A group of benzimidazole analogs of sildenafil, 3-benzimidazolyl-4-methoxy-phenylsulfonylpiperazines 2-4 and 3-benzimidazolyl-4-methoxy-N,N-dimethyl- benzenesulfonamide (5), were efficiently synthesized. Compounds 2-5 were characterized by NMR and MS and contrary to the reported mass spectra of sildenafil, the spectra of the piperazine-containing compounds 2-4 showed a novel fragmentation pattern leading to an m/z = 316. A mechanism for the formation of this fragment was proposed.
