Selectivity of Hydrogenations. Part 4. 6- and 8-Substituted Quinaldines. Yield of Tetrahydroderivatives and Basicities of Quinolines

Article abstract of DOI:10.1007/BF00809353

Hydrogenation of 6- or 8-R-substituted quinaldines over platinum in trifluoracetic acid gave higher yields (ca.90percent) of 5,6,7,8-tetrahydroderivatives than hydrogenation of the corresponding quinolines.The pKa-values of 20 quinolines and quinaldines were determined by measuring the half-neutralisation potentials in acetic anhydride.More basic quinolines gave higher yields of 5,6,7,8-tetrahydroproduct; exceptions are 6- and 8-methylquinoline and 8-tert. butylquinoline.Explanations for these observations are suggested. - Keywords:Catalytic hydrogenation; PKa-Values; Quinaldines; Quinolines; 5,6,7,8-Tetrahydroquinolines, yields of.