Synthesis of aryloxyacetylthiourea derivatives for the development of radicle elongation inhibitor of parasitic weeds

Abstract

Aryloxyacetylthiourea, 1-(3,4-dichlorophenyl)-3-(2-phenoxyacetyl)thiourea (PI-28), has attracted attention as a lead compound for the development of radicle elongation inhibitors in Orobanche minor seeds germination. In this study, we synthesized PI-28 and its derivatives in two steps using commercially available phenols, 2-chloroacetamide, and N-aryl isothiocyanates. In this method, 2-aryloxyacetanilides, which are also attractive as bioactive compounds, were obtained as byproducts. According to the result of the control experiment, the formation of byproducts was due to the loss of isothiocyanate moiety from the formed aroyloxyacetylthioureas caused by the action of another aryl isothiocyanate during the reaction. Moreover, we have developed a one-pot synthesis method for PI-28 derivatives with comparable overall yields.