Synthesis of N-vinylic carbodiimides through Aza-Wittig reaction of N-vinylic phosphazenes with isocyanates is reported. These heterocumulenes are used for the preparation of unsymmetrical ureas and nitrogen heterocycles such as hydantoins, 1,3-diazetidines, imidazolidinones, and bis-imidazolidinone azines.