Keto Oxetanes Produced from Photocycloaddition of o-Quinone and Their Thermolysis. Reaction of 9,10-Phenanthrenequinone with Internally Highly Strained Cyclic Olefins

Article abstract of DOI:10.1021/jo00318a026

The photocycloaddition reaction of 9,10-phenanthrenequinone (PQ) with alicyclic (1a-e) and bicyclic olefins (1f-l) was examined upon irradiation with visible light (>420 nm).Alicyclic olefins gave three kinds of products, keto oxetanes (2), dihydrodioxines (3), and 4, while bicyclic olefins exclusively gave keto oxetanes in fair to high yields (21-90percent).These marked differences were elucidated in terms of the s character of intermediary biradicals.Thermolysis of the five keto oxetanes obtained (2a,d,g,i,l) was examined in basic media and occurred in two different fashions (paths A and B in Scheme I).Correlation between the bond strength of the oxetane ring and the structure of intermediary biradicals is discussed.