Investigations Concerning an Unexpected Reaction between the Dimsyl Anion ( = (Methylsulfinyl)methanide) and a γ,δ‐Epoxy‐ketone

The reaction of 2,2‐dimethyl‐5‐(1,2‐epoxypropyl)cyclohexanone ( 7 ) with t ‐BuOK in DMSO furnished a small amount of 5‐(1‐hydroxyprop‐2‐enyl)‐2,2‐dimethylcyclohexanone ( 12 ) and the 4 unexpected products 13–16 which contain one to three additional C‐atoms ( Scheme 2 ). The relative configuration of the major product 1‐(4′,4′‐dimethyl‐2′,3′‐dimethylidenecyclohexyl)propane‐1,2‐diol ( 15 ) was shown to be 1 RS , 2 RS ,1′ SR via NOE measurements performed on a derivative thereof. A crossover experiment in DMSO/[ 13 C 2 ]DMSO 1:1 as solvent showed that the two additional C‐atoms of this product originate from a single molecule of DMSO ( Scheme 5 ). A tentative mechanistic scheme, consistent with all experimental observations, is proposed which involves a [2,3]‐sigmatropic rearrangement of an (allylsulfinyl)methanide 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‐1,8‐diene ( 32/33 ), readily prepared in two steps from perilla alcohol ( 30 )), which reacted as predicted by the proposed mechanism ( Schemes 9 and 10 ).