The Condensation of Cyclic Anhydrides with Schiff Bases. A Convenient Synthesis of 1,4,6-Triaryl-5-carboxy-2-oxo-1,2-dihydropyridines and 2,3-Diaryl-4-carboxy-1-oxo-1,2-dihydroisoquinolines

Condensation of Schiff bases of o-hydroxyarenecarboxaldehydes with 3-arylpentenedioic or homophthalic acid anhydrides was found to give 1,4,6-triaryl-5-carboxy-2-oxo-1,2-dihydropyridines and 2,3-diaryl-4-carboxy-1-oxo-1,2-dihydropyridines and 2,3-diaryl-4-carboxy-1-oxo-1,2-dihydroisoquinolines, respectively, instead of the expected tetrahydro products. The Schiff bases (used in excess) oxidize the intermediate tetrahydro products to the title compounds