A challenging synthetic approach to phosphonium ylide-betaines of the pyrimidine series

Article abstract of DOI:10.1016/0040-4020(96)00425-5

Adducts of the available ylide Ph₃P-CHCN with acylisocyanates and their thio analogues undergo facile cyclization, promoted by hydrogen chloride in methanol, to give high yields of 2-alkyl(aryl)-4-hydroxy(mercapto)-6-oxo-1,6-dihydropyrimidin-5-yl-trip henylphosphonium chlorides suitable to prepare several types of phosphonium ylide-betaines of the pyrimidine series, the structure of which was established by chemical transformations and X-ray diffraction analysis. Despite the mesomeric character of these heterocyclic nucleophilic agents, they are alkylated in a regioselective manner, which proves this approach to be important for the synthesis of non-phosphorylated pyrimidine derivatives, which are otherwise difficult to obtain.