Facile synthesis and fungicidal activity of novel 4,4<i>'</i>-bis[2<i>''</i>-(5<i>'''</i>-substituted rhodanin-3<i>'''</i>-yl)thiazol-4<i>"</i>-yl]bibenzyls<b></b>

Abstract

Acylation of bibenzyl, followed by reaction with thiourea and I₂ in the presence of NH₃, yields 4,4<i style="">'</i>-bis(2<i style="">"</i>-aminothiazol-4<i style="">"</i>-yl)bibenzyl <b style="">3</b>. Compound <b style="">3</b>, on treatment with CS₂ in the presence of NH₃ and cyclization with ClCH₂COONa and HCl, furnishes 4,4<i style="">'</i>-bis[2<i style="">"</i>-(rhodanin-3<i style="">"'</i>-yl)thiazol-4<i style="">"</i>-yl]bibenzyl <b style="">4</b>. Compound <b style="">4</b>, on Knoevenagel condensation with aromatic aldehydes by conventional methods as well as microwave irradiation in the presence of NaCl as catalyst under solvent-free conditions, gives 4,4<i style="">'</i>-bis[2<i style="">''</i>-(5<i style="">'''</i>-substituted rhodanin-3<i style="">'''</i>-yl)thiazol-4<i style="">"</i>-yl]bibenzyls <b style="">5a-p</b>. The reaction rate is enhanced 230 times by using microwave heating with improved yields in comparison with conventional method. All compounds show promising antifungal activity against <i style="">Fusarium oxysporum </i>and <i style="">Penicillium citrinum</i>. Structure-activity relationships for the screened compounds are discussed.