The reactions of 4,5-dihydro [1,2,4]triazolo [3,4-c]benzo[1,2,4]-triazines with aromatic aldehydes gave stable iminium salts which were deprotonated to give new azomethine imines. These new mesomeric betaines underwent 1,3-dipolar cyclization reactions to yield new tetra-and pentacyclic heterocycles. X-ray analysis and decoupling NMR experiments un-

Selective Synthesis and Cycloaddition Reactions of New Azomethine Imines Containing a 1,2,4-Triazine Ring. -The reaction of triazines (I) with aldehydes (II) gives stable iminium salts (III) on treatment with a base, they afford tetra-and pentacyclic aza heterocycles in the presence of dipolarophiles. -(GROF, C.; HEGEDUS, G.; RIEDL, Z.; HAJOS*, G.; EGYED, O.; CSAMPAI, A.; KUDAR, V.; STANOVNIK, B.; Eur.