5-(N-Ethylcarbazol-3-yl)thiophene-2-carbaldehyde (ECTC): a novel fluorescent sensor for ferric ion
  11. Novel 5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine derivatives
  12. Halogenoheterocyclization of 2-(allylthio)quinolin-3-carbaldehyde and 2-(propargylthio)quinolin-3-carbaldehyde
  13. Convenient synthesis of the functionalized 1′,3′-dihydrospiro[cyclopentane-1,2′-inden]-2-enes via a three-component reaction
  14. Synthesis of spiro[pyrazole-4,8′-pyrazolo [3,4-f]quinolin]-5(1H)-ones by the reaction of aldehydes with 1H-indazol-6-amine and 1H-pyrazol-5(4H)-one
https://doi.org/10.1515/hc-2016-0137
Keywords for this article
4-piperidone; 5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo [5,4-c]pyridine; synthesis
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Articles in the same Issue

  1. Frontmatter
  2. Preliminary Communications
  3. Efficient synthesis of 4-amino-2,6-dichloropyridine and its derivatives
  4. Reactions of 3-arylmethylene-3H-furan(pyrrol)-2-ones with azomethine ylide: synthesis of substituted azaspirononenes
  5. Research Articles
  6. Microwave-assisted one-pot synthesis and antimicrobial evaluation of 2-(1-phenyl-3-(2-thienyl)-1H-pyrazol-4-yl)chroman-4-one derivatives
  7. Structural characterization of copper complexes with chiral 1,2,4-triazine-oxazoline ligands
  8. Synthesis of metallophthalocyanines with four oxy-2,2-diphenylacetic acid substituents and their structural and electronic properties
  9. Polymeric (anion-π)n interactions in crystals of 2-(2,4,6-trioxo-[1,3,5]triazinan-1-yl)ethylammonium iodide
  10. 5-(N-Ethylcarbazol-3-yl)thiophene-2-carbaldehyde (ECTC): a novel fluorescent sensor for ferric ion
  11. Novel 5,6,7,8-tetrahydroimidazo[2′,1′:2,3]thiazolo[5,4-c]pyridine derivatives
  12. Halogenoheterocyclization of 2-(allylthio)quinolin-3-carbaldehyde and 2-(propargylthio)quinolin-3-carbaldehyde
  13. Convenient synthesis of the functionalized 1′,3′-dihydrospiro[cyclopentane-1,2′-inden]-2-enes via a three-component reaction
  14. Synthesis of spiro[pyrazole-4,8′-pyrazolo [3,4-f]quinolin]-5(1H)-ones by the reaction of aldehydes with 1H-indazol-6-amine and 1H-pyrazol-5(4H)-one
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