[CH2:1]([N:8]1[CH2:13][CH2:12][N:11]([CH2:14][C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=2)[CH2:10][CH:9]1[C:21](OCC)=[O:22])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.CCOCC.[H-].C([Al+]CC(C)C)C(C)C.[OH-].[Na+]>C1(C)C=CC=CC=1>[CH2:1]([N:8]1[CH2:13][CH2:12][N:11]([CH2:14][C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=2)[CH2:10][CH:9]1[CH:21]=[O:22])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1To a solution of 5.0 g (13.9 mmoles) of ethyl 1,4-dibenzylpiperazin-2-carboxylate [prepared in the manner described in Helv. Chim. Acta, 298, 2646(1963) by E. Jucker and E. Rissi] in 40 l ml of dry ether is dropwise added 30 ml of a solution of 1.46 moles of diisobutylaluminium hydride in toluene at -56° to -66° C. under nitrogen atmosphere in a period of 15 minutes, and the mixture is stirred at the same temperature for 1 hour. 10% Aqueous sodium hydroxide solution (20 ml) is slowly dropwise added thereto, and the mixture is warmed up to room temperature and extracted with ether. The extract is washed with water, dried over magnesium sulfate and evaporated under reduced pressure to yield 5.2 g of crude 1,4-dibenzyl-2-formylpiperazine.
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