[CH3:1][P:2](=[O:7])([O:5][CH3:6])[O:3][CH3:4].C([Li])CCC.[CH3:13][CH:14]([CH2:20][CH2:21][CH2:22][CH3:23])[C:15](OCC)=[O:16].C(O)(=O)C>O1CCCC1.CCCCC>[CH3:13][CH:14]([CH2:20][CH2:21][CH2:22][CH3:23])[C:15](=[O:16])[CH2:1][P:2](=[O:7])([O:5][CH3:6])[O:3][CH3:4]
A stirred solution of dimethyl methylphosphonate (54 g.) in dry tetrahydrofuran (390 ml.) at -45° to -50° C. was treated, dropwise during 20 minutes, with a solution of butyl lithium (32 g.) in pentane (250 ml.). Stirring was continued at that temperature for a further 10 minutes, and then the mixture was cooled to -60° C. and treated, dropwise during 15 minutes, with a solution of ethyl 2-methyl-hexanoate (34.5 g.) in tetrahydrofuran (120 ml.). The mixture was stirred at -60° C. for a further 90 minutes and then at room temperature for 3 hours, and then it was treated with acetic acid (42 ml.), evaporated to dryness in vacuo, and the residue treated with water (170 ml.). The mixture was extracted twice with diethyl ether and the combined ethereal extracts washed with water, dried over sodium sulphate and evaporated to dryness in vacuo. The residue was distilled to give dimethyl 3-methyl-2-oxoheptylphosphonate (16.8 g.), b.p. 93°-94° C./0.2mm.Hg.
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