Regioselective Functionalization of 7-Azaindole by Controlled Annular Isomerism: The Directed Metalation-Group Dance

Abstract

The regioselective functionalization of 7-azaindole by controlled annular isomerism employing a directed metalation-group migration is reported. The N7 carbamoyl azaindoles undergo regioselective metalation and quenching with an electrophile to furnish C6-substituted derivatives which, in the presence of a catalytic amount of ClCONR₂ promotes a carbamoyl group shift or dance from N7 to N1. A second directed metalation/electrophile quench sequence leads to 2,6-substituted azaindoles. Optimization of the metalation conditions for C2 and C6, separately and iteratively, is presented. Using the directed metalation group dance strategy, a late-stage deuteration of an antipsychotic drug is described. Overall, the controlled migration of the carbamoyl directing group allows multiple functionalization events of the bioactive azaindole scaffold.

Keywords: deuterium; heterocycles; lithiation; regioselectivity; synthetic methods.