ELECTROSYNTHESIS OF ALPHA-KETO ACETALS BY A SELENIUM-CATALYZED TRANSFORMATION OF ARYL METHYL KETONES

An indirect electrochemical pathway exists for the conversion of aryl methyl ketones to their corresponding alpha-keto acetals. Cyclic volta mmetry demonstrates that diphenyl diselenide can act as an electron me diator in the conversion because it has the lowest oxidation potential in the reaction mixture. Diphenyl diselenide, upon oxidation at the a node, forms an electrophilic phenylselenenylating reagent which can th en react with the aryl methyl ketone in the presence of methanol to fo rm the desired alpha-keto acetal. Moreover, the diphenyl diselenide ca n be used in catalytic amounts because it can be recycled by oxidizing the phenylselenenyl anion which results from the formation of the alp ha-keto acetal. Current efficiencies up to 64% were obtained without o ptmization. Low yields can be attributed to the diffusion of reactant, catalyst, and product through the diaphragm of the divided cell. (C) 1997 Elsevier Science Ltd.