New efficient synthesis of trisubstituted imidazolidine-2-thiones and thiazoles via vinyliminophosphoranes

Isothiocyanate 6, obtained from vinyliminophosphorane 4 with CS2, reacted with various aliphatic primary amines to afford directly the 1,4,5-trisubstituted imidazolidine-2-thiones 5. However, the reaction of isothiocyanate 6 with aliphatic secondary amines provided 2,4,5-trisubstituted thiazoles 10 in good yields.