Starting from isoquinoline, the cyano substituted N‐methoxyisoquinolinium salts 1.1 and 1.4 are prepared. Their behaviour in the presence of O‐, C‐ and N‐nucleophiles in different aprotic solvents is examined: from the 1‐cyano substituted isoquinolinium derivative 1.1, 1‐ and 3‐animals or 1‐iminium salts are obtained depending on the amine used, and N‐methoxyisocarbostyril 4.1.1 in H2O and OH−. The reaction of the 4‐cyano‐N‐methoxyisoquinolinium salt 1.4 with amines yields 1‐aminals and with OH− the corresponding hemiaminal. Conversion with CN− results in dinitrile derivatives and N‐oxides.

No abstract