Carbofuran → 2,3-Dihydro-2,2-dimethyl-7-benzofuranyl (dibutylaminothio)methylcarbamate

Participants

Reaction Conditions

Reaction Steps

Over a period of 24 minutes a solution of sulfur monochloride (170.8 g., 1.27 mole) in 385 ml of hexane was added to a stirred mixture of dibutylamine (284.4 g, 2.2 mole) 263 ml of hexane, sodium hydroxide (106.3 g, 2.66 mole), and 801 ml of water. Addition rate was controlled to prevent the temperature from rising above 40° C. The mixture was stirred for an additional twenty minutes, and the aqueous layer was removed. The thermometer, stirrer blades, and reactor walls above the mixture were wiped to remove any moisture. Sulfuryl chloride (148.5 g, 1.1 moles) was added dropwise to the stirred mixture under nitrogen over a period of 19 minutes at a temperature of 20° C. 2,3-Dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate (98%, 451.4 g, 2.0 moles) was added to the mixture, followed by dropwise addition of triethylamine (354.2 g, 3.5 mole) over a period of 28 minutes. The mixture was stirred for two hours from the start of addition at 35° C. At the end of this time the mixture was cooled to 10° C. and 880 ml of water was added at a rate slow enough to keep the temperature at or below 20° C. The mixture was stirred for five minutes, then vacuum-filtered. The layers were separated and the organic layer was concentrated to provide 763.6 g of 93% (by hplc) 2,3-dihydro-2,2-dimethyl-7-benzofuranyl (dibutylaminothio)methylcarbamate (93% chemical yield based on the starting carbamate). During the filtration 15.88 g of unreacted 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate and tars was recovered.

Provenance & Evidence