Organocatalytic asymmetric domino sulfa-Michael-aldol reactions of 2-mercaptobenzaldehyde with α,β-unsaturated N-acylpyrazoles for the construction of thiochromane

An efficient protocol for the direct construction of bioactive thiochromanes was developed via a catalytic asymmetric cascade sulfa-Michael-aldol reaction of 2-mercaptobenzaldehyde with alpha,beta-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.