CAUTION: Use a well-ventilated hood and take all precautions before using phosgene.
To a flask equipped as in Preparation 3-1 is added 1.27 kg (10.0 moles) of N-cyclohexylformamide, 3.20 liters of triethylamine, and 4.50 liters of methylene chloride. The solution is stirred while phosgene is rapidly added (300-400 gm/hr) to cause vigorous refluxing. Refluxing ceases after 1.04 kg (10.2 moles) of phosgene have been added and the addition is stopped. The reaction mixture is cooled to 22-25°C, 400 gm (23.5 moles) of ammonia gas added over a period of 1-2 hr, the mixture filtered then concentrated under reduced pressure, and the residue distilled to afford 955 gm (88%), b.p. 67-72°C (14 mm Hg).
