A consecutive 2-step synthesis of N-unprotected polysubstituted indoles bearing an electron-withdrawing group at the C-3 position from readily available nitroarenes is reported. The protocol is based on the [3,3]-sigmatropic rearrangement of N-oxyenamines generated by the DABCO-catalyzed reaction of N-arylhydroxylamines and conjugated terminal alkynes, and delivers indoles endowed with a wide array of substitution patterns and topologies.
Keywords: 3-acylindoles; 3-aroylindoles; DABCO; N-oxyenamines; [3,3]-sigmatropic rearrangement; annulation; indol; indole-3-carboxyamides; indole-3-carboxylates; organocatalysis.