Science of Synthesis

Whitehead, A.; Sieck, S. R.; Mukherjee, S.; Hanson, P. R., Science of Synthesis, (2005) 21, 922.

C-Alkylation of acylphosphonates ‌57‌ can be achieved via a [3,3]-sigmatropic shift of the corresponding allyl enol ethers ‌58‌, as shown in ‌Scheme 18‌.[‌51‌] Thus, O-alkylation of acylphosphonates ‌57‌ by treatment with potassium hexamethyldisilazanide, followed by addition of excess electrophile such as allyl bromide, crotyl chloride, or cinnamyl bromide, gives allyl enol ethers ‌58‌ in 12–44% yield. When refluxed in toluene, facile [3,3]-sigmatropic rearrangement of enolates ‌58‌ occurs to give the corresponding C-alkylated acylphosphonates ‌59‌. Compounds ‌59‌ are obtained in quantitative yield and as a single diastereomer.

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References