Cyclization of 2-Biphenylthiols to Dibenzothiophenes under PdCl2/DMSO Catalysis.

A palladium-catalyzed synthesis of dibenzothiophenes from 2-biphenylthiols is described. This highly efficient reaction employs a simple PdCl2/DMSO catalytic system, in which PdCl2 is the sole metal catalyst and DMSO functions as an oxidant and solvent. This transformation has broad substrate scope and operational simplicity and proceeds in high yield. The synthetic utility was demonstrated by the facile synthesis of helical dinapthothiophene 3 and an eminent organic semiconductor DBTDT 4. Importantly, highly strained trithiasumanene 5, a buckybowl of considerable synthetic challenge, was observed under this catalytic system.