Unexpected [4 + 2] Cycloaddition through Chromium Non-Heteroatom-Stabilized Alkynyl Carbene Complexes: Regioselective Access to Substituted 6-Azaindoles

Org Lett. 2018 Jul 6;20(13):4099-4102. doi: 10.1021/acs.orglett.8b01650. Epub 2018 Jun 27.

Abstract

A formal [4 + 2] heterocycloaddition of non-heteroatom-stabilized alkynyl carbene complexes and iminopyrroles is described. The reaction implies a totally regioselective synthesis of 6-azaindole derivatives through the formation of the pyridine ring. The mechanism of the reaction has been explored by means of density functional theory calculations, which showed a preference for the [4 + 2] cycloaddition instead of the [2 + 2] or [3 + 3] cycloadditions observed with other imines. The structure of the products also shows an unusual connectivity pattern from carbene complexes.

Publication types

  • Research Support, Non-U.S. Gov't