Journal of the American Chemical Society, Vol.137, No.1, 122-125, 2015
Enantioconvergent Synthesis of Functionalized gamma-Butyrolactones via (3+2)-Annulation
A dynamic kinetic resolution of beta-halo alpha-keto esters in an asymmetric homoenolate reaction is described. A chiral N-hetereocyclic carbene catalyzes the a(3) -> d(3)-umpolung addition of alpha,beta-enals to racemic alpha-keto esters, forming gamma-butyrolactones with three contiguous stereocenters. The addition occurs with high regio-, diastereo-, and enantiocontrol. This methodology constitutes an intermolecular DKR process to set three stereocenters during the key bond forming event.