Reactions of cyclic oxalyl compounds - 32. : Photochemical and thermal 2+2-cycloadditions of diphenylketene and diphenylketen-N-methyl-phenyl-imine to five-membered heterocyclic 23-diones

Abstract The heterocyclic 2,3-diones 1 – 3 have been found to undergo photochemical and thermal 2 + 2-cycloaddition reactions via their 3-carbonyl group to diphenylketene and the diphenylketen-N-(4-methylphenyl)-imine. These reactions afford rearranged cycloadducts as well as 2 + 2-cycloreversion products.