Photochemistry of Diaryl Vicinal Tetraketones and Chemistry of Intermediate (Aroyloxy)arylketenes1
journal contributionposted on 22.01.1998 by Mordecai B. Rubin, Marina Etinger, Moshe Kapon, Eric C. Krochmal, Raisa Monosov, Stephan Wierlacher, Wolfram Sander
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Photolysis of diaryl vic-tetraketones results in formation of tricyclic-γ-lactones 3 and 4 with low quantum but high chemical yield. (Aroyloxy)arylketenes and carbon monoxide are the initial photochemical products of these photolyses. Subsequent reaction of ketene with ground-state tetraketone results in formation of the observed photoproducts via intermediate β-lactones. The latter are formed with a high degree of stereoselectivity. The failure of a cyclic tetraketone to react is attributed to its inability to undergo the cyclic mechanism proposed for formation of ketenes from tetraketones. Dimesityl and di-tert-butyl tetraketones react by a competing intramolecular hydrogen atom transfer mechanism. Dimerization of (benzoyloxy)phenylketene and its reactions with a number of tetraketones are described.