Esterase BioH,which is obligatory for biotin synthesis in Escherichia coli,was found to exhibit a promiscuous ability to catalyse Aldol and Knoevenagel reactions with moderate to good yields.The reaction conditions in...Esterase BioH,which is obligatory for biotin synthesis in Escherichia coli,was found to exhibit a promiscuous ability to catalyse Aldol and Knoevenagel reactions with moderate to good yields.The reaction conditions including organic solvent,molar ratio of ketone to aldehyde,enzyme amount,and reaction time were investigated to evaluate the effect of different reaction conditions on yield.Target compounds were afforded in the best yield of 91.2％ for Aldol reaction and 54.7％ for Knoevenagel reaction.In addition,because the enzyme could be prepared with a low cost,this protocol could provide an economic route to conduct Aldol and Knoevenagel reactions,which expand the field of enzymatic promiscuity.展开更多
A catalyst system of Sevelamer, a phosphate-binding drug, has been prepared and used in the Knoevenagel reaction of aromatic aldehydes in water to produce substituted electrophilic alkenes. The products were obtained ...A catalyst system of Sevelamer, a phosphate-binding drug, has been prepared and used in the Knoevenagel reaction of aromatic aldehydes in water to produce substituted electrophilic alkenes. The products were obtained in excellent yields. Several novel, related catalytic systems showed promising catalytic properties for aromatic and heterocyclic aldehydes. The Sevelamer catalyst can be recovered using simple filtration and reused numerous times（up to 15 times） in the aqueous Knoevenagel reaction without any significant lowering of activity.展开更多
A direct three-component approach has been developed for the synthesis of a-cyano acrylates starting from al- dehydes, alcohols and a-cyano acetamide by employing cyanuric chloride as an organocatalyst. A class of str...A direct three-component approach has been developed for the synthesis of a-cyano acrylates starting from al- dehydes, alcohols and a-cyano acetamide by employing cyanuric chloride as an organocatalyst. A class of structur- ally diverse a-cyano acrylates have been provided with good to excellent yields via the cascade transformation of Knoevenagel condensation and amide esterification.展开更多
Knoevenagel condensation of malonic acid with aldehyde or ketone is brought about by an organic base, such as pyridine, to give a-alkenyl carboxylic acid. Because the base must be separated and recovered, and the prod...Knoevenagel condensation of malonic acid with aldehyde or ketone is brought about by an organic base, such as pyridine, to give a-alkenyl carboxylic acid. Because the base must be separated and recovered, and the product was extracted after refluxing of condensation, the procedure is rather complicated. The authors展开更多
Stereoselective synthesis by an aldol reaction between chloroacetone and aldehyde was studied using a synthesized chiral organocatalyst and triethylamine. The reaction gave α-chloro-β-hydroxy ketones in excellent yi...Stereoselective synthesis by an aldol reaction between chloroacetone and aldehyde was studied using a synthesized chiral organocatalyst and triethylamine. The reaction gave α-chloro-β-hydroxy ketones in excellent yield with high anti selectivity and enantioselectivity. The chiral organocatalyst was also used in the Knoevenagel reaction, which gave α-cyano-β-hydroxy ketones at a low temperature and the usual Knoevenagel product at a high temperature. Both products were obtained in good to moderate yield with good anti selectivity in the case of α-cyano-β-hydroxy ketone derivatives.展开更多
基金Supported by the National Natural Science Foundation of China（No.21176215）.
文摘Esterase BioH,which is obligatory for biotin synthesis in Escherichia coli,was found to exhibit a promiscuous ability to catalyse Aldol and Knoevenagel reactions with moderate to good yields.The reaction conditions including organic solvent,molar ratio of ketone to aldehyde,enzyme amount,and reaction time were investigated to evaluate the effect of different reaction conditions on yield.Target compounds were afforded in the best yield of 91.2％ for Aldol reaction and 54.7％ for Knoevenagel reaction.In addition,because the enzyme could be prepared with a low cost,this protocol could provide an economic route to conduct Aldol and Knoevenagel reactions,which expand the field of enzymatic promiscuity.
基金financial support by the National Natural Science Foundation of China (Nos. 21242004, 21302168)
文摘A catalyst system of Sevelamer, a phosphate-binding drug, has been prepared and used in the Knoevenagel reaction of aromatic aldehydes in water to produce substituted electrophilic alkenes. The products were obtained in excellent yields. Several novel, related catalytic systems showed promising catalytic properties for aromatic and heterocyclic aldehydes. The Sevelamer catalyst can be recovered using simple filtration and reused numerous times（up to 15 times） in the aqueous Knoevenagel reaction without any significant lowering of activity.
文摘A direct three-component approach has been developed for the synthesis of a-cyano acrylates starting from al- dehydes, alcohols and a-cyano acetamide by employing cyanuric chloride as an organocatalyst. A class of structur- ally diverse a-cyano acrylates have been provided with good to excellent yields via the cascade transformation of Knoevenagel condensation and amide esterification.
文摘Knoevenagel condensation of malonic acid with aldehyde or ketone is brought about by an organic base, such as pyridine, to give a-alkenyl carboxylic acid. Because the base must be separated and recovered, and the product was extracted after refluxing of condensation, the procedure is rather complicated. The authors
文摘Stereoselective synthesis by an aldol reaction between chloroacetone and aldehyde was studied using a synthesized chiral organocatalyst and triethylamine. The reaction gave α-chloro-β-hydroxy ketones in excellent yield with high anti selectivity and enantioselectivity. The chiral organocatalyst was also used in the Knoevenagel reaction, which gave α-cyano-β-hydroxy ketones at a low temperature and the usual Knoevenagel product at a high temperature. Both products were obtained in good to moderate yield with good anti selectivity in the case of α-cyano-β-hydroxy ketone derivatives.
