Isomerism of 9-arylaminomethylene-6,7,8,9-tetrahydro-4-oxo-4H-pyrido[1,2-a]pyrimidines

Abstract

Several 9-arylaminomethylnene-6,7,8,9-tetrahydro-4-oxo-4H-pyrido[1,2-a]pyrimidines have been synthesized and studied by ¹H and ¹³C n.m.r. spectroscopy. The dominant tautomeric form has been established. Fast Z–E isomerisation has been found around the enamino CC double bond. The effect of the solvent, temperature, and various structural modifications on the equilibrium Z : E isomeric ratios has been measured.