Co(III)-Catalyzed, Internal and Terminal Alkyne-Compatible Synthesis of Indoles

A Co­(III)-catalyzed, internal and terminal alkyne-compatible indole synthesis protocol is reported herein. The N-amino (hydrazine) group imparts distinct, diverse reactivity patterns for directed C–H functionalization/cyclization reactions. Notable synthetic features include regioselectivity for a meta-substituted arylhydrazine, regioselectivity for a chain-branched terminal alkyne, formal incorporation of an acetylenic unit through C2-desilylation on a C2-silylated indole derivative, formal inversion of regioselectivity through consecutive C3-derivatization and C2-desilylation processes, and formal bond migration for a linear-chain terminal alkyne.