Primisulfuron-methyl

There are several commercially available sulfonylurea herbicides that contain a 2-pyrimidine group <2006H(68)561>. These compounds, which function by inhibition of acetolactate synthase (ALS), an enzyme involved in the early stage of branched-chain amino acid synthesis, include sulfometuron-methyl 1095, primisulfuron-methyl 1096, chlorimuron-ethyl 1097, bensulfuron-methyl 1098, ethoxysulfuron 1099, nicosulfuron 1100, and pyrazosulfuron-ethyl 1101. Related nonsulfonylureas include the sulfide pyrftalid 1102 and the ether pyriminobac-methyl 1103. 

Weeds are rapidly becoming resistant to some of the newer herbicides, and it is important to realize the consequences. For example, in Missouri, Bader et al. (1995) conducted a study on corn-soybean rotations in which they used only ALS-inhibitor herbicides, that is, imazethapyr in soybean and primisulfuron-methyl in corn. Within 4 years, a common waterhemp biotype resistant to 5-fold higher rates of ALS inhibitors was flourishing. Greenhouse tests confirmed that ALS-resistant common waterhemp biotypes were present in several plots in the experiment. Within the same state, Bader et al. (1994) reported one case of atrazine-resistant common waterhemp, which developed where a farmer grew continuous com and used only atrazine for more than 10 years. Table 11.1 shows trends in the numbers of herbicide-resistant weeds. 

Test dependent product = flumetsulam, halosulfuron, imazethapyr, primisulfuron-methyl, or prosulfuron. 

Primisulfuron-methyl CisHigNgOgS 2-[4,6-bis(difluoromethoxy)pyrimidin-2-ylcarbomoylsulfamoyl]benzoic acid 468.3 3.5 0.24 4 to 29 n.f. 

Du Pont de Nemour and Company), Primisulfuron-methyl (Syngenta Corporation), and the experimental herbidde HNPC-C9908 (Hunan Branch of the National Pesticide R D South Center, Changsha, China). 

Primisulfuron-methyl, Beacon , Tell Syngenta (1998) COOMe H CH OCHF2 OCHF2 CH... 

Primisulfuron-methyl (99) [191] is a maize-selective herbicide. Comparison with the unfluorinated triazine counterpart metsulfuron-methyl (94) indicates that crop safety for maize is achieved by replacement of the triazine methoxy (R ) and methyl (R" ) group in ring B with two difluoromethoxy groups (R, R" ). 

Primisulfuron-methyl [14], a selective fluorosulfonylurea herbicide bears two difluoromethoxy subunits (Fig. 9). 

Primisulfuron-methyl is a selective herbicide for the control of grasses in maize. Comparison [81] with its unfluorinated triazine counterpart methsulfuron-methyl indicates that crop safety for maize is achieved by the replacanent of the triazine methoxy and methyl substituents with two difluoromethoxy groups. It has been shown that primisulfuron-methyl is deactivated in maize by hydroxylation of the phenyl and pyrimidyl moieties followed by hydrolysis or conjugation [82]. 

The synthesis of Primisulfuron-methyl (299) started from reaction of diethyl malonate and thiourea (Scheme 77) [284]. The resulting pyrimidine derivative 348 was methylated, difluoromethylated and then oxidized to give sulfone 351. Reaction of 351 with aqueous ammonia gave heteroaromatic amine 352, which was transformed to Primisulfuron-methyl (299) upon treatment with isocyanate 353. 

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