Syntheses of heterocyclic compounds. Part XI. Quinolines and pyrones from the reaction of N-aminophenyl heterocycles with β-ketoesters in polyphosphoric acid

Abstract

N-o-Aminophenyl heterocycles react with β-keto-esters in hot polyphosphoric acid to give quinaldines with the heterocycle in the 8-position. The N-o-acetoacetamidophenyl derivatives, however, yield a mixture of these quinaldines and γ-pyrones. From o-fluoroacetoacetanilide three compounds are obtained under similar conditions, namely the expected 8-fluoro-2-hydroxylepidine in addition to 8-fluoro-4-hydroxyquinaldine and an o-fluorophenyl-substituted γ-pyronecarboxylic acid amide. By contrast, reaction between o-fluoroaniline and methyl acetoacetate gives a pyridone as well as the expected quinaldine. Aspects of mechanism are discussed.