The asymmetricdirect vinylogous aldolreaction of unactivated γ-butenolide with aldehydes has been developed, giving the corresponding 5-(1′-hydroxy)butenolide derivatives in high yields (up to 93%) and enantioselectivities (up to 83% ee) under mild conditions.
Asymmetric direct vinylogous aldolreactions of furan-2(5H)-one with aldehydes in the presence of a catalytic amount of novel squaramide–sulfonamide organocatalyst resulted in the corresponding addition products with high to excellent enantioselectivities. This is the first successful report illustrating an example of highly stereoselective reactions using a squaramide–sulfonamide organocatalyst.