THE SYNTHESIS OF N-SUBSTITUTED UREAS .1. THE N-ALKYLATION OF UREAS

Urea and N-alkylureas are N'-alkylated in low yields using aprotic dipolar solvents, like dimethylsulfoxide, solid potassium hydroxide, and alkyl halides. Phase transfer catalysis with tetrabutylammonium chloride in refluxing toluene results in high yield regioselective N'-alkylation of N-alkylureas by means of alkyl halides, tosylates, mesylates, and sulfates as alkylating agents and alkali hydroxide as the base - however, N-arylureas are not alkylated under these conditions. Kinetic studies point to a S(N)2 type reaction which obeys the Kornblum rule.