Reactions of Vinylcyclopropane Epoxides with Samarium and Phosphorus Iodides

Abstract

Samarium diiodide on one hand, diphosphorus tetra­iodide, and phosphorus triiodide on the other, react with vinyl­cyclopropane epoxides to produce either allylic alcohols or vinylcyclopropanes resulting from cyclopropane ring-opening or deoxygenation of the epoxide, respectively.

Key words

deoxygenation - epoxides - olefins - radical reaction - ring-opening

References

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• 4a

  They result from the epoxidation of the corresponding vinyl cyclopropanes with m-chloro-perbenzoic acid in CH₂Cl₂.

• 4b

  Ethyl oxido-chrysanthemate used in this work has been synthesized by epoxidation of a 83:17 mixture of trans/cis-stereoisomers of ethyl chrysanthemate (93% yield).

• For related transformations using different strategies which are effectively used on large scale at the Sumitomo Company:
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3

This reaction leads, when carried out in THF in the absence of t-BuOH at 20 °C for 150 h, to the allyl alcohol 3a (7% yield, compare to Scheme [1] , entry a) or to an intractable mixture of compounds if instead performed at reflux.

5

One of the referee made the following observation which is in agreament with the author view: it is paradoxal that the phenyl group, which is a better spin delocalized entity than methyl carboxyl, methyl or methoxymethyl groups, is the one which leads to the lower amount of ring-opened product.