Abstract
Iminophosphorane 1 reacted with an aromatic isocyanate to unexpectedly give a mixture of carbodiimides 2, 3 and 4 through both the normal and the abnormal aza‐Wittig reactions. 3‐Aminoimidazolone 10 was obtained from the reaction of hydrazine hydrate with carbodiimide 2. Reaction of 10 with triphenyphosphane, hexachloroethane and triethylamine produced iminophosphorane 11 in good yield. A tandem aza‐Wittig reaction of iminophosphorane 11 with isocyanate or CS~2~ generated 3,5‐dihydro‐6__H__‐imidazo[1,2‐b]‐1,2,4‐triazol‐6‐ones 13 or 15 in satisfactory yield. Carbodiimides 18, obtained from normal aza‐Wittig reactions of vinyl iminophosphorane 17 with aromatic isocyanates, reacted with hydrazine to give 2‐arylamino‐3‐amino‐4__H__‐imidazol‐4‐ones 20. One‐pot reactions of 2‐arylamino‐3‐amino‐4__H__‐imidazol‐4‐ones 20 with isocyanates (or acyl chlorides), triphenyphosphane, hexachloroethane and triethylamine produced 3,5‐dihydro‐6__H__‐imidazo[1,2‐b]‐1,2,4‐triazol‐6‐ones 22 (or 23) in good yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)