Regioselectivity of the Cyclization of Dithiol Esters. An Alternative Route to Cyclic γ-Substituted β-Keto Thiolesters

References

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• See ref. 4 for examples of synthetic applications of the β-keto thiolester group
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• All new compounds were adequately characterized by spectro-scopic methods and by exact mass measurement and/or elemental analysis. Yields given are for isolated products
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• A similar rationale has been used to account for the regio-selectivity observed for Dieckmann condensation.2
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• Prepared in situ using sodium hydride
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• This compound was prepared in 80% yield by the alkylation of 2-ethylthiocarbonyl cyclohexanone with ethyl bromoacetate using the reported procedure.4
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• It is pertinent to point out that similar isomerization has been occasionally used for the preparation of the γ-alkyl β-keto esters from the α-substituted isomers.11,12 These transformations however require longer reaction time under considerably more drastic conditions (alkoxide in refluxing alcohol or xylene) and often suffer from operational complexity and/or low yield of products
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• We are grateful to Natural Science and Engineering Research Council of Canada and the University of Alberta for financial support
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