Cascade alkyl migration in 2-alkynylanilines for the synthesis of benzenoid ring multi-functionalized indoles

Cascade alkyl migration of 2-alkynylanilines via an aromaticity destruction and reconstruction process is reported. The first alkyl migration is triggered by generation of a dearomatized arenium species via oxidation and cyclization, and the second is driven by the force to restore the aromaticity of rearrangement products. The reaction gave rise to a range of multi-functionalized indoles. Cascade alkyl migration of 2-alkynylanilines via an aromaticity destruction and reconstruction process for the synthesis of 6,7-fused indoles was reported.