Synthesis,structure, and properties of a new multiredox-active Sn(IV) complex based on 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzoquinone and ferrocenylaldimine phenol

A new mixed-ligand tin(IV) complex 2 derived from 3,6-di-tert-butyl-o-benzoquinone and ferrocenylaldimine phenol 1 has been prepared and characterized by different physicochemical methods (IR, ¹HNMR, and ¹¹⁹Sn NMR spectroscopies). Electrochemical transformations of complex 2 have been studied by cyclic voltammetry. Catecholate and ferrocenyl groups have been found to take part in the redox transformations. Chemical oxidation of complex 2 with silver triflate in a dichloromethane solution has been studied. Formation of monocationic complex 2 ⁺ has been detected by EPR spectroscopy. The catecholate ligand has been found to be the primary redox center subjected to oxidation.     

Geometrical and energetical aspects of structure of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o-</Emphasis>benzoquinones

From the geometrical point of view, all observed conformations of the 3,6-di-tert-butyl-o-benzoquinone fragments are determined by the inequivalent positions of the Me groups of the tBu substitutes relative to the carbonyl oxygen atoms. The geometrical inequivalence is believed to cause the energetic inequivalence of the Me groups. The relevant quantum mechanical computations revealed intramolecular contacts of the C=O···H-(tBu)-type (2.37–3.83 kcal/mole) that can be interpreted to be hydrogen bonding interactions.     

Chlorination of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone in two-phase catalytic system

Chlorination of 3,6-di-tert-butyl-1,2-benzoquinone in a two-phase catalytic system (CH₂Cl₂, HCl- H₂O, H₂O₂, Bu₄NCl) led to halogen addition at the C=C bond, and subsequent dehydrochlorination of the adduct gave 3,6-di-tert-butyl-4-chloro-1,2-benzoquinone. Chlorination of the latter afforded 3,6-di-tert-butyl-4,5-dichloro-1,2-benzoquinone.     

Alkoxylation of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone. New bis-1,2-benzoquinones

Alkoxylation of 3,6-di-tert-butyl-1,2-benzoquinone with a number of diols, including propane-1,3-diol, butane-1,4-diol, di-, and triethylene glycols, and cyclohexane-1,4-diyldimethanol, was studied. Nine new 4-alkoxy-3,6-di-tert-butyl-1,2-benzoquinones were synthesized, four of which were bis-1,2-benzoquinones with different tethers (6–13 atoms) between the quinone fragments. Depending on the length of the chain between the hydroxy groups in glycols, bicyclic 4,5-disubstituted 3,6-di-tert-butyl-1,2-benzoquinones were formed or their stepwise alkoxylation occurred. The newly synthesized o-benzoquinone derivatives can be reduced with alkali metals to give radical anions and converted into semiquinone chelates with manganese carbonyl.     

Chromium(III) and indium(III) 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-semiquinolate complexes as redox mediators of hydrogen sulfide oxidation in reactions with cycloalkanes

The electrochemical oxidation of the chromium(III) and indium(III) complexes with 3,6-di-tert-butyl-o-semiquinolate leading to the formation of active monocationic species is studied by cyclic voltammetry. The reactions of the latter with hydrogen sulfide generate the radical cation of H₂S, whose fragmentation affords the proton and thiyl radical. These complexes are proposed for the first time as redox mediators for the one-pot thiolation of inert cycloalkanes C₆–C₈, which decreases the activation energy of hydrogen sulfide compared to that for direct electrochemical oxidation. The major products of cycloalkane functionalization involving H₂S are thiols and organic di- and trisulfides. The yield of the synthesized compounds depends on the type of the mediator: the chromium(III) complex exhibits the highest efficiency in the electrocatalytic transformations.     

Synthesis and photochemical properties of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-9<Emphasis Type="Italic">H</Emphasis>-carbazole derivatives

Method of synthesis has been developed for a series of 3,6-di-tert-butyl-9H-carbazole derivatives and their photochemical properties have been investigated. The dependence of the Steglich esterification reaction on the nature of the catalyst was studied. The synthesized compounds show fluorescent emission in the range 400–600 nm with a high quantum yield.     

Reactions of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone with mercapto carboxylic acids

Heating of an equimolar mixture of 3,5-di-tert-butyl-1,2-benzoquinone with thiosalicylic acid led to 2-[(4,6-di-tert-butyl-2,3-dihydroxyphenyl)thio]benzoic acid. In the case of β-mercaptopropionic acid, 2-[(4,6-di-tert-butyl-2,3-dihydroxyphenyl)thio]propionic acid was formed, which upon reflux in Ac2O was converted to 6,8-di-tert-butyl-9-hydroxy-3,4-dihydro-2H-1,5benzoxathiepin-2-one.     

Development of a one-stage synthesis of 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-4-ethylbutylphenol from 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenol

Investigation of the catalyzed reaction of 2,6-di-tert-butylphenol with ethanol, ethylene glycol, oligomeric glycols, and paraldehyde in a strongly basic medium permitted to develop a technologically suitable procedure for manufacture of 2,6-di-tert-4-ethyl-butylphenol, used in the synthesis of Antioxidant-425.     

Investigation of cobalt (1,10-phenanthroline)-bis-(3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzosemiquinolate) by X-ray diffraction,IR and ESR spectroscopy,magnetochemistry, and precision calorimetry

The bistable cobalt complex containing two symmetrical 3,6-di-tert-butyl-o-benzoquinone and one 1,10-phenanthroline moieties as ligands (1) was synthesized. Complex 1 was isolated in the individual state and characterized by IR and ESR spectroscopy, X-ray diffraction, magnetochemical studies, and precision calorimetry. A change in temperature causes the reversible metal-ligand electron transfer and spin crossover (redox isomerism) in complex 1 in the crystalline state. The redox-isomeric transformation at ∼250 K is accompanied by the phase transition. The structural study at two temperatures confirmed the changes in the molecular and crystal structure associated with the redox-isomeric transformation.     

Syntheses,structures, and electrochemical properties of the tin(IV) complexes based on the 2-hydroxy-4-<Emphasis Type="Italic">N</Emphasis>-(phenyl)-3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">p</Emphasis>-iminobenzoquinone ligand

A series of the new tin(IV) complexes based on the 2-hydroxy-4-N-(phenyl)-3,6-di-tert-butyl-p-iminobenzoquinone ligand (LH) containing various hydrocarbon substituents R at the metal atom (R = Me, Et, ⁿ Bu, ^t Bu, and Ph) is synthesized. The structures of the synthesized compounds were determined by elemental analysis, IR spectroscopy, and ¹H and ¹¹⁹Sn NMR spectroscopy. The X-ray diffraction analyses are carried out for the LSnPh³ (I) and L²SnEt² (IV) complexes (CIF files CCDC no. 1557840 (I) and 1557839 (IV)). The main electrochemical characteristics in a solution are obtained for the whole series by cyclic voltammetry.     

5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl}-3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl<Emphasis Type="Italic">o</Emphasis>-benzoquinone and related polymers. Synthesis and some properties

A norbornene-containing ortho-quinone, 5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl)-3,6-ditert-butyl-o-benzoquinone, was synthesized by the nucleophilic addition of 5-(hydroxymethyl)bicyclo[2.2.1] hept-2-ene to 3,6-di-tert-butyl-o-benzoquinone. The structure of the compound was established by the X-ray analysis. The monomer obtained undergoes metathesis polymerization in the presence of Grubbs catalyst of the third generation with the formation of polynorbornene containing quinone fragments in the side chains.     

Synthesis of magnesium catecholate and <Emphasis Type="Italic">o</Emphasis>-semiquinone complexes by oxidation of the metal with 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzoquinone

Oxidation of amalgamated magnesium metal with 3,6-di-tert-butyl-o-benzoquinone (1) in different aprotic organic solvents afforded magnesium catecholate and bis-o-semiquinolate complexes. The catecholate derivatives of magnesium CatMgL₂ (Cat is the 3,6-di-tert-butyl-o-benzoquinone dianion, L = THF or Py) were synthesized in high yields in pyridine and tetrahydrofuran, respectively. The reactions in diethyl ether or dimethoxyethane produced hexacoordinated metal bis-o-semiquinolates SQ₂MgL_n (SQ is the 3,6-di-tert-butyl-o-benzoquinone radical anion, L = Et₂O, n = 2; L = DME, n = 1). The reaction with the use of toluene as the solvent gave a magnesium bis-o-semiquinolate complex containing the coordinated unreduced o-quinone molecule. The molecular structures of the [CatMgPy₂]₂ and SQ₂Mg·DME complexes were established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 92–98, January, 2007.     

Novel diphenylsulfimide antioxidants containing 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenol moieties

New diphenylsulfimide derivatives containing substituents with the 2,6-di-tert-butylphenol moiety at the nitrogen atom were synthesized. Their molecular structures were established by X-ray diffraction. Antioxidant activity was experimentally evaluated by spectrophotometry based on hydrogen transfer to the stable radicals, namely, 2,2-diphenyl-1-picrylhydrazyl and the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS^·+), and using in vitro lipid peroxidation in rat brain and liver homogenates. The presence of phenol and diphenylsulfimide moieties in one molecule leads to a significant enhancement of antioxidant activity. The new compounds exhibit moderate inhibitory activity against enzymes involved in carbohydrate and lipid metabolism. The evaluation of antiglycation activity showed that the new sulfimides taken at a concentration of 100 μmol L^–1 have activity comparable with that of aminoguanidine.     

Urotropin synthesis of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylsalicylic acid derivatives

The stability of 3,5-di-tert-butylsalicylic aldehyde against oxidation is due to autoinhibiting of the chain process. However its oxidation into 3,5-di-tert-butylsalicylic acid was performed at the use of acetyl protection of the hydroxy group. In reaction of 6-bromo-2,4-di-tert-butylphenol with urotropin the formation was discovered of 3,5-di-tert-butylsalicylic acid, its nitrile and amide.     

Mono-<Emphasis Type="Italic">meso</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylporphyrin

Summary. Treatment of meso-tetra(tert-butyl)porphyrin with sulfuric acid/n-butanol affords a mixture of porphyrin and mono-tert-butylporphyrin in relatively high yield.     

Synthesis of new hydrazones based on <Emphasis Type="Italic">o</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzohydrazides

o- and p-Hydroxybenzohydrazides reacted with various unsaturated aromatic aldehydes to give the corresponding N′-(hydroxybenzoyl)hydrazones. Inhibitory activity of the obtained hydrazones against cathepsin E was evaluated.     

Synthesis of derivatives of <Emphasis Type="Italic">o</Emphasis>-aminoacetophenone and <Emphasis Type="Italic">o</Emphasis>-aminobenzyl alcohol

Oxidation of 2′-hydroxy-8-methylspiro[4H-benz-1,3-oxazin-2-one-6,1′-cyclopentane] or N-mesyl-2-(cyclopent-1-en-1-yl)-6-methylaniline provided the corresponding ketones. The rearrangement of these ketones oximes under treatment with thionyl chloride gave rise to nitriles of 5-(2-amino-3-methylphenyl)-5-oxopentanoic or 5-(2-methanesulfamido-3-methylphenyl)-5-hydroxypentanoic acids. By heating 5-(2-acetylamido-3-methylphenyl)-5-oxopentanoic acid with LiH in THF3-(2,8-dimethylquinol-4-on-3-yl)propanoic acid was obtained.     

Alkaline hydrolysis of diethyl <Emphasis Type="Italic">N</Emphasis>-acetylamino(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzyl)malonate

Alkaline hydrolysis of diethyl N-acetylamino(3,5-di-tert-butyl-4-hydroxybenzyl)malonate is accompanied by decarboxylation. The efficiency of this process depends on the temperature and ratio of the reactants. A possibility of tautomerism with migration of the proton of phenolic hydroxyl and the influence of the structure on the antioxidation properties were considered on the basis of analysis of the IR spectral data and quantum chemical (PM6) calculation of the structures. The energies of homolysis of the O-H bond of phenolic hydroxyl were calculated for a series of the synthesized compounds. It is proposed to predict the antioxidation activity on the basis of these values.     

Conformational Polymorphism in Racemic 2,4-Di-<Emphasis Type="Italic">o</Emphasis>-Benzoyl-6-<Emphasis Type="Italic">o</Emphasis>-Tosyl <Emphasis Type="Italic">myo</Emphasis>-Inositol 1,3,5-Orthoacetate

The title compound, C₂₉H₂₆O₁₀S, yields two conformational polymorphs concomitantly from dichloromethane-methanol mixture; the major polymorph grows as plates (Form I, monoclinic, P2₁/n) and the minor polymorph grows as needles (Form II, triclinic, P-1). The two forms differ mainly in orientation of the tosyl group. In Form I, sulfonyl oxygen of the tosyl group makes intermolecular C −H…O interactions, whereas the same group in Form II is involved in an intramolecular short dipolar S=O…C=O (sulfonyl-carbonyl) contact. The molecular organization and the influence of various weak non-covalent interactions that stabilize these conformers in the crystal lattices are discussed.     

Binuclear nickel(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylbenzoate and 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzoate anions and 2,3-lutidine: the synthesis,structure, and magnetic properties

Two novel binuclear nickel(II) complexes [Ni₂(O₂CR)₄(2,3-lut)₂] (O₂CR is anion of 3,5-di(tert-butyl)benzoic acid (bzo, 1) and 4-hydroxy-3,5-di(tert-butyl)benzoic acid (hbzo, 2); 2,3-lut is 2,3-lutidine) with four carboxylate bridges were synthesized. The structure of complex 1 was determined by X-ray diffraction. Both dimers 1 and 2 were characterized by elemental analysis, IR spectroscopy, and magnetic measurements. The presence of the α-substituent in the apical lutidine ligand leads to a distortion of the geometry of the metal carboxylate core in complex 1 as a result of short steric contacts Me(Lut)…O(OOCR) (3.134(7) Å). This is apparently responsible for a considerable decrease in the exchange parameters of complexes 1 and 2 (J =–30.0 and–23.6 cm^–1, respectively) as compared to known analogues. Density functional calculations of the structure and magnetic properties of 1 and 2 were carried out by the UB3LYP/6-31G(d,p) method.