Alkene ketones from allyl vinyl ethers

PdCl2(PhCN)2-catalysed Claisen rearrangement of the allyl vinyl ether 474 derived from cyclic ketone at room temperature affords the syn product 475 with high diastereoselectivity [203]. In contrast to thermal Claisen rearrangement, the Pd(II)-catalysed Claisen rearrangement is always stereoselective, irrespective of the geometry of allylic alkenes. The anti product is obtained by the thermal rearrangement in the presence of 2,6-dimethylphenol at 100 °C for lOh. 

Two new routes to allyl vinyl ethers, suitable substrates for Claisen rearrangement, are summarized in Scheme 41 and equation (22) one involves copper-catalysed solvolytic cleavage by an allylic alcohol of (E)-alkenylpentafluorosili-cates available from hydrosilylation of alkynes," and the other is based on the base-promoted reaction of dimethyl diazomethylphosphonate with aliphatic ketones in the presence of an allylic alcohol." Electrolytic synthesis of allylic ethers direct from alkenes has been discussed earlier in this Report (Scheme 11). ... 

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