Investigations Concerning an Unexpected Reaction between the Dimsyl Anion ( = (Methylsulfinyl)methanide) and a γ,δ-Epoxy-ketone |
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Authors: | Ren Beerli Hans-Jürg Borschberg |
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Institution: | René Beerli,Hans-Jürg Borschberg |
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Abstract: | 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 1RS, 2RS,1′SR via NOE measurements performed on a derivative thereof. A crossover experiment in DMSO/13C2]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). |
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