Towards the Antimicrobial Finishing of Poly(isoprene)

Summary: Anionically polymerised (poly)isoprene was functionalized with cysteamine applying thiol-ene click chemistry. Subsequent quaternisation of the primary amino groups gave polymers with antimicrobial activity against Listeria monocytogenes, Eschericchia coli, Pseudomonas fluorescens and Staphylococcus aureus as revealed from tests performed according to the Japanese Industrial Standard Z2801:2000. The novel polymers feature sufficient thermal stability for the compounding with commodity polymers such as poly(propylene) and might be used as a non leaching additive to finish commodity polymers with antimicrobial acitivity.     

Unusual regioselectivity in a Diels-Alder reaction of isoprene with levoglucosenone

The ZnCl₂-catalyzed [4+2]-cycloaddition of isoprene with levoglucosenone is highly regio- and stereoselective.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2047–2049, August, 1996.     

New insights into the palladium-catalysed synthesis of δ-lactones from 1,3-dienes and carbon dioxide

Two-coordinate Pd(0) complexes are shown to be important intermediates in the telomerization of 1,3-dienes and CO₂ using palladium/phosphine catalysts without additives. Only one phosphorus atom is bound to palladium during the C–C bond forming steps, but the second phosphorus atom is crucial in the early stages of the catalytic cycle and for the elimination of the product. A ligand that gave an active palladium catalyst for the coupling of 1,3-butadiene and CO₂ has been designed. Use of a palladium catalyst in the reaction of isoprene with CO₂ allowed for the first time isolation and NMR spectroscopic characterization of the resulting mixture of lactones.     

Reaction between isoprene and aniline on complex palladium catalysts

Isoprene and aniline have been reacted on the catalytic system Pd(acac)₂-Ph₃P to form a mixture of isomeric telomers: N-(dimethyloctadien-2,7-yl-1)anilines and N-(dimethyloctadien-1,7-yl-3)anilines but on the catalytic system Pd(acac)₂-Ph₃P-CF₃COOH the main product is a mixture of N-(methylbuten-2-yl)aniline adducts. The reaction between N-methylaniline and isoprene on the latter catalyst also gives a mixture of N-methyl and N-(methylbuten-2-yl)aniline adducts.A. N. Nesmeyanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1794–1798, August, 1992.     

Palladium-based telomerization of 1,3-butadiene with glycerol using methoxy-functionalized triphenylphosphine ligands

Glycerol is considered a potential renewable building block for the synthesis of existing as well as new chemicals. A promising route is the telomerization of 1,3-butadiene with glycerol leading to C8 chain ethers of glycerol with applications in, for example, surfactant chemistry. Recently, we reported a new set of palladium-based homogeneous catalytic systems for the telomerization of 1,3-butadiene with glycerol and found that palladium complexes bearing methoxy-functionalized triphenylphosphine ligands are highly active catalysts capable of converting crude glycerol without any significant loss of activity. Herein, we present a detailed account of these investigations by reporting on the influence of the butadiene/glycerol ratio, temperature, and reaction time on product selectivity and activity allowing further optimization of catalyst performance. Maximum activity and yield were reached for high 1,3-butadiene/glycerol ratios at a temperature of 90 degrees C, whereas the selectivity for mono- and diethers of glycerol could be optimized by combining high reaction temperatures and short reaction times with low butadiene/glycerol ratios. Variation of the PdII metal precursors and the metal/ligand ratio showed that palladium precursors with halogen ligands gave unsatisfying results, in contrast to precursors with weakly coordinated ligands such as [Pd(OAc)2] and [Pd(acac)2]. [Pd(dba)2], the only Pd0 precursor tested, gave the best results in terms of activity, which illustrates the importance of the ability to form a Pd0 species in the catalytic cycle. Finally, base addition resulted in a shortening of the reaction time and most likely facilitates the formation of a Pd0 species. Based on these results, we were able to realize the first attempts towards a rational ligand design aimed at a high selectivity for mono- and diether formation.     

Tetrafluoroethylene telomerization using dibromohaloethanes as telogens

Carrier mediated telomerization (CMT) between C₂F₄ and bromochlorofluoroethanes has been evaluated in terms of product distributions arising from CMT and ‘normal’ telomerization. The effect of parameters like type of initiator and telogen, TFE pressure and temperature on the reaction has been studied. The peroxide initiated telomerization between dibromohaloethanes and C₂F₄ offers an easy synthetic route to α,ω-dibromo perfluoroalkanes Br(CF₂)_nBr with n = 2, 4, 6 and 8. The selectivity of the CMT products versus those from “normal” telomerization depends mainly on the choice of telogen and on its ability to act as ‘bromine donor’ in the radical telomerization. These perfluoroalkyl dibromides are useful intermediates for other derivatives, for example, perfluorinated mono- and diolefins, Br(CF₂)_nCHCH₂ and CH₂CH(CF₂)_nCHCH₂.     

Radical telomerization of 3,3,3-trifluoropropene with 2-methyl-1,3-dioxolane

The telomerization of 3,3,3-trifluoropropene with 2-methyl-1,3-dioxolane gives predominantly cyclic telomers as shown by¹³C NMR and gas chromatography-mass spectrometry. This reaction is accompanied by the rearrangement of transient free radical intermediates via 1,5-H-migration.Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow, Russia. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2768–2772, December, 1992.     

A facile synthetic strategy for hyperbranched polymer via combining free radical telomerization and polycondensation

A facile strategy combining free radical telomerization and polycondensation to prepare hyperbranched polymers was developed. By selecting a suitable telogen and a vinyl monomer, the product obtained by telomerization could be regarded as an AB_n type monomer for preparing a hyperbranched polymer via conventional polycondensation. The principles for selecting vinyl monomers and telogens were proposed. The feed ratio of vinyl monomer to telogen was discussed in the theory. For demonstrating the strategy, methyl (meth)acrylate (MA or MMA) and 2‐mercaptoethanol were used as a vinyl monomer and a telogen, respectively. The two‐unit adduct of MA or MMA obtained after purifying was regarded as a model ABB′ monomer. The sequential transesterification demonstrated that the carboxylate group at the terminal unit has higher reactivity than that at penultimate unit because of the different substituents at the respective α‐positions, resulting in lower degree of branching (DB) of obtained polymer. As substitutes, 2‐hydroxyethyl (meth)acrylate and thioglycolic acid were used as a vinyl monomer and a telogen, respectively. The results showed that the hyperbranched polymer obtained by using pseudo one‐pot approach had moderate DB. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7543–7555, 2008     

异戊二烯与OH自由基光化学反应的二次有机气溶胶的生成

利用烟雾箱模拟装置,研究了异戊二烯与OH自由基反应的二次有机气溶胶(SOA)的生成.反应中生成的气相产物通过质子转移反应质谱仪(PTR-MS)测定,SOA的浓度及粒径谱分布通过高分辨率粒径谱仪(EEPS3090)测定.研究表明:甲基丙烯醛(MAC)/甲基乙烯基酮(MVK)、乙醛、甲醛、甲醇、甲酸/乙醇、乙醇醛、甲基乙二醛、丙酮/丙醛等为主要气相产物,各组实验中MAC/MVK和乙醛浓度达到最大时,其产率分别介于13.78%～37.72%和5.38%～9.34%(以C计)范围内;SOA生成量及其中值粒径随异戊二烯反应量的增加而增加,气相物质稳定后,SOA产率在5.6%～11.7%范围内,粒径在22～165nm范围内.     

Radical telomerization of 3,3,3-trifluoropropene with diethyl hydrogen phosphonate: Characterization of the first telomeric adducts and assessment of the transfer constants

The radical telomerization of 3,3,3-trifluoropropene (TFP) with diethyl phosphate (or diethyl hydrogen phosphonate, DEHP) was investigated to synthesize fluorinated telomers bearing a phosphonate end-group, as H(TFP)_nP(O)(OEt)₂. Di-tert-butyl peroxide was the most efficient radical initiator. A careful structural study of typical TFP/DEHP telomers was performed by ¹H, ¹⁹F, and ³¹P nuclear magnetic resonance spectroscopies. These analytical methods allowed us to prove the selective addition of the phosphonyl radical onto the hydrogenated side of TFP, while the telomers containing more than two TFP units were composed of TFP isomers containing normal and reversed adducts. The kinetics of telomerization led to the assessment of the first four order transfer constants giving an infinite transfer constant of 0.75 at 140 °C for DEHP.     

芳香类化合物异戊烯基化的研究进展

结构多样的芳香类化合物一直被用作新药发现的线索或主要来源。通过对类药物天然产物进行异戊烯基化结构修饰,能有效提高芳香类化合物生物活性及生物利用度,为新药研究与开发提供简便高效的方法。本文综述了近年来芳香类化合物异戊烯基化的各种方法,以为今后研究提供参考。     

FeCl_3/磷酸三丁酯催化四氯化碳与氯乙烯的调聚反应:结构与活性

以四氯化碳与氯乙烯的调聚反应为目标反应,研究了Fe Cl3/磷酸三丁酯(TBP)配合物在反应体系中的结构,并关联了其结构与催化活性.采用摩尔电导、红外光谱和紫外吸收光谱对配合物的结构进行表征,结果表明Fe Cl3/TBP配合物在四氯化碳溶剂中为加合物Fe Cl3(TBP)n(n=1,2和3),配位数n由TBP与Fe Cl3的化学计量数决定.通过表观动力学实验研究了该配合物的催化反应活性,实验结果表明反应表观速率常数(kobs)随着TBP与Fe Cl3的摩尔比(r)的增大而增大,反应引发期(t0)随着r的增大而减小.假定反应遵循链式氧化还原机理,推导了kobs和t0的表达式,表达式和实验结果一致,均表明kobs只与配合物Fe Cl3(TBP)n的配位数和浓度有关.     

Solvent dependence of the palladium catalyzed telomerization of isoprene with methanol

The palladium catalyzed telomerization of isoprene with methanol as a nucleophilic agent has been investigated, applying the reaction system Pd-complex, tributylphosphine, sodium methylate, isoprene and methanol in a ratio of 1232002000. Two main products were found: 1-methoxy-3,6-dimethylocta-2,7-diene with a head-head coupling (I) and 1-methoxy-2,6-dimethylocta-2,7-diene with a tail-head-coupling (II). By substituting part of the methanol by different solvents the formation of I and II, respectively, can be controlled to a large extent.     

Development of palladium-carbene catalysts for telomerization and dimerization of 1,3-dienes: from basic research to industrial applications

The following account summarises recent developments in the area of palladium-catalysed telomerisation and dimerisation reactions of 1,3-dienes. The most active types of catalyst, palladium-carbene complexes, were tested in pilot plant and proved to be industrially viable.     

Dissociative photoionization of isoprene: experiments and calculations

Vacuum ultraviolet (VUV) dissociative photoionization of isoprene in the energy region 8.5–18 eV was investigated with photoionization mass spectroscopy (PIMS) using synchrotron radiation (SR). The ionization energy (IE) of isoprene as well as the appearance energies (AEs) of its fragment ions C₅H₇⁺, C₅H₅⁺, C₄H₅⁺, C₃H₆⁺, C₃H₅⁺, C₃H₄⁺, C₃H₃⁺ and C₂H₃⁺ were determined with photoionization efficiency (PIE) curves. The dissociation energies of some possible dissociation channels to produce those fragment ions were also determined experimentally. The total energies of C₅H₈ and its main fragments were calculated using the Gaussian 03 program and the Gaussian‐2 method. The IE of C₅H₈, the AEs for its fragment ions, and the dissociation energies to produce them were predicted using the high‐accuracy energy model. According to our results, the experimental dissociation energies were in reasonable agreement with the calculated values of the proposed photodissociation channels of C₅H₈. Copyright © 2009 John Wiley & Sons, Ltd.     

Kinetic modeling of vinyl acetate telomerization catalyzed by metal transition complexes under thermal and microwave heating

A kinetic model for the redox-initiated radical telomerization of vinyl acetate activated by microwave irradiation is presented. Four approaches based on the “microwave” or “thermal” effects were used to study the cases under microwave irradiation. One of the models assumes microwave-induced generation of radicals from monomer. The second model considers higher reaction temperatures than those reported in the experiments. The third model assumes that microwave radiation affects specifically catalyst-involved reactions. The fourth model is a combination of the second and third ones. The kinetic model captures well the effect of initiator, catalyst and solvent contents, as well as absence or presence of microwave irradiation, on polymerization rate and molecular weight development. Limiting monomer conversions and fairly constant values of number average molecular weight and molar mass dispersity were predicted by the model, which agrees with experimental observations.     

Radiation telomerization of tetrafluoroethylene in butyl chloride solution

The kinetics of the radiation-initiated polymerization of tetrafluoroethylene (TFE) in butyl chloride has been studied. The rate of the process, the properties and yield of telomers obtained depend on the initial concentration of TFE (2.6–22 wt %) in the solution and the dose of γ-irradiation. The analysis of the measured IR absorption spectra and a possible scheme of the process allow to suggest that the main product of the reaction is C₄H₈Cl(C₂F₄) _n−1CF₂CF₂H with the formation of small amounts of C₄H₉(C₂F₄) _n−1CF₂CF₂H and Cl(C₂F₄) _n−1CF₂CF₂H. The average number of links in the telomer (n) increases from 7.6 to 16.1 when the concentration of the monomer in the solution varies in the range of 7–22 wt %. The length of the chain of the soluble telomers (n) does not depend on the initial concentration of TFE and makes ∼7.     

Kinetics of radical telomerization of vinylidene fluoride in the presence of CCl3Z chain transfer agents

The kinetics of radical telomerization of VDF at 141 °C, initiated by ditertbutylperoxide, in the presence of three chain transfer agents (CTAs), HCCl₃, CCl₄ and CCl₃Br, are presented. The values of the chain transfer constants were assessed as 35, 0.25 and 0.06 at 141 °C for CCl₃Br, CCl₄ and HCCl₃, respectively. The values of the degree of polymerization (DP_n) were obtained for each CTA and were compared for the same CTA concentration. Hence, CCl₃Br behaved as an efficient CTA towards VDF and usually afforded the monoadduct selectively, but in certain conditions the VDF diadduct can also be produced. In contrast, HCCl₃ was not so efficient since a polymeric structure was identified as the major product.