Photo-induced transformations. Part 63. Photorearrangement of 17β-acetoxy-4,4-dimethylestr-5-en-3β-yl nitrite with monochromatic light

Abstract

Photolysis of 17β-acetoxy-4,4-dimethylestr-5-en-3β-yl nitrite (4) with 377 nm monochromatic light gave (E)17β-acetoxy-4,4-dimethyl-6-oxo-3,4-secoestr-4-en-3-al 6-oxime (9), its (Z)-isomer (10), and 17β-acetoxy-4-hydroxy-4a,4a-dimethyl-4-aza-A-homoestr-5-en-3-one (8). Nitric oxide generated from the nitrite (4) thus combines predominantly with the C-6 terminus of an allyl radical intermediate formed by a β-scission of the corresponding oxyl radical. The reverse regioselectivities observed in the radical combinations between the allyl radical (B) and nitric oxide, generated from the nitrite (4) and from 4,4-dimethylcholest-5-en-3β-yl nitrite (2), are discussed.