The red isoquinolinium N‐arylimides 19−23 are azomethine imines of which the C=N bond is part of an aromatic ring. The N‐(4‐nitrophenyl)imide 22 and the N‐(2‐pyridyl)imide 23 were obtained crystalline; in solution the latter equilibrates with the hexahydrotetrazine 24 as its dimer. The N‐phenylimide 19 is not stable; an isolated solid appears to be a tetramer. Generated by deprotonation of 11−13, the N‐arylimides 19−21 undergo in situ cycloadditions to carbon disulfide, phenyl isocyanate, phenyl isothiocyanate, and diphenylketene. The storable CS2 adduct 29 offers a neutral source of theN‐phenylimide 19, since a cycloreversion equilibrium is established in solution.

The red isoquinolinium N-arylimides 19؊23 are azomethine mer. Generated by deprotonation of 11؊13, the N-arylimides 19؊21 undergo in situ cycloadditions to carbon disulfide, imines of which the C=N bond is part of an aromatic ring. The N-(4-nitrophenyl)imide 22 and the N-(2-pyridyl)imide 23 phenyl isocyanate, phenyl isothiocyanate, and diphenylketene. The storable CS 2 adduct 29 offers a neutral source of were obtained crystalline; in solution the latter equilibrates with the hexahydrotetrazine 24 as its dimer. The N-phenyl-the N-phenylimide 19, since a cycloreversion equilibrium is established in solution. imide 19 is not stable; an isolated solid appears to be a tetra-