[CH3:1][P:2](=[O:7])([O:5][CH3:6])[O:3][CH3:4].C([Li])CCC.[F:13][CH:14]([CH2:20][CH2:21][CH2:22][CH3:23])[C:15](OCC)=[O:16].S(=O)(=O)(O)O>CCCCCC.O1CCCC1>[CH3:4][O:3][P:2]([CH2:1][C:15](=[O:16])[CH:14]([F:13])[CH2:20][CH2:21][CH2:22][CH3:23])(=[O:7])[O:5][CH3:6]To a solution of 7.7 g. (0.06 mole) of dimethyl methyl-phosphonate in 80 ml. of tetrahydrofuran at -73° C. was added dropwise 43.4 ml. of a 1.42 molar solution of butyl lithium in hexane. After stirring for 5 minutes, a solution of 4 g. (0.03 mole) of ethyl 2-fluorohexanoate in 20 ml. of tetrahydrofuran was added dropwise. The resulting solution was then allowed to warm to 0° and then acidified (pH3) with 2 N sulfuric acid. The mixture was then extracted with hexane, the hexane solution washed with a saturated sodium chloride solution and then dried (MgSO4). The solvent was then removed under reduced pressure and the residue distilled to give 5.8 g of dimethyl(2-oxo-3-fluoroheptyl)phosphonate, b.p. 116°-118°/0.4 mm.
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