In a 1-liter stainless steel autoclave equipped with stirrer were placed 51.6 g (0.150 mole) of 1,2-diphenyl-4-m-anisylbutane-1,4-dione, 100 ml of xylene and 30 g (0.0675 mole) of phosphorus pentasulfide. The autoclave was cooled in Dry Ice and charged with 130 g (3.81 moles) of hydrogen sulfide. The mixture was then heated and stirred 235 minutes at 154°-177° C. (1120-1320 psig). The vessel was cooled to room temperature. The hydrogen sulfide was vented into a sodium hydroxide solution. The residue was treated with 150 ml of absolute ethanol to destroy excess phosphorus sulfides. Washing the product with another 330 ml of ethanol gave 32 g (62.3%) of crude product. Recrystallization from 50 ml of toluene and 150 ml of ethanol gave 19.8 g (38.5%) of pure 2,3-diphenyl-5-m-anisylthiophene, m.p. 100°-102° C.
