The insertion and extrusion of heterosulfur bridges. VIII. Dibenzothiophene from biphenyl and derivatives

Sulfur bridging of biphenyl (4), 4‐methylbiphenyl, and the biphenylthiol isomers (7) to yield dibenzothiophene (3) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide‐molybdic oxide‐alumina (CMA‐1) catalyst at 450° in a flow system. Alumina also catalyzes a number of these transformations. The possibility that compounds 7 (especially the 2‐isomer) are intermediates in the conversion 4 → 3 is noted.