Auxiliary controlled singlet-oxygen ene reactions of cyclohexenes |
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Authors: | Werner Fudickar |
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Affiliation: | Department of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam/Golm, Germany |
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Abstract: | The photooxygenation of homochiral cyclohexene ketals, which are easily available from 2-cyclohexenone and l-tartrates, affords hydroperoxides and after reduction the corresponding allylic alcohols in good yields and high regioselectivities. This can be rationalized by electronic repulsions in a perepoxide intermediate and provides evidence for unfavorable 1,3 diaxial interactions with a dioxolane oxygen atom. Only low stereoselectivities were observed, due to the flexibility of the cyclohexene ring. However, the diastereomers could be separated and after cleavage of the auxiliary, 4-hydroxy-2-cyclohexen-1-one was isolated in enantiomerically pure form, which can serve as a building block for natural product synthesis. |
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Keywords: | Singlet oxygen Auxiliary control Regioselectivity Stereoselectivity |
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