InCl-Catalyzed One-Pot Synthesis of Pyrrolo/Indolo- and Benzooxazepino-Fused Quinoxalines.

In this paper, we describe an efficient InCl-catalyzed two-component reaction of 1-(2-aminophenyl)pyrroles/indoles and 2-propargyloxybenzaldehydes for the direct synthesis of 12b-benzo[6,7]1,4-oxazepino[4,5-]pyrrolo/indolo[2,1-]quinoxalines. This high atom- and step-economical one-pot process generates three new C/N-C bonds in a single synthetic operation, resulting in the formation of new six- and seven-membered heterocyclic rings. The easy availability of the starting materials, the use of the relatively inexpensive indium catalyst, and the good substrate scope are the salient features of this strategy. The proposed mechanistic pathway involves imine formation, two consecutive cyclizations via electrophilic aromatic substitution and nucleophilic addition reactions, and the H shift step.