N,N'-Dicyclohexylurea

synthetischeAn excess of dry ice (200 g) was added gradually to a solution of dicyclohexylcarbodiimide (2.06 g, 0.01 mol), cyclohexylamine (1.98 g, 0.02 mol), and triethylamine (2.2 g, 0.02 mol) in THF at 75 ℃ over a period of 8 h. After stirring for 8 h, the reaction mixture was concentrated under reduced pressure and the resultant precipitate was collected. Fractional recrystallization of the precipitate from acetone/methanol gave N,N'-dicyclohexylurea; yield 2.2 g (98% based on dicyclohexylcarbodiimide and cyclohexylamine).