Organocatalytic Enantioselective Synthesis of Chiral Allenes: Remote Asymmetric 1,8‐Addition of Indole Imine Methides

An organocatalytic enantioconvergent synthesis of chiral tetrasubstituted allenes is disclosed. With suitable chiral phosphoric acid catalysts, a range of racemic indole‐substituted propargylic alcohols reacted with nucleophiles to provide efficient access to a series of enantioenriched allenes with high enantioselectivities. Control experiments suggested a mechanism involving remotely controlled asymmetric 1,8‐addition of the in situ generated indole imine methide via a bifunctional transition state. An organocatalytic enantioconvergent synthesis of chiral tetrasubstituted allenes by remote asymmetric 1,8‐addition of an in situ generated indole imine methide is disclosed. With suitable chiral phosphoric acid catalysts, a range of racemic indole‐substituted propargylic alcohols reacted smoothly with nucleophiles to provide mild and efficient access to enantioenriched allenes with high enantioselectivities.