Process for the preparation of substituted carbodiimides

摘要

Prepn. of a disubstituted carbodiimide (I) comprises phosgenating an N,N'-disubstituted urea deriv. (II) in an organic solvent and then adding ammonia, without having previously isolated the intermediate. Phosgenation involves treating a soln. or suspension of (II) in an organic solvent (pref. a dialkyl ether) with COCl2 over a period of at least 3 hrs. at 15-25 degrees C, then degassing the reaction mixt. with an inert gas or under reduced pressure, at 3-10 degrees C below the b.pt. of the solvent at atmospheric pressure, but not above 70 degrees C. (II) is pref. N,N'-dicyclohexylurea and the solvent is a dialkyl ether.