A simple and efficient procedure for the synthesis of 2-arylquinazolin-4（3H）-ones has been developed through cyclocondensation of 2-aminobenzamide with aromatic aldehydes using tetrabutylammonium bromide（TBAB） as ...A simple and efficient procedure for the synthesis of 2-arylquinazolin-4（3H）-ones has been developed through cyclocondensation of 2-aminobenzamide with aromatic aldehydes using tetrabutylammonium bromide（TBAB） as novel neutral ionic liquid catalyst in the presence of copper（Ⅱ） chloride（CuCl;） as oxidizing agent under solvent-free conditions at 100℃.In the absence of CuCl;and under a nitrogen atmosphere,the unoxidized intermediates,2-aryl-2,3-dihydroquinazolin-4（1H）-ones,were isolated. Treatment of these intermediates with CuCl;in TBAB media gave the oxidized products 2-arylquinazolin-4（3H）-ones.On the other hand,cyclocondensation of 2-aminobenzamide with aromatic aldehydes in TBAB under microwave irradiation directly gave 2- arylquinazolin-4（3H）-ones.展开更多
Semiclathrate hydrates of tetra-n-butyl ammonium bromide （TBAB） offer potential solution for gas storage, transportation, separation of flue gases and CO2 sequestration. Models for phase equilibria for these systems...Semiclathrate hydrates of tetra-n-butyl ammonium bromide （TBAB） offer potential solution for gas storage, transportation, separation of flue gases and CO2 sequestration. Models for phase equilibria for these systems have not yet been developed in open literatures and thus require urgent attention. In this work, the first attempt has been made to model phase equilibria of semiclathrate hydrates of CH4, CO2 and N2 in aqueous solution of TBAB. A thermodynamic model for gas hydrate system as proposed by Chen and Guo has been extended for semiclathrate hydrates of gases in aqueous solution of TBAB. A correlation for the activity of water relating to the system temperature, concentration of TBAB in the system and the nature of guest gas molecule has been proposed. The model results have been validated against available experimental data on phase equilibria of semiclathrate hydrate systems of aqueous TBAB with different gases as guest molecule. The extended Chen and Guo＇s model is found to be suitable to explain the promotion effect of TBAB for the studied gaseous system such as, methane, carbon dioxide and nitrogen as a guest molecule. Additionally, a correlation for the increase in equilibrium formation temperature （hydrate promotion temperature, ATp） of semiclathrate hydrate system with respect to pure gas hydrate system has been developed and applied to semiclathrate hydrate of TBAB with several gases as guest molecules. The developed correlation is found to predict the promotion effect satisfactorily for the system studied.展开更多
A mild and efficient n Bu4 NBr-mediated oxidative cycloaromatization to prepareβ-carbolines from readily available tryptophans and aldehydes is described.The reaction is practical and allows the synthesis ofβ-carbol...A mild and efficient n Bu4 NBr-mediated oxidative cycloaromatization to prepareβ-carbolines from readily available tryptophans and aldehydes is described.The reaction is practical and allows the synthesis ofβ-carbolines on gram-scale.Some of products crystallized from the reaction mixture and were easily removed by filtration,obviating the need for chromatographic separation.展开更多
The mechanism of the adsorption-parallel catalytic wave of cinnamic acid (C6H5-CH = CH-COOH) in acetate buffer (pH = 4.0)-H2O2-tetra-n-butylammonium bromide (Bu4N · Br) solution was studied by the linear-sweep po...The mechanism of the adsorption-parallel catalytic wave of cinnamic acid (C6H5-CH = CH-COOH) in acetate buffer (pH = 4.0)-H2O2-tetra-n-butylammonium bromide (Bu4N · Br) solution was studied by the linear-sweep polarography, cyclic voltammetry and digital simulation approach. Experimental results indicate that the reduction mechanism of cinnamic acid isEC dim E’ process, in which the C = C double bond of cinnamic acid first undergoes 1e, 1H+ reduction to produce an intermediate free radical C6H5-CH-CH2-COOH(E), then the further reduction of the free radical in 1e, 1H+ addition (E’) occurs simultaneously with a dimerization reaction between two free radicals (Cdim). Bu4N· Br enhances the polarographic current of cinnamic acid and shifts the peak potential to positive direction. The enhancement action of Bu4N· Br is due to the adsorption of cinnamic acid induced by Bu4N+ species. In addition, H2O2 causes the parallel catalytic wave of cinnamic acid. The mechanism of the catalytic wave isEC’ process because H2O2 oxidizes the free radical of cinnamic acid to regenerate the original C =C bond(C’), preventing both the further reduction and the dimerization of the free radicals. The apparent rate constantk f of the oxidation reaction is 1.35×102 mol· L-1· s-1. A new class of catalytic waves for organic compounds, the adsorption-parallel catalytic waves upon the dual enhancement action of both the surfactant and oxidant, has been presented.展开更多
A practical procedure for palladium catalyzed Suzuki cross-coupling reaction of arylboronic acids with aryl hal-ides, including aryl chlorides in molten tetra-n-butylammonium bromide (TBAB) was developed. The reaction...A practical procedure for palladium catalyzed Suzuki cross-coupling reaction of arylboronic acids with aryl hal-ides, including aryl chlorides in molten tetra-n-butylammonium bromide (TBAB) was developed. The reaction exhibits high efficiency and functional group tolerance. The recovery of the catalyst and molten n-Bu4NBr was also investigated.展开更多
文摘A simple and efficient procedure for the synthesis of 2-arylquinazolin-4（3H）-ones has been developed through cyclocondensation of 2-aminobenzamide with aromatic aldehydes using tetrabutylammonium bromide（TBAB） as novel neutral ionic liquid catalyst in the presence of copper（Ⅱ） chloride（CuCl;） as oxidizing agent under solvent-free conditions at 100℃.In the absence of CuCl;and under a nitrogen atmosphere,the unoxidized intermediates,2-aryl-2,3-dihydroquinazolin-4（1H）-ones,were isolated. Treatment of these intermediates with CuCl;in TBAB media gave the oxidized products 2-arylquinazolin-4（3H）-ones.On the other hand,cyclocondensation of 2-aminobenzamide with aromatic aldehydes in TBAB under microwave irradiation directly gave 2- arylquinazolin-4（3H）-ones.
基金supported by the the Industrial Consultancy and Sponsored Research (ICSR),Indian Institute of Technology Madras,Chennai (Project Number OEC/10 11/530/NFSC/JITE)the National Institute of Ocean Technology (NIOT),Chennai,India (Project Number OEC/10-11/105/NIOT/JITE)
文摘Semiclathrate hydrates of tetra-n-butyl ammonium bromide （TBAB） offer potential solution for gas storage, transportation, separation of flue gases and CO2 sequestration. Models for phase equilibria for these systems have not yet been developed in open literatures and thus require urgent attention. In this work, the first attempt has been made to model phase equilibria of semiclathrate hydrates of CH4, CO2 and N2 in aqueous solution of TBAB. A thermodynamic model for gas hydrate system as proposed by Chen and Guo has been extended for semiclathrate hydrates of gases in aqueous solution of TBAB. A correlation for the activity of water relating to the system temperature, concentration of TBAB in the system and the nature of guest gas molecule has been proposed. The model results have been validated against available experimental data on phase equilibria of semiclathrate hydrate systems of aqueous TBAB with different gases as guest molecule. The extended Chen and Guo＇s model is found to be suitable to explain the promotion effect of TBAB for the studied gaseous system such as, methane, carbon dioxide and nitrogen as a guest molecule. Additionally, a correlation for the increase in equilibrium formation temperature （hydrate promotion temperature, ATp） of semiclathrate hydrate system with respect to pure gas hydrate system has been developed and applied to semiclathrate hydrate of TBAB with several gases as guest molecules. The developed correlation is found to predict the promotion effect satisfactorily for the system studied.
基金National Natural Science Foundation of China (Nos. 21172120 and 21472093)Tianjin Municipal Science and Technology Commission (No. 14JCYBJC20600) for financial support
文摘A mild and efficient n Bu4 NBr-mediated oxidative cycloaromatization to prepareβ-carbolines from readily available tryptophans and aldehydes is described.The reaction is practical and allows the synthesis ofβ-carbolines on gram-scale.Some of products crystallized from the reaction mixture and were easily removed by filtration,obviating the need for chromatographic separation.
文摘The mechanism of the adsorption-parallel catalytic wave of cinnamic acid (C6H5-CH = CH-COOH) in acetate buffer (pH = 4.0)-H2O2-tetra-n-butylammonium bromide (Bu4N · Br) solution was studied by the linear-sweep polarography, cyclic voltammetry and digital simulation approach. Experimental results indicate that the reduction mechanism of cinnamic acid isEC dim E’ process, in which the C = C double bond of cinnamic acid first undergoes 1e, 1H+ reduction to produce an intermediate free radical C6H5-CH-CH2-COOH(E), then the further reduction of the free radical in 1e, 1H+ addition (E’) occurs simultaneously with a dimerization reaction between two free radicals (Cdim). Bu4N· Br enhances the polarographic current of cinnamic acid and shifts the peak potential to positive direction. The enhancement action of Bu4N· Br is due to the adsorption of cinnamic acid induced by Bu4N+ species. In addition, H2O2 causes the parallel catalytic wave of cinnamic acid. The mechanism of the catalytic wave isEC’ process because H2O2 oxidizes the free radical of cinnamic acid to regenerate the original C =C bond(C’), preventing both the further reduction and the dimerization of the free radicals. The apparent rate constantk f of the oxidation reaction is 1.35×102 mol· L-1· s-1. A new class of catalytic waves for organic compounds, the adsorption-parallel catalytic waves upon the dual enhancement action of both the surfactant and oxidant, has been presented.
文摘A practical procedure for palladium catalyzed Suzuki cross-coupling reaction of arylboronic acids with aryl hal-ides, including aryl chlorides in molten tetra-n-butylammonium bromide (TBAB) was developed. The reaction exhibits high efficiency and functional group tolerance. The recovery of the catalyst and molten n-Bu4NBr was also investigated.
