Allyl sulfoxides transposition reaction

During the final stages of the total synthesis of (-)-subergorgic acid by L.A. Paquette and co-workers, the transposition of a tricyclic enone was needed. The enone was exposed to the Luche conditions and an 85 15 mixture of diastereomers was obtained. In order to achieve this level of diastereoselectivity, the reaction temperature had to be lowered to -50 °C instead of the usual 0 °C. The major product was formed via the exo attack of the carbonyl group by the hydride. The allylic alcohol was later converted to the corresponding sulfoxide followed by a Mislow-Evans rearrangement to the isomeric allylic alcohol. 

The products of these reactions are easily transformed into allylamines by sequential treatment with (Me3Si)2NH and KOH. Quatemization of the nitrogen of 1.25, followed by reaction with PhMgBr at -78°C, gives sulfoxides 8.4 with an excellent enantiomeric excess. In turn, these sulfoxides undergo [2,3] sigmatropic transposition to allyl alcohols 8.5. In the ene reactions of 1.24, the enophile approaches the face of the N=S double bond opposite to the phenyl substituent of the auxiliary so that the A (1,3) strain is minimized (Figure 8.2). 

A similar transposition can be applied to saturated ketones. For example, a ketone is treated with a vinyl organometallic reagent to generate a derivative of an allylic alcohol. Reaction with benzenesulfenyl chloride then gives an ally lie sulfoxide by means of a (2,31 sigmatropic rearrangement. The remain-... 

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