Photochemical reactions of 6-isobutyrylbenzocycloalken-5-ones with oxygen. Photochemistry of enolic 1,3-diketones

Abstract

6-Isobutyrylbenzocycloalken-5-ones (4) exist in the enol form in solution. The seven- and eight-membered enolic 1,3-diketones (4c) and (4d) underwent photoketonization and subsequent type II reaction to generate biradicals which were trapped by oxygen to yield the furanones (5) and (6), and the peroxide (7)[only formed from (4c)] in various solvents in the presence of oxygen, whereas the six-membered enolic 1,3-diketone (4a) underwent oxidative dehydrogenation to yield the naphthol (10). Photoreaction of the six-membered enolic 1,3-diketone (4b) in the presence of oxygen gave the naphthalenone (11) and the epoxide (12).