Herbicidal Sulfonylureas, Their Preparation and Use

Difluoroacetic anhydride (0.4 mol) dissolved in 200 ml diethyl ether, treated with N-(trichloroacetamidino)guanidine (0.2 mol) at 0°C, and then stirred at ambient temperature 3 hours. The volatile fractions were removed at 40 °C, the residue partitioned between 400 ml water and 200 ml CH2CI2, and the organic phase neutralized with 2% 

NaOH solution. The mixture was concentrated, the crude product isolated in 75% yield, and used without further purification. H-NMR data supplied. 

The product from Step 1 (85 mmol) was dissolved in 100 ml methyl alcohol, treated at 0°C with 1.6 g 30% sodium methoxide (9 mmol) in methyl alcohol, and the mixture stirred at ambient temperature 16 hours. Thereafter, an additional 1.6 g of 30% sodium methoxide (9 mmol) in methyl alcohol was added and the mixture stirred an additional 3 hours. The solution pH was lowered to 7 using 3 M HCl, the mixture concentrated, stirred in 400 ml water, and the product isolated in 71% yield. H-NMR data supplied. 

Methyl [2-[[(4-chlorodifluoromethyl-6-methoxy-l,3,5-triazin-2-yl)-aminocarbonyl] aminosulfonyljbenzoate 

The product from Step 2 (20 mmol) was dissolved in 20 ml of CH2CI2 at 25 °C, 2-methoxycarbonylbenzenesulfonyl isocyanate (20 mmol) dissolved in 5 ml CH2CI2 added, the mixture stirred 16 hours, then concentrated. The residue was stirred with 100 ml hexane/diethyl ether, 1 1, the product separated by filtration, recrystallized using methanol/water, and isolated in 35% yield, mp = 174-175 °C. 

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