Mechanism of photostabilization of a europium(III) complex in polyethylene with Tinuvin-622

The mechanism by which selected photostabilizing sterically hindered amines (Tinuvin-622, Diacetam-5, Polyacetam-81) affect the photostability of the complex Eu(Phen)₂(NO₃)₃ in low-density polyethylene was studied by the luminescence, ESR, and ¹H NMR spectroscopy.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1543–1546.Original Russian Text Copyright © 2004 by Mirochnik, Zhikhareva, Karasev, Kuryavyi.     

Photostabilizing activity of tertiary hindered amines

The influence of the N-alkyl group of tertiary hindered amines on the photostabilization of polymers was studied. The photostabilizing effects of the tertiary amine derivatives of 4-benzoyloxy-2,2,6,6-tetramethylpiperidine ( 1a ) in polypropylene were compared. All tertiary amine derivatives having α-H to hindered N showed higher effectiveness than 1a . Model liquid phase photoxidations were carried out by irradiating (UV-lamp) the solutions of tertiary hindered amines containing tert-butyl hydroperoxide as a photoinitiator. The tertiary hindered amines were oxidized more easily than corresponding parent hindered amine and converted to the parent amine, which was identified as its salt, resulting from the carboxylic acid produced from the N-alkyl group by oxidation. The thermal reaction of the tertiary hindered amines with tert-butyl hydroperoxide was also studied in the liquid phase. The tertiary hindered amines decomposed tert-butyl hydroperoxide more rapidly than the parent secondary hindered amine, and generated the parent amine. It was also found that the photostabilizing effects of tertiary hindered amines for polyolefins were higher than that of the parent secondary hindered amine.     

Synthesis of sterically hindered benzodioxane analogs of isoflavone and a study of their atropoisomerism

Syntheses are reported far sterically hindered 2-substituted benzodioxane analogs of isoflavone. An optically active lanthanide shift reagent (LSR) was used to show that these products exist as mixtures of atropoisomers. The difference in the chemical shifts of the enantiomeric protons in the presence of the LSR may reach 2–3 ppm with decreasing temperature. Conclusions were drawn concerning the structure of the LSR-substrate adducts and their conformations.Taras Shevchenko Kiev University, 252033 Kiev. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 902–908, July, 1996. Original article submitted March 27, 1996.     

Structure of ketoenamine derivatives of 5,5-dimethyl-2,4-hexanedione

Conclusions The addition of amines to 5,5-dimethyl-2,4-hexanedione goes preferentially at the acetyl group as the less sterically hindered.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1795–1800, August, 1979.The authors express their gratitude to A. I. Kol't-sov for assistance in the interpretation of the PMR spectra.     

An improved aldehyde linker for the solid phase synthesis of hindered amides

A novel aldehyde dual-linker system has been developed for the solid phase synthesis of sterically hindered amides. The linker [5-(4-formyl-3-hydroxyphenoxy)pentanoic acid] exploits an intramolecular oxygen-nitrogen acyl transfer mechanism to prepare compounds that are unattainable with current commercially available linkers. A dual linker system, exploiting the hyper-acid labile Sieber amide linker as part of the construct, enabled the initial reductive alkylation reactions of hindered amines and their subsequent acylation with a range of carboxylic acids with varying stereoelectronic properties to be monitored. Simple acylation conditions (HBTU/HOBt/NMM) sufficed to provide near quantitative reaction of test acids with support-bound hindered amines, reaction conditions which failed when commercial linkers were used.     

A new route to hindered tertiary amines

The Rh(2)(OAc)(4)-stabilized carbenoid derived from dimethyl diazomalonate has been found to insert into the N-H bond of sterically hindered secondary aliphatic amines to afford hindered tertiary aliphatic amines in quite satisfactory yields. For example dimethyl 2-(dicyclohexylamino)propanedioate was formed in 85% yield from dicyclohexylamine, and the severely hindered dimethyl 2-(2,2,6,6-tetramethyl-1-piperidinyl)propanedioate was formed in 38% yield from 2,2,6,6-tetramethylpiperidine. The Rh(2)(OAc)(4) - dimethyl diazomalonate reaction was found to work also for arylalkylamines and diarylamines. In these cases, small amounts of products resulting from formal insertion of the carbenoid into an aromatic C-H bond were detected. Substitution at ortho positions caused the yield of C-H insertion products to increase. Other diazo compounds, viz. ethyl diazoacetoacetate, 2-diazocyclohexane-1,3-dione, and 2-diazo-5,5-dimethylcyclohexane-1,3-dione, performed satisfactorily in Rh(2)(OAc)(4)-catalyzed reactions with arylalkylamines and diarylamines, but led to complicated reaction mixtures with dialkylamines.     

Complexes of tertiary amines with hindered quinones

The generation of radical pairs by low-temperature photolysis of solutions of sterically hindered quinones in aliphatic amines has been studied by ESR. The process of stabilization of radical pairs is related to molecular complexes between amines and quinones in solution.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1736–1738, September, 1995.This work was financially supported by the Russian Foundation for Basic Research (Project No. 95-03-09233a).     

一些氮氧自由基和受阻胺化合物对单重态氧的猝灭能力及其与光稳定作用的关系

本工作测定了一系列稳定氟氧自由基( )化合物及一些受阻胺光稳定剂对单重态氧(¹O₂)的猝灭速率常数(k_q^1O₂),发现不同结构的 对¹O₂的猝灭能力很接近,但它们对聚丙烯(PP)膜的光稳定作用却相差很大。四甲基哌啶醇(TMP)及其衍生物对¹O₂的猝灭能力远不如相应的五甲基哌啶醇(PMP)及其衍生物,但前者对PP的光稳定能力却胜于后者。这说明在对聚合物的光稳定作用中, 和受阻胺光稳定剂对¹O₂的粹灭作用不占重要地位,也说明¹O₂在PP的光氧化过程中很可能不是主要因素。     

Synthesis and properties of sym-triazine derivatives. 6. Synthesis of 2-amino- and 2,4-diamino-sym-triazines containing sterically hindered phenol segments

2-Amino-4,6-disubstituted-sym-triazines containing sterically hindered phenol segments were synthesized by cyclocondensation of N-acrylguanidines with nitriles or thiocyanates. The same compounds can be obtained by condensation of N-acylguanidine with iminoester hydrochlorides. The reaction of methyl -(4-hydroxy-3,5-di-tert-butylphenyl)propionate with biguanides gives N-substituted 2,4-diamino-6-R-sym-triazines that contain a shielded phenol residue.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1392–1397, October, 1987.     

Well-defined NHC–Pd(II)–Im (NHC=N-heterocyclic carbene; Im=1-methylimidazole) complex catalyzed C–N coupling of primary amines with aryl chlorides

We report herein a well-defined NHC–Pd(II)–Im (NHC=N-heterocyclic carbene; Im=1-methylimidazole) complex catalyzed C–N coupling of primary amines with aryl chlorides. Under the optimal reaction conditions, a variety of primary amines can be coupled with aryl chlorides to give the amination products in good to high yields within 4 h. It is worthy of noting here that the NHC–Pd(II)–Im complex showed especially high catalytic activity toward challenging sterically hindered substrates including both of aryl amines and aryl chlorides. In addition, alkyl amines were also proved to be suitable reaction partners to give the corresponding amination products in good to high yields.     

Synthesis and properties of sterically hindered hydroxystyrlpyridines

A number of new sterically hindered hydroxystyrylpyridines were synthesized, and their antioxidative activity as a function of structure was studied. The antitumorigenic characteristics of three of the synthesized compounds are given.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1660–1664, December, 1971.The authors thank L. S. Vasil'eva, R. F. D'yachkovskaya, and N. A. Zakharova for their assistance in this research.     

Synthesis of sterically hindered aromatic aldehydes

Formylation of mesitylene, durene, and m-xylene derivatives containing electron-donor and electron-acceptor substituents by dichloromethyl methyl ether was studied in the presence of TiCl₄. A series of functionally substituted sterically hindered benzaldehydes was prepared from the products of these reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1609–1615, July, 1991.     

Synthesis of 2,3-disubstituted thiazolidin-4-ones containing the sterically hindered 4-hydroxy-3,5-di(tert-butyl)phenyl grouping

A series of 2,3-disubstituted thiazolidin-4-ones containing 4-hydroxy-3,5-di(tert-butyl)phenyl groups has been synthesized. For preparation of these sterically hindered compounds the condensation of thioglycolic acid with azomethines — derivatives of 4-hydroxy-3,5-di(tert-butyl)benzaldehyde was used.I. M. Gubkin Russian State University for Petroleum and Gas, Moscow 117917. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 256–260, February, 2000.     

Ringöffnung von Nitrothiazolen

The reaction between 2-halogeno-5-nitro-thiazoles and amines has been studied. Especially the sterically hindered strongly basic secondary aliphatic amines tend to cause opening of the thiazole ring system, resulting in the formation of the heretofore unknown (1-nitro-2-amino-vinyl)-thiocyanates. The ring opening is favored by a highly polar solvent, such as dimethyl sulfoxide. A simple reaction mechanism is proposed and some properties of these new compounds are discussed.     

Synthesis and properties of derivatives ofsym-triazine. 16. Synthesis of amine and diamine derivatives ofsym-triazine containing sterically hindered phenol groups from 6-alkyl(aryl)thio-2,4-bis(trichloromethyl)-sym-triazine

The reaction of 6-alkyl(aryl)thio-2,4-bis(trichloromethyl)-sym-triazines with ammonia and primary and secondary amines is studies. It is shown that, depending on the reaction conditions, the replacement of either one or both of the trichloromethyl groups takes place. 6-alkyl(aryl)thio-2,4-diamono-sym-triazines containing sterically hindered phenol groups are synthesized.I. M. Gubkin State Petroleum and Gas Academy, Moscow, 117917. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 224–231., Ferbruary, 1995. Original article submitted December 21, 1994.     

Complexation of sterically hindered cobalt porphyrin with 1-methylimidazole along the axial coordinate and the reaction of reversible binding of oxygen

The complexation of a sterically hindered cobalt porphyrin with 1-methyl imidazole and its reaction of reversible binding of oxygen was studied. Spectrophotometry and potentiometry were used to determine the equilibrium constant of the oxygenation process.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1634–1637.Original Russian Text Copyright © 2004 by Valiotti, Abakumova.     

Solid-phase synthesis of 1,2,3,4-tetrahydro-2-pyridones via aza-annulation of enamines

An efficient solid-phase approach has been developed to prepare nitrogen heterocycles with a 1,2,3,4-tetrahydro-2-pyridone core via aza-annulation of enamines. Immobilized enamines were prepared from the reaction of primary amines with propynoic acid derivatives or ketones. Aza-annulation reactions were carried out by reacting resin-bound enamines with symmetrical alpha,beta-unsaturated acid anhydrides or alpha,beta-unsaturated acids in the presence of DPPA and TEA. The annulation products were isolated in good to high crude yields. Influence of sterically hindered amines as well as alpha- and beta-substituted acrylic acid derivatives on the annulation reaction was also investigated.     

Synthesis and electrophilic trichloromethylation of 2,4-dialkylthiophenes. Some transformations of 2,4-di-tert-butyl-5-(trichloromethyl)thiophene

The disproportionation products of the C-protonation of 5-tert-butyl-2-methyl- and 2-ethylthiophene first give 4-tert-butyl-2-methyl- and 2-ethylthiophene. We studied the electrophilic trichloromethylation of a series of 2,4-dialkyl thiophenes and showed that the reaction goes smoothly only for the most sterically hindered 2,4-di-tertbutyl-thiophene. We studied the reaction of 2,4-di-tert-butyl-5-(trichloromethyl)thiophene with some O- and N-nucleophiles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1040–1045, August, 1993.     

Synthesis and properties of sym-triazine derivatives. 2. Synthesis of amino-sym-triazines containing fragments of sterically hindered phenol

The reaction of mono- and dichloro-sym-triazines with 4-hydroxy-3,5-di-tert-butyl-aniline was studied. N-substituted derivatives of 2,4,6-triamino-sym-triazine were synthesized, containing fragments of sterically hindered phenol.For article 1, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.12, pp. 1678–1682, December, 1984.     

Reaction of 4-nitro-2,4,6-tri-tert-butyl-2,5-cyclohexadienone with sterically hindered phenols and diphenylpicrylhydrazine

Conclusions The EPR method was used to study the reaction of 4-nitro-4-methyl-2,6-di-tert-butyl-2,5-cyclohexadienone with some sterically hindered phenols and diphenylpicrylhydrazine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1333–1335, June, 1971.The authors express their gratitude to S. L. Soshk for assistance in the work when taking the oxidation polarograms.