One-pot Synthesis of Benzo[b]thiophenes and Benzo[b]selenophenes from o-Halo-Substituted Ethynylbenzenes: Convenient Approach to Mono-, Bis-, and Tris-Chalcogenophene-Annulated Benzenes

A convenient one-pot procedure for the synthesis of benzo[b]thiophenes and selenophenes from readily available o-halo-ethynylbenzene precursors is described. Regardless of the substituent on the acetylene terminus or the number of cyclization moieties on the precursors, various benzo[b]thiophenes and selenophenes, including not only the parent, alkyl-, and phenyl-substituted derivatives but also benzo[1,2-b:4,5-b']dithiophenes and diselenophenes and benzo[1,2-b:3,4-b':5,6-b'']trithiophenes and triselenophenes can be prepared in good to high yields.