Am. Cuadro et al., 2-ALKOXYCARBONYLCYCLOIMMONIUM YLIDES, EFFICIENT 1,4-DIPOLE EQUIVALENTS IN THE SYNTHESIS OF NEW CONJUGATED BETAINES, Tetrahedron, 49(15), 1993, pp. 3185-3192
Several heterocyclic mesomeric betaines containing the bicyclic system
s pyrido[1,2-a]pyrazine and pyrido [2,1-f][1,2,4]triazine have been pr
epared by reaction of 2-alkoxycarbonyl pyridinium N-ylides with phenyl
isocyanate and isothiocyanate.