The Pivotal Role of Oxyallyl Diradicals in Photo-Favorskii Rearrangements: Transient Spectroscopic and Computational Studies

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• 作者：Tom谩拧 艩olomek ; Dominik Heger ; Bokolombe P. Ngoy ; Richard S. Givens ; Petr Kl谩n
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：October 9, 2013
• 年：2013
• 卷：135
• 期：40
• 页码：15209-15215
• 全文大小：378K
• 年卷期：v.135,no.40(October 9, 2013)
• ISSN：1520-5126

文摘

The photochemistry of the hydroxybenzocycloalkanonyl derivatives 6b鈥?b>e provides the triplet oxyallyl diradicals ³9 that decay via intersystem crossing to their more stable singlet isomers ¹9. Vibrationally resolved transient spectra of ³9 were recorded by pump鈥損robe spectroscopy and laser flash photolysis. It was found that the ring strain dependent rate of intersystem crossing is the rate-limiting step in the formation of photo-Favorskii or solvolysis reaction products in water. The reactivities of open-shell singlet oxyallyls ¹9a鈥?b>e determine the product ratios due to their relative abilities to form the corresponding cyclopropanones 10. The smallest five-membered derivative, ¹9b, represents the first example of an oxyallyl diradicaloid that cannot form cyclopropanone 10b or the isomeric allene oxide 13b; instead, it is eventually trapped by water to form the sole solvolysis product 12b. Our observations provide a comprehensive overview of the role of oxyallyl diradicals in reaction mechanisms and offer a new strategy to stabilize open-shell singlet diradicals.