A highly effective and mild protocol for ring opening of epoxides with NH4SCN in the presence of catalytic amount of a multi- site phase-transfer catalyst, α,α',α"-N-hexakis(triethylammoniummethylene chloride)-...A highly effective and mild protocol for ring opening of epoxides with NH4SCN in the presence of catalytic amount of a multi- site phase-transfer catalyst, α,α',α"-N-hexakis(triethylammoniummethylene chloride)-melamine, is developed. A variety of ^-hydroxy thiocyanates as important intermediates in agricultural and pharmaceutical chemistry were obtained in high yields with excellent regioselectivity and in short reaction times. 2009 Ali Reza Kiasat. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
Ionic liquids (ILs) based on 1,3-dialkylimidazolium and tetraalkylammonium cations were employed as a series of efficient, environmentally benign phase-transfer catalysts (PTCs) for the base-promoted monoalkylatio...Ionic liquids (ILs) based on 1,3-dialkylimidazolium and tetraalkylammonium cations were employed as a series of efficient, environmentally benign phase-transfer catalysts (PTCs) for the base-promoted monoalkylation of diethyl malonate. The influence of various heterogeneous bases on yields was studied. Good yields and high selectivity were obtained. Solvent-free, mild reaction condition, short reaction time, and easy purification were the merits of this method. The catalytic system (IL-hase) could also be recycled after the extraction of products with ether.展开更多
A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxida...A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxidant. The conversion of H2O2 was 100% and the yield of cyclohexene oxide was 87.1% based on cyclohexene. Infrared spectra showed that both fresh catalyst and the recovered catalyst do have completely same absorption peak, indicating the structure of catalyst is very stability and can be recycled.展开更多
A new catalytic process for the synthesis of aldehyde from alcohol by oxidation with H202 with high selectivity, was studied. In this system, heteropolymolybdate [C7H7N(CH3)3]3 {PO4[MoO(O2)2]4} was utilized as the...A new catalytic process for the synthesis of aldehyde from alcohol by oxidation with H202 with high selectivity, was studied. In this system, heteropolymolybdate [C7H7N(CH3)3]3 {PO4[MoO(O2)2]4} was utilized as the reaction-controlled phase-transfer catalyst to catalyze oxidation of benzyl and aliphatic alcohols. The molar ratio of H2O2 and alcohol was 0.75, no other by-products were detected by gas chromatography, the results of oxidation reaction indicated that the catalyst has high activity and stability.展开更多
Using 4-Dialkylaminopyridinium salt as a thermal stable phase-transfer catalyst (PTC), the excellent results were obtained in the halogen-exchange fluorination.
Fast phase-transferring was adopted in ethanol solution at the condition of n (oil-soluble tea pol-yphenol): N (As3﹢) = 2:1, 4:1, 6:1, pH = 4.0, temperature 40°C - 45°C, action period of 15 h to compo...Fast phase-transferring was adopted in ethanol solution at the condition of n (oil-soluble tea pol-yphenol): N (As3﹢) = 2:1, 4:1, 6:1, pH = 4.0, temperature 40°C - 45°C, action period of 15 h to compose the target, of which the productivity was 59%, UV was 267.50, 218.00, 220.50 nm, FTIR was 6291, 34158.6, 2850.2, 1708.2;1457.3;1370.4, 1224.2, 1144.0, 760.5 cm﹣1, fluorescence value λmax = 257, 591.1, 593.7, 590.3, 591.0, 591.5, XRD λ/nm is 3.6974, 4.186, 12.0762, 15.4747, 1H-NMRδ = 0.782, 1.193, 1.483 - 1.586, 1.959 - 2.184, 2.479, 3.116, 3.970 - 3.981, 5.231 - 5.753, 6.537 - 7.300. Finally it was ascertained through XRD as double-coordinated polycrystal compound.展开更多
Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quater...Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quaternary ammoniums bearing different cationic sizes,i.e.MTOA+(methyltrioctylammonium,[(C_(8)H_(17))_(3)CH_(3)N]+),HTMA+(hexadecyltrimethylammonium,[(C_(16)H_(33))(CH_(3))_(3)N]+) and DMDOA+(dimethyldioctadecylammonium,[(C_(18)H_(37))_(2)(CH_(3))_(2)N]+) were incorporated with polyoxometalate (POM) anions to prepare phase transfer catalysts (PTCs),which were used in the styrene epoxidations.Among them,(MTOA)_(3)PW_(4)O_(24)exhibits the best catalytic performance judged from the highest styrene conversion rate(52%) and styrene oxide selectivity (93%),during which the styrene epoxidation conditions were optimized.Meanwhile,the deactivation mechanism of this kind of PTCs was proposed firstly,i.e.in the case of low H_(2)O_(2) content,the oxidant can only be used in the styrene epoxidation,in which the catalyst can transform into stable Keggin-type POM.But when the content of H_(2)O_(2) is higher,the excess H_(2)O_(2) can reactivate the Keggin-type POM into active (PW_(4)O_(24))_(3)-anions,which can trigger the ring-opening polymerization of styrene oxide.Consequently,the catalyst is deactivated by adhered poly(styrene oxide)irreversibly,which was determined by NMR spectra.In this situation,the active moiety{PO_(4)[WO(O_(2))_(2)]_(4)}_(3)-in phase-transfer catalytic system can break into some unidentified species with low W/P ratio with the presence of epoxides.This work will be beneficial for the design of new PTCs in alkene epoxidation in fine chemical industry.展开更多
The selective oxidation of cyclopentene by aqueous H2O2 using H3PW12O40 and tetrabutyl ammonium bromide(TBAB) as a phase transfer catalyst has been investigated. The results show that the presence of TBAB significantl...The selective oxidation of cyclopentene by aqueous H2O2 using H3PW12O40 and tetrabutyl ammonium bromide(TBAB) as a phase transfer catalyst has been investigated. The results show that the presence of TBAB significantly improved the oxidation selectivity of cyclopentene. The effects of the reaction conditions on the conversion of cyclopentene were investigated in detail. The optimal reaction conditions are as follows: the H3PW12O40 to TBAB molar ratio, 1:1–1:3;H3PW12O40 to cyclopentene molar ratio,0.54:100–0.64:100;and molar ratio of H2O2 to cyclopentene, 1.6:1. The conversion reached to 59.8% in 4h at 35.0 ℃, while the selectivity of glutaraldehyde was 38.0% and the selectivity of 1,2-cyclopentanediol was 55.6%. In addition, a route for oxidation of cyclopentene by aqueous H2O2 using a heteropoly acid and quaternary ammonium salt as a phase transfer catalyst was proposed.展开更多
This article presents a novel catalytic method by combining phase-transfer catalyst, benzyltriethylammonium chloride, with 4-dimethylaminopyridine for the syntheses of glycosyl esters from substituted phenoxyaeetie ac...This article presents a novel catalytic method by combining phase-transfer catalyst, benzyltriethylammonium chloride, with 4-dimethylaminopyridine for the syntheses of glycosyl esters from substituted phenoxyaeetie acids and the peracetate of α-D-l-bromosugars to produee eight novel β-glyeosyl esters in high yields. The struetures of the syn-thesized eompounds were established by IR, MS, ^1H NMR, and ^13C NMR speetra and elemental analyses.展开更多
A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared. The degree of functionalization with aldehyde groups is well suited for the subseq...A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared. The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents. The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers. The reactions were carded out in phase transfer catalysis conditions. A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.展开更多
A new quatemary ammonium heteropolyoxotungstant (cat.C) is prepared andcharacterized. And the cat.C also is an reaction-controlled phase-transfer catalyst The catalyticsystem of O_2/EAHQ (2-ethylanthrahydroquinone)/ca...A new quatemary ammonium heteropolyoxotungstant (cat.C) is prepared andcharacterized. And the cat.C also is an reaction-controlled phase-transfer catalyst The catalyticsystem of O_2/EAHQ (2-ethylanthrahydroquinone)/cat.c is used for the epoxidation of propylene.Under the optimal conditions, the yield of propylene oxide based on EAHQ is 84.1%, theselectivity for propylene oxide based on propylene is 99.8% and the conversion of propylene basedon EAHQ is 84.3%. The cat.c precipitates after the epoxidation reaction for easy separation.The cat C is stable enough to be recycled three times without any loss in selectivity.展开更多
Various 3,4-dihydropyrimidinones can be prepared via Biginelli reaction in aqueous media by using quaternary ammonium salts of different alkyl groups (C4 and C8) and anions (Cl-?and Br-) as catalysts. The use of quate...Various 3,4-dihydropyrimidinones can be prepared via Biginelli reaction in aqueous media by using quaternary ammonium salts of different alkyl groups (C4 and C8) and anions (Cl-?and Br-) as catalysts. The use of quaternary ammonium salts along with longer alkyl chains increases the yield of the Biginelli reaction;however, bromide ammonium salts are less active than the chloride ones.展开更多
An asymmetric fluorinative dearomatization reaction of tryptophol derivatives was developed via chiral anion phase-transfer catalysis. Vari- ous fluorinated furoindolines were obtained in moderate to excellent yields ...An asymmetric fluorinative dearomatization reaction of tryptophol derivatives was developed via chiral anion phase-transfer catalysis. Vari- ous fluorinated furoindolines were obtained in moderate to excellent yields and enantioselectivity in the presence of Selectfluor. The preliminary mecha- nistic studies suggested the existence of an in situ formed tryptophol boronic ester plays a critical role in determining the enantioselectivity. This method features the facile introduction of a fluorine atom in a highly enantioselective manner and construction of two contiguous quaternary stereogenic cen- ters.展开更多
A highly effective phase transfer of a quaternary ammonium gemini surfactant with ester groups((diethylhexanedioate) diyl-a,v-bis(dimethyl dodecyl ammonium bromide) referred to as 12-10-12)was synthesized with h...A highly effective phase transfer of a quaternary ammonium gemini surfactant with ester groups((diethylhexanedioate) diyl-a,v-bis(dimethyl dodecyl ammonium bromide) referred to as 12-10-12)was synthesized with high yield and characterized by infrared spectroscopy, elemental analysis and1 HNMR. Then, 12-10-12 was used as a phase transfer catalyst to study the catalytic effect on the reaction of anhydrous sodium acetate and 4-methylbenzyl chloride. The possible catalytic mechanism and the influence of surfactant concentration, temperature and type are also discussed. The experimental results showed that the catalysis efficiency was more active than the traditional, single-chained surfactant,tetrabutyl ammonium bromide. It also revealed that the reaction was first-order with respect to the concentration of 4-methylbenzyl chloride. The concentration of 4-methylbenzyl chloride grew linearly with the concentration of 12-10-12 and as the reaction temperature increased. The optimum reaction time was 7 h.展开更多
A new reaction-controlled phase-transfer catalyst system, lacunary Keggin polyoxotungstate [C7H7N(CH3)3]9PW9O34 has been synthesized and used for catalytic epoxidation of olefins with H2O2 as t...A new reaction-controlled phase-transfer catalyst system, lacunary Keggin polyoxotungstate [C7H7N(CH3)3]9PW9O34 has been synthesized and used for catalytic epoxidation of olefins with H2O2 as the oxidant. Infrared spectra were used to analyze the behavior of the phase transfer of catalyst. In this system, the catalyst not only can act as homogeneous catalyst but also as heterogeneous catalyst to be easily filtered and reused. The epoxi- dation reaction is clean and exhibits high conversion and selectivity as well as excellent catalyst stability.展开更多
The asymmetric nitro-Mannich reaction is one of the traditional methods for forming carbon-carbon bond. By this reaction, the corresponding products with two contiguous stereocenters containing nitrogen substituents c...The asymmetric nitro-Mannich reaction is one of the traditional methods for forming carbon-carbon bond. By this reaction, the corresponding products with two contiguous stereocenters containing nitrogen substituents can be obtained. These β-nitro amine products can be easily transformed into 1,2-diamines by reduction of the corresponding nitro groups by means of the Nef reaction. It is well known that chiral 1,2-diamines Nay an important role in many fields.展开更多
A series of chiral salen-Mn(Ⅲ) complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-...A series of chiral salen-Mn(Ⅲ) complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-dimethylpyridine N-oxide as proximal ligands, respectively. Moderate to high enantioselectivity and acceptable yields were achieved when NaClO was used as terminal oxidant under CH2Cl2/H2O biphasic media. Methyl iodide was found to be an effective additive to accelerate the epoxidation, possibly owing to the formation of quaternary ammonium units on catalysts, which may facilitate the reaction in an oil/water biphasic medium. The subsequent stimulation experiment was carried out, and the resulting ESI-HRMS analysis revealed the formation of a novel (salen)manganese(m) intermediate featuring two quaternary ammonium units, and bearing a pyridine N-oxide and a molecule of water simultaneously axially-coordinated backbone.展开更多
A chiral phase-transfer catalyst,derived from the combination of cinchona alkaloid backbone and BINOL skeleton,enabled a Mannich reaction of glycine Schiff base with N-Boc-imines to generateα,β-diamino acid derivati...A chiral phase-transfer catalyst,derived from the combination of cinchona alkaloid backbone and BINOL skeleton,enabled a Mannich reaction of glycine Schiff base with N-Boc-imines to generateα,β-diamino acid derivatives in excellent yields(up to 99%)and with high diastereo-and enantioselectivities(up to>20∶1 dr,96%ee).展开更多
A facile one-pot, economical approach to 1,2,3-thiadiazol-5-ylureas was developed via seleniumcatalyzed oxidative carbonylation of 1,2,3-thiadiazol-5-amine with a series of amines in one-pot manner in the presence of ...A facile one-pot, economical approach to 1,2,3-thiadiazol-5-ylureas was developed via seleniumcatalyzed oxidative carbonylation of 1,2,3-thiadiazol-5-amine with a series of amines in one-pot manner in the presence of CO and O_2. This approach is featured with cheap and easily available raw materials,cheap and reusable catalyst selenium, one-pot procedure, high atomic economy, simple operations and no emission of corrosive wastes.展开更多
基金the partial support of this work by Shahid Chamran Research Council
文摘A highly effective and mild protocol for ring opening of epoxides with NH4SCN in the presence of catalytic amount of a multi- site phase-transfer catalyst, α,α',α"-N-hexakis(triethylammoniummethylene chloride)-melamine, is developed. A variety of ^-hydroxy thiocyanates as important intermediates in agricultural and pharmaceutical chemistry were obtained in high yields with excellent regioselectivity and in short reaction times. 2009 Ali Reza Kiasat. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
文摘Ionic liquids (ILs) based on 1,3-dialkylimidazolium and tetraalkylammonium cations were employed as a series of efficient, environmentally benign phase-transfer catalysts (PTCs) for the base-promoted monoalkylation of diethyl malonate. The influence of various heterogeneous bases on yields was studied. Good yields and high selectivity were obtained. Solvent-free, mild reaction condition, short reaction time, and easy purification were the merits of this method. The catalytic system (IL-hase) could also be recycled after the extraction of products with ether.
文摘A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxidant. The conversion of H2O2 was 100% and the yield of cyclohexene oxide was 87.1% based on cyclohexene. Infrared spectra showed that both fresh catalyst and the recovered catalyst do have completely same absorption peak, indicating the structure of catalyst is very stability and can be recycled.
文摘A new catalytic process for the synthesis of aldehyde from alcohol by oxidation with H202 with high selectivity, was studied. In this system, heteropolymolybdate [C7H7N(CH3)3]3 {PO4[MoO(O2)2]4} was utilized as the reaction-controlled phase-transfer catalyst to catalyze oxidation of benzyl and aliphatic alcohols. The molar ratio of H2O2 and alcohol was 0.75, no other by-products were detected by gas chromatography, the results of oxidation reaction indicated that the catalyst has high activity and stability.
基金the Natural Science Foundation of Zhejiang Province (No. 299024).
文摘Using 4-Dialkylaminopyridinium salt as a thermal stable phase-transfer catalyst (PTC), the excellent results were obtained in the halogen-exchange fluorination.
文摘Fast phase-transferring was adopted in ethanol solution at the condition of n (oil-soluble tea pol-yphenol): N (As3﹢) = 2:1, 4:1, 6:1, pH = 4.0, temperature 40°C - 45°C, action period of 15 h to compose the target, of which the productivity was 59%, UV was 267.50, 218.00, 220.50 nm, FTIR was 6291, 34158.6, 2850.2, 1708.2;1457.3;1370.4, 1224.2, 1144.0, 760.5 cm﹣1, fluorescence value λmax = 257, 591.1, 593.7, 590.3, 591.0, 591.5, XRD λ/nm is 3.6974, 4.186, 12.0762, 15.4747, 1H-NMRδ = 0.782, 1.193, 1.483 - 1.586, 1.959 - 2.184, 2.479, 3.116, 3.970 - 3.981, 5.231 - 5.753, 6.537 - 7.300. Finally it was ascertained through XRD as double-coordinated polycrystal compound.
基金financial supported by the National Natural Science Foundation of China (22078065)Key Program of Qingyuan Innovation Laboratory (00221001)Quanzhou City Science & Technology Program of China (2020C008R)。
文摘Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quaternary ammoniums bearing different cationic sizes,i.e.MTOA+(methyltrioctylammonium,[(C_(8)H_(17))_(3)CH_(3)N]+),HTMA+(hexadecyltrimethylammonium,[(C_(16)H_(33))(CH_(3))_(3)N]+) and DMDOA+(dimethyldioctadecylammonium,[(C_(18)H_(37))_(2)(CH_(3))_(2)N]+) were incorporated with polyoxometalate (POM) anions to prepare phase transfer catalysts (PTCs),which were used in the styrene epoxidations.Among them,(MTOA)_(3)PW_(4)O_(24)exhibits the best catalytic performance judged from the highest styrene conversion rate(52%) and styrene oxide selectivity (93%),during which the styrene epoxidation conditions were optimized.Meanwhile,the deactivation mechanism of this kind of PTCs was proposed firstly,i.e.in the case of low H_(2)O_(2) content,the oxidant can only be used in the styrene epoxidation,in which the catalyst can transform into stable Keggin-type POM.But when the content of H_(2)O_(2) is higher,the excess H_(2)O_(2) can reactivate the Keggin-type POM into active (PW_(4)O_(24))_(3)-anions,which can trigger the ring-opening polymerization of styrene oxide.Consequently,the catalyst is deactivated by adhered poly(styrene oxide)irreversibly,which was determined by NMR spectra.In this situation,the active moiety{PO_(4)[WO(O_(2))_(2)]_(4)}_(3)-in phase-transfer catalytic system can break into some unidentified species with low W/P ratio with the presence of epoxides.This work will be beneficial for the design of new PTCs in alkene epoxidation in fine chemical industry.
基金Supported by the National Natural Science Foundation of China(21406146)
文摘The selective oxidation of cyclopentene by aqueous H2O2 using H3PW12O40 and tetrabutyl ammonium bromide(TBAB) as a phase transfer catalyst has been investigated. The results show that the presence of TBAB significantly improved the oxidation selectivity of cyclopentene. The effects of the reaction conditions on the conversion of cyclopentene were investigated in detail. The optimal reaction conditions are as follows: the H3PW12O40 to TBAB molar ratio, 1:1–1:3;H3PW12O40 to cyclopentene molar ratio,0.54:100–0.64:100;and molar ratio of H2O2 to cyclopentene, 1.6:1. The conversion reached to 59.8% in 4h at 35.0 ℃, while the selectivity of glutaraldehyde was 38.0% and the selectivity of 1,2-cyclopentanediol was 55.6%. In addition, a route for oxidation of cyclopentene by aqueous H2O2 using a heteropoly acid and quaternary ammonium salt as a phase transfer catalyst was proposed.
基金Supported by the National Natural Science Foundation of China(No.20674023).
文摘This article presents a novel catalytic method by combining phase-transfer catalyst, benzyltriethylammonium chloride, with 4-dimethylaminopyridine for the syntheses of glycosyl esters from substituted phenoxyaeetie acids and the peracetate of α-D-l-bromosugars to produee eight novel β-glyeosyl esters in high yields. The struetures of the syn-thesized eompounds were established by IR, MS, ^1H NMR, and ^13C NMR speetra and elemental analyses.
文摘A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared. The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents. The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers. The reactions were carded out in phase transfer catalysis conditions. A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.
文摘A new quatemary ammonium heteropolyoxotungstant (cat.C) is prepared andcharacterized. And the cat.C also is an reaction-controlled phase-transfer catalyst The catalyticsystem of O_2/EAHQ (2-ethylanthrahydroquinone)/cat.c is used for the epoxidation of propylene.Under the optimal conditions, the yield of propylene oxide based on EAHQ is 84.1%, theselectivity for propylene oxide based on propylene is 99.8% and the conversion of propylene basedon EAHQ is 84.3%. The cat.c precipitates after the epoxidation reaction for easy separation.The cat C is stable enough to be recycled three times without any loss in selectivity.
基金financial support of the Ministry of Higher Education and Scientific Research of Tunisia.
文摘Various 3,4-dihydropyrimidinones can be prepared via Biginelli reaction in aqueous media by using quaternary ammonium salts of different alkyl groups (C4 and C8) and anions (Cl-?and Br-) as catalysts. The use of quaternary ammonium salts along with longer alkyl chains increases the yield of the Biginelli reaction;however, bromide ammonium salts are less active than the chloride ones.
文摘An asymmetric fluorinative dearomatization reaction of tryptophol derivatives was developed via chiral anion phase-transfer catalysis. Vari- ous fluorinated furoindolines were obtained in moderate to excellent yields and enantioselectivity in the presence of Selectfluor. The preliminary mecha- nistic studies suggested the existence of an in situ formed tryptophol boronic ester plays a critical role in determining the enantioselectivity. This method features the facile introduction of a fluorine atom in a highly enantioselective manner and construction of two contiguous quaternary stereogenic cen- ters.
基金supported by the Talent Foundation of Anhui Science and Technology University (No. ZRC2014401)
文摘A highly effective phase transfer of a quaternary ammonium gemini surfactant with ester groups((diethylhexanedioate) diyl-a,v-bis(dimethyl dodecyl ammonium bromide) referred to as 12-10-12)was synthesized with high yield and characterized by infrared spectroscopy, elemental analysis and1 HNMR. Then, 12-10-12 was used as a phase transfer catalyst to study the catalytic effect on the reaction of anhydrous sodium acetate and 4-methylbenzyl chloride. The possible catalytic mechanism and the influence of surfactant concentration, temperature and type are also discussed. The experimental results showed that the catalysis efficiency was more active than the traditional, single-chained surfactant,tetrabutyl ammonium bromide. It also revealed that the reaction was first-order with respect to the concentration of 4-methylbenzyl chloride. The concentration of 4-methylbenzyl chloride grew linearly with the concentration of 12-10-12 and as the reaction temperature increased. The optimum reaction time was 7 h.
基金Project supported by the National Natural 863 Plan of China (No. 2001AA33440203).
文摘A new reaction-controlled phase-transfer catalyst system, lacunary Keggin polyoxotungstate [C7H7N(CH3)3]9PW9O34 has been synthesized and used for catalytic epoxidation of olefins with H2O2 as the oxidant. Infrared spectra were used to analyze the behavior of the phase transfer of catalyst. In this system, the catalyst not only can act as homogeneous catalyst but also as heterogeneous catalyst to be easily filtered and reused. The epoxi- dation reaction is clean and exhibits high conversion and selectivity as well as excellent catalyst stability.
基金Supported by the National Natural Science Foundation of China(No. 51373067).
文摘The asymmetric nitro-Mannich reaction is one of the traditional methods for forming carbon-carbon bond. By this reaction, the corresponding products with two contiguous stereocenters containing nitrogen substituents can be obtained. These β-nitro amine products can be easily transformed into 1,2-diamines by reduction of the corresponding nitro groups by means of the Nef reaction. It is well known that chiral 1,2-diamines Nay an important role in many fields.
基金Project supported by the National Natural Science Founclation of China (No. 20571035), the Gansu Natural Science Foundation of China (No. 3ZS051-A25-003).Acknowledgement The authors are grateful to the Instrumental Analysis and Research Center of Lanzhou University and State Key Laboratory of Applied 0rganic Chemistry for providing instrumentation facilities.
文摘A series of chiral salen-Mn(Ⅲ) complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-dimethylpyridine N-oxide as proximal ligands, respectively. Moderate to high enantioselectivity and acceptable yields were achieved when NaClO was used as terminal oxidant under CH2Cl2/H2O biphasic media. Methyl iodide was found to be an effective additive to accelerate the epoxidation, possibly owing to the formation of quaternary ammonium units on catalysts, which may facilitate the reaction in an oil/water biphasic medium. The subsequent stimulation experiment was carried out, and the resulting ESI-HRMS analysis revealed the formation of a novel (salen)manganese(m) intermediate featuring two quaternary ammonium units, and bearing a pyridine N-oxide and a molecule of water simultaneously axially-coordinated backbone.
基金We are grateful for financial support from the National Natural Science Foundation of China(No.21232007).
文摘A chiral phase-transfer catalyst,derived from the combination of cinchona alkaloid backbone and BINOL skeleton,enabled a Mannich reaction of glycine Schiff base with N-Boc-imines to generateα,β-diamino acid derivatives in excellent yields(up to 99%)and with high diastereo-and enantioselectivities(up to>20∶1 dr,96%ee).
基金financial support from the National Natural Science Foundation of China(No.21772033)Program for Innovative Research Team in Science and Technology in University of Henan Province(No. 15IRTSTHN003)
文摘A facile one-pot, economical approach to 1,2,3-thiadiazol-5-ylureas was developed via seleniumcatalyzed oxidative carbonylation of 1,2,3-thiadiazol-5-amine with a series of amines in one-pot manner in the presence of CO and O_2. This approach is featured with cheap and easily available raw materials,cheap and reusable catalyst selenium, one-pot procedure, high atomic economy, simple operations and no emission of corrosive wastes.