Direct asymmetric aldol additions of acetone/and butanone to a-ketoesters were achieved using L-proline as a chiral catalyst. Various optically active a-hydroxyesters were obtained in the yields of 43%-93% with enanti...Direct asymmetric aldol additions of acetone/and butanone to a-ketoesters were achieved using L-proline as a chiral catalyst. Various optically active a-hydroxyesters were obtained in the yields of 43%-93% with enantioselectivities up. to 81% e.e. The steric effect seems to be an important factor which influences the activity and the selectivity of the reaction. Acetone showed higher reactivity than butanone while the latter provided better enantioselectivity in some cases.展开更多
A series of coumarin-chalcone hybrid compounds and coumarins linked to pyrazoline was synthesized in good yield and short time using a simple and efficient method. This method involved the one-pot reaction of salicyla...A series of coumarin-chalcone hybrid compounds and coumarins linked to pyrazoline was synthesized in good yield and short time using a simple and efficient method. This method involved the one-pot reaction of salicylaldehyde, an α-ketoester and an aromatic aldehyde(in the case of the coumarin-chalcone derivatives) in addition to hydrazine hydrate(in the case of the pyrazolyl coumarins) in the presence of a catalytic amount of bismuth triflate [Bi(OTf)3, 5 mol%]. The synthesized compounds showed scavenging activity towards the free radical 2,2-diphenyl-1-picrylhydrazyl. All compounds were characterized using IR, 1H NMR and 13 C NMR spectroscopy.展开更多
A Lewis acid-catalyzed[4+2]cycloaddition of 3-alkyl-2-vinylindoles withβ,γ-unsaturatedα-ketoesters has been established in the presence of Sc(OTf)3,which afforded a series of indole-containing pyran derivatives in ...A Lewis acid-catalyzed[4+2]cycloaddition of 3-alkyl-2-vinylindoles withβ,γ-unsaturatedα-ketoesters has been established in the presence of Sc(OTf)3,which afforded a series of indole-containing pyran derivatives in generally good yields(up to 90%yield)with excellent diastereoselectivities(up to >95:5 dr)under mild conditions.This approach not only enriches the chemistry of 3-alkyl-2-vinylindoles,but also has provided an atom-economic method for the synthesis of indole-containing pyran derivatives with potential bioactivity.展开更多
Interesting and diverse tautomerizations and intramolecular hydrogen bondings of the chiral α-nitroester, α-nitrosoester and α-ketoester are described and rationally interpreted.
文摘Direct asymmetric aldol additions of acetone/and butanone to a-ketoesters were achieved using L-proline as a chiral catalyst. Various optically active a-hydroxyesters were obtained in the yields of 43%-93% with enantioselectivities up. to 81% e.e. The steric effect seems to be an important factor which influences the activity and the selectivity of the reaction. Acetone showed higher reactivity than butanone while the latter provided better enantioselectivity in some cases.
基金Sohag University in Egypt for supporting and facilitating this study
文摘A series of coumarin-chalcone hybrid compounds and coumarins linked to pyrazoline was synthesized in good yield and short time using a simple and efficient method. This method involved the one-pot reaction of salicylaldehyde, an α-ketoester and an aromatic aldehyde(in the case of the coumarin-chalcone derivatives) in addition to hydrazine hydrate(in the case of the pyrazolyl coumarins) in the presence of a catalytic amount of bismuth triflate [Bi(OTf)3, 5 mol%]. The synthesized compounds showed scavenging activity towards the free radical 2,2-diphenyl-1-picrylhydrazyl. All compounds were characterized using IR, 1H NMR and 13 C NMR spectroscopy.
基金This work was supported by National Natural Science Foundation of China(No.21772069)Natural Science Foundation of Jiangsu Province(No.BK20201018)+1 种基金Undergraduate Students Project of Jiangsu Province(No.202010320050Z)High-level Innovative and Entrepreneurial Talents Introduction Plan of Jiangsu Province,and Natural Science Foundation of JSNU(No.19XSRX010).
文摘A Lewis acid-catalyzed[4+2]cycloaddition of 3-alkyl-2-vinylindoles withβ,γ-unsaturatedα-ketoesters has been established in the presence of Sc(OTf)3,which afforded a series of indole-containing pyran derivatives in generally good yields(up to 90%yield)with excellent diastereoselectivities(up to >95:5 dr)under mild conditions.This approach not only enriches the chemistry of 3-alkyl-2-vinylindoles,but also has provided an atom-economic method for the synthesis of indole-containing pyran derivatives with potential bioactivity.
文摘Interesting and diverse tautomerizations and intramolecular hydrogen bondings of the chiral α-nitroester, α-nitrosoester and α-ketoester are described and rationally interpreted.
