[CH3:1][N:2]([CH3:14])[C:3]1[CH:10]=[CH:9][C:6]([CH:7]=O)=[C:5]([N+:11]([O-:13])=[O:12])[CH:4]=1.[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>C1(C)C=CC=CC=1>[CH2:20]([O:19][C:17](=[O:18])[C:16]([C:15]([O:23][CH2:24][CH3:25])=[O:22])=[CH:7][C:6]1[CH:9]=[CH:10][C:3]([N:2]([CH3:14])[CH3:1])=[CH:4][C:5]=1[N+:11]([O-:13])=[O:12])[CH3:21]A mixture of 8.9 grams (g) [50 millimoles (mmol)] of 4-dimethylamino-2-nitrobenzaldehyde [H. Baumann et al, German Pat. No. 2,363,458], 23.7 g (148 mmol) of diethyl malonate, 3.44 g (40.4 mmol) of piperidine and 2.43 g (40.4 mmol) of acetic acid in 400 milliliters (mL) of toluene was refluxed for 16 hours under argon with a Dean Stark trap attached. The solution was cooled to room temperature and washed with 200 mL of 5% aqueous potassium hydroxide (KOH). The organic phase was separated, dried over sodium sulfate (Na2SO4), filtered, and the solvent evaporated. The dark red solid residue was dissolved in 40 mL of methylene chloride (CH2Cl2) and 100 mL of hexane added. After standing for one hour, the solution was filtered to yield 10.4 g of orange crystals. Recrystallization from CH2Cl2 -hexane produced an analytical sample, m.p. 101°-102° C.
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