The photochemistry of 2-acetoxynaphthalen-1(2H)-ones

Abstract

The photochemistry of the 2-acetoxynaphthalen-1(2H)-ones (4), (13), (20), and (26) has been examined. In each case there was rapid formation of a mixture of products, which arose either by homolytic dissociation of the C–OAc bond or by rearrangement involving acetoxy group migration. Two types of rearrangement were observed. The first involved 1,2-acetoxy group migration with C(2)–C(4) bond formation to give the dihydrocyclopropindenones (7), (15), (22), and (28). This reaction, which is stereospecific, yields the endo-6-acetoxy isomer only, and it is thought to proceed by a concerted non-ionic pathway. The second rearrangement, which is believed to have an ionic mechanism, resulted in formation of 3-acetoxynaphthols from naphthalenones (4) and (26), and 4-acetoxynaphthols from naphthalenones (13) and (20), in which the 3-position is substituted.