Dissolve 3-piperazin-1-yl-benzonitrile (0.19 g, 1.00 mmol), 3-formyl-benzoic acid methyl ester (0.33 g, 2.00 mmol) and AcOH (0.64 mL, 10.0 mmol) in 5 mL dichloroethane. Add NaBH(OAc)3 (0.42 g, 2.00 mmol) and stir the mixture overnight. Add another portion of NaBH(OAc)3 (0.42 g, 2.00 mmol) and stir the mixture an additional 24 h. Concentrate the crude reaction mixture under a stream of N2. Dissolve the residue into 5% HCl and apply to a Dowex column. Wash the column with 1×50 mL 5% HCl, 2×50 mL H2O, 2×50 mL of MeOH and 2×50 mL of dichloromethane. Liberate the basic residues by washing the resin with 3×30 mL of 10% NH3/MeOH and 2×20 mL of dichloromethane. Concentrate the basic washings to give 0.27 g of 3-[4-(3-cyano-phenyl)-piperazin-1-ylmethyl]-benzoic acid methyl ester as a clear oil. 1H NMR indicates some contamination with starting amine. The mixture is carried on without further purification.
