Homer-Wittig reaction enol ether preparation

Alkenation of carbonyl compounds can be used as a general method for the synthesis of enol ethers. The Homer-Wittig reaction of the phosphorus-stabilized carbanion (8) with aldehydes or ketones gives the adducts (9), which on heating eliminate to give the enol ethers (10) as a mixture of ( )- and (Z)-isomers. Since the two diastereomeric adducts (9) can be separated and the elimination reaction is stereospecific, this method can be used to prepare the individual geometrical isomers of (10) according to Scheme 2. 

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