Vinylamine—XII : Untersuchungen zur substituentenabhängigkeit der imin-enamin-tautomerie an β-aryl-vinylaminen

The equilibria of imine-enamine tautomeric compounds 3–6 have been determined by NMR spectroscopy. With exception of the 4-nitro group, the influence of the substituents R² is represented by the Hammett σ-values. The same is true for the cis-trans-isomerism of 3E–5E. It is shown that the trans-enamine is stabilized by electron-withdrawing substituents R². Slopes and intercepts of the regression lines depend largely on the substituents on nitrogen or α-carbon. The enamine isomer is favored by an aryl substituent in the α-position.