Stereospecific positional alkene isomerization enables bidirectional central-to-axial chirality transfer.

Abstract

Positional alkene isomerization is a powerful reaction for moving a C=C bond from one position to another. This transformation, as a high atom-economy and easy-to-handle process, has gained increasing prominence in both organic and material chemistry. Despite these advances, the stereospecific positional alkene isomerization to achieve bidirectional chirality transfer remains challenging. We report herein a bidirectional stereospecific positional alkene isomerization of chiral exocyclic alkene analogues by achiral Lewis base catalysis. By using this central-to-axial chirality transfer strategy, the axially chiral N-indolylquinolinones can be readily obtained from one configuration to two different configurations. Mechanistic studies indicated that the competitive alkene isomerization and Michael/retro-Michael addition would affect the conformation of exocyclic alkenes, thus achieving the bidirectional central-to-axial chirality transfer. In addition, combining the asymmetric allylic substitution-isomerization and photocatalytic Z/E isomerization, all eight stereoisomers of diaxially chiral quinolinones could be easily obtained in high enantioselectivities and diastereselectivities.