Lactam and acid amide acetals 57. Synthesis, protonation, and acid-base properties of condensed derivatives of 4-oxo-1,4-dihydro-1,8-naphthyridine

Abstract

A number of 4-oxo-1,4-dihydro-1,8-naphthyridine derivatives that differ with respect to the sizes of the azaand carbocycles were synthesized by the reaction of 3-amino-4-ethoxycarbonyl-5,6-dihydro-7H-pyrindine and 3-amino-4-ethoxycarbonyl-5,6,7,8-tetrahydroisoquinoline with N,N-dimethylacetamide diethylacetal and N-methylbutyrolactam, N-methylvalerolactam, and N-methylcaprolactam diethylacetals and subsequent cyclization of the intermediate amidines. It was established by UV and 1H and 13C NMR spectroscopy that the protonation of these compounds takes place at the exocyclic oxygen atom. The dependence of the ionization constants of the compounds obtained in 70% DMFA on the size of the saturated cyclic fragments of the molecules was established.