Enantiodivergent RhIII -Catalyzed Synthesis of Imidazo[1,5-a]indole

Abstract

A general and efficient [4+1]-annulation of indole-N-carboxamide with cyclopropene has been accomplished in the presence of chiral cyclopentadienyl rhodium catalyst for the synthesis of imidazo[1,5-a]indole. Introduction of one bulky substituent in the chiral cyclopentadienyl ligand without altering the chirality of binaphthyl fragment reverses enantioselectivity of the catalytic reaction. Important features of the method include ligand-controlled enantiodivergence, a base-free and redox-neutral approach, synthetic application, and isolation of the potential intermediate.