[CH2:1]([O:3][C:4]1[CH:11]=[CH:10][C:9]([O:12][CH2:13][CH3:14])=[CH:8][C:5]=1[CH:6]=O)[CH3:2].[C:15]([O:23][CH2:24][CH3:25])(=[O:22])[CH2:16][C:17]([O:19][CH2:20][CH3:21])=[O:18].N1CCCCC1.C(O)(=O)C>C1C=CC=CC=1.O>[CH2:1]([O:3][C:4]1[CH:11]=[CH:10][C:9]([O:12][CH2:13][CH3:14])=[CH:8][C:5]=1[CH:6]=[C:16]([C:17]([O:19][CH2:20][CH3:21])=[O:18])[C:15]([O:23][CH2:24][CH3:25])=[O:22])[CH3:2]2,5-Diethoxybenzaldehyde (24 g., 0.124 mole) and diethyl malonate (20 g., 0.125 mole) are added to a solution of piperidine (3.0 g.) and glacial acetic acid (6 ml.) in benzene (160 ml.). The mixture is heated under reflux utilizing a Dean-Stark water separater until water ceased to be separated. After 8 hours of distillation 2.3 ml. of water out of a theoretical yield of 2.23 ml. are obtained and the reaction mixture cooled. The cooled reaction mixture is washed with aqueous hydrochloric acid (6 N, 70 ml.) water (70 ml.) and aqueous sodium bicarbonate (5% w/w, 50 ml.). The organic layer is separated, dried over magnesium sulfate, filtered, and the solvent removed under reduced pressure to yield a yellow oil (42.7 g., 0.127 mole, 100%). Trituration with petroleum ether yields diethyl 2,5-Diethoxybenzylidenemalonate (38.4 g., 0.114 mole, 92%) m.p. (from petroleum ether) 52°-53° C. I.R.: 1720 cm- 1 mass spec m/e 336.
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