Organocatalytic Enantioselective 1,10-Addition of Alkynyl Indole Imine Methides with Thiazolones: An Access to Axially Chiral Tetrasubstituted Allenes

ABSTRACT: An asymmetric organocatalytic remote 1,10-addition of alkynyl indole imine methides generated in situ from alpha-(6indolyl) propargylic alcohols with thiazolones has been developed for the first time, affording axially chiral tetrasubstituted allenes featuring vicinal sulfur-containing quaternary carbon stereocenters in high yields with excellent stereoselectivities. The representative scale-up reaction and transformations of the 1,10-adduct were examined. The reaction mechanism was expounded by control experiments and DFT calculations.

Automated summary

In this study, an asymmetric organocatalytic reaction was developed for the first time, enabling the remote 1,10-addition of alkynyl indole imine methides generated in situ from alpha-(6indolyl) propargylic alcohols with thiazolones. The reaction yielded axially chiral tetrasubstituted allenes featuring vicinal sulfur-containing quaternary carbon stereocenters, with high yields and excellent stereoselectivities. The scalability of the reaction and the chemical transformations of the 1,10-adduct were also investigated. Control experiments and DFT calculations were conducted to elucidate the reaction mechanism.