N-Methylcyclohexylamine → 1,3-dicyclohexyl-1-methylurea

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Reaction Steps

18.38 g of cyclohexyl isocyanate (0.147 mol) are added, dropwise, to a solution of 19.12 g of N-methyl-N-cyclohexylamine (0.169 mol) in 160 ml of hexane, and then the cloudy mixture is refluxed for 2 h and then evaporated to dryness, to give 35 g of crude N,N′-dicyclohexyl-N-methylurea. 12 g of POCl3 (78 mmol) are added, over the course of 1 h, to a suspension of 17 g of said crude N,N′-dicyclohexyl-N-methylurea (71.33 mmol) in 65 ml of dry toluene, and then, after a few hours at 20° C., 15.5 g of N-butyl-N-methylamine (0.178 mmol) are added over the course of 2 h, and then, after a further 2 h at 20° C., 50 ml of water are added. 49 g of 35% sodium hydroxide are then added while cooling, and then the two-phase medium is extracted with diisopropyl ether. After drying and evaporation to dryness, the oil obtained, 26.5 g, is distilled at 180° C. under 1 mbar, to give 21.25 g of the expected guanidine (yield 97%).

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