Resistance of polyfluorinated complete esters of polyhydric alcohols to thermal oxidation: Comparison with nonfluorinated analogs

Complete esters of pentaerythritol, trimethylolpropane, and 2,2-dimethyl-1,3-propanediol with polyfluorinated carboxylic acids were prepared by esterification. As determined by differential thermal gravimetric analysis in air, the resistance of the esters to thermal oxidation decreases in going from pentaerythritol derivatives to those of trimethylolpropane and then to those of 2,2-dimethyl-1,3-propanediol. The compounds synthesized surpass their nonfluorinated analogs in the resistance to thermal oxidation.     

Peroxy radical reactivities in the cooxidation of ethylbenzene and substituted 3-phenylindans

The rate constants of peroxy radical recombination in the oxidation of 1-methyl-3-phenylindan, 1,3-dimethyl-3-phenylindan, and 1,1-dimethyl-3-phenylindan were measured using the nonstationary-state technique. A cooxidation method was applied to obtain the reactivities of these compounds with respect to α-phenylethyl peroxy radicals.     

Analysis of the stable free radical scavenging capability of artificial polyphenol mixtures and plant extracts by capillary electrophoresis and liquid chromatography–diode array detection–tandem mass spectrometry

The oxidation process of phenolic compounds of an artificial mixture consisting of six polyphenols and the extract of eggplant (Solanum melongena) skin was monitored by using capillary zone electrophoresis and liquid chromatography–diode array detection–tandem mass spectrometry. The methods developed enabled simultaneous evaluation of the antioxidative capability of each compound. The above oxidation process was carried out using two radicals, viz. the 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radicals generated via the Fenton reaction. The radical scavenging effects of artificial and natural polyphenol mixtures were compared.     

Reactions of bromine-containing organozinc compounds derived from α,α-dibromo ketones with 2-arylmethylideneindan-1,3-diones and 5-arylmethylidene-2,2-dimethyl-1,3-dioxane-4,6-diones

Bromine-containing organozinc compounds generated from 1,1-dibromo-3,3-dimethylbutan-2-one reacted with 2-arylmethylideneindan-1,3-diones and 5-arylmethylidene-2,2-dimethyl-1,3-dioxane-4,6-diones to give 3-aryl-2-(2,2-dimethylpropanoyl)spiro[cyclopropane-1,2′-indan]-1′,3′-diones and 1-aryl-6,6-dimethyl-2-(2,2-dimethylpropanoyl)-5,7-dioxaspiro[2.5]octan-4,8-diones, respectively. Reactions of 2-arylmethylideneindan-1,3-diones with bromine-containing zinc enolates derived from 1-aryl-2,2-dibromopropan-1-ones and 2,2-dibromo-1,2,3,4-tetrahydronaphthalen-1-one resulted in the formation of 2-aroyl-3-aryl-2-methylspiro-[cyclopropane-1,2′-indan]-1′,3′-diones and 2,3: 8,9-dibenzo-12-phenyldispiro[4.0.5.1]dodecane-1,4,7-trione, respectively.     

Photochemical and radical initiator-induced reaction of allylic indium compounds

Intramolecular cyclization of allylic radicals generated from allylindium compounds both by photolysis or by the reaction of radical initiators was examined. The photolysis of allylic indium compounds, prepared from 8-bromo- or 8-iodooct-1,6-dienes and powdered indium metal, led to the formation of the 5-exo-trig products. Benzoyl peroxide as a radical initiator was also effective for the cyclization. In contrast, the radical initiators with oxidizing nature, such as tert-butyl hypochlorite, induced iodocyclization producing iodomethylcyclopentane via an oxidation of the iodide on the indium atom.     

The reductive dimerization of some 1,3-dienes and of 1,3,5-cycloheptatriene in the presence of trimethylchlorosilane: a DFT investigation

Treatment of 1,3-dienes and 1,3,5-cycloheptatriene by chlorotrimethylsilane in the presence of wire of lithium led mainly to reductive dimerization with formation of bis(allylsilane) derivatives. Bis-silyl compounds obtained: from 1,3-butadiene, 1,8-bis(trimethylsilyl)-2,6-octadiene (70%); from isoprene, (Z,Z)-2,7-dimethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (44%) and 2,6-dimethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (19%); from butadiene-isoprene mixture (1:1), 3-methyl-1,8-bis(trimethylsilyl)-2,6-octadiene (55%); from 2,3-dimethylbutadiene, (E,E)-2,3,6,7-tetramethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (36%), from 1,3-cyclohexadiene, 4,4′-bis(trimethylsilyl)-bicyclohexyl-2,2′-diene (48%); from 1,3,5-cycloheptatriene, 1,1′-bi[(S^∗,S^∗)-6-(trimethylsilyl)cyclohepta-2,4-dien-1-yl] (53%). The structure of the various intermediates (radical anion, dianion, silylated radical, silylated anion) has been established by calculations at the B3LYP/6-311++G(d,p) level of theory with zero-point energy correction. These results are in accordance with a pathway including the formation of a radical anion, its silylation furnishing to a γ-silylated allylic radical followed by a dimerization reaction in the head to head manner.     

Preparation and some properties of 2H-imidazole 1,3-dioxides,derivatives of alicyclic 1,2-dioximes

The corresponding 2H-imidazole 1,3-dioxides were obtained by the reaction of cyclohexanedione and cycloheptadione 1,2-dioximes with acetone, cyclopentanone, and methyl ethyl ketone. The reactions of these compounds with hydroxylamine hydrochloride, NaBH₄, a Grignard reagent, and acetic anhydride in the presence of H₂SO₄ were studied in the case of 2,2-dimethyl-4,5,6,7-tetrahydro-2H-benzimidazole 1,3-dioxide. Bromination of the latter and 2,2-dimethylcyclohepta-2H-imidazole 1,3-dioxide with N-bromosuccinimide gave the corresponding dibromo derivatives, the bromine atoms in which are replaced by acetoxy and hydroxy groups. 4,7-Dihydroxy-2, 2-dimethyl-4,5,6,7-tetrahydro-2H-benzimidazole 1,3-dioxide, which was obtained by oxidation with MnO₂ was converted to a quinone, viz., 2,2-dimethyl-4,7-dioxo-4,7-dihydro-2H-benzimidazole 1,3-dioxide. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 808–813, June, 1980.     

Radical and Electrophilic Reactions of Anodic Oxidation Intermediates of Organophosphorus Compounds

Abstract

Cationic radicals generated by anodic oxidation of organophosphorus(III) compounds are superelectrophilic radicals. This determines the pattern of their reactivity towards various substrates. The oxidation of (RO)₂ PO^? and (RO)₂PS^? gives corresponding radicals. Interaction of the mentioned radical species with ArH and olefines includes a common stage of radical adduct formation. It has been stated that the oxidation of the adduct into corresponding carbonium ion plays an important role in the following adduct conversions. This is particularly confirmed by the difference in the composition of products obtained in conditions of homogeneous (via photolysis or with stable radical cations) and heterogeneous (on the anode surface) generation of phosphorylating species.     

Reactions of dialkyl 4-bromo-2,2-dimethyl-3-oxohexane-1,6-dioates,-heptane-1,7-dioates with zinc and aromatic aldehydes

Zinc enolates generated from dimethyl 4-bromo-2,2-dimethyl-3-oxohexane-1,6-dioate and zinc reacted with aromatic aldehydes giving methyl 2,2-dimethyl-3-oxo-3-(5-oxo-2-aryltetrahydrofuran-3-yl)propanoates. The reaction of zinc enolates obtained from dimethyl 4-bromo-2,2-dimethyl-3-oxoheptane-1,7-dioate and zinc with aromatic aldehydes depending on the synthesis conditions led to the formation either methyl 2,2-dimethyl-3-oxo-3-(6-oxo-2-aryltetrahydropyran-3-yl)propanoates or 3-(5,5-dimethyl-4,6-dioxo-2-aryltetrahydropyran-3-yl)propanoates. The compounds synthesized formed as a single diastereomer of E-configuration.     

Three-component condensation of Meldrum’s acid with 2-naphthylamine and esters derived from vanillin

Three-component condensation of Meldrum’s acid (2,2-dimethyl-1,3-dioxane-4,6-dione) with 2-naphthylamine and esters derived from vanillin involves intermediate formation of N-arylmethylidene-2-naphthylamines which are cleaved with Meldrum’s acid to give 5-arylmethylidene-2,2-dimethyl-1,3-dioxane-4,6-diones and arylmethylideneketenes. Reaction of the latter with 2-naphthylamine leads to formation of 2-methoxy-4-(3-oxo-1,2,3,4-tetrahydrobenzo[f]quinolin-1-yl)phenyl carboxylates.     

Study of the radical chemistry promoted by tributylborane

The structures of radicals generated in the oxidation process of trialkylborane were detected based on ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC/Q-ToF MS) combined with the spin trapping method. Structural identification of the spin adducts produced by 5,5-dimethyl-1-pyrroline-1-oxide with radicals could be carried out unambiguously by combining the data obtained by UPLC/Q-ToF MS analyses. Then the oxidation mechanism was described. To specify the inter-relationships between the oxidation process of trialkylborane and the concomitant radical chemistry, four kinds of alkanes providing different H-abstraction reactivity to alkoxy radical were chosen as radical capturers. The final oxidation products of trialkylborane were characterized by GC?CMS and ¹¹B-NMR. The results indicted that the radical content was not only affected by the oxidation degree of trialkylborane, but also done by the activity of alkane. Especially the hydrogen atom abstraction by n-butoxy radical played an important role in the oxidation process of tributylborane, which would promote the oxidizability of tributylborane and deepen the oxidation degree of tributylborane.     

Dérivés C-glycosyliques XXIII. Radicaux libres stables dérivés de sucre Communication préliminaire

Treated with 2,3-dimethyl-2,3-bis-(hydroxylamino)-butane, aldehydo-dialdofuranoses ( 1 ) gave a mixture of two compounds: a 1,3-dihydroxyimidazolidine ( 2 ) and a 1-hydroxyimidazoline ( 3 ). Oxidation (PbO₂) of compounds 3 gave stable free radicals having the structure of 2-C-Glycosyl-4,4,5,5-tetramethylimidazolines 1-oxyl ( 4 ), whereas 2-C-Glycosyl-4,4,5,5-tetramethylimidazolines 3-oxide 1-oxyl ( 5 ) were formed by oxidation of 2 . The ESR. spectra of compounds 4 and 5 establish the structure of the imidazoline part of these radicals and provide informations on the sugar moiety.     

Electrochemical oxidation of 2H-imidazole N-oxides

Electrochemical oxidation of 2H-imidazole N-oxides was studied using cyclic voltammetry and ESR spectroscopy. The formation of the 2,2-dimethyl-4,5-diphenyl-2H-imidazole 1,3-dioxide radical cation was noticed for the first time. The possibility of reaction between the 2H-imidazole N,N-dioxide radical cation and methanol including the detachment of a hydrogen atom from the MeOH methyl group was demonstrated.     

Antioxidant activity of 2-methyl-1,3-benzoxazol-6-ol

Antioxidant effect of 2-methyl-1,3-benzoxazol-6-ol in radical chain oxidation of organic compounds with molecular oxygen was studied. Antiradical activity in the reaction with stable diphenylpicrylhydrazyl radical was examined by photocolorimetry. The kinetic parameters of the reaction of 2-methyl-1,3-benzoxazol-6-ol with peroxy radicals of different natures were determined by volumetric and chemiluminescence methods. A relation was found between the antioxidant activity and electronic structure parameters calculated by quantum-chemical methods. Factors responsible for differences in chemiluminescence in the oxidation of organic substances with different polarities in the presence of the title compound were analyzed.     

New Chiral Diamines of the Dioxolane Series: (+)-(4S,5S)-2,2-Dimethyl-4,5-bis(diphenylaminomethyl)- 1,3-dioxolane and (+)-(4S,5S)-2,2-Dimethyl-4,5-bis(methyl- aminomethyl)-1,3-dioxolane

The reaction of sodium diphenylamide with 2,2-dimethyl-4,5-bis(tosyloxymethyl)-1,3-dioxolane gave (+)-(4S,5S)-2,2-dimethyl-4,5-bis(diphenylaminomethyl)-1,3-dioxolane, which was brought into complex formation with cobalt chloride. Treatment of 2,2-dimethyl-4,5-bis(tosyloxymethyl)-1,3-dioxolane with sodium N-methylanilide resulted in cleavage of the SÄO bond in the p-toluenesulfonate moiety with formation of N-methyl-N-phenyl-p-toluenesulfonamide and 4,5-bis(hydroxymethyl)-2,2-dimethyl-1,3-dioxolane disodium salt. Diethyl (4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-dicarboxylate reacted with methylamine to give the corresponding dicarboxamide which was reduced with lithium aluminum hydride to (4S,5S)-2,2-dimethyl-4,5-bis(methylaminomethyl)-1,3-dioxolane having chiral carbon and nitrogen atoms.     

Temperature-adaptable fibers containing substances with solid—solid transitions

Incorporation of 50% aqueous solutions of compounds (exhibiting high ΔH values due to solid—solid transitions prior to melting or crystallization) into hollow fibers or treatment of conventional fibers with these solutions, produced after drying and conditioning, modified fibers with 2–4 times the heat content (Q) of the corresponding untreated fibers in a given temperature interval. Of the compounds evaluated, 2,2-dimethyl-1,3-propanediol and 2-hydroxymethyl-2-methyl-1,3-propanediol produced the most reliable and reproducible thermal effects in the modified fibers that lasted through 50 heating and cooling cycles. Of the treated fibers, hollow rayon was the most effective, followed by cotton, then hollow polypropylene relative to the corresponding untreated fibers. As monitored by differential scanning calorimetry, these modified fibers had thermal storage and release values useful at temperatures as high as 72–102°C on heating and as low as 37-7°C on cooling, with generally little variability in their Q values within the same fiber or between different batches of the same fiber. Other compounds of this type were not effective for use with the fibers due to sublimation/high vapor pressure characteristics (2,2-dimethyl-1-propanol and pentaerythritol) or because of their anomalous and inconsistent thermal behavior (2-amino-2-methyl-1,3-propanediol).     

Heterocyclizations of 5-methylpyrazol-3-amine with unsaturated arylaliphatic carboxylic acid derivatives

Cyclocondensation of 5-methylpyrazol-3-amine with methyl cinnamate and arylmethylidenemalonic acids in DMF and methanol leads to the formation of 7-aryl-2-methyl-6,7-dihydropyrazolo[1,5-a]-pyrimidin-5(4H)-ones. Arylmethylidenemalonic acids react with the title amine at a ratio of 1:2 in nitrobenzene to give 4-aryl-3,5-dimethyl-1,7-dihydrodipyrazolo[3,4-b:4′,3′-e]pyridines. Heterocyclizations of 5-methylpyrazol-3-amine with 5-arylmethylidene-2,2-dimethyl-1,3-dioxane-4,6-diones or their precursors, para-substituted benzaldehydes and 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum’s acid) in all solvents (methanol, DMF, and nitrobenzene) give the corresponding 4-aryl-3-methyl-2,4,5,7-tetrahydropyrazolo[3,4-b]pyridin-6-ones. The structure of 3-methyl-4-(4-nitrophenyl)-2,4,5,7-tetrahydropyrazolo[3,4-b]pyridin-6-one was proved by X-ray analysis.     

Lactam and amide acetals. 52. Reaction of dimethylformamide diethylacetal with 2,2-dimethyl-4,6-dioxo-1,3-dioxane (Meldrum's acid)

Depending on the conditions of carrying out the reaction of dimethylformamide diethylacetal with the Meldrum's acid, either 2,2-dimethyl-4,6-dioxo-5-(N,N-dimethyl-aminomethylene)-1,3-dioxane or N,N,N¹N¹-tetramethylformamidinium salt of 2,2-dimethyl-4,6-dioxo-5-(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl)methylene-1,3-di-oxane are formed. The two compounds can react with primary amines to form N-substituted 2,2-dimethyl-4.,6-dioxo-5-aminomethylene-1,3-dioxanes.For Communication 51, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 184–187, February, 1988.     

Synthesis of some substituted 1,3-thiazolines and 1,3-thiazolidines

Sodium salts of 2, 2-dimethyl-4-mercapto-5-oxo-1,3-thiazoline and 2-oxo-3-mercapto-1-thia-4-azaspiro[4.5]dec-3-ene, obtained from a solvate of sodium cyanodithioformate with three molecules of dimethylformamide, acetone, or cyclohexanone in the presence of morpholine, react with chlorothioformic dimethylamide with the formation of 2,2-dimethyl-5-oxo-4-(dimethylaminothiocarbonylthio)-1,3-thiazoline and 2-oxo-3-(dimethylaminothiocarbonylthio)-1-thia-4-azaspiro[4.5]dec-3-ene, respectively, and during acidolysis by hydrochloric acid they are converted to 2,2-dimethyl-5-oxo-4-thiono-1,3-thiazolidine and 2-oxo-3-thiono-1-thia-4-azaspiro[4.5]decane. The latter compounds are facilely phosphorylated by dialkyl chlorophosphonates at the nitrogen atom. The reaction of the solvate of sodium cyanodithioformate with three molecules of dimethylformamide with chloroacetone in the presence of morpho-line occurs anomalously with the formation of cyanothioformic morpholide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2590–2593, November, 1990.     

New method for the synthesis of N-tert-alkoxyarylaminyl radicals

The reactions of 2,4-diaryl-6-tert-butylnitrosobenzenes with 2,2'-azobis[2-(methoxycarbonyl)propane] (5a), 2,2'-azobis(2-cyano-4-methylpentane) (5b), and 2,2'-azobis(2-cyano-4-methyl-4-methoxypentane) (5c) in refluxing benzene gave stable N-tert-alkoxy-2,4-diaryl-6-tert-butylphenylaminyls, which were successfully isolated as radical crystals in 13-52% yields after column chromatography. The radical yields depended on the reaction time and the molar ratio of azo compounds to nitroso compounds. In the same manner, acetyl- and cyano-group-carrying N-tert-alkoxyarylaminyls were generated by the reaction of 2-phenyl-4-(4-acetylphenyl)-6-tert-butylnitrosobenzene and 2-phenyl-4-(4-cyanophenyl)-6-tert-butylnitrosobenzene with 5a and 5b, and they were isolated as radical crystals. X-ray crystallographic analyses were performed for two radicals, and their molecular structures were discussed in detail. The magnetic properties were measured for the two isolated radicals with SQUID in the temperature range 1.8-300 K. One radical showed a weak ferromagnetic interaction (theta = 0.2 K) between the radicals, and the other showed a weak antiferromagnetic interaction (theta = -3.8 K). The ferromagnetic interaction was analyzed based on the X-ray crystallographic structure.