Phosgene → Methyl N-(3-chloro-4-hydroxyphenyl)carbamate

Powdered 4-amino-2-chlorophenol (210 grams, 1.46 moles) is added to a dry ethylacetate solution (2100 ml.) of phosgene (210 grams, 2.05 moles) and the mixture is stirred at 0°C. to 10°C. Slowly the reaction mixture is raised to reflux temperature after 1 hour. Further phosgene (20 grams) is passed through the solution during a one-half hour period, then the mixture is heated under reflux during another 30 minute period, cooled to 40°C., and rapidly filtered. The filtrate is evaporated under reduced pressure to a volume of 900 ml. An infrared spectrum of this oil has a peak at 2260 cm.-1 (N=C=O). The isocyanate solution is added to methanol (1.8 liters) with stirring, and the reaction is brought to reflux for 16 hours, then set aside at 20°C. for 48 hours. Evaporation of the reaction mixture affords a viscous oil. Addition of benzene (2 × 300 ml.) followed by evaporation causes the oil to solidify. The crude solid is vacuum dried, melting point 96°C. to 98°C., 250.5 grams (86%). Crystallization of a 5 gram sample from benzene (trace n-hexane) affords crystals, melting point 104°C. to 105°C., 2.76 grams (47%).