Synthesis and nuclear magnetic resonance spectra of 2H‐pyrido [1,2‐a] pyrimidin‐2‐ones

Abstract

AbstractReaction of ethyl phenylpropiolate with several 2‐aminopyridines afforded the corresponding 2H‐pyrido[1,2‐a] pyrimidin‐2‐ones in good yields. Analysis of the nmr spectra of these compounds and their hydrobromides were based on comparing their spectra with their 3‐deuterated analogues. It was found that in these 2‐oxo compounds, the proton at position‐7 is shielded and absorbs together with the olefinie proton at position‐3 in the region of 5 6.35‐6.70 ppm. The latter proton could be used for differentiating these compounds from the corresponding 4‐oxo isomers which have already been identified by the deshielded proton at pusition‐6 near § 9.0 ppm. The ir and nmr spectral data for all these compounds are tabulated and discussed.