To a solution of 171 mg of 1-phenyl pyrrole-3-carboxaldehyde in 1 mL of methanol was added 525 mg of 4-benzylpiperidine, 175 mg of 4-benzylpiperidine·HCl and 63 mg of sodium cyanoborohydride. The reaction mixture was stirred overnight at room temperature under an atmosphere of nitrogen. The methanol was removed by evaporation under reduced pressure and the residue was extracted into 50 mL of ethyl acetate, then washed successively with 50 mL aliquots of 10% sodium hydroxide and water. The ethyl acetate extract was dried over anhydrous sodium sulfate and the solvent evaporated under reduced pressure to yield 1-phenyl-3[(4-benzyl-piperidin-1-yl)methyl]pyrrole, which was purified by chromatography on silica gel using 5% methanol in dichloromethane as elvent. On evaporation of the solvent, the free base was dissolved in ethanol and treated with 1 equivalent of maleic acid. The 1-phenyl-3[(4-benzyl-piperidin-1-yl)methyl]pyrrole maleate salt (compound 7) had a melting point of 159°-161° C.
