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

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Publikace nespadá pod Filozofickou fakultu, ale pod Přírodovědeckou fakultu. Oficiální stránka publikace je na webu muni.cz.
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KAMMATH Viju Balachandran ŠOLOMEK Tomáš NGOY Bokolombe Pitchou HEGER Dominik KLÁN Petr RUBINA Marina GIVENS Richard

Rok publikování 2013
Druh Článek v odborném periodiku
Časopis / Zdroj Journal of Organic Chemistry
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
www http://pubs.acs.org/doi/abs/10.1021/jo300850a
Doi http://dx.doi.org/10.1021/jo300850a
Obor Organická chemie
Klíčová slova Photochemistry; hydroxyphenacyl; ring contraction
Popis 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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