Boron trifluoride-catalyzed Diels-Alder reaction of α,β-unsaturated iminoindoles for the construction of 2-imino-3-spiroindoles.

Abstract

Despite the relevance of 2-imino-3-spiroindoles, particularly in medicinal chemistry, their synthesis still relies on highly reactive coupling partners. Herein, a novel approach to 2-imino-3-spiroindoles, involving the BF3-catalyzed Diels-Alder reaction of α,β-unsaturated iminoindoles with substituted dienes, is presented. The synthetic utility of this approach is demonstrated through the divergent derivatization of the resulting 2-imino-3-spiroindoles to produce various 3-spiroindole derivatives, including a 2-amino-3-spiroindole derivative with high stereoselectivity.