Copper‐Mediated Relay Strategy Using Chlorination/Oxidation: An Effective Synthesis of Functionalized Coumarin Derivatives

Abstract

AbstractChromene‐fused heterocyclic compounds have shown fascinating biological and physiochemical properties and thus, the design and development of chromene‐fused heterocyclic molecules is of significant interest in the field of synthetic organic chemistry. We report an innovative ligand‐ and additive‐free synthetic approach of 4‐(phenylethynyl)‐2H‐chromene‐3‐carbaldehyde with phenylacetylenes has been described through sequential chlorination, benzannulation, benzylic sp3 C−H bond functionalization, and ether oxidation for the formation of chloro‐substituted‐9‐phenyl‐6H‐benzo[c]chromen‐6‐ones with readily available chemicals under one‐pot, base‐free conditions using CuCl2 as sustainable catalyst. In this regioselective approach, we defined a reasonably longer cascade, which reveals the multiple role of chlorine as chlorine supplier, Lewis acid catalyst and oxidation rate promoter that tolerates a broad substrate scope and allows good product yields. The authenticated mechanism proceeds in a cascading fashion through the formation of multiple bonds.