Iodine-catalyzed, highly atom-economic synthesis of 9-sulfenylphenanthrenes and polycyclic heteroaromatics in water

Abstract

A highly atom-economical and green synthetic method is developed for the oxidative thiolative annulation of 2-alkynyl biaryls with disulfides to synthesize a wide variety of 9-sulfenylphenanthrenes and polycyclic heteroaromatics in water. The transformation requires only a couple of inexpensive reagents, i.e., iodine as a catalyst and hydrogen peroxide (H₂O₂) as a green oxidant, to furnish the desired products in good to excellent yield. The notable advantages of this protocol over the previously developed synthetic methods are a metal-free, cost-effective, and highly atom economic (>90%) protocol, use of inexpensive reagents as the catalyst and green oxidant, use of water as the reaction medium, very high (>95%) carbon efficiency (water as the major waste), broad substrate scope, high functional group tolerance, high yields of products up to 95%, straight-forward scale-up process upto 10 g scale and significantly, low E-factor (2.25) and high EcoScale score (67).