Acetic Acid → Dimethyl 2-oxo-2-phenylethylphosphonate

Participants

Reaction Steps

A solution of 74.5 g (600 mmoles) dimethyl methylphosphonate (Aldrich) in 750 ml dry tetrahydrofuran was cooled to -78° in a dry nitrogen atmosphere. To the stirred phosphonate solution was added 265 ml of 2.34 M n-butyllithium in hexane solution (Alfa Inorganics, Inc.) dropwise over a period of 30 minutes at such a rate that the reaction temperature never rose above -65°. After an additional 5 minutes stirring at -78°, 41 g (300 mmole) of methyl azoate was added dropwise at a rate that kept the reaction temperature less than -70° (10 minutes). After 1 hour at -78° the reaction mixture was allowed to warm to ambient temperature, neutralized with 35 ml acetic acid and rotary evaporated to a white gel. The gelatinous material was taken up in 75 ml water, the aqueous phase extracted with 300 ml portions of ether (3x), the combined organic extracts were backwashed (50 cc H2O), dried (MgSO4), and concentrated (water aspirator) to a crude residue and distilled, b.p. 130°-5° (0.04 mm) to give 35 g (29%) dimethyl 2-oxo-2-phenylethylphosphonate (2a).

Provenance & Evidence