Abstract The carbodiimides 2, obtained from aza-Wittig reactions of iminophosphorane 1 with aromatic isocyanates, react with hydrazine to give, selectively, the 3-amino-2- arylaminoquinazolin-4 (3H)-ones 4. Reaction of 4 with triphenylphosphane, hexachloroethane and triethylamine produces iminophosphoranes 5. A tandem aza-Wittig reaction of iminophosphorane 5 with isocyanate or acyl chloride generates the 1, 2, 4- ...