Copper-catalyzed [4+1] cycloannulation of 2-aminochalcones with ethyl diazophenylacetates via ester rearrangement

A copper-catalyzed [4+1] cycloannulation of 2-aminochalcones with ethyl 2-diazo-2-phenylacetates, along with migration of the ester group, has been developed in this study, providing a simple and effective method for the synthesis of various indole heterocyclic compounds. This strategy displayed a wide range of substrates and good tolerance of functional groups. Mechanistic studies show that the reaction occurred in a step-by-step sequence, which includes carbine N-H insertion, intramolecular hydroxaldehyde-type condensation and 1,2-acyl migration.