Heterocyclic imines and amines. Part 19. Isoquinoline and other products from α,o-dicyanostilbene and basic reagents
α,o-Dicyanostilbene (1) was cleaved by hydrazine or hydroxylamine under mildly acid conditions to o-cyanobenzyl cyanide (2) and benzaldehyde, isolated as derivatives. Sodamide with compound (1) gave 1-amino-4-cyano-3-phenylisoquinoline: alkoxides similarly gave the 1-alkoxy compounds, the presumed intermediate 3,4-dihydroisoquinoline from the methoxide reaction being isolated and separately dehydrogenated. Acid hydrolysis of the 1-ethoxy compound gave the known 4-cyano-3-phenylisoquinolin-1(2H)-one. With the anion of o-cyanobenzyl cyanide, compound (1) gave a 1-amino-4-cyano-3-(2-substituted phenyl)isoquinoline, which was oxidised to 1-amino-4-cyano-3-(2-carboxyphenyl)isoquinoline. The latter lost water at 210 °C to give yellow 12-cyano-5-iminoisoindolo[2,1-b]isoquinolin-7(5H)-one, closely related to known compounds.