Thermal and photochemical transformations of tetraphenyl-p-dioxin and tetraphenyl-p-dithiin

Abstract

The thermal transformation of tetraphenyl-p-dioxin (1) to 2, 2, 3, 4-tetraphenylbut-3-enolide (5) has been shown to proceed through the intermediacy of cisdibenzoylstilbene (6) and a reasonable mechanism for this transformation has been suggested. The photolysis of tetraphenyl-p-dioxin, on the other hand, has been found to give a mixture of products consisting of mainly benzil and small amounts of tolan. Thermolysis and photolysis of tetraphenyl-p-dithiin (31) follow a different pathway giving rise to tetraphenylthiophene, in each case. The photo-oxygenation of tetraphenyl-p-dithiin, on the other hand, gave a mixture of products consisting of, tetraphenylthiophene, benzil and benzoic acid.