Photoreaction of 1-aryl 1,3-diketones. Trapping reaction of the biradicals generated in the type II reaction with oxygen

Abstract

The biradicals generated in the type II photoreaction of 1-aryl-2,4-dimethylpentane-1,3-diones (1) were trapped by oxygen to form biradical–oxygen complexes. In acetonitrile, pentane, or benzene, 5-aryl-2,2,4-trimethylfuran-3(2H)-ones (2), 6-aryl-6-hydroxy-3,3,4-trimethyl-1,2-dioxan-4-ones (3), and arene carboxylic acids (4) were produced via the biradical–oxygen complexes, whereas in alcoholic solvents, 4-aryl-4-hydroxy-3,5,5-trimethyl-4,5-dihydrofuran-2(3H)-ones (5) were produced in addition to (2), (3), and (4).