National Chemical Laboratory Pune 41 1 008, INDIA sym-NN-Diethyldiphenylurea (Centralite I) is used commercially as stabilizer for a number of explosives.'Recently a non- phosgene route involving the N-ethy lation of sym-N, Ndiphenylurea (DPU) using phase- transfer catalyst (EC) has been reported? As an extension of our work on the N-alkylation of benzanilides3 and aminoanthraquinones, 4 we now describe the alkylation of diarylureas ...