Isoquinolinium N-arylimides and some cycloadditions to heterocumulenes

Article abstract of DOI:10.1002/(SICI)1099-0690(199802)1998:2<379::AID-EJOC379>3.0.CO;2-F

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-phenyl-imide 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 the N-phenylimide 19, since a cycloreversion equilibrium is established in solution.