L. Vanmeervelt et al., A CHALLENGING SYNTHETIC APPROACH TO PHOSPHONIUM YLIDE-BETAINES OF THEPYRIMIDINE SERIES, Tetrahedron, 52(26), 1996, pp. 8835-8852
Adducts of the available ylide [GRAPHICS] with acylisocyanates and the
ir thio analogues undergo facile cyclization, promoted by hydrogen chl
oride in methanol, to give high yields of oxo-1,6-dihydropyrimidin-5-y
l-triphenylphosphonium 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 diffractio
n analysis. Despite the mesomeric character of these heterocyclic nucl
eophilic agents, they are alkylated in a regioselective manner, which
proves this approach to be important for the synthesis of non-phosphor
ylated pyrimidine derivatives, which are otherwise difficult to obtain
. (C) 1996 Elsevier Science Ltd