Synthesis of indole-4-carboxaldehydes and 4-Acetylindole from N-alkyl-5-aminoisoquinolinium salts

Article abstract of DOI:10.1002/jhet.5570370545

N-Alkyl-5-aminoisoquinolinium salts (8a-d) are converted into indole-4-carboxaldehydes (1a-c) on heating in a two phase alkyl acetate-water system containing an excess of a 2:1 sodium bisulfite-sodium sulfite mixture, 4-Acetylindole 1e is prepared in the same way from 1-methyl-2-cyanomethylisoquinolinium bromide 8f.