Acetic Acid → Dimethyl(2-oxo-3,6-dimethyl-5-heptenyl)phosphonate

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Reaction Steps

Under argon at-60° C., 474.7 ml of a 1.61-molar butyllithium solution in hexane is added dropwise to a solution of 59 g of methanephosphonic acid dimethyl ester in 400 ml of absolute tetrahydrofuran. After 15 minutes of agitation, a solution of 34.05 g of the 2,5-dimethyl-4-hexenoic acid ethyl ester described in Example 27(b) in 100 ml of absolute tetrahydrofuran is added dropwise thereto. The reaction mixture is allowed to warm up to room temperature within 4 hours and then stirred for another 3 hours. Thereafter the mixture is combined with 26.5 ml of glacial acetic acid and concentrated under vacuum. The residue is taken up in ether/water, the aqueous phase is combined with solid sodium chloride and extracted with ether. The combined organic phases are dried over magnesium sulfate and concentrated by using a forced-circulation evaporator. The evaporation residue is purified by column chromatography on silica gel with hexane/50-100% ethyl acetate as the eluent, thus obtaining 32 g of the title compound.

Provenance & Evidence