反应详情

A solution of 110.5 parts of O-methylisourea hydrochloride in 475 parts of water is adjusted with 8.9 parts of 50% NaOH solution to pH 6. After raising the pH to 9, 114.5 parts of methyl chloroformate is added, while maintaining the pH at 9 by the simultaneous addition of 175.3 parts of 50% NaOH solution. The resulting reaction mass is then extracted 5 times with 134 parts methylene chloride, and the combined extracts are then dried by removing the dissolved water by azeotropic distillation. The resulting methylene chloride solution shows by gas chromatographic analysis the presence of 121.0 parts (92.2% yield) of methyl N-[(amino) (methoxy)methylene]carbamate. One half of the above methylene chloride solution is gradually added to 45 parts of neat phosgene at 0° C within 10 minutes. Initally, gummy solids are formed, which gradually dissolve, as a white crystalline solid precipitates. After holding the temperature to 0° C for 30 minutes, 51.7 parts of solids are isolated by filtration. The filtrate is then evaporated to produce 23.5 parts of residue, which is almost completely soluble in water, and represents (based on equation (I) and the starting 0-methylisourea hydrochloride) a 89.3% yield of crude dimethyl N,N'-{[(2,4-dioxo-1,3-diazetidine)-1,3-diyl]-bis[(methoxy)methylidyne]}biscarbamate.

1. additionis added
2. temperaturewhile maintaining the pH at 9
3. customThe resulting reaction mass
4. extractionis then extracted 5 times with 134 parts methylene chloride
5. customthe combined extracts are then dried
6. customby removing the dissolved water
7. distillationby azeotropic distillation