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

Abstract

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.

Catechol-Containing Schiff Bases on Thiacalixarene: Synthesis, Copper (II) Recognition, and Formation of Organic-Inorganic Copper-Based Materials

“…Figure 2 and Figures S17–S20 show the UV-vis spectra of the mixtures of thiacalixarenes 8 – 10 and the monomer 11 with a 10-fold excess of all the studied metal cations in the mixture CH 3 OH-CHCl 3 (1:1). UV-vis spectra of the macrocyclic compounds 8 – 10 are typical for catecholaldimines in polar solvents [ 48 ]. There are four main bands in the UV spectra of pure macrocyclic compounds 8 – 10 .…”

Synthesis and Antioxidant Activity of New Catechol Thioethers with the Methylene Linker

“…The lengths of the oxygen-carbon bonds O(1)–C(1) and O(2)–C(2) as well as the carbon-carbon of the C(1–6) ring are characteristic of catechols [ 25 , 65 , 66 , 67 , 68 ]: O(1)–C(1), 1.377(2) Å; O(2)–C(2), 1.362(2) Å. The carbon-carbon bonds of the six-membered carbon ring C(1–6) average 1.395 ± 0.015 Å and ones are aromatic.…”

“…Intramolecular hydrogen bonds are observed in the structure: the O(2)–H(2)...N(1) contact has a distance of 1.82(1) Å, the corresponding O(2)–H(2)–N(1) angle is 172.8 (1)°, and the distance O(1)–H(1)...O(2) is 2.01(1) Å (the corresponding O(1)–H(1)–O(2) angle is 123.8(1)°). These values are typical for intramolecular hydrogen bonding in catechols [ 68 ].…”

Catechol‐ and Phenol‐Containing Thio‐Schiff Bases: Synthesis, Electrochemical Properties and Biological Evaluation

“…The benzothiazoline (imino‐thiol) and catechol groups are both redox‐active. The compounds with benzothiazoline fragment have low oxidation potentials (0.77–0.80 V) [19] in comparison with the sterically‐hindered catechols with electron‐withdrawing group (1.10–1.25 V) [17b] . The previously studied 2,6‐di‐ tert ‐butyl‐4‐((2‐mercaptophenyl)iminomethyl)phenol ((2‐HSPh)−N=CH−Ph‐4‐OH) is also capable of cyclization with a formation of benzothiazoline fragment.…”