A Photo-Favorskii Ring Contraction Reaction: The Effect of Ring

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Issue Date
2013-03-01Author
Kammath, Viju Balachandran
Šolomek, Tomáš
Ngoy, Bokolombe Pitchou
Heger, Dominik
Klán, Petr
Rubina, Marina
Givens, Richard S.
Publisher
American Chemical Society
Type
Article
Article Version
Scholarly/refereed, author accepted manuscript
Rights
This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Journal of Organic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jo300850a.
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Show full item recordAbstract
The effect of ring size on the photo-Favorskii induced ring-contraction reaction of the hydroxybenzocycloalkanonyl acetate and mesylate esters (7a–d, 8a–c) has provided new insight into the mechanism of the rearrangement. By monotonically decreasing the ring size in these cyclic derivatives, the increasing ring strain imposed on the formation of the elusive bicyclic spirocyclopropanone 20 results in a divergence away from rearrangement and toward solvolysis. Cycloalkanones of seven or eight carbons undergo a highly efficient photo-Favorskii rearrangement with ring contraction paralleling the photochemistry of p-hydroxyphenacyl esters. In contrast, the five-carbon ring does not rearrange but is diverted to the photosolvolysis channel avoiding the increased strain energy that would accompany the formation of the spirobicyclic ketone, the “Favorskii intermediate 20”. The six-carbon analogue demonstrates the bifurcation in reaction channels, yielding a solvent-sensitive mixture of both. Employing a combination of time-resolved absorption measurements, quantum yield determinations, isotopic labeling, and solvent variation studies coupled with theoretical treatment, a more comprehensive mechanistic description of the rearrangement has emerged.
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Citation
Kammath, V. B., Šolomek, T., Ngoy, B. P., Heger, D., Klán, P., Rubina, M., & Givens, R. S. (2013). A Photo-Favorskii Ring Contraction Reaction: The Effect of Ring Size. The Journal of Organic Chemistry, 78(5), 1718–1729. http://doi.org/10.1021/jo300850a
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