The synthesis, spectral analysis and biological activities of 5-phenyl-2- hydroxy-chlorosubstituted-2-amino-1,3 thiazoles have been carried out. In this case 5- (2’-hydroxy-3’,5’-dichlorophenyl)-4-(heptan-1-one)-2-phenyl amino-1,3-thiazole (K) has been screened. The compound K was synthesized from 1-(2’-hydroxy-3’,5’- dichlorophenyl)-2-bromo-1,3-nonanedione (a4) by the action of phenylthiourea. The nanoparticles of the compound K has been prepared by using ultrasonic technique. The titled compound and its nanoparticles were assayed for antipathogenic impact against some common crop pathogens viz - Aspergillus niger, Pseudomonas lachrymans, Fusarium oxysporum and Fusarium solani.