2-Alkoxycarbonylcycloimmonium ylides, efficient 1,4-dipole equivalents in the synthesis of new conjugated betaines

Several heterocyclic mesomeric betaines containing the bicyclic systems pyrido[1,2-a]pyrazine and pyrido [2,1-f][1,2,4]triazine have been prepared by reaction of 2-alkoxycarbonyl pyridinium N-ylides with phenyl isocyanate and isothiocyanate.We wish to express our thanks to the Comisión Interministerial de Ciencia y Tecnología (CICYT ) for financial support (Project PB90-0284), and to the Ministerio de Educación y Ciencia by a grant to one of us (A.M.C