Chemodivergent Synthesis of Benzofurans and 2,<scp>3‐Dihydrobenzofurans</scp> via Tandem Oxidative Annulation of Enaminones and Salicylaldehydes
Xiyan Duan, Hui Li, Junqi Wang, Kun Liu, Meixin Shi, Weidong Lian, Ran Chen, Pu Liu
Abstract
Comprehensive Summary Chemodivergent synthesis of benzofurans and 2,3‐dihydrobenzofurans has been realized. Under a reaction system consisting of DBDMH and K 2 CO 3 as promotors, controlled conditions enabled the formation of two sets of valuable heterocycles from the tandem transformation of enaminones and salicylaldehydes. The key to success was the identification of the reaction parameters, in which the imine intermediate which was formed by transient halogenation coupling and substitution processes underwent either aldol condensation/annulation or imine hydrolysis/aldol condensation. The additives NH 4 Cl or Fe 2 (SO 4 ) 3 controlled the unique selectivity of this reaction. A broad substrate scope of enaminones and salicylaldehydes has been employed in this reaction, demonstrating excellent functional group tolerance and versatility.