Enantioselective 2-Alkylation of 3-Substituted Indoles with Dual Chiral Lewis Acid/Hydrogen-Bond-Mediated Catalyst.

A chiral-at-metal bis-cyclometalated iridium complex combines electrophile activation via metal coordination with nucleophile activation through hydrogen bond formation. This new bifunctional chiral Lewis acid/hydrogen-bond-mediated catalyst permits the challenging enantioselective 2-alkylation of 3-substituted indoles with α,β-unsaturated 2-acyl imidazoles in up to 99% yield and with up to 98% enantiomeric excess at a catalyst loading of 2 mol %. As an application, the straightforward synthesis of a chiral pyrrolo[1,2-a]indole is demonstrated.