Ultrasonic irradiated synthesis and herbicidal activities of 5,7-disubstituted-2- (substituted pyridine-3-formylimino)-2H-1,2,4-thiadiazolo[2,3-a]pyrimidine derivatives

College of Life and Environmental Science, Department of Chemistry, Shanghai Normal University, Shanghai, 200234, P. R. China E-mail: keshaoyong@ 163.com Manuscript received 13 January 2004, revised 17 May 2004, accepted 3 August 2004 Eight new substituted-pyridine-3-formylimino-2H-1,2,4-thiadiazolo[2,3-a] derivatives containing substituted pyrimidine ring were synthesized in good yield under ultrasonic irradiation (USI). The structures of all newly synthesized compounds were elucidated and confirmed by IR. 1H NMR and elemental analysis. The target compounds have been screened for activity against a number of monoeotyledones and dicotyledones. The preliminary herbicidal tests show that some of the target compounds have better inhibitory activities against weeds