New efficient synthesis of 1,2,4-trisubstituted imidazoles and imidazo[1,2-c]quinazolines by a tandem aza-Wittig/electrocyclic ring-closure process

A series of 1,2,4-trisubstituted imidazoles 5 were synthesized efficiently by a tandem aza-Wittig/1,5-electrocyclic ring-closure reaction of vinyliminophosphoranes 3 with aldehydes. Reactions of 5s,t with triphenylphosphine produced iminophosphoranes 7. A tandem aza-Wittig reaction of iminophosphorane 7 with isocyanate generated imidazo[1,2-c]quinazolines 9 in high yields.