Ouverture acide de bis-(alkylthio)-2,2 cyclopropanols: Une nouvelle methode d'homologation et d'extension de cycle

Solvolysis of 2,2-bis(alkylthio) cyclopropanols by aqueous trifluoroacetic acid occurs easily to yield conjugated α-alkylthio emone and/or β-oxo-S alkylthioesters. The formation of the former most probably involves a disrotary rink opening concerted with the departure of the alkylthio group trans to hydoxyl, or, alternatively with monocyclic compounds, a 1,2-emigration of the same akylthio group synchronous with OH departure and cleavage. A nucleophilic substitution at the thioacetal centre followed by oxidative opening of the intermediate cyclopropandiol accounts for the formation latter. In 70% aqueous perchloric acid the formation of enones in favoured.