Abstract
Cyclopentannulation of 4-tert-butyldimethylsilyloxy-2-cyclopenten-1-one from a β-metallated dioxolane-type orthoester affords 4-tert-butyldimethylsilyloxy-8,8-ethylenedioxy-6-phenylsuiphonyl-2-oxobicyclo [3·3·0] octanes as a mixture of two diastereoisomers. Their stereochemical structures were established by NMR and x-ray analysis. The minor product possesses a cis ring fusion, the sulphonyl and the tert-butyldimethylsilyloxy groups being endo and exo, respectively. The major isomer also has a cis ring fusion but an exo position for both dimethylsilyloxy and sulphonyl groups. Both cyclopentannulation products result from an anti addition with respect to the 4-tert-butyldimethylsilyloxy group on the enone.
Published Version
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