Photochemische Reaktionen. 50. Mitteilung [1]. Zur Photochemie von gesättigten β‐Ketosulfiden II . Synthese von 6‐Hydroxy‐2‐thia‐7‐oxa‐isotwistan

The results of the ultraviolet irradiation of the saturated β‐ketosulfide 2 are discussed. The photochemistry of 2 is characterized by the occurrence of two primary photoprocesses. Their efficiences depend markedly on the excited transition, (charge‐transfer)‐ or ( n → π*)‐excitation, respectively. In methanol solution (charge‐transfer)‐excitation leads almost exclusively to product 7 , due to (C α – S)‐fission, and ( n → π*)‐excitation to nearly equal amounts of 7 and of products 4 and 6 which result from α‐cleavage. On solvent sensibilization in benzene products 4, 6, 7 and the still unidentified product 5 2 are formed. Compounds 4 and 6 have been described earlier [2]. The structure elucidation of 7 is reported in this paper. Acid‐induced transformation of 7 yields the dihetero‐isotwistane 15 .