Imine-Based Catechols and -Benzoquinones: Synthesis, Structure, and Features of Redox Behavior.

Novel sterically hindered catechols of the type 3-(RN=CH)-4,6-DBCatH with iminoalkyl or iminoaryl groups in the third position of the aromatic ring have been synthesized and characterized in detail. The -benzoquinones 3-(RN=CH)-4,6-DBBQ have been synthesized by the oxidation of the corresponding catechols. The oxidation of methylimino-substituted catechol with K[Fe(CN)] in alkaline medium leads to the formation of two products: -quinone and diene-dione, the product of the water addition to the corresponding -quinone. Some -benzoquinones react with water or methanol to yield products of water or methanol addition. A prototropic tautomerism is characteristic of catecholaldimines: a quinomethide form is observed in the case of aliphatic amine derivatives, while aryl-substituted catecholaldimines can exist both in the catechol and quinomethide forms in the crystalline state. The formation of dimeric structures motifs is observed in crystals. The electrochemical oxidation of imino-based catechols proceeds via two one-electron processes; the second wave is quasi-reversible, which is unusual for catechols.