The synthesis of a series of di-, tri-, and tetrasubstituted non-sym. ureas is described. Di- and trisubstituted ureas are prepd. in excellent yield by treatment of a Ph carbamate in a self-tunable single-mode microwave synthesizer with a primary or secondary amine. The synthetically more challenging tetrasubstituted urea can be prepd. using the 4-nitrophenyl carbamate and a secondary amine.
- microwave-assisted synthesis