Synthesis of 1,2,4,5-Tetrasubstituted Imidazoles by a Sequential Aza-Wittig/Michael/Isomerization Reaction

Carbodiimides 4, obtained from aza-Wittig reactions of iminophosphorane 3 with aryl isocyanates, reacted with secondary amines in the presence of a catalytic amount of sodium alkoxide to give 1,2,4,5-tetrasubstituted imidazoles 7 in good yields. However, 4-acylimidazoles 11 were obtained, as phenols were used in the presence of a catalytic amount of potassium carbonate due to further air oxidation of the expected products 10.