The Synthesis of Precursors of 3-Isoacequinoline

Attempts to synthesize 3-isoacequinoline by heterocyclic ring formation via the Pomeranz-Fritsch synthesis have been unfruitful. Cyclization of ±-(l-indanimino)-acetaldehyde diethylacetal, and ±-(5-methoxy-l-indanimino)-acetaldehyde diethylacetal have been investigated using concentrated sulfuric acid, or a mixture of concentrated sulfuric acid and phosphoric anhydride in different reaction conditions. None proved to be effective. Modification of the Pomeranz-Fritsch method, in which the reduced Schiff base from ±-(5,6-dimethoxy-l- indanimino)-acetaldehyde diethylacetal was treated with concentrated hydrochloric acid also gave unsatisfactory results. An inverse Friedel-Crafts method employed to cyclize N-tosyl-±-(l-indanamino) acetyl chloride by an intramolecular acylation has been investigated and gives promise of leading to the desired 3-isoacequinoline