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

Novel sterically hindered catechols of the type 3-(RN=CH)-4,6-DBCatH 2 with iminoalkyl or iminoaryl groups in the third position of the aromatic ring have been synthesized and characterized in detail. The o -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 3 [Fe(CN) 6 ] in alkaline medium leads to the formation of two products: o -quinone and diene-dione, the product of the water addition to the corresponding o -quinone. Some o -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.