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