PHOTO-INDUCED REACTIONS .16. PHOTOPINACOLIZATION OF TRIKETOINDANE DERIVATIVES

The photochemical reaction of triketoindane and its derivatives in various solvents has been investigated. It was found that hydrindantin is the major product from the photochemical reactions of, (i) triketoindane hydrate (ninhydrin) in water, (ii) the isopropyl alcohol adduct of triketoindane in isopropyl alcohol or in benzene, and (iii) the t-butyl alcohol adduct of triketoindane in t-butyl alcohol. Irradiation of an aqueous solution of alloxan hydrate also affords a corresponding pinacol, alloxanthin. During the course of the reactions (ii) and (iii), the formation of acetone was observed. The above results indicate that he photopinacolization of triketoindane does not involve photoreduction processes but proceeds by a homolytic cleavage of CO single bond in its hydrate (ninhydrin) and hemiketal (alcohol adducts) at the C-2 position. © 1968.