Ring-chain tautomerism and other versatile behaviour of 1,4-diimino- and 1,2-phenylene derivatives of some C-substituted serinols

The behaviour of the title compounds, obtained from terephthaldicarboxaldehyde or 1,2-phthaldicarboxaldehyde and certain (non)chiral C-substituted serinols is discussed in terms of ring (chain)–chain (ring) tautomerism (1,4-phenylene derivatives) or formal intramolecular redox isomerisation (1,2-derivatives).