Microwave-assisted solvent-free synthesis of 3-[(4-substituted piperazin-1-yl)alkyl] imidazo[2,1-b][1,3]benzothiazol-2(3H)-ones as serotonin3 (5-HT3) receptor antagonists

Abstract

A series of novel 3-[(4-substituted piperazin-1-yl)alkyl]imidazo[2,1-b][1,3]benzothiazol-2(3H)-ones were prepared by microwave irradiation using alumina as solid support and also by a conventional method. The compounds were characterized by spectral data and the purity was ascertained by microanalysis. The synthesized compounds were evaluated for 5-hydroxytryptamine3 antagonisms in a longitudinal muscle-myenteric plexus preparation from guinea pig ileum against the 5-hydroxytryptamine3 agonist, 2-methyl-5-hydroxytryptamine. Among the test compounds, 3-[2-(4-methylpiperazin-1-yl)ethyl]imidazo[2,1-b][1,3]benzothiazol-2(3H)-one (3b) showed most favorable 5-hydroxytryptamine3 antagonism (pA2 6.7) in the isolated guinea pig ileum.