Synthesis And Herbicidal Activity Of Trifluoromethylpyrimidylsulfonylureas

The sulfonylurea herbicides have been characterized by broad-spectrum of weed control at ultra-low dosage of application, good crop selectivity and crop low mammalian toxicity. The compounds are composed of 3 parts: aromatic ring, urea bridge and heterocycle. Heterocycle is always pyrimidine or triazine. The substituted groups of heterocycle are mainly alkyl, alkoxyl, halogen, methoxyflurane, while heterocyclic compounds with trifluoromethyl group are seldom reported. In this paper, heterocyclic compounds with trifluoromethyl group are prepared directly by heterocyclization.On one hand, condensation of guanidine hydrochloride with ethyl 4,4,4-trifluoroaceto -acetate and chlorination results in 2-amino-4-chloro-6-trifluoromethylpyrimidine( I b), which, upon reaction with nucleophiles, gives high yields of the corresponding 2-amino-4 -substituted-6-trifluoromethylpyrimidines (â…  c~ â…  e). On the other hand, benzene sulfonylamide reacts with oxaxyl chloride, giving the correspounding compounds benzene sulfonylisocyanate. Seven different sulfonylureas are gained by nucleophilic addition of benzene sulfonylisocyanate and â…  .Biological activity testing in the greenhouse indicates that compound â…¡ c with methoxy group has high activity on Echinochloa Crusgalli L (ECHCG) and Digitaria Sanguinalis L (DIGSG). With 200 ga.i./ha provides 70% and 40% inhibition rate of ECHCG and DIGSG respectively. Whereas the dimethylamino group deriviate â…¡e is weaker. The chloro group deriviate â…¡b loses inhibition rate notably, with 200 ga.i./ha provides 10% inhibition rate of ECHCG. The compound â…¡ f and â…¡ i provide no inhibition rate of ECHCG or DIGSG. There are three pyrimidylsulfonylureas with trifluoromethyl group have herbicidal activities. 4-substituent in pyrimidine and benzene's substituent have some relationship with herbicidal activity. When 4-substituent in pyrimidine is electron donating group and benzene ortho-position is electron withdraw group, herbicidal activity increases notably. Therefore it can be optimized structure for further research.