Regioselective Acceptorless Dehydrogenative Coupling of N-Heterocycles toward Functionalized Quinolines, Phenanthrolines, and Indoles

A new strategy has been developed for the oxidant and base-free dehydrogenative coupling of N-heterocycles at mild conditions. Under the action of an iridium catalyst, N-heterocycles undergo multiple sp(3) C-H activation steps, generating a nucleophilic enamine that reacts in situ with various electrophiles to give highly functionalized products. The dehydrogenative coupling can be cascaded with Friedel-Crafts addition, resulting in a double functionalization of the N-heterocycles.