Photochemistry of a-diketones. I. Some photochemical reactions of 1,1,4,4-Tetramethyl-2,3-dioxotetralin

Abstract

The photochemical reactions (at λ > 3000 A) of the non-enolizable α- diketone (XIV) have been investigated in the solvents methanol, isopropanol. cyclohexane, toluene, n-butyraldehyde, methyl formate, acetic acid, dioxan, and benzene. In general, selective 1,2-addition of solvent to one carbonyl group to give a-hydroxy ketones is the predominant reaction. Competing reactions include reduction to the acyloin (XXI) and loss of carbon monoxide to give 1,1,3,3- tetramethylindanone (XVII). In methanol, two isomeric diols (XXIII) and (XXIV) were unexpectedly formed.