A facile synthesis of dithieno[3,2-b:6,7-b]fluorenes via a tandem annulation–reduction

Abstract

A concise and facile synthesis of 2,8-disubstituted dithieno[3,2-b:6,7-b]fluorenes starting from 2,7-dihydroxyfluorenone is reported. The key step involved is the tandem annulation–reduction of a 3,6-dichloro-2,7-di(alkynyl)fluorenone using Na₂S·9H₂O as a sulfur surrogate and reductant. The final dithiophene-fused fluorenes are obtained in reasonable yields (23–43%).