Synthesis of benzo[<i>b</i>]chalcogenophenes fused to selenophenes <i>via</i> intramolecular electrophilic cyclization of 1,3-diynes
Paola S. Hellwig, Jonatan S. Guedes, Angelita M. Barcellos, Raquel G. Jacob, Cláudio C. Silveira, Eder J. Lenardão, Gelson Perin
Abstract
We describe herein an alternative and transition-metal-free procedure for the access of benzo[b]chalcogenophenes fused to selenophenes via intramolecular cyclization of 1,3-diynes. This efficient protocol involves a double cyclization of 1,3-diynyl chalcogen derivatives promoted by the electrophilic species of organoselenium generated in situ by the oxidative cleavage of the Se-Se bond of dibutyl diselenide using Oxone® in acetonitrile as solvent in an open-flask at 80 °C. In this study, 15 selenophenes with broad substrate scope were prepared in moderate to excellent yields (55-98%) with short reaction times (0.5-3.0 h).