Nitrogen bridgehead compounds. Part 69 . Studies on quinolizine derivatives. Part 3 . Infrared and 1 H NMR spectroscopic studies of quinolizine derivatives and their monocyclic tautomers

Infrared and 1 H nmr spectra of 4‐oxo, 1 , and 4‐imino, 2 , quinolizine derivatives or their monocyclic tautomers 3, 4 have been comparatively studied. The number of ethoxycarbonyl groups, the signals of the hetero proton, the C(9)‐H, and the C(6)‐CH 3 group in the 1 H nmr spectrum, moreover the N‐H stretching vibration bands proved to be diagnostically important for monocyclic or bicyclic as well as for 4‐oxo or 4‐imino structures. A weak intramolecular hydrogen bridge in compounds 2b and 2f , a strong chelate type hydrogen bridge in 4E and 4F=G could have been demonstrated as well.