Ring-opening reactions, Paterno-Biichi reaction

Photoaddition of carboxylate esters to diphenylacetylene has also been reported. For example, irradiation of methyl p-cyanobenzoate and diphenylacetylene gave in 86% overall yield the enol ether (71), presumably a result of carbonyl n,tt triplet addition to the alkyne to form the unstable oxetene, which r idly ring opens. This complements the utility of aromatic esters in the Paterno-Biichi reaction with al-kenes as discussed by Cantrell. - ... 

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