TAUTOMERISM IN KETOMETHYLQUINOLINES .4. THE ULTRAVIOLET-SPECTRA OF 2-KETOMETHYLQUINOLINES

Ultraviolet spectral data for a series of 36 2-ketomethylquinolines have been recorded. Members previously shown to be exclusively keto tautomers had spectra closely similar to that of 2-methylquinoline. Most of the rest, which were largely or exclusively in the enaminone forms, showed strong long wavelength absorptions. These are shown to be consistent with cis-s-cis enaminone structures. In aqueous acid, most of the enaminones protonated on carbon and those with electron-withdrawing groups were deprotonated in molar aqueous sodium hydroxide. © 1990.