Synthesis,crystal structures and catalytic epoxidation properties of dioxomolybdenum(VI) complexes with hydrazone ligands

A series of dioxomolybdenum(VI) complexes with similar hydrazone ligands have been prepared, specifically [MoO₂L¹(MeOH)] (1), [MoO₂L²(MeOH)] (2) and [MoO₂L³(MeOH)] (3), where L¹, L² and L³ are the dianionic forms of 2-chloro-N′-(2-hydroxybenzylidene)benzohydrazide, 2-chloro-N′-(2-hydroxy-5-methylbenzylidene)benzohydrazide and N′-(3-bromo-5-chloro-2-hydroxybenzylidene)-2-chlorobenzohydrazide, respectively. The complexes were characterized by physicochemical and spectroscopic methods and also by single-crystal X-ray determination. The hydrazone ligands coordinate to the Mo atoms through their phenolate O, imine N and enolic O atoms. The Mo atoms are six-coordinated in octahedral geometries. The complexes show high catalytic activities and selectivities in the epoxidation of cyclohexene with tert-butylhydroperoxide as primary oxidant.     

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.     

Interaction of Fluosilicic Acid with <Emphasis Type="Italic">N-tert</Emphasis>-Butyl-Substituted Urea. Crystal Structure of <Emphasis Type="Italic">N,N</Emphasis>-Di-<Emphasis Type="Italic">tert</Emphasis>-butylurea

Fluosilicic acid reacts with solutions of N,N-di-tert-butylurea (DTBU) in methanol or acetone to form crystalline compounds 2DTBU ? H₂SiF₆ and 2DTBU ? H₂SiF₆ ? Me₂CO, which were characterized by the IR and ¹⁹F NMR spectra and mass spectroscopy supplemented by theoretical calculations. According to the data of IR and ¹⁹F NMR spectra, the complexes are hexafluorosilicates of O-protonated DTBU. They undergo hydrolysis in organic media with water traces; their solubility in water is very low (0.10 and 0.14 wt %, respectively). In the DTBU structure, two independent ligand molecules are joined by hydrogen bonds NH?O(N?O) 2.888(5)–2.944(5) Å).     

Oxidation of Iron and Nickel with 3,5-Di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone in Coordinating Solvents

The final products of oxidation of iron and nickel with 3,5-di-tert-butyl-1,2-benzoquinone in DMSO were identified, and the formal-kinetics relationships of the process were elucidated. The apparent equilibrium constants, enthalpies, and entropies of adsorption of the reactants on the metal surfaces and the rate constants and activation energies of the reactions were determined.     

Syntheses,crystal structures,and catalytic properties of dioxomolybdenum(VI) complexes with hydrazone ligands

Two new dioxomolybdenum(VI) complexes, [MoO₂L¹(CH₃OH)] (1) and [MoO₂L²(H₂O)] (2), where L¹ and L² are dianionic form of N′-(2-hydroxy-3-methoxybenzylidene)-4methoxybenzohydrazide and N′-(2-hydroxy-3methoxybenzylidene)-2-hydroxybenzohydrazide, respectively, have been synthesized and structurally characterized by spectroscopic methods and single-crystal X-ray determination. The complexes are mononuclear molybdenum(VI) compounds. Mo in each complex is octahedral. The difference in the substituent groups in the benzohydrazides leads to coordination of different solvent molecules. Crystals of the complexes are stabilized by hydrogen bonds. The complexes are effective catalysts for sulfoxidation.     

Synthesis of substituted 3,4-dihydropyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones and pyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones by the Biginelli reaction with 3,5-Di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzaldehyde

Three-component acid-catalyzed cyclocondensation of 3,5-di-tret-butyl-4-hydroxybenzaldehyde with urea and ethyl acetoacetate or α-nitroacetophenone (Biginelli reaction) under homogeneous conditions gave the corresponding 5-substituted 3,4-dihydropyrimidin-2(1H)-ones having in position 4 of the heteroring an aryl substituent with sterically shielded hydroxy group. The condensation catalyzed by inorganic salts (Fe³⁺, Co²⁺, Zn²⁺, Li⁺) was successful only with ethyl acetoacetate as initial methylene-active component. Under analogous conditions, acetophenone and 4-fluoroacetophenone gave rise to 4,6-diarylpyrimidin-2(1H)-ones which are capable of undergoing phenol-quinonemethide tautomerism.     

3,5-Di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone in the synthesis of quinolino[4,5-<Emphasis Type="Italic">bc</Emphasis>][1,5]benzoxazepines,aminophenols, and phenoxazines

Reaction of 3,5-di-tert-butyl-1,2-benzoquinone with 5-amino-4-chloroquinolines gave derivatives of a new fused heterocyclic system, substituted quinolino[4,5-bc][1,5]benzoxazepines. The molecular structure of 9,11-di-tert-butyl-2,4,6-trimethyl-7H-quinolino[4,5-bc][1,5]benzoxazepine was determined by X-ray analysis. 3,5-Di-tert-butyl-1,2-benzoquinone reacted with o-nitro-, o-acyl-, and o-methoxycarbonylanilines and some amino-substituted nitrogen-containing heterocycles to form the corresponding sterically hindered N-aryl-(hetaryl)-o-aminophenols. Di-tert-butyl-substituted phenoxazines were obtained as a result of thermal cyclization of intermediately formed quinone imines.     

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.     

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.     

Interaction of 9-substituted anthracenes with oxidation systems <Emphasis Type="Italic">tert</Emphasis>-butylhydroperoxide-metal <Emphasis Type="Italic">tert</Emphasis>-butoxide

9-R-Anthracenes (R = Me, Ph) are effective acceptors of peroxyl and metalalkoxyl radicals in the systems tert-butylhydroperoxide-metal tert-butoxide (M = Al, V, Cr; C₆H₆, 20°C). Isolation of 9-R-9,10-dihydro-9,10-di-tert-butylperoxyanthracenes, 10-R-10-tert-butylperoxy-9-anthrones as major products reliably confirms the formation of tert-butylperoxy radicals and can be used for quantitative assessment of their content.     

Titanium tetra-<Emphasis Type="Italic">tert</Emphasis>-butoxide-<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide oxidizing system: Physicochemical and chemical aspects

The reaction of titanium tetra-tert-butoxide with tert-butyl hydroperoxide (1: 2) (C₆H₆, 20 C) involves the steps of formation of the titanium-containing peroxide (t-BuO)₃TiOOBu-t and peroxytrioxide (t-BuO)₃TiOOOBu-t. The latter decomposes with the release of oxygen, often in the singlet form, and also homolytically with cleavage of both peroxy bonds. The corresponding alkoxy and peroxy radicals were identified by ESR using spin traps. The title system oxidizes organic substrates under mild conditions. Depending on the substrate structure, the active oxidant species can be titanium-containing peroxide, peroxytrioxide, and oxygen generated by the system.     

Two dioxomolybdenum(VI) complexes with hydrazone ligands: synthesis,characterization, crystal structures and catalytic properties

A pair of Mo(VI) complexes, [MoO₂L¹(MeOH)] (1) and [MoO₂L²(MeOH)] (2), where L¹ and L² are the dianions of 2-amino-N’-(3-bromo-5-chloro-2-hydroxybenzylidene)benzohydrazide (H₂L¹) and 2-amino-N’-(3,5-dibromo-2-hydroxybenzylidene)benzohydrazide (H₂L²), respectively, have been prepared and characterized by physico-chemical methods and single-crystal X-ray diffraction. The Mo atom in each complex is coordinated by the phenolate oxygen, imino nitrogen and enolate oxygen of the hydrazone ligand, together with a methanol ligand and two oxo groups, giving a distorted octahedral geometry. The complexes proved to be effective catalysts for the oxidation of various olefins.     

Synthesis,crystal structures,and catalytic property of dioxomolybdenum(VI) complexes with hydrazones

Two new dioxomolybdenum(VI) complexes, [MoO₂(L₁)] _n · 0.5 _n CH₃OH (I) and [MoO₂(L₂)(CH₃OH)] (II), where L1 and L₂ are the dianionic form of N′-[1-(4-diethylamino-2-hydroxyphenyl)methylidene]isonicotinohydrazide and N′-(2-hydroxy-4-methoxybenzylidene)-3-methylbenzohydrazide, respectively, were prepared and structurally characterized by physicochemical and spectroscopic methods and single-crystal X-ray determination. For complex I, a polymeric structure is obtained, which is linked by coordination of the pyridine N atoms to the Mo atoms of other [MoO₂(L₁)] units. Complex II is a mononuclear molybdenum compound. In both complexes, the Mo atoms are in octahedral coordination. The catalytic properties of the complexes indicate that they are efficient catalysts for sulfoxidation.     

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.     

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.     

Reactions of [(3,5-Di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-oxocyclohexa-2,5-dien- 1-ylidene)methyl]phosphonates with Phenols

Dialkyl [(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)methyl]phosphonates reacted with phenol and benzenediols in the presence of trifluoromethanesulfonic acid to give products of electrophilic substitution in the benzene ring, the corresponding diarylmethylphosphonates or [phenylenebis(arylmethylene)]- diphosphonates. The reaction of diphenyl [(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)methyl]phosphonate with 2-methylbenzene-1,3-diol at a ratio of 1: 1 afforded 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-6-hydroxy-7-methyl-2-phenoxy-2,3-dihydro-1,2λ⁵-benzoxaphosphol-6-one.     

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.     

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.     

Synthesis and crystal structure of 5-(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxyphenyl)-1,2,3,5-tetrahydrophenazine

5-(3,5-Di-tert-butyl-4-hydroxyphenyl)-1,2,3,5-tetrahydrophenazine was synthesized by the reaction of 2,6-di-tert-butyl-1,4-benzoquinone-4-(o-aminophenyl)imine with cyclohexanone. The structure of the reaction product was established by X-ray diffraction.     

Yttrium complexes with 3,6-bis(<Emphasis Type="Italic">tert</Emphasis>-butylcatecholate)

Heterometallic complex [K₃Y(Cat³⁶)₃(Dme)₄] (I) or binuclear complex [Y₂(Cat³⁶)₃(Dme)₃] · Dme (II · Dme) is synthesized, depending on the reactant ratio, by the reaction of YCl₃ with 3,6-bis(tertbutylcatecholate) potassium salt (K₂Cat³⁶) in 1,2-dimethoxyethane (Dme). Both complexes are characterized by single-crystal X-ray diffraction analysis (CIF files CCDC nos. 1527929 (I) and 1527930 (II)) and ¹H and ¹³C NMR spectroscopy.