Mechanistic studies on the atmosphere and light tuned synthesis of cyclobuta/penta[b]indoles

Abstract

The mechanism of the atmosphere and light tuned highly diastereoselective synthesis of cyclobuta/penta[b]indoles from aniline-tethered alkylidenecyclopropanes with alkynes has been investigated using kinetic and spectroscopic methods. The mechanistic studies indicate that the reaction undergoes hydroamination through aza-Michael addition, [2 + 2] cycloaddition to furnish the cyclobuta[b]indoles, and a photocatalytic process assisted by molecular oxygen to form the cyclopenta[b]indoles. Oxygen acts as a redox catalyst under household light irradiation in this process. An important triplet intermediate has been observed using time-resolved transient absorption spectroscopy.