Ultrasound-assisted synthesis and preliminary bioactivity of novel 2H-1,2,4-thiadiazolo[2,3-a]pyrimidine derivatives containing fluorine

Eight novel 5,7-disubstituted-2-{5-methyl-3-(4-trifluoromethylphenyl)isoxazol-4-ylcarbonylimin} -2H-1,2,4-thiadiazolo[2,3-a]pyrimidines were synthesized by multi-step reactions in yields 68-85%. Reactions were carried out either by ultrasound irradiation or conventional method, and found it was faster and more efficient under ultrasonic irradiation. Preliminary herbicidal activities against Echinochloa crus-galli, Digitaria sanguinalis and Chenopodium serotinum were also evaluated by flat-utensil method, and the results indicated that the target compounds exhibited significant activities, some were even higher than the control herbicide. (C) 2012 Lin Jiang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.