The Pivotal Role of Oxyallyl Diradicals in Photo-Favorskii Rearrangements: Transient Spectroscopic and Computational Studies
| Authors | |
|---|---|
| Year of publication | 2013 |
| Type | Article in Periodical |
| Magazine / Source | Journal of the American Chemical Society |
| MU Faculty or unit | |
| Citation | |
| Web | http://pubs.acs.org/doi/abs/10.1021/ja407588p |
| Doi | http://dx.doi.org/10.1021/ja407588p |
| Field | Organic chemistry |
| Keywords | Photochemistry; Biradicals; Rearrangement |
| Description | The photochemistry of the hydroxybenzocycloalkanonyl derivatives 6b-e provides the triplet oxyallyl diradicals (3)9 that decay via intersystem crossing to their more stable singlet isomers (1)9. Vibrationally resolved transient spectra of 39 were recorded by pump-probe 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 (1)9a-e determine the product ratios due to their relative abilities to form the corresponding cyclopropanones 10. The smallest five-membered derivative, (1)9b, 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. |
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