66 Quinolines and Isoquinolines
Oxidation and reduction
N-Alkylquinolinium and -isoquinolinium salts are oxidised in alkaline solution to N-alkyl-quinolin-2-ones and
- isoquinolin-1-ones, respectively – the adduct formed by the ready addition of hydroxide is oxidised.
The heterocyclic ring is more easily reduced than the benzene ring. Hydride reagents bring about selective reductions
of the heterocyclic ring of N-alkylquinolinium or -isoquinolinium salts.
Alkyl substituents
The particular acidity of the protons of pyridine - and -alkyl groups is echoed by quinoline-2- and 4-alkyl groups
and by alkyl at the isoquinoline 1-position. Condensation reactions with alkyl groups at these activated positions can
be achieved with either basic or acidic catalysis.