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). The isomerisation of 1,4-diiminophenylene derivatives is discussed as chain→ring or ring→chain tautomerism; the synthesis of (masked) isoindolines is described starting from 1,2-phthaldicarboxaldehyde.