New benzopyrans and pyridine derivatives from [2-hydroxyaryl] - propenones

ABSTRACT

The [2-hydroxyaryl]-propenones [1] react with malononitrile in the presence of piperidine or catalytic amount of potassium hydroxide to give the corresponding benzopyrans. Warming [3] with excess ammonium acetate in absolute ethanol affords the hitherto unknown dihydropyridines [4], whereas, on boiling the propenones [1] with malononitrile in presence of ammonium acetate. Benzopyranopyridines [7] are produced along with the dihydropyridines [4]. [7] could be also obtained by reacting 3- cyano-8-methoxy coumarinimide with the corresponding ketone. Hydrolysis of both benzopyranopyridines [7] and dihydropyridines [4] affords oxo-analogues [8]. Reaction mechanisms have been discussed