Insertion of Benzyne into a Bi–S Bond: A New Synthetic Route to ortho-Functionalized Bismuthanes and Its Application to the Synthesis of Dibenzothiophene

ortho-Arylthio triarylbismuthanes [2-(Ar′S)C6H4]nBiAr3–n have been conveniently synthesized by insertion of benzyne into the bismuth–sulfur bond of (Ar′S)nBiAr3–n (n = 1, 2). A similar insertion takes place when a homologous antimony congener is used, but no reaction is observed with its phosphorus analogue. This suggests a clear difference in the bond strength between pnictogen–sulfur bonds. The carbon–bismuth bond of [2-(2-BrC6H4S)C6H4]nBiAr3–n undergoes Pd-catalyzed intramolecular cross-coupling to produce dibenzothiophene in good yield. An X-ray crystallographic study of 2-(2-BrC6H4S)C6H4BiTol2 (Tol = 4-MeC6H4) reveals that this molecule is present in a dimeric structure, where the six heteroatoms including bismuth, sulfur, and bromine are linked through the nonbonded intramolecular bismuth–sulfur and intermolecular sulfur–bromine and bromine–bromine interactions.