A novel acylative ring cleavage of benzothieno[3,2-b]pyran-4-ols: application to the synthesis of dibenzothiophenes and fused-ring derivatives

Abstract

The benzothienopyranols 3, readily available from the ketone 1, are transformed to the carbamates 5 on treatment with N,N-dimethylcarbamoyl chloride, subsequent thermal electrocyclisation provides access to dibenzothiophene derivatives 6 and 11–13.