[CH2:1]([CH:4]([C:10]([O:12][CH2:13][CH3:14])=[O:11])[C:5]([O:7][CH2:8][CH3:9])=[O:6])[CH2:2][CH3:3].[H-].[Na+].Br[CH2:18][C:19]([O:21][CH2:22][CH3:23])=[O:20]>CN(C)C=O.O>[CH2:1]([C:4]([C:10]([O:12][CH2:13][CH3:14])=[O:11])([CH2:18][C:19]([O:21][CH2:22][CH3:23])=[O:20])[C:5]([O:7][CH2:8][CH3:9])=[O:6])[CH2:2][CH3:3]Diethyl prop-1-ylmalonate (70.23 g) was added dropwise to a stirred suspension of sodium hydride (8.35 g) in dimethylformamide (400 ml) under an atmosphere of nitrogen at 10° to 15° C. Following the addition, the mixture was allowed to stir at room temperature until effervescence ceased. The resulting clear solution was cooled again and ethyl bromoacetate (58.06 g) was added. The mixture was heated at 70° C. for 2 hours then allowed to cool, diluted with water, and extracted with ether. The extracts were washed with water, dried over magnesium sulphate, and concentrated to give almost pure diethyl 2-prop-1-yl-2-ethoxycarbonylsuccinate (97.35 g, 97%) as a pale yellow liquid.
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