Startseite Green synthesis and structural characterization of novel N1-substituted 3,4-dihydropyrimidin-2(1H)-ones
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Green synthesis and structural characterization of novel N1-substituted 3,4-dihydropyrimidin-2(1H)-ones

  • Min Wang EMAIL logo , Shun Zhang , Hong X. Jiang und Hao H. Zhang
Veröffentlicht/Copyright: 13. November 2018
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Abstract

Novel N1-substituted 3,4-dihydropyrimidin-2(1H)-one derivatives were synthesized through Biginelli condensation of aromatic aldehydes, β-ketoesters, and monosubstituted (thio)ureas in the presence of copper methanesulfonate at 90°C under solvent-free conditions. The screening of the catalysts showed the copper methanesulfonate was the best. Its catalytic activity remained after three times of use. The products were characterized by IR, 1H NMR, 13C NMR, elemental analysis, and X-ray single crystal diffraction technique. A reasonable reaction mechanism was proposed.

1 Introduction

3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) have special therapeutic properties and pharmacological activity. They can be used as calcium channel agents, antiallergic agents, antihypertensive agents and antagonists, and so on [1], [2], [3], [4], [5], [6]. Such derivatives have broad applications in antimicrobial, antiviral, anticancer, sterilization, and other fields [7], [8], [9]. Several marine alkaloids containing DHPM core were also found. The most notable betzelladine alkaloids can inhibit the binding of HIV gp120 membrane protein. It is expected to treat AIDS [10]. Therefore, the research for the synthesis of DHPMs draws more and more attention.

In recent decades, scientists discovered that N1-substituted DHPMs have better pharmacological activity [11], [12]. However, little attention was paid to them. Few papers about the synthesis were reported. One of the most important synthetic methods is the Biginelli reaction. New catalysts [13], [14], [15], [16], [17], [18], [19], [20] and the explored new ways [21], [22], [23], [24] were reported. Nevertheless, some disadvantages such as the expensive catalysts, complex operations, toxic reagents, and the single structure of the product still existed. Consequently, an efficient and green method to synthesize the title products is worth an exploration.

In this study, the N1-substituted DHPMs were synthesized with aromatic aldehydes, ethyl acetoacetate (methyl acetoacetate), and N-substituted (thio)ureas using copper methanesulfonate [Cu(CH3SO3)2·4H2O, abbreviated as CMS] as a catalyst [Eq. (1)]. The N-substituted (thio)ureas include methylurea, ethylurea, p-tolylurea, and methylthiourea. This method avoids the use of a toxic solvent and a high cost. It is convenient, effective, and green. Twenty-one products were synthesized and many of them are new compounds.

      (1)

2 Materials and methods

2.1 Materials and general methods

All reagents were analytic grade and were obtained commercially (Shanghai Chemical Reagent Company, China). CMS was synthesized according to a reported literature [25]. Thin layer chromatography was performed on Merck Silica gel 60 F254 plates using ethyl acetate/petroleum ether (V/V=3:7) mixture as a mobile phase. Melting points were determined in an open glass capillary on an RY-1 micromelting point apparatus (Tianjin Tianguang Optical Instrument Limited Company, China). A Varian Scimitar 2000 series Fourier transform instrument (Agilent Technologies Inc., Santa Clara, CA, USA) was used for recording the IR spectra using potassium bromide pellets in the range of 400–4000 cm–1. The 1H and 13C NMR spectra were recorded on an Agilent 400-MR instrument (Agilent Technologies Inc., Santa Clara, CA, USA) in DMSO-d6 using TMS as an internal standard. Elemental analyses (C, H, N) were conducted using the Elemental Analyser EA 2400II (Perkin Elmer, Waltham, MA, USA), their results were found to be in good agreement (±0.3%) with the calculated values. Crystallographic data for compound t were collected on a Bruker Smart Apex II diffractometer (Bruker Corporation, Karlsruhe, Germany) with Mo Kα radiation (λ=0.71069 Å) at 296 K using ω-scan technique. The diffraction data were integrated by using the SAINT program, which was also used for the intensity corrections for the Lorentz and polarization effects. Semiempirical absorption corrections were applied using SADABS program. The structures were solved by direct methods, and all of the non-hydrogen atoms were refined anisotropically on F2 by the full-matrix least-squares technique using the SHELXTL crystallographic software package.

2.2 General procedure for the synthesis of N1-substituted DHPMs

Aromatic aldehyde (10 mmol), ethyl acetoacetate (methyl acetoacetate) (10 mmol), N-substituted urea or a thiourea (13 mmol), and CMS (0.3 mmol) were added in a 25-ml reaction flask. The reaction mixture was then stirred at 90°C in an oil bath for an appropriate time (as indicated by TLC). In this process, a solid precipitate was observed in the reaction flask. After completion, the mixture was cooled to room temperature and ice water was added. The crude products were filtrated through a funnel and then purified further by recrystallization with anhydrous ethanol. All title products were characterized by melting point, IR, 1H NMR, 13C NMR, and elemental analysis. The following are spectral data for some of the new compounds:

2.2.1 5-Ethoxycarbonyl-1,6-dimethyl-4-(4-hydroxy-3-methoxyphenyl)-3,4-dihydropyrimidin-2(1H)-one (h)

Orange solid. 1H NMR (400 MHz, DMSO-d6) δ: 8.94 (s, 1H, OH), 7.87 (s, 1H, NH), 6.60–6.78 (m, 3H, ArH), 5.08 (s, 1H, CH), 4.06 (q, 2H, J=6.0 Hz, CH2), 3.74 (s, 3H, OCH3), 3.11 (s, 3H, NCH3), 2.49 (s, 3H, C=CCH3), 1.15 (t, 3H, J=6.0 Hz, OCH2CH3); 13C NMR (100 MHz, DMSO-d6) δ: 166.12, 153.65, 150.47, 147.74, 146.24, 135.50, 118.50, 115.70, 110.95, 103.32, 59.91, 55.93, 52.46, 30.07, 16.43, 14.56; IR (KBr): 3336, 2968, 1683, 1644, 767 cm−1. Anal. calcd. for C16H20N2O5: C 59.99, H 6.29, N 8.74; found C 59.90, H 6.22, N 8.68.

2.2.2 5-Methoxycarbonyl-1,6-dimethyl-4-(4-chlorophenyl)-3,4-dihydropyrimidin-2(1H)-one (k)

Pale yellow solid. 1H NMR (400 MHz, DMSO-d6) δ: 8.07 (s, 1H, NH), 7.39 (d, 2H, J=8.0 Hz, ArH), 7.26 (d, 2H, J=8.0 Hz, ArH), 5.19 (s, 1H, CH), 3.58 (s, 3H, OCH3), 3.11 (s, 3H, NCH3), 2.51 (s, 3H, C=CCH3); 13C NMR (100 MHz, DMSO-d6) δ: 166.37, 153.37, 151.72, 143.25, 132.37, 128.89, 128.39, 102.13, 52.14, 51.53, 30.19, 16.51; IR (KBr): 3215, 2950, 1691, 1622, 793 cm−1. Anal. calcd. for C14H15N2O3Cl: C 57.05, H 5.13, N 9.50; found C 56.96, H 5.09, N 9.54.

2.2.3 5-Methoxycarbonyl-1,6-dimethyl-4-(3-hydroxyphenyl)-3,4-dihydropyrimidin-2(1H)-one (m)

Pale yellow solid. 1H NMR (400 MHz, DMSO-d6) δ: 9.39 (s, 1H, OH), 7.96 (s, 1H, NH), 7.10-6.61 (m, 4H, ArH), 5.08 (s, 1H, CH), 3.58 (s, 3H, OCH3), 3.08 (s, 3H, NCH3), 2.47 (s, 3H, C=CCH3); 13C NMR (100 MHz, DMSO-d6) δ: 166.57, 157.84, 153.67, 151.04, 145.74, 129.88, 116.93, 114.66, 113.25, 102.78, 52.47, 51.54, 30.20, 16.51; IR (KBr): 3377, 2951, 1682, 1598, 787 cm−1. Anal. calcd. for C14H16N2O4: C 60.86, H 5.84, N 10.14; found C 60.75, H 5.81, N 10.17.

2.2.4 5-Ethoxycarbonyl-1-ethyl-6-methyl-4-(4-chlorophenyl)-3,4-dihydropyrimidin-2(1H)-one (p)

White solid. 1H NMR (400 MHz, DMSO-d6) δ: 7.91 (d, 1H, J=4 Hz, NH), 7.35 (d, 2H, J=8.0 Hz, ArH), 7.19 (d, 2H, J=8.0 Hz, ArH), 5.10 (d, 1H, J=4.0 Hz, CH), 3.98 (q, 2H, J=8.0 Hz, CH2), 3.76 (dd, 1H, J=16.0, 8.0 Hz, NCH2), 3.57 (dd, 1H, J=16.0, 8.0 Hz, NCH2), 2.47 (s, 3H, C=CCH3), 1.09-1.01 (m, 6H, OCH2CH3, NCH2CH3); 13C NMR (100 MHz, DMSO-d6) δ: 165.88, 152.72, 150.28, 143.56, 132.28, 128.86, 128.44, 102.74, 60.03, 52.42, 37.40, 15.91, 15.20, 14.46; IR (KBr): 3413, 2985, 1686, 1616, 768 cm−1. Anal. calcd. for C16H19N2O3Cl: C 59.54, H 5.93, N 8.68; found C 59.60, H 5.91, N 8.72.

2.2.5 5-Ethoxycarbonyl-1-ethyl-6-methyl-4-(4-nitrophenyl)-3,4-dihydropyrimidin-2(1H)-one (q)

Yellow solid. 1H NMR (400 MHz, DMSO-d6) δ: 8.18 (d, 2H, J=8.0 Hz, ArH), 8.05 (d, 1H, J=4.0 Hz, NH), 7.44 (d, 2H, J=8.0 Hz, ArH), 5.23 (d, 1H, J=4.0 Hz, CH), 4.00 (q, 2H, J=8.0 Hz, CH2), 3.76 (dd, 1H, J=16.0, 8.0 Hz, NCH2), 3.58 (dd, 1H, J=16.0, 8.0 Hz, NCH2), 2.48 (s, 3H, C=CCH3), 1.09-1.02 (m, 6H, OCH2CH3, NCH2CH3); 13C NMR (100 MHz, DMSO-d6) δ: 165.72, 152.56, 151.78, 151.02, 147.16, 127.88, 124.28, 102.02, 60.17, 52.63, 37.52 15.97 15.18 14.44; IR (KBr): 3405, 2985, 1692, 1616, 768 cm−1. Anal. calcd. for C16H19N3O5: C 57.65, H 5.74, N 12.60; found C 57.56, H 5.71, N 12.66.

2.2.6 5-Methoxycarbonyl-1-ethyl-6-methyl-4-(4-nitrophenyl)-3,4-dihydropyrimidin-2(1H)-one (r)

Pale yellow solid. 1H NMR (400 MHz, DMSO-d6) δ: 8.22 (d, 2H, J=8.0 Hz, ArH), 8.12 (d, 1H, J=4.0 Hz, NH), 7.49 (d, 2H, J=8.0 Hz, ArH), 5.26 (d, 1H, J=4.0 Hz, CH), 3.81 (dd, 1H, J=16.0 Hz, 8.0 Hz, NCH2), 3.63 (dd, 1H, J=16.0, 8.0 Hz, NCH2), 3.58 (s, 3H, OCH3), 2.53 (s, 3H, C=CCH3), 1.07 (t, 3H, J=8.0 Hz, NCH2CH3); 13C NMR (100 MHz, DMSO-d6) δ: 166.23, 152.61, 151.58, 151.30, 147.18, 127.83, 124.31, 101.81, 52.44, 51.68, 37.54, 16.02, 15.18; IR (KBr): 3397, 2992, 1686, 1616, 768 cm−1. Anal. calcd. for C15H17N3O5: C 56.42, H 5.37, N 13.16; found C 56.35, H 5.41, N 13.12.

2.2.7 5-Methoxycarbonyl-1-ethyl-6-methyl-4-(2-chlorophenyl)-3,4-dihydropyrimidin-2(1H)-one (s)

Pale yellow solid. 1H NMR (400 MHz, DMSO-d6) δ: 7.89 (d, 1H, J=4.0 Hz, NH), 7.42 (d, 1H, J=8.0 Hz, ArH), 7.32-7.25 (m, 3H, ArH), 5.59 (s, 1H, CH), 3.83 (dd, 1H, J=16.0, 8.0 Hz, NCH2), 3.65 (dd, 1H, J=16.0, 8.0 Hz, NCH2), 3.48 (s, 3H, OCH3), 2.56 (s, 3H, C=CCH3), 1.12 (t, 3H, J=8.0 Hz, NCH2CH3); 13C NMR (100 MHz, DMSO-d6) δ: 166.21, 152.12, 151.07, 141.21, 132.16, 130.02, 129.70, 128.77, 128.15, 101.44, 51.50, 50.52, 37.45, 15.90, 15.23; IR (KBr): 3417, 2983, 1683, 1634, 768 cm−1. Anal. calcd. for C15H17N2O3Cl: C 58.35, H 5.55, N 9.07; found C 58.42, H 5.60, N 9.01.

2.2.8 5-Ethoxycarbonyl-1-(4-methylphenyl)-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (t)

Pale yellow solid. 1H NMR (400 MHz, DMSO-d6) δ: 8.18 (s, 1H, NH), 7.12-7.43 (m, 9H, ArH), 5.34 (s, 1H, CH), 4.07 (q, 2H, J =4.0 Hz, OCH2), 2.36 (s, 3H, C=CCH3), 2.07 (s, 3H, ArCH3), 1.14 (t, 3H, J=4.0 Hz, CH2CH3); 13C NMR (100 MHz, DMSO-d6) δ: 165.89, 152.62, 149.55, 144.54, 137.86, 135.55, 129.83, 129.58, 129.05, 127.92, 126.71, 118.64, 60.14, 53.55, 21.10, 18.49, 14.46; IR (KBr): 3234, 2978, 1693, 1624, 758 cm−1. Anal. calcd. for C21H22N2O3: C 71.98, H 6.33, N 7.99; found C 71.87, H 6.26, N 7.96.

2.2.9 5-Methoxycarbonyl-1-(4-methylphenyl)-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (u)

Pale yellow solid. 1H NMR (400 MHz, DMSO-d6) δ: 8.21 (s, 1H, NH), 7.43-7.04 (m, 9H, ArH), 5.34 (s, 1H, CH), 3.61 (s, 3H, OCH3), 2.35 (s, 3H, C=CCH3), 2.08 (s, 3H, ArCH3); 13C NMR (100 MHz, DMSO-d6) δ: 166.41, 156.57, 152.67, 144.34, 137.90, 135.50, 129.85, 129.42, 129.12, 127.95, 126.64, 118.29, 53.36, 51.63, 21.09, 18.55; IR (KBr): 3430, 2922, 1693, 1654, 763 cm−1. Anal. calcd. for C20H20N2O3: C 71.41, H 5.99, N 8.33; found C 71.33, H 6.02, N 8.37.

3 Results and discussion

3.1 Screening of catalysts

First, we compared the catalytic activity of different metal methanesulfonates in Table 1. The activity of CMS is higher than that of the other methanesulfonates. 5-Ethoxycarbonyl-1,6-dimethyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one was obtained in 94% yield within 0.3 h (entry 1). However, only 40% product yield was obtained in the absence of a catalyst (entry 14).

Table 1:

Comparison of the catalytic activity among different metal methanesulfonates.

Entry1234567891011121314
MetalCuLaFe(II)ZnPrYbCe(III)MgNiSrCaCdAl
Time (h)0.30.40.70.30.30.51.01.51.02.51.51.32.03.0
Yield (%)9492928887828272706663625640
  1. Reaction conditions: benzaldehyde (10 mmol), ethyl acetoacetate (10 mmol), methylurea (13 mmol), metal methanesulfonates (0.3 mmol), solvent-free, 80°C.

3.2 Reaction temperature and reusable catalyst

Then, we investigated the reaction temperature using the model reaction of benzaldehyde, ethyl acetoacetate, and methylurea. As shown in Table 2, the reaction at 90°C gave the best result (entry 3). When the reaction was completed, the reaction mixture was washed with water. The catalyst remained in aqueous phase and could be recovered by evaporating the filtrate. The CMS can be reused for the next two consecutive reactions. It demonstrated that CMS was water-tolerant and recyclable.

Table 2:

Different reaction temperatures and the reusability of CMS.

EntryTemperature (°C)Time (h)Yield (%)
1700.793
2800.394
3900.296, 93, 89
  1. Reaction conditions: benzaldehyde (10 mmol), ethyl acetoacetate (10 mmol), methylurea (13 mmol), CMS (0.3 mmol), solvent-free.

3.3 One-pot synthesis of N1-substituted DHPMs

Next, N1-substituted DHPMs were synthesized under optimum conditions (Table 3). The Biginelli three-component reaction of aromatic aldehydes, β-ketoesters, and N-substituted (thio)ureas gave good yields of the products in a short time. The reaction accommodated a variety of aromatic aldehydes. Whether the substituents on the aromatic aldehyde are electron-withdrawing or -donating groups all afforded high yields. Unfortunately, substrates with aliphatic aldehydes gave no desired product. Ethyl acetoacetate and methyl acetoacetate were equally effective in carrying out the reaction. N-Methylurea, N-ethylurea, p-tolylurea, and N-methylthiourea were varied. In all cases, the pure products were obtained by simple filtration and recrystallization. No column chromatography or any cumbersome workup technique was applied. The methodology using a reusable catalyst without solvent is a green protocol obviously.

Table 3:

Three-component one-pot synthesis of N1-substituted DHPMs catalyzed by CMS.

ProductR1R2R3XYield (%) (time/h)Mp (°C)
FoundReported
aHEtMeO96 (0.2)178–180175–176 [14]
b4-ClEtMeO94 (1.0)132–134133–135 [14]
c4-CH3EtMeO94 (1.0)116–118119–120 [14]
d2-CH3OEtMeO89 (0.8)147–149145–146 [15]
e4-CH3OEtMeO93 (1.5)138–140138–140 [16]
f3-NO2EtMeO92 (0.5)137–139136–137 [13]
g4-OHEtMeO85 (0.4)183–184178–180 [16]
h4-OH-3-CH3OEtMeO94 (0.3)181–183
iHEtMeS40 (6.0)145–147146–147 [17]
JHMeMeO94 (0.2)193–195190–192 [16]
k4-ClMeMeO97 (0.5)134–137
l2-CH3OMeMeO78 (0.2)171–173170–172 [15]
m3-OHMeMeO93 (0.1)220–223
nHMeMeS46 (6.0)159–160160–162 [18]
oHEtEtO63 (3.0)112–115118 [11]
p4-ClEtEtO93 (2.0)146–148
q4-NO2EtEtO92 (1.5)152–154
r4-NO2MeEtO94 (0.8)198–200
s2-ClMeEtO70 (1.5)121–123
tHEtp-CH3C6H4O82 (3.0)179–181
uHMep-CH3C6H4O95 (3.0)152–158
  1. Reaction conditions: aromatic aldehydes (10 mmol), β-ketoesters (10 mmol), N-substituted (thio)ureas (13 mmol), CMS (0.3 mmol), solvent-free, 90°C.

All the structures of the products were determined by IR, 1H NMR, 13C NMR, and elemental analysis. Furthermore, a single crystal detection of the product t was obtained to investigate the molecular structure (Figure 1). The pyrimidine ring composed of N1-C2-N3-C4-C5-C6 is a boat conformation. The C-4 is a choral carbon and its configuration is R. An X-ray structure analysis verified the synthesized products.

Figure 1: The molecular structure of the compound t.
Figure 1:

The molecular structure of the compound t.

3.4 Reaction mechanism

A possible reaction mechanism was proposed for this transformation [26]. At first, an aldehyde reacted with a (thio)urea to form an acylimine intermediate under the catalysis of CMS. Then, an open-chain ureide is obtained by the addition of a β-ketoester to the acylimine, which undergoes cyclization and dehydration to form the target product [Eq. (2)].

      (2)

4 Conclusions

In conclusion, we have reported a simple, efficient, and environmentally friendly method to synthesize N1-substituted DHPMs from aromatic aldehydes, ethyl acetoacetate/methyl acetoacetate, and monosubstituted (thio)ureas with CMS as a catalyst at 90°C. Neither toxic solvent nor expensive catalyst was used. It has mild reaction conditions, simple operation, short reaction time, high yield, and other environmentally friendly advantages. The most notable feature is the expansion of the substrates. The substituents on the urea were beyond just Me or Et. The reaction scope is fairly general with regard to various substrates. Many novel N1-substituted DHPMs were synthesized first. The catalyst can be reused several times. The green methodology provides a better alternative to the existing reports.

Acknowledgments

This research work was financially supported by the Program for Liaoning Excellent Talents in University (no. LJQ2015002), the Natural Science Foundation of Liaoning Province (no. 2015020201), and the National Natural Science Foundation of China (no. 21406016).

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Received: 2018-04-08
Accepted: 2018-08-02
Published Online: 2018-11-13
Published in Print: 2019-01-28

©2019 Walter de Gruyter GmbH, Berlin/Boston

This work is licensed under the Creative Commons Attribution 4.0 Public License.

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  10. Evaluation of the saponin green extraction from Ziziphus spina-christi leaves using hydrothermal, microwave and Bain-Marie water bath heating methods
  11. Oxidation of dibenzothiophene using the heterogeneous catalyst of tungsten-based carbon nanotubes
  12. Calcined sodium silicate as an efficient and benign heterogeneous catalyst for the transesterification of natural lecithin to L-α-glycerophosphocholine
  13. Synergistic effect between CO2 and H2O2 on ethylbenzene oxidation catalyzed by carbon supported heteropolyanion catalysts
  14. Hydrocyanation of 2-arylmethyleneindan-1,3-diones using potassium hexacyanoferrate(II) as a nontoxic cyanating agent
  15. Green synthesis of hydratropic aldehyde from α-methylstyrene catalyzed by Al2O3-supported metal phthalocyanines
  16. Environmentally benign chemical recycling of polycarbonate wastes: comparison of micro- and nano-TiO2 solid support efficiencies
  17. Medicago polymorpha-mediated antibacterial silver nanoparticles in the reduction of methyl orange
  18. Production of value-added chemicals from esterification of waste glycerol over MCM-41 supported catalysts
  19. Green synthesis of zerovalent copper nanoparticles for efficient reduction of toxic azo dyes congo red and methyl orange
  20. Optimization of the biological synthesis of silver nanoparticles using Penicillium oxalicum GRS-1 and their antimicrobial effects against common food-borne pathogens
  21. Optimization of submerged fermentation conditions to overproduce bioethanol using two industrial and traditional Saccharomyces cerevisiae strains
  22. Extraction of In3+ and Fe3+ from sulfate solutions by using a 3D-printed “Y”-shaped microreactor
  23. Foliar-mediated Ag:ZnO nanophotocatalysts: green synthesis, characterization, pollutants degradation, and in vitro biocidal activity
  24. Green cyclic acetals production by glycerol etherification reaction with benzaldehyde using cationic acidic resin
  25. Biosynthesis, characterization and antimicrobial activities assessment of fabricated selenium nanoparticles using Pelargonium zonale leaf extract
  26. Synthesis of high surface area magnesia by using walnut shell as a template
  27. Controllable biosynthesis of silver nanoparticles using actinobacterial strains
  28. Green vegetation: a promising source of color dyes
  29. Mechano-chemical synthesis of ammonia and acetic acid from inorganic materials in water
  30. Green synthesis and structural characterization of novel N1-substituted 3,4-dihydropyrimidin-2(1H)-ones
  31. Biodiesel production from cotton oil using heterogeneous CaO catalysts from eggshells prepared at different calcination temperatures
  32. Regeneration of spent mercury catalyst for the treatment of dye wastewater by the microwave and ultrasonic spray-assisted method
  33. Green synthesis of the innovative super paramagnetic nanoparticles from the leaves extract of Fraxinus chinensis Roxb and their application for the decolourisation of toxic dyes
  34. Biogenic ZnO nanoparticles: a study of blueshift of optical band gap and photocatalytic degradation of reactive yellow 186 dye under direct sunlight
  35. Leached compounds from the extracts of pomegranate peel, green coconut shell, and karuvelam wood for the removal of hexavalent chromium
  36. Enhancement of molecular weight reduction of natural rubber in triphasic CO2/toluene/H2O systems with hydrogen peroxide for preparation of biobased polyurethanes
  37. An efficient green synthesis of novel 1H-imidazo[1,2-a]imidazole-3-amine and imidazo[2,1-c][1,2,4]triazole-5-amine derivatives via Strecker reaction under controlled microwave heating
  38. Evaluation of three different green fabrication methods for the synthesis of crystalline ZnO nanoparticles using Pelargonium zonale leaf extract
  39. A highly efficient and multifunctional biomass supporting Ag, Ni, and Cu nanoparticles through wetness impregnation for environmental remediation
  40. Simple one-pot green method for large-scale production of mesalamine, an anti-inflammatory agent
  41. Relationships between step and cumulative PMI and E-factors: implications on estimating material efficiency with respect to charting synthesis optimization strategies
  42. A comparative sorption study of Cr3+ and Cr6+ using mango peels: kinetic, equilibrium and thermodynamic
  43. Effects of acid hydrolysis waste liquid recycle on preparation of microcrystalline cellulose
  44. Use of deep eutectic solvents as catalyst: A mini-review
  45. Microwave-assisted synthesis of pyrrolidinone derivatives using 1,1’-butylenebis(3-sulfo-3H-imidazol-1-ium) chloride in ethylene glycol
  46. Green and eco-friendly synthesis of Co3O4 and Ag-Co3O4: Characterization and photo-catalytic activity
  47. Adsorption optimized of the coal-based material and application for cyanide wastewater treatment
  48. Aloe vera leaf extract mediated green synthesis of selenium nanoparticles and assessment of their In vitro antimicrobial activity against spoilage fungi and pathogenic bacteria strains
  49. Waste phenolic resin derived activated carbon by microwave-assisted KOH activation and application to dye wastewater treatment
  50. Direct ethanol production from cellulose by consortium of Trichoderma reesei and Candida molischiana
  51. Agricultural waste biomass-assisted nanostructures: Synthesis and application
  52. Biodiesel production from rubber seed oil using calcium oxide derived from eggshell as catalyst – optimization and modeling studies
  53. Study of fabrication of fully aqueous solution processed SnS quantum dot-sensitized solar cell
  54. Assessment of aqueous extract of Gypsophila aretioides for inhibitory effects on calcium carbonate formation
  55. An environmentally friendly acylation reaction of 2-methylnaphthalene in solvent-free condition in a micro-channel reactor
  56. Aegle marmelos phytochemical stabilized synthesis and characterization of ZnO nanoparticles and their role against agriculture and food pathogen
  57. A reactive coupling process for co-production of solketal and biodiesel
  58. Optimization of the asymmetric synthesis of (S)-1-phenylethanol using Ispir bean as whole-cell biocatalyst
  59. Synthesis of pyrazolopyridine and pyrazoloquinoline derivatives by one-pot, three-component reactions of arylglyoxals, 3-methyl-1-aryl-1H-pyrazol-5-amines and cyclic 1,3-dicarbonyl compounds in the presence of tetrapropylammonium bromide
  60. Preconcentration of morphine in urine sample using a green and solvent-free microextraction method
  61. Extraction of glycyrrhizic acid by aqueous two-phase system formed by PEG and two environmentally friendly organic acid salts - sodium citrate and sodium tartrate
  62. Green synthesis of copper oxide nanoparticles using Juglans regia leaf extract and assessment of their physico-chemical and biological properties
  63. Deep eutectic solvents (DESs) as powerful and recyclable catalysts and solvents for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones
  64. Biosynthesis, characterization and anti-microbial activity of silver nanoparticle based gel hand wash
  65. Efficient and selective microwave-assisted O-methylation of phenolic compounds using tetramethylammonium hydroxide (TMAH)
  66. Anticoagulant, thrombolytic and antibacterial activities of Euphorbia acruensis latex-mediated bioengineered silver nanoparticles
  67. Volcanic ash as reusable catalyst in the green synthesis of 3H-1,5-benzodiazepines
  68. Green synthesis, anionic polymerization of 1,4-bis(methacryloyl)piperazine using Algerian clay as catalyst
  69. Selenium supplementation during fermentation with sugar beet molasses and Saccharomyces cerevisiae to increase bioethanol production
  70. Biosynthetic potential assessment of four food pathogenic bacteria in hydrothermally silver nanoparticles fabrication
  71. Investigating the effectiveness of classical and eco-friendly approaches for synthesis of dialdehydes from organic dihalides
  72. Pyrolysis of palm oil using zeolite catalyst and characterization of the boil-oil
  73. Azadirachta indica leaves extract assisted green synthesis of Ag-TiO2 for degradation of Methylene blue and Rhodamine B dyes in aqueous medium
  74. Synthesis of vitamin E succinate catalyzed by nano-SiO2 immobilized DMAP derivative in mixed solvent system
  75. Extraction of phytosterols from melon (Cucumis melo) seeds by supercritical CO2 as a clean technology
  76. Production of uronic acids by hydrothermolysis of pectin as a model substance for plant biomass waste
  77. Biofabrication of highly pure copper oxide nanoparticles using wheat seed extract and their catalytic activity: A mechanistic approach
  78. Intelligent modeling and optimization of emulsion aggregation method for producing green printing ink
  79. Improved removal of methylene blue on modified hierarchical zeolite Y: Achieved by a “destructive-constructive” method
  80. Two different facile and efficient approaches for the synthesis of various N-arylacetamides via N-acetylation of arylamines and straightforward one-pot reductive acetylation of nitroarenes promoted by recyclable CuFe2O4 nanoparticles in water
  81. Optimization of acid catalyzed esterification and mixed metal oxide catalyzed transesterification for biodiesel production from Moringa oleifera oil
  82. Kinetics and the fluidity of the stearic acid esters with different carbon backbones
  83. Aiming for a standardized protocol for preparing a process green synthesis report and for ranking multiple synthesis plans to a common target product
  84. Microstructure and luminescence of VO2 (B) nanoparticle synthesis by hydrothermal method
  85. Optimization of uranium removal from uranium plant wastewater by response surface methodology (RSM)
  86. Microwave drying of nickel-containing residue: dielectric properties, kinetics, and energy aspects
  87. Simple and convenient two step synthesis of 5-bromo-2,3-dimethoxy-6-methyl-1,4-benzoquinone
  88. Biodiesel production from waste cooking oil
  89. The effect of activation temperature on structure and properties of blue coke-based activated carbon by CO2 activation
  90. Optimization of reaction parameters for the green synthesis of zero valent iron nanoparticles using pine tree needles
  91. Microwave-assisted protocol for squalene isolation and conversion from oil-deodoriser distillates
  92. Denitrification performance of rare earth tailings-based catalysts
  93. Facile synthesis of silver nanoparticles using Averrhoa bilimbi L and Plum extracts and investigation on the synergistic bioactivity using in vitro models
  94. Green production of AgNPs and their phytostimulatory impact
  95. Photocatalytic activity of Ag/Ni bi-metallic nanoparticles on textile dye removal
  96. Topical Issue: Green Process Engineering / Guest Editors: Martine Poux, Patrick Cognet
  97. Modelling and optimisation of oxidative desulphurisation of tyre-derived oil via central composite design approach
  98. CO2 sequestration by carbonation of olivine: a new process for optimal separation of the solids produced
  99. Organic carbonates synthesis improved by pervaporation for CO2 utilisation
  100. Production of starch nanoparticles through solvent-antisolvent precipitation in a spinning disc reactor
  101. A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate
  102. Topical on Green Process Engineering
Heruntergeladen am 7.9.2025 von https://www.degruyterbrill.com/document/doi/10.1515/gps-2018-0074/html?lang=de
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