Organocatalytic Asymmetric 3-Allenylation of Indoles via Remote Stereocontrolled 1,10-Additions of Alkynyl Indole Imine Methides

A chiral phosphoric acids catalyzed regio- and enantioselective 1,10-conjugate addition of 2-arylindoles to alkynyl indole imine methides formed in situ from alpha-(6-indolyl)propargylic alcohols has been developed. With the established system, organocatalytic asymmetric 3-allenylation of indoles was realized, affording a broad scope of axially chiral tetrasubstituted allenes bearing two indole motifs in high yields with stereoselectivities. Importantly, the organocatalytic remote stereocontrolled strategy disclosed the asymmetric 3-allenylation of indoles via 1,10-conjugate addition for the first time.