A mixture of 3.2 parts of N-[1-(2-phenylethyl)-4-piperidinyl]-1H-benzimidazol-2-amine, 2.9 parts of [2-(2-thienyl)ethyl] 4-methylbenzenesulfonate, 1 part of sodium carbonate and 135 parts of 4-methyl-2-pentanone is stirred and refluxed overnight with water-separator. The reaction mixture is poured onto water and the layers are separated. The organic phase is dried, filtered and evaporated. The residue is purified by column-chromatography over silica gel using a mixture of trichloromethane and methanol (98:2 by volume) as eluent. The pure fractions are collected and the eluent is evaporated. The residue is crystallized from a mixture of 2,2'-oxybispropane and 2-propanone, yielding 1 part (23.2%) of N-[1-(2-phenylethyl)-4-piperidinyl]-1-[2-(2-thienyl)ethyl]-1H-benzimidazol-2-amine; mp. 118.3° C.
