The Decarbonylation of Diphenyl Triketone1

Abstract

One of the characteristic reactions of α-polycarbonyl compounds is their tendency to undergo “decarbonylation” with the formation of a compound with one less carbon atom and carbon monoxide or carbon dioxide. An important synthetic example of this type of reaction is the thermal decomposition of oxalylacetic esters which yield the corresponding malonic esters and carbon monoxide. The related thermal decarbonylation of ethyl pyruvate has been studied by Calvin and Lemmon. These workers found that ethyl pyruvate-2-C^(14) gave only non-radioactive carbon monoxide which result indicates that the ester carbonyl group is lost exclusively. The decarbonylation reactions of diphenyl triketone (diphenylpropane-1,2,3-trione, I) are particularly interesting since they have been reported to be brought about by a wide variety of agents such as bases, acids, cupric acetate, aluminum chlorides and sunlight. In the present investigation, a study was made of some of these reactions using C^(14)-labeled diphenyl triketones in order to determine whether the center or side carbonyl groups are lost in the decarbonylation process.