Enantioselective Propargylation of Oxonium Ylide with α-Propargylic-3-Indolymethanol: Access to Chiral Propargylic Indoles.

An enantioselective three-component reaction of α-propargylic-3-indolymethanol with diazoindolinone and alcohol under cocatalysis of Rh(II) and chiral phosphoric acid (CPA) has been reported. It proceeds through the regio- and enantiospecific addition of the in situ formed oxonium ylide to the α-propargylic indole iminium ion that is generated from 3-indolyl propargylic alcohol with CPA. This work features an asymmetric counteranion-directed propargylation of oxonium ylide, and provides an efficient access to chiral propargylic indole derivatives with high yields and enantioselectivities.