T. Linker, Tobias Krüger, W. Hess
Oct 27, 2006
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Journal
Arkivoc
Abstract
Four different chiral 1,3-cyclohexadienes were synthesized and investigated in photooxygenations with singlet oxygen. A strong influence of substituents at the double bond was observed for the mode selectivity of the reactions. Phenyl and alkyl groups afford mixtures of ene and (4 + 2) products, whereas a trimethylsilyl group yields exclusively hydroperoxides, presumably due to a "large group effect". Additionally, the same diastereoselectivity for both reaction modes gives evidence for common perepoxide intermediates. Finally, the photooxygenation of a methylensulfonyl substituted 1,3-cyclohexadiene proceeds with very high diastereoselectivity, which can be explained by an intramolecular hydrogen bridge, shielding one face of the compound.