C([O:3][P:4](Cl)[O:5][CH2:6][CH3:7])C.C([Mg]Cl)[C:10]1[CH:15]=[CH:14]C=[CH:12][CH:11]=1.O.Cl.[CH2:20](OCC)C>>[CH3:20][PH:4](=[O:3])[O:5][CH2:6][C:7]1[CH:14]=[CH:15][CH:10]=[CH:11][CH:12]=1Diethylchlorophosphite (25 g, 0.16 mol) in 100 mL of dry diethyl ether was cooled to 0° C. under an atmosphere of nitrogen. Benzylmagnesium chloride (80 mL, 0.16 mol, 2.0 M solution in Et2O) was added dropwise over two hours while maintaining a temperature below 10° C. A thick white slurry formed and stirring was continued at room temperature for 1 hour. The mixture was filtered under a nitrogen atmosphere and the filtrate evaporated under reduced pressure to give a clear and colorless liquid. The liquid was stirred as 15 mL of water was added followed by 0.5ml concentrated hydrochloric acid. An exothermic reaction was observed and stirring was continued for an additional 30 minutes followed by extraction with ethyl acetate. The organics were combined, washed with brine, dried (MgSo4) and evaporated. The clear light golden liquid was added to sodium hydroxide (50 mL, 2.0 M NaOH), stirred for one hour and washed with diethyl ether. The aqueous layer was acidified to pH 1.0 with concentrated hydrochloric acid and extracted with ethyl acetate. The organics were combined, dried (MgSO4) and evaporated to give benzylphosphinic acid (1, R=CH2Ph, R1+H) (8 g, 32%) as a clear light golden oil.
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