The insertion and extrusion of heterosulfur bridges. IX: Sulfur bridging in 2‐phenylnaphthalene

Sulfur bridging of 2‐phenylnaphlhalene (3) to form benzo[b ]naphtho[2,1‐d]thiophene (5) (main product) and the isomeric benzo[b]naphtho[2,3‐d]thiophene (4) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide‐molybdic oxide‐alumina (CMA‐1) catalyst at 450–630° in a flow system (maximum yield 33% at 500°). The low yield is ascribed to decompositions of both 4 and 5 under reaction conditions.