Construction of 2,3-quaternary fused indolines from alkynyl tethered oximes and diaryliodonium salts through a cascade strategy of N-arylation/cycloaddition/[3,3]-rearrangement

A variety of 2,3-quaternary fused indolines could be prepared in good yields with high diastereoselectivity from alkynyl tethered oximes and diaryliodonium salts under mild metal-free conditions. The reaction initially goes through a selective N-arylation to provide alkynyl tethered nitrones and regioselectively undergoes an intramolecular (3 + 2) cycloaddition followed by a [3,3]-sigmatropic rearrangement to afford 2,3-quaternary fused indolines in a one-pot fashion. The method features easily available cheap materials, multiple bond formation, gram scalable preparation and diversity of fused indoline scaffolds.