The Condensation of Cyclic Anhydrides (I) with Schiff Bases (II). A Convenient Synthesis of 1,4,6-Triaryl-5-carboxy-2-oxo-1,2-dihydropyridines (IIIa) - (IIIc) and 2,3-Diaryl-4-carboxy-1-oxo-1,2-dihydroisoquinolines (IIId), (IIIe).