A novel method for the determination of five carbamate pesticides (metolcarb, carbofuran, carbaryl, isoprocard and diethofencard) in water samples was developed by dispersive liquid-liquid microextraction (DLLME) ...A novel method for the determination of five carbamate pesticides (metolcarb, carbofuran, carbaryl, isoprocard and diethofencard) in water samples was developed by dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography-diode array detector (HPLC-DAD). Some experimental parameters that influence the extraction efficiency were studied and optimized to obtain the best extraction results. Under the optimum conditions for the method, the calibration curve was linear in the concentration range from 5 to 1000 ng mL^-1 for all the five carbamate pesticides, with the correlation coefficients (r^2) varying from 0.9984 to 0.9994. Good enrichment factors were achieved ranging from 80 to 177- fold, depending on the compound. The limits of detection (LODs) (S/N = 3) were ranged from 0.1 to 0.5 ng mL^-1. The method has been successfully applied to the analysis of the pesticide residues in environmental water samples.展开更多
Soybean esterase, a cholinesterase-like enzyme, was purified by differential centrifugation firstly, then, ammonium sulfate precipitation, dialysis, and finally, DEAE-cellulose-32 ion-exchange chromatography after ext...Soybean esterase, a cholinesterase-like enzyme, was purified by differential centrifugation firstly, then, ammonium sulfate precipitation, dialysis, and finally, DEAE-cellulose-32 ion-exchange chromatography after extracting it from soybean seeds with phosphate buffer (0.3 mol L^-1, pH 7.0). The extract recovery rate of the purified enzyme was 8.18% and purification fold was 91.58. The soybean esterase appeared as two bands on the denaturing SDS-PAGE with molecular weights of 24 and 37.2 kDa, respectively, which proved that it is a dimer protein consisting of two subunits. The result of nondenaturing PAGE revealed that the soybean esterase is a single band with cholinesterase-like activity using α- naphthyl acetate as the substrate and fast blue B salt as coloring agent. The esterase showed very high sensitivity to 18 kinds of organophosphate pesticides and 6 kinds of carbamate pesticides with the lowest detective limits of 0.03125- 0.0625 and 0.03125-0.25 mg kg^-1, respectively, and can meet the demands of MRL specified by the most countries.展开更多
Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at so...Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at soil-water interface, were analyzed by the probit method. Growth enhancing concentration, no-observed effective concentration, minimum inhibitory concentration, the highest permissive concentration and lethal concentration100 (LCloo) were determined experimentally. The LC^o values of carbaryl, carbofuran, ziram, zineb and mancozeb in N2-fixing liquid medium were 56.2, 588.8, 0.07, 4.2 and 3.4 IJg/mL, respectively, whereas the corresponding LCloo values were 100.0, 1500.0, 0.17, 25.0 and 9.0 IJg/mL, respectively. The LC50 values of these pesticides in succession in N2-fixing agar medium were 44.7, 239.9, 0.07, 1.8 and 2.3 IJg/mL, respectively, whereas the corresponding LC100 values were 100.0, 600.0, 0.17, 10.0 and 7.0 IJg/mL, respectively. Similar results with nitrate supplemented liquid and agar media indicated that nitrate supplementation had toxicity reducing effect. The LCso and LC^oo values of toxicity in the N2-fixing liquid medium at soil-water interface were 91.2 and 200.0 IJg/mL for carbaryl, 2 317 and 6 000 pg/mL for carbofuran, 0.15 and 0.50 pg/mL for ziram, 16.4 and 50.0 pg/mL for zineb, and 7.2 and 25.0 pg/mL for mancozeb, respectively. Each LC^oo value at soil- water interface with a pesticide was significantly higher than its corresponding LCloo value at liquid/agar media. It can be concluded that, under the N2-fixing conditions, the cyanobacterium tolerated higher levels of each pesticide at soil-water interface.展开更多
[Objectives ] The paper was to explore enzyme inhibition rate method for rapid detection of organophosphorus and carbamate pesticides in cowpea. [ Methods ] Acetylcholinesterase (ACHE) was added to cowpea extract, t...[Objectives ] The paper was to explore enzyme inhibition rate method for rapid detection of organophosphorus and carbamate pesticides in cowpea. [ Methods ] Acetylcholinesterase (ACHE) was added to cowpea extract, to determine the inhibition rate of extract against enzyme. The influences of different sampiing methods and sampling parts on detection results were compared. [ Results] The positive rate of standard sampling was 18.18% higher than that of non-stand- ard sampling, and the positive rate of samples collected from cowpea tail was 16.67% higher than that collected from other parts. [ Condmions] Enzyme inhibi- tion rate method is suitable for rapid detection of organophosphorus and carbamate pesticides in cowpea.展开更多
Carbamates are important intermediates in the syntheses of pesticides, herbicides, drugs, polyurethane-based polymers, and other fine and commodity chemicals.
A facile synthesis of N-methyl-N-aryl carbamates from aromatic amines and dimethyl carbonate (DMC) has been achieved with high yields in the presence of potassium carbonate (K2CO3)and tetrabutylammonium bromide (Bu4NB...A facile synthesis of N-methyl-N-aryl carbamates from aromatic amines and dimethyl carbonate (DMC) has been achieved with high yields in the presence of potassium carbonate (K2CO3)and tetrabutylammonium bromide (Bu4NBr) under solvent-free conditions.展开更多
Four 4-monosubstituted pyrimidine pyridyl sulfonylureas were synthesized from pyridinesulfonamide and phenyl pyrimidylcarbamate and screened for herbicidal activities. We also reported a convenient preparation process...Four 4-monosubstituted pyrimidine pyridyl sulfonylureas were synthesized from pyridinesulfonamide and phenyl pyrimidylcarbamate and screened for herbicidal activities. We also reported a convenient preparation process of phenyl pyrimidylcarbamates from pyrimidineamine and phenyl chloroformate.展开更多
A new method was developed for the quantitative determination of the neurotoxic nonprotein amino acid, 3-N-oxalyl-L-2,3-diaminopropioni acid (β-ODAP), its nontoxic α-isomer and other non-protein amino acids in the p...A new method was developed for the quantitative determination of the neurotoxic nonprotein amino acid, 3-N-oxalyl-L-2,3-diaminopropioni acid (β-ODAP), its nontoxic α-isomer and other non-protein amino acids in the plant samples of Lathyrus sativus after derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) by reversed-phase high-performance liquid chromatography (HPLC). 2-Amino butyric acid (ABA) was used as an internal standard.The RP HPLC detection limit for both isomers is 1.8 ng with good response linearity. The results are compared with a colorimetric method.展开更多
A convenient, efficient, one-pot, novel process has been developed for the synthesis of carbamates from corresponding alkyl halides and amines using basic resin/CO2 system.
Sulfamic acid has been proved to be the most efficient and recyclable catalyst in carbamate synthesis from alkylamine and dialkyl carbonate.High selectivity,cost-efficiency and simple product separation were the advan...Sulfamic acid has been proved to be the most efficient and recyclable catalyst in carbamate synthesis from alkylamine and dialkyl carbonate.High selectivity,cost-efficiency and simple product separation were the advantageous features obtained in this process.Sulfamic acid could be reused several times and keep its initial activity in the recycle runs.In addition,sulfamic acid has also exhibited the potential catalytic ability for alkylation of aromatic amines.展开更多
The density functional theory at the B3LYP/6-311G(d, p) level was applied to exploring the inhibition mechanism of cholinesterases by carbamate. The results indicate that the inhibition reactions with or without the...The density functional theory at the B3LYP/6-311G(d, p) level was applied to exploring the inhibition mechanism of cholinesterases by carbamate. The results indicate that the inhibition reactions with or without the catalytic effect of the catalytic triad in eholinesterases underwent a two-step addition-elimination mechanism, which is in good agreement with the proposed mechanism. The solvent has a strong effect on the inhibition reactions and the reaction with the catalytic triad in the solvent phase is close to the real reaction under biological condition.展开更多
Cellulose carbamates (CC) were synthesized with microcrystalline cellulose as raw materials. The Fourier transform infrared spectra of CC with different nitrogen content were recorded. The accurate results of the nitr...Cellulose carbamates (CC) were synthesized with microcrystalline cellulose as raw materials. The Fourier transform infrared spectra of CC with different nitrogen content were recorded. The accurate results of the nitrogen content for CC can be obtained by using the deconvolution method when the nitrogen content is less than 3.5%. The relationship between the nitrogen content and the absorption intensity ratio of the corresponding separated absorption peaks in FTIR spectra has been expressed bg an equation precisely.展开更多
The title compound N-octyl rotenone oximino carbamate(C32H40N2O7) has been synthesized by the reaction of rotenone oxime with octyl isocyanate,and its crystal structure was determined by single-crystal X-ray diffrac...The title compound N-octyl rotenone oximino carbamate(C32H40N2O7) has been synthesized by the reaction of rotenone oxime with octyl isocyanate,and its crystal structure was determined by single-crystal X-ray diffraction.The crystal belongs to the monoclinic system,space group P21 with a=11.4311(8),b=10.3717(7),c=12.7490(9)A,β=105.0770(10)°,Z=2,V=1459.49(18)A^3,Mr=564.66,Dc=1.285g/cm^3,S=1.087,μ=0.090 mm^-1,F(000)=604,the final R=0.0426 and wR=0.0937 for 2599 observed reflections(I〉2σ(I)).X-ray analysis reveals that the molecule has an approximately V-shaped structure,and the absolute configurations of C(7),C(8) and C(18) are R,S and R,respectively.The oxime ester is in an E configuration.Intermolecular N-H…O hydrogen bond exists in the crystal.The preliminary bioassay shows that the title compound possesses strong insecticidal activity against Mythimna separate,and displays moderate fungicidal activity against Erysiphe graminis.展开更多
Analytical difficulties encountered in the determination of ethyl carbamate, a known cancinogen, in a wide variety of wines and spirits have been overcome by spe- cific, sensitive GC/GC and CC/CC/MS methods with a rel...Analytical difficulties encountered in the determination of ethyl carbamate, a known cancinogen, in a wide variety of wines and spirits have been overcome by spe- cific, sensitive GC/GC and CC/CC/MS methods with a relatively shorter extraction procedure. The lowest detection limits were estimated to be 0. 1 and 0. 01μg/L for GC/GC and GC/GC/MS respectively. The RSD of the GC/GC method was 2. 5%.展开更多
[Objective]The paper was to study a synthetic method suitable for industrial production of intermediate N-Chloroformyl-N-[4-(trifluoromethoxy)phenyl]methyl carbamate of indoxacarb.[Method]Using 4-trifluoromethoxy anil...[Objective]The paper was to study a synthetic method suitable for industrial production of intermediate N-Chloroformyl-N-[4-(trifluoromethoxy)phenyl]methyl carbamate of indoxacarb.[Method]Using 4-trifluoromethoxy aniline as the starting material,[4-(trifluoromethoxy)phenyl]carbamate was synthesized by homogeneous formylation method without acid-binding agent.Subsequently,it was reacted with sodium methoxide/potassium methoxide by reactive distillation to obtain[4-(trifluoromethoxy)phenyl]carbamate ammonium sodium/potassium,then directly reacted with triphosgene to obtain crude products of N-carbonochloridoyl-N-[4-(trifluoromethoxy)phenyl]carbamate;finally,competing product was obtained by recrystallization.[Result]The intermediate N-chloroformyl-N-[4-(trifluoromethoxy)phenyl]carbamate was synthesized by the method.The content of products was higher than 98%.The yield of product reached above 96%(calculated by 4-trifluoromethoxy aniline).[Conclusion]The method used for the synthesis of intermediate N-chloroformyl-N-[4-(trifluoromethoxy)phenyl]methyl carbamate was simple,with less three wastes,higher safety and lower cost.展开更多
The present work sought to characterize the cyanogenic glycoside dhurrin in five sugarcane varieties and to determine its possible relationship with the formation of ethyl carbamate in cachaca. For each variety, metha...The present work sought to characterize the cyanogenic glycoside dhurrin in five sugarcane varieties and to determine its possible relationship with the formation of ethyl carbamate in cachaca. For each variety, methanol, ethyl acetate and hexane extracts were prepared and submitted to thin layer chromatography. Chromatographic spots were revealed with iodine vapors. The physical and chemical parameters of the spirits produced from the five different varieties of sugar cane and by different production processes were within the legal limits. Although not exceeding the limit for ethyl carbamate, a significant variation in the final concentration of this compound was observed for each sample analyzed. The Rf values for the dhurrin standard and for the sugarcane variety SP 83-2847 were equal, similar to those for SP 80-3280 and CTC 11 and different from the Rf values for the RB 86-7515 and IAC 86-2480 samples.展开更多
Nitrene transfer reactions are powerful tools in synthetic organic chemistry.In recent years,transitionmetal catalyzed nitrene transfer reactions with carbamates as the nitrene precursors have been widely pursued.Such...Nitrene transfer reactions are powerful tools in synthetic organic chemistry.In recent years,transitionmetal catalyzed nitrene transfer reactions with carbamates as the nitrene precursors have been widely pursued.Such species undergoes facile C-H amination,aziridination,and bifunctionalization of alkenes under the catalysis of different transition metals including Rh,Fe,Ru and others,enabling the efficient construction of various nitrogen-containing molecules.In this review,the recent developments in nitrene transfer reactions with carbamates via N-O bond cleavage were introduced based on different types of reaction,and the key mechanistic information and synthetic applications of the methodologies were discussed.展开更多
Ureas are widely used in drugs,materials and catalysts because of their diamide structure,which can form strong hydrogen bonds.Therefore,it is of great scientific significance to develop efficient and green methods fo...Ureas are widely used in drugs,materials and catalysts because of their diamide structure,which can form strong hydrogen bonds.Therefore,it is of great scientific significance to develop efficient and green methods for the synthesis of urea compounds,especially unsymmetrical ureas.Here,we have disclosed novel and highly efficient three-component coupling reactions of organic halides,sodium cyanate and amines enabled by nickel/photoredox dual catalysis for the preparation of unsymmetrical ureas.The reaction features simple and safe operations,broad substrate scopes,and product diversities.It allows the facile synthesis of N-aryl/vinyl ureas from readily available,user-friendly feedstocks under mild conditions(27 examples,36%—98%yields).In addition,this method is further derived to alcohols as nucleophiles to synthesize a series of carbamates(15 examples,40%—95%yields).The mechanism experiment shows that the isocyanate produced by the coupling of halide and sodium cyanate may be the key intermediate in this reaction.展开更多
基金supported both by the Natural Science Foundations of Hebei(No.B2008000210)the Scientific Research Foundation of Agricultural University of Hebei.
文摘A novel method for the determination of five carbamate pesticides (metolcarb, carbofuran, carbaryl, isoprocard and diethofencard) in water samples was developed by dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography-diode array detector (HPLC-DAD). Some experimental parameters that influence the extraction efficiency were studied and optimized to obtain the best extraction results. Under the optimum conditions for the method, the calibration curve was linear in the concentration range from 5 to 1000 ng mL^-1 for all the five carbamate pesticides, with the correlation coefficients (r^2) varying from 0.9984 to 0.9994. Good enrichment factors were achieved ranging from 80 to 177- fold, depending on the compound. The limits of detection (LODs) (S/N = 3) were ranged from 0.1 to 0.5 ng mL^-1. The method has been successfully applied to the analysis of the pesticide residues in environmental water samples.
基金the financial supports from the Ministry of Science and Technology of China(2006BAK02A24)the Ministry of Agriculture of China(2007-2011)Xi'an Bureau of Science and Technology,China (GG05112)
文摘Soybean esterase, a cholinesterase-like enzyme, was purified by differential centrifugation firstly, then, ammonium sulfate precipitation, dialysis, and finally, DEAE-cellulose-32 ion-exchange chromatography after extracting it from soybean seeds with phosphate buffer (0.3 mol L^-1, pH 7.0). The extract recovery rate of the purified enzyme was 8.18% and purification fold was 91.58. The soybean esterase appeared as two bands on the denaturing SDS-PAGE with molecular weights of 24 and 37.2 kDa, respectively, which proved that it is a dimer protein consisting of two subunits. The result of nondenaturing PAGE revealed that the soybean esterase is a single band with cholinesterase-like activity using α- naphthyl acetate as the substrate and fast blue B salt as coloring agent. The esterase showed very high sensitivity to 18 kinds of organophosphate pesticides and 6 kinds of carbamate pesticides with the lowest detective limits of 0.03125- 0.0625 and 0.03125-0.25 mg kg^-1, respectively, and can meet the demands of MRL specified by the most countries.
基金supported by an ES project on ‘Cyanobacteria’ (Grant No.21 (0859)/11/EMR-II),from Council of Scientific and Industrial Research (CSIR),New Delhi,India
文摘Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at soil-water interface, were analyzed by the probit method. Growth enhancing concentration, no-observed effective concentration, minimum inhibitory concentration, the highest permissive concentration and lethal concentration100 (LCloo) were determined experimentally. The LC^o values of carbaryl, carbofuran, ziram, zineb and mancozeb in N2-fixing liquid medium were 56.2, 588.8, 0.07, 4.2 and 3.4 IJg/mL, respectively, whereas the corresponding LCloo values were 100.0, 1500.0, 0.17, 25.0 and 9.0 IJg/mL, respectively. The LC50 values of these pesticides in succession in N2-fixing agar medium were 44.7, 239.9, 0.07, 1.8 and 2.3 IJg/mL, respectively, whereas the corresponding LC100 values were 100.0, 600.0, 0.17, 10.0 and 7.0 IJg/mL, respectively. Similar results with nitrate supplemented liquid and agar media indicated that nitrate supplementation had toxicity reducing effect. The LCso and LC^oo values of toxicity in the N2-fixing liquid medium at soil-water interface were 91.2 and 200.0 IJg/mL for carbaryl, 2 317 and 6 000 pg/mL for carbofuran, 0.15 and 0.50 pg/mL for ziram, 16.4 and 50.0 pg/mL for zineb, and 7.2 and 25.0 pg/mL for mancozeb, respectively. Each LC^oo value at soil- water interface with a pesticide was significantly higher than its corresponding LCloo value at liquid/agar media. It can be concluded that, under the N2-fixing conditions, the cyanobacterium tolerated higher levels of each pesticide at soil-water interface.
文摘[Objectives ] The paper was to explore enzyme inhibition rate method for rapid detection of organophosphorus and carbamate pesticides in cowpea. [ Methods ] Acetylcholinesterase (ACHE) was added to cowpea extract, to determine the inhibition rate of extract against enzyme. The influences of different sampiing methods and sampling parts on detection results were compared. [ Results] The positive rate of standard sampling was 18.18% higher than that of non-stand- ard sampling, and the positive rate of samples collected from cowpea tail was 16.67% higher than that collected from other parts. [ Condmions] Enzyme inhibi- tion rate method is suitable for rapid detection of organophosphorus and carbamate pesticides in cowpea.
文摘Carbamates are important intermediates in the syntheses of pesticides, herbicides, drugs, polyurethane-based polymers, and other fine and commodity chemicals.
文摘A facile synthesis of N-methyl-N-aryl carbamates from aromatic amines and dimethyl carbonate (DMC) has been achieved with high yields in the presence of potassium carbonate (K2CO3)and tetrabutylammonium bromide (Bu4NBr) under solvent-free conditions.
基金supported by the National Basic Research Program (No.2003CB 114406)the National Natural Science Foundation of China (No.20672062)the Tianjin Natural Science Foundation (No.07JCYBJC01200).
文摘Four 4-monosubstituted pyrimidine pyridyl sulfonylureas were synthesized from pyridinesulfonamide and phenyl pyrimidylcarbamate and screened for herbicidal activities. We also reported a convenient preparation process of phenyl pyrimidylcarbamates from pyrimidineamine and phenyl chloroformate.
文摘A new method was developed for the quantitative determination of the neurotoxic nonprotein amino acid, 3-N-oxalyl-L-2,3-diaminopropioni acid (β-ODAP), its nontoxic α-isomer and other non-protein amino acids in the plant samples of Lathyrus sativus after derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) by reversed-phase high-performance liquid chromatography (HPLC). 2-Amino butyric acid (ABA) was used as an internal standard.The RP HPLC detection limit for both isomers is 1.8 ng with good response linearity. The results are compared with a colorimetric method.
文摘A convenient, efficient, one-pot, novel process has been developed for the synthesis of carbamates from corresponding alkyl halides and amines using basic resin/CO2 system.
基金the Beijing Forestry University Excellent Young Scientist Fund(No.BLYX200904)National Innovation Experiment Program for University Students(No.091002234)Major State Basic Research Development Program of China(973 Program,No.2010CB732204) are gratefully acknowledged.
文摘Sulfamic acid has been proved to be the most efficient and recyclable catalyst in carbamate synthesis from alkylamine and dialkyl carbonate.High selectivity,cost-efficiency and simple product separation were the advantageous features obtained in this process.Sulfamic acid could be reused several times and keep its initial activity in the recycle runs.In addition,sulfamic acid has also exhibited the potential catalytic ability for alkylation of aromatic amines.
基金Supported by the National Natural Science Foundation of China(Nos.20333050 and 20673044), PCSIRT(No.IRT0625) Key Subject of Science and Technology by Jilin Province, China
文摘The density functional theory at the B3LYP/6-311G(d, p) level was applied to exploring the inhibition mechanism of cholinesterases by carbamate. The results indicate that the inhibition reactions with or without the catalytic effect of the catalytic triad in eholinesterases underwent a two-step addition-elimination mechanism, which is in good agreement with the proposed mechanism. The solvent has a strong effect on the inhibition reactions and the reaction with the catalytic triad in the solvent phase is close to the real reaction under biological condition.
文摘Cellulose carbamates (CC) were synthesized with microcrystalline cellulose as raw materials. The Fourier transform infrared spectra of CC with different nitrogen content were recorded. The accurate results of the nitrogen content for CC can be obtained by using the deconvolution method when the nitrogen content is less than 3.5%. The relationship between the nitrogen content and the absorption intensity ratio of the corresponding separated absorption peaks in FTIR spectra has been expressed bg an equation precisely.
基金Supported by the Central University Basic Scientific Research Fund of Hunan University(2009)
文摘The title compound N-octyl rotenone oximino carbamate(C32H40N2O7) has been synthesized by the reaction of rotenone oxime with octyl isocyanate,and its crystal structure was determined by single-crystal X-ray diffraction.The crystal belongs to the monoclinic system,space group P21 with a=11.4311(8),b=10.3717(7),c=12.7490(9)A,β=105.0770(10)°,Z=2,V=1459.49(18)A^3,Mr=564.66,Dc=1.285g/cm^3,S=1.087,μ=0.090 mm^-1,F(000)=604,the final R=0.0426 and wR=0.0937 for 2599 observed reflections(I〉2σ(I)).X-ray analysis reveals that the molecule has an approximately V-shaped structure,and the absolute configurations of C(7),C(8) and C(18) are R,S and R,respectively.The oxime ester is in an E configuration.Intermolecular N-H…O hydrogen bond exists in the crystal.The preliminary bioassay shows that the title compound possesses strong insecticidal activity against Mythimna separate,and displays moderate fungicidal activity against Erysiphe graminis.
文摘Analytical difficulties encountered in the determination of ethyl carbamate, a known cancinogen, in a wide variety of wines and spirits have been overcome by spe- cific, sensitive GC/GC and CC/CC/MS methods with a relatively shorter extraction procedure. The lowest detection limits were estimated to be 0. 1 and 0. 01μg/L for GC/GC and GC/GC/MS respectively. The RSD of the GC/GC method was 2. 5%.
文摘[Objective]The paper was to study a synthetic method suitable for industrial production of intermediate N-Chloroformyl-N-[4-(trifluoromethoxy)phenyl]methyl carbamate of indoxacarb.[Method]Using 4-trifluoromethoxy aniline as the starting material,[4-(trifluoromethoxy)phenyl]carbamate was synthesized by homogeneous formylation method without acid-binding agent.Subsequently,it was reacted with sodium methoxide/potassium methoxide by reactive distillation to obtain[4-(trifluoromethoxy)phenyl]carbamate ammonium sodium/potassium,then directly reacted with triphosgene to obtain crude products of N-carbonochloridoyl-N-[4-(trifluoromethoxy)phenyl]carbamate;finally,competing product was obtained by recrystallization.[Result]The intermediate N-chloroformyl-N-[4-(trifluoromethoxy)phenyl]carbamate was synthesized by the method.The content of products was higher than 98%.The yield of product reached above 96%(calculated by 4-trifluoromethoxy aniline).[Conclusion]The method used for the synthesis of intermediate N-chloroformyl-N-[4-(trifluoromethoxy)phenyl]methyl carbamate was simple,with less three wastes,higher safety and lower cost.
基金the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico(CNPQ),the Fundacao de Amparo a Pesquisa do Estado de Minas Gerais(FAPEMIG),and the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior(CAPES)for financial support.
文摘The present work sought to characterize the cyanogenic glycoside dhurrin in five sugarcane varieties and to determine its possible relationship with the formation of ethyl carbamate in cachaca. For each variety, methanol, ethyl acetate and hexane extracts were prepared and submitted to thin layer chromatography. Chromatographic spots were revealed with iodine vapors. The physical and chemical parameters of the spirits produced from the five different varieties of sugar cane and by different production processes were within the legal limits. Although not exceeding the limit for ethyl carbamate, a significant variation in the final concentration of this compound was observed for each sample analyzed. The Rf values for the dhurrin standard and for the sugarcane variety SP 83-2847 were equal, similar to those for SP 80-3280 and CTC 11 and different from the Rf values for the RB 86-7515 and IAC 86-2480 samples.
基金the financial support provided by the National Natural Science Foundation of China(Nos.21572163 and 21873074)the Wenzhou Science&Technology Bureau(No.G20210032)。
文摘Nitrene transfer reactions are powerful tools in synthetic organic chemistry.In recent years,transitionmetal catalyzed nitrene transfer reactions with carbamates as the nitrene precursors have been widely pursued.Such species undergoes facile C-H amination,aziridination,and bifunctionalization of alkenes under the catalysis of different transition metals including Rh,Fe,Ru and others,enabling the efficient construction of various nitrogen-containing molecules.In this review,the recent developments in nitrene transfer reactions with carbamates via N-O bond cleavage were introduced based on different types of reaction,and the key mechanistic information and synthetic applications of the methodologies were discussed.
基金the National Natural Science Foundation of Chinaa(Nos.22271113,92256301,21822103,91956201,21820102003 and 21602052)the Natural Science Foundation of Hubei Province(No.2022CFB413)the fund from Central China Normal University for support of this research.
文摘Ureas are widely used in drugs,materials and catalysts because of their diamide structure,which can form strong hydrogen bonds.Therefore,it is of great scientific significance to develop efficient and green methods for the synthesis of urea compounds,especially unsymmetrical ureas.Here,we have disclosed novel and highly efficient three-component coupling reactions of organic halides,sodium cyanate and amines enabled by nickel/photoredox dual catalysis for the preparation of unsymmetrical ureas.The reaction features simple and safe operations,broad substrate scopes,and product diversities.It allows the facile synthesis of N-aryl/vinyl ureas from readily available,user-friendly feedstocks under mild conditions(27 examples,36%—98%yields).In addition,this method is further derived to alcohols as nucleophiles to synthesize a series of carbamates(15 examples,40%—95%yields).The mechanism experiment shows that the isocyanate produced by the coupling of halide and sodium cyanate may be the key intermediate in this reaction.