Reactions of dialkyl (3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-oxocyclohex-2,5-dienylidenemethyl)phosphonates with alcohols and some transformations of the adducts

Reactions of dialkyl [(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)methyl]phosphonates with butyl, benzyl and propargyl alcohols in the presence of catalytic amounts of trifluoromethanesulfonic acid resulted in the formation of nucleophilic 1,6-addition products. Azide-alkyne cycloaddition reaction of dimethyl (3,5-di-tert-butyl-4-hydroxyphenyl)(prop-2-ynyloxy)methylphosphonate with benzyl azide and 1,3-bis-(2-azidoethoxy)benzene in the presence of copper sulfate and sodium ascorbate afforded 1,2,3-triazoles with sterically hindered phenol fragments.     

Reactions of benzazole-2-thiones with 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzyl acetate

The benzylation of benzothiazole(oxazole, imidazole)-2-thiones with 3,5-di-tert-butyl-4-hydroxybenzyl acetate involves either the sulfur or nitrogen atom depending on the reaction conditions. The S- and N-benzylation products of benzazole-2-thiones are kinetically and thermodynamically controlled products, respectively. The use of 3,5-di-tert-butyl-4-hydroxy-benzyl acetate allows sterically hindered hydroxybenzyl derivatives of benzаzole-2-thiones to be generally synthesized under milder conditions than in known methods of their synthesis.     

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.     

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.     

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.     

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.     

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.     

Antistress properties of sodium 1-<Emphasis Type="Italic">N</Emphasis>-acetylamino-1-carboxy-2-(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxyphenyl)propionate

The effect of a spatially-hindered phenol, namely sodium 1-N-acetylamino-1-carboxy-2-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, on the functionality of mitochondria of rat liver was studied. Stress impact caused a 3 to 4-fold increase in the fluorescence intensity of the products of lipid peroxidation (LPO) in the membranes of these organelles. The preparation reduced the intensity of LPO to the control level, which was conductive to maintaining high functional activity of the mitochondria. Prevention of mitochondrial dysfunction was probably associated with an increase in the resistance of animals to stress factors.     

About selective methods of synthesis of 6-<Emphasis Type="Italic">tert</Emphasis>-butyl-2-methylphenol and 6-<Emphasis Type="Italic">tert</Emphasis>-butyl-2,4-dimethylphenol

Vapor phase catalytic methylation with methanol of 2-tert-butylphenol at the temperature 280–300°C proceeds selectively with formation of 6-tert-butyl-2-methylphenol. Elevating reaction temperature above 300°C leads to formation of 2,6-dimethylphenol. Reaction of 2-tert-butylphenol with methanol in alkaline medium in the presence of zinc oxide is shown to lead initially to formation of a mixture of calixarenes and methylenebisphenols that at elevated temperature exert splitting leading in future to 6-tert-butyl-2,4-dimethylphenol. Obtaining it in this reaction from 2,2′-methylenebis-(6-tert-butyl-4-methylphenol) proceeds selectively. Pathways of the reductive methylation of methylenebisphenols with methanol in alkaline medium is considered.     

Synthesis of substituted 3-[(4-oxocyclohexa-2,5-dien-1-ylidene)-hydrazinylidene]-1,3-dihydro-2<Emphasis Type="Italic">H</Emphasis>-indol-2-ones and their reactions with hydrogen chloride

4-Hydroxyphenylhydrazones of isatin derivatives were synthesized and oxidized with lead compounds to the corresponding azines. The introduction of isatin fragment in a quinoid system increases the redox potential of the system compared with 1,4-benzoquinone thus presumably resulting in the prevalence of 1,4-addition process. By an example of the reaction of N-methylisatins with hydrogen chloride it was shown that the reaction proceeded in keeping with the theoretically predicted direction. Azines, derivatives of isatin unsubstituted at the nitrogen atom, do not react with hydrogen chloride because of the presence of a strong intramolecular hydrogen bond.     

Synthesis and some properties of tetrakis-3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzylated calix[4]resorcinols

A method for the synthesis of new calix[4]resorcinols tetra-3,5-di-tert-butyl-4-hydroxybenzyl derivatives is developed. Their interaction with methyldichlorophosphonate, dimethyldichlorosilane in the presence of a base leads to formation of organophosphorus-organosilicon cavitands. Acetylation of hydroxybenzylated calix[4]resorcinols with acetic anhydride leads to products of either incomplete or full acetylation depending on experimental conditions.     

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.     

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.     

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).     

Anionic condensations of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4(2)-hydroxybenzaldehydes in the presence of weak bases

Products of the reactions of 4- and 2-hydroxy-3,5-di-tert-butyl-benzaldehydes with malonic acid, diethyl malonate, and acetic anhydride in the presence of weak bases were isolated and identified. The reactions of 3,5-di-tert-butyl-4-hydroxybenzaldehyde with malonic acid and acetic anhydride in the presence of sodium acetate and piperidine gave 3,5-di-tert-butyl-4-hydroxycinnamic acid. The reaction of its 2-hydroxy isomer with acetic anhydride stopped at the stage of formation of the corresponding O-acetyl derivative, while in the reaction with malonic acid the corresponding substituted cinnamic acid and its lactone (coumarin derivative) were formed as intermediate products in a transformation sequence finally leading to 3-(3,5-di-tertbutyl-2-hydroxyphenyl)-3-piperidinopropionic acid and 6,8-di-tert-butyl-2-oxo-3,4-dihydro-2H-chromen-4-ylacetic acid. Analogous differences were typical of reactions of isomeric 4- and 2-hydroxy-3,5-di-tert-butylbenzaldehydes with diethyl malonate. The transformations of the 2-hydroxy isomer were accompanied by hydrolysis and formation of an adduct of intermediate coumarin derivative with diethyl malonate and piperidine.     

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 properties of tetra-(4-<Emphasis Type="Italic">tert</Emphasis>-butyl-5-nitro)phthalocyanines

The interaction of 4-tert-butyl-5-nitrophthalonitrile with a series of metal acetates has yielded the corresponding metal phthalocyaninates. The treatment of magnesium tetra(4-tert-butyl-5-nitro)phthalocyaninate with hydrochloric acid has afforded tetra(4-tert-butyl-5-nitro)phthalocyanine. Spectral properties of the prepared macrocycles have been studied. The nature of the organic solvent and the complex forming metal marginally affect the position of the Q band in the electron absorption spectra of the studied compounds. It has been demonstrated that the prepared phthalocyanines can dye polymer materials and are catalytically active towards oxidation of a model sulfur-containing compound.     

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.     

DFT-calculated structure of protonated tetraphenyl <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene tetraketone

Using DFT calculations, two of the most probable structures (A, B) of the tetraphenyl p-tert-butylcalix[4]arene tetraketone·H₃O⁺ cationic complex species were derived. The hydroxonium ion H₃O⁺, placed in the coordination cavity formed by the calix[4]arene lower-rim groups, is bound by strong hydrogen bonds to the phenoxy oxygen atoms of the calix[4]arene ligand (structures A, B) and also to one carbonyl oxygen (structure B). Correspondence: Emanuel Makrlík, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic.