Photo-induced transformations. Part 50. The photo-Beckmann rearrangement of 3α,5-cyclo-5α-cholestan-7-one oxime, a βγ-cyclopropyl ketone oxime

Abstract

Photolysis of the title βγ-cyclopropyl ketone oxime in methanol gave 7-aza-3α,5-cyclo-B-homo-5α-cholestan-7a-one (3), 7a-aza-3α,5α-cyclo-B-homo-5α-cholestan-7-one (4), and 3α,5-cyclo-7,8-seco-5α-cholestan-7-amide (5), together with the parent ketone (2), with no olefinic products resulting from cleavage of the cyclopropane ring. The results entirely parallel those obtained in the photolysis of cyclic ketone oximes and are compatible with the suggested mechanism that the normal photo- Beckmann rearrangement of cyclic ketone oximes does not involve any intimate radical pair or diradical species resulting from α-fission. The seco-amide (5) was identified by its synthesis from methyl 3α,5-cyclo-7,8-seco-5α-cholestan-7-oate (7) prepared by the photolysis of 3α,5-cyclo-5α-cholestan-7-one in methanol.