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.
