A highly enantioselective tandem Michael/ring‐closurereaction of α,β‐unsaturated pyrazoleamides and amidomalonates has been accomplished in the presence of a chiral N,N′‐dioxide–Yb(OTf)3 complex (Tf: trifluoromethanesulfonyl) to give various substituted chiral glutarimides with high yields and diastereo‐ and enantioselectivities. Moreover, this methodology could be used for gram‐scale manipulation
A highly efficient N,N′-dioxide/Gd(III) complex has been developed for the enantioselective conjugate addition of nitroalkanes to α,β-unsaturated pyrazolamides. Under mild reaction conditions, a series of γ-nitropyrazolamides were obtained in good to excellent yields (up to 99%) with excellent enantioselectivities (up to 99% ee). What’s more, the optically active products could be easily transformed
Organocatalytic asymmetric domino sulfa-Michael–aldol reactions of 2-mercaptobenzaldehyde with α,β-unsaturated N-acylpyrazoles for the construction of thiochromane
作者:Xiu-Qin Dong、Xin Fang、Hai-Yan Tao、Xiang Zhou、Chun-Jiang Wang
DOI:10.1039/c2cc31891a
日期:——
An efficient protocol for the direct construction of bioactive thiochromanes was developed via a catalytic asymmetric cascade sulfa-Michaelâaldol reaction of 2-mercaptobenzaldehyde with α,β-unsaturated N-acyl imides. The key to the present methodology is introducing a pyrazole moiety as H-bond acceptor, which allowed for better organization and activation and hence higher enantioselectivity.