| Research Abstract |
(1) photosensitized Ring-Cleavage Reaction of 2,2-Diaryloxetanes by Aromatic Nitriles. Photosensitized reactions of 2,2-diaryloxetanes by electron acceptors, which give such ring-cleavage products as substituted benzophenones and alkenes, have been investigated. Quantum yields for the ring cleavage vary with substituents on both the aryl group and oxetane ring. The quantum yield increases with increase in electron-donating ability of the oxetane. The limiting quantum yields in the case of 1,4-dicyanonaphthalene-photosensitized reaction of 2,2-di-p-tolyl- or 2,2-bis(p-methoxyphenyl)-3,3,4-trimethyloxetane exceed unity.
(2) Photochemical Reactions of 2,2-Diaryloxetanes in the Presence of Electron Donor. Photochemical ring-cleavage reactions of 2,2-diaryloxetanes in the presence of triethyl-amine occurred to give 1,1-diarylethene selectively.
(3) Ring-Cleavage Reactions of 1,2-Diarylcyclobutanes. We found that aryl-substituted cyclobutanes reveal remarkable structure dependences in photochemical and thermal ring-splitting reactions. The reactivities of cyclobutanes are explic-itly classified into two groups of "reactive" and "unreactive" cyclobutances. Therefore, molecular structures of diarylcyclobutanes have been determined by single-crystal X-ray analyses. Although the distances and angles of cyclobutane rings are relatively normal, the torsional angles between the aryl ring and the plane involving the ipso carbon and the aryl-substituted carbons of cyclobutane ring are close to 90゜ in the cases of "reactive" cyclobutanes but vary small in the cases of "unreactive" cyclobutanes.
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