The reaction of 2,2-dimethyl-5-(l,2-epoxypropyl)cyclohexanone (7) with t -BuOK in DMSO furnished a small amount of 5-( l-hydroxyprop-2-enyl)-2,2-dimethylcyclohexanone (12) and the 4 unexpected products 1>16 which contain one to three additional C-atoms (Scheme 2). The relative configuration of the major product 1-(4',4-dimethyl-2',:~'-dimcthylidenecyclohexyl)propane-1,2-diol(l5) was shown to he 1 RS,2RS, 1'SR via NOE measurements performed on a derivative thereof. A crossover experiment in DMSO/['3C,]DMS0 1 :I as solvent showed that the two additional C-atoms of this product originate from a single molecule of DMSO (Scheme 5). A tentative mechanistic schemc, consistent with all experimental observations, is proposed which involves a [2,3]-sigmatropic rearrangement of an (allylsu1finyl)methauide to a sulfenic acid as one of the key steps (V + 24, Scheme 8). We corroborated part of this hypothetic scheme by taking recourse to a model compound (7-(methylsulfinyl)-p-mentha-l&diene (32/33), readily prepared in two steps from perilla alcohol (30)), which reacted as predicted by the proposed mechanism (Schemes 9 and 10).