Functionalization of polymeric organolithium compounds. Carbonation

The carbonation reactions of polymeric organolithium compounds with high purity, gaseous carbon dioxide have been investigated in benzene and benzene/tetrahydrofuran (75/25) solutions. The polymers investigated were poly(styryl)lithium, poly(isoprenyl)lithium, and poly(styrene-b-isoprenyl)lithium. In Benzene solution the products are a mixture of the carboxylic acid and the ketone (dimer). No tertiary alcohol product (trimer) was observed. In benzene/tetrahydrofuran solution, the quantitative carboxylation of chain ends was observed.     

Overall and individual effects in systems including organolithium compounds

Experimental and quantum chemical data are used for the problem of the relative rǒle of individual factors considering the overall effects which are characteristic of certain Licontaining systems. Recourse is made to the following processes: polymerization of isoprene in the presence of subcatalytic amounts of electron donors; polymerization of acrylonitrile by RLi and ROLi initiators; polymerization of dienes by butyllithium (n-BuLi) and tert-butyllithium (tert-BuLi).     

Polymerization of cyclotrisiloxanes by organolithium compounds and P2-Et base

The use of the phosphazene base P₂-Et^(a) as a promoter for the anionic polymerization of hexamethylcyclotrisiloxane (D₃^Me) or hexaethylcyclotrisiloxane (D₃^Et) initiated by an organolithium compound leads to well-defined polysiloxanes. At low conversion (< ca. 9%) the polymerization of D₃^Me behaves like a living polymerization, however, polymers with a narrow molecular weight distribution (M?_w/M?_n < 1.1) are obtained up to much higher conversions (ca. 70%). Kinetic data and NMR spectroscopy revealed the existence of a dynamic equilibrium between complexed and uncomplexed lithium silanolates. Below ambient temperature several different types of aggregates were indicated. The occurrence of an acceleration was observed after ca. 9% conversion.     

The effect of electron donors on the polymerization of styrene initiated with organolithium compounds

The kinetics of the polymerization of styrene with oligostyryllithium and butyllithium in the presence of electron donors was investigated calorimetrically. There is no simple correlation between the accelerating effect (1,2-dimethoxyethane > tetrahydrofuran > N,N,N′,N′-tetramethylethylenediamine = triethylamine) of the individual electron donors upon the polymerization and their ability to form complexes with the respective organolithium compounds. This is qualitatively explained by considering preceding coordination reactions between organolithium compounds (or their complexes with electron donors) and the monomer in the reaction scheme. An irreversible degradation reaction between butyllithium and 1,2-dimethoxyethane occurring at T > 278 K is described. The products of this reaction are lithium methoxide, decane and hexyl methyl ether.     

Addition reactions of polymers containing pendant cyclic iminoethers with thiols,carboxylic, thiocarboxylic and sulfinic acids

Poly[1-(2-oxazoline-2-yl)ethylene] ( 2a ), poly[1-(5-methyl-2-oxazoline-2-yl)ethylene] ( 2b ), poly[1-(4,4-dimethyl-2-oxazoline-2-yl)ethylene] ( 2c ), poly[1-(4,4-dimethyl-5,6-dihydro-4H-1,3-oxazine-2-yl)ethylene] ( 2d ), and poly[1-(4,4,6-trimethyl-5,6-dihydro-4H-1,3-oxazine-2-yl)ethylene] ( 2e ) were synthesized with high yields by radical polymerization, using AIBN as initiator. Polymer 2a was found to be soluble in water and in organic solvents such as methanol, acetone, chloroform and benzene, polymer 2b in hot water and in the same organic solvents, and polymers 2c and 2d are insoluble in cold and hot water. However, polymers 2d and 2e are soluble in diethyl ether and hexane. Addition reactions of polymers 2a–e with carboxylic acids and thiols were investigated. Reactions of polymer 2a with acetic acid, benzoic acid and cinnamic acid at 110°C for 10 h proceeded with 57–74 mol-% conversion in DMF, NMP and DMSO, and reactions with benzenethiol and thiobenzoic acid quantitatively under the same reactions conditions. Reactions of polymers 2b and 2c with carboxylic acids proceeded with 4–36 mol-% conversion, and with benzenethiol and thiobenzoic acid with 80–96 mol-% conversion. From the results the following order of reactivities of these polymers may be suggested: 2a ? 2d > 2e > 2b > 2c . According to their higher nucleophilicity, the reactivities of benzenethiol and thiobenzoic acid towards the pendant 2-oxazoline ring are much higher than those of carboxylic acids.     

Study of exchange reactions in polycarbonate/polyarylcarboxylate mixtures with model compounds

The exchange reaction between a polycarbonate and a polyarylcarboxylate, both based on bisphenol A, was simulated by studying the reaction between the polycarbonate and diphenyl terephthalate or isophthalate used as model compounds of a polyarylcarboxylate. The kinetic results indicate the presence of a transesterification reaction occurring without any catalyst. Some results from reactions in the melt between both polymers also point to an exchange reaction.     

Radical efficiency and ionic reactions of some unsymmetrical azo compounds

Compounds with the structure R¹? N?N? R² decompose either thermally or photochemically to yield nitrogen and the radicals \documentclass{article}\pagestyle{empty}\begin{document}${\rm R}^{1 \atop {^\bullet}}\hbox{and}\ {\rm R}^{2\atop ^\bullet}$\end{document}. These radicals, under appropriate conditions, can either act as polymerization initiators or can be trapped by radical scavengers such as iodine. In the presence of suitable reagents the title compounds behave like diazonium salts and thus, since they are relatively stable, may provide a safe and readily available diazonium ion source.     

Studies on elementary reactions in the polymerization of 1,2-epoxycyclohexane with organozinc compounds as initiators

1,2-Epoxycyclohexane ( 1 ) was found to behave differently from propylene oxide (PO) in polymerization reactions with organozinc compounds as initiators. A chair-type complex, [Zn-MP]_2,2, is the only compound that shows high catalytic activity for both polymerization of 1 and PO, following an anionic coordination mechanism. On the other hand, the polymerization of 1 with ZnEt₂ or (EtZnOMe)₄ as initiator proceeds according to a cationic mechanism. Cationic polymerization of 1 with ZnEt₂ has two modes of termination reaction resulting in the formation of terminal units containing vinyl ether and allyl ether moieties. The initiation and propagation mechanism of 1 by [Zn-MP]_2;2 is similar to that of PO, but chain transfer reaction takes place in the polymerization of 1 owing to the low stability of the growing chain end. By using [Zn-MP]_2,2 as initiator, it was possible to prepare a block copolymer consisting of an isotactic sequence of monomeric units of PO and a syndiotactic sequence of monomeric units of 1 .     

Single-dose oral tolerance test with alternative compounds for the management of adverse reactions to drugs

BACKGROUND: Adverse reactions to drugs are common in the clinical practice. Many outpatients are frequently referred to allergists in order to determine which drugs they can safely take in the future. OBJECTIVE: We set up an oral single-dose tolerance test procedure to find out for each patient one or more alternative drugs that can be taken when needed. METHODS: 452 outpatients (130 male, 322 female) with well-documented reactions (urticaria/angioedema, respiratory symptoms, laryngeal edema, anaphylaxis, exfoliative skin diseases) underwent the challenge. All tests were preceded by a single-blind placebo: if a reaction occurred, a second placebo was administered. Otherwise, a single dose (1/10 of the therapeutic one) of an alternative drug was given blindly and the patient was then observed for 6 h. The drugs used were different in structure from those suspected of having caused the adverse reaction. The patients were followed up at 4- to 6-month intervals, in order to detect any reaction that may have occurred with the tested drugs. RESULTS: 98 patients (89 women) had untoward reactions after the first placebo and 34 out of them reacted to the second placebo, too. During challenges the reaction rate ranged between 4.6 and 9.0%; these reactions were easily managed and none of them was severe. We followed up 407 patients: 87.2% of them were able to use one or more of the suggested drugs without reactions, 9.3% did not take the drugs and only 3.5% reported reactions to the previously tested drugs. CONCLUSION: The challenge procedure proved to be a simple tool for managing patients with adverse reactions to drugs. Its safety and reliability were validated by a long-term follow-up.     

A formylstyrene-styrene-divinylbenzene resin. Synthesis,condensation reactions,and low-molecular-weight model compounds

A formylated resin ( 1a ) containing 4-formylphenyl groups was obtained from poly[styrene-co-divinylbenzene (2%)] by reaction with Cl₂CHOCH₃/SnCl₄ and subsequent hydrolysis of the intermediate. 1a reacted with N-methyltrimethylenediamine with the formation of azomethine groups. From the nitrogen content of the product the degree of functionalization of 1a was calculated to be 50%. Condensation reactions between 1a and N-ethylethylenediamine, cystamine, methanol, 1,2-ethanedithiol, 2,3-dimercapto-1-propanol (BAL), and 2-aminobenzene-thiol were also studied. A new chloromethylated resin was prepared from 1a and BAL in the presence of conc. hydrochloric acid (OH/Cl exchange). The formylation of 2,4-diphenylpentane yielded the low-molecular-weight model compounds 4-(1-methyl-3-phenylbutyl)benzaldehyde ( 2a ) and 2-(1-methyl-3-phenylbutyl)benzaldehyde ( 2b ) in an 87:13 mole ratio, suggesting that ca. 90% of the aldehyde groups in 1a are in para-position.     

Modulation of myoglobin-H2O2-mediated peroxidation reactions by sulfhydryl compounds

The ability of specific low molecular weight sulfhydryl compounds to inhibit the myoglobin-H2O2 peroxidation of uric acid and arachidonic acid was investigated. alpha-Mercaptopropionyl glycine, N-acetylcysteine, and reduced glutathione inhibited both the oxymyoglobin and metmyoglobin H2O2-mediated peroxidation of uric acid in a dose-dependent manner. The IC50 for each drug ranged between 20 to 100 microM and was dependent on the presence of a reduced sulfhydryl group since neither oxidized glutathione nor methionine effectively blocked uric acid peroxidation. Similar inhibition of oxymyoglobin and metmyoglobin H2O2-mediated peroxidation of arachidonic acid was also observed with alpha-mercaptopropionyl glycine, reduced glutathione, and cysteine. Under conditions of this assay, the ferrous form of myoglobin and H2O2 produced approximately three times the amount of formaldehyde from dimethylsulfoxide than ferric myoglobin (metmyoglobin) and H2O2. However, metmyoglobin and H2O2 were more effective than either oxymyoglobin and deoxymyoglobin in mediating arachidonic acid peroxidation. Further, neither mannitol nor benzoic acid (known scavengers of .OH) effectively blocked myoglobin H2O2-induced peroxidation of either uric acid or arachidonic acid. Visible absorption spectra of oxymyoglobin and metmyoglobin after incubation with H2O2 indicates the formation of a relatively stable ferriperoxide derivative of myoglobin. The formation of the ferriperoxide myoglobin derivative was partially inhibited by the addition of reduced sulfhydryl compounds. These data are consistent with the hypothesis that during reperfusion injury of the ischemic myocardium, the phagocytic cell or intracellular-derived H2O2 may react with myoglobin and initiate peroxidation reactions independent of .OH formation leading to cell injury. The cardioprotective effects of alpha-mercaptopropionyl glycine and other sulfhydryl-containing compounds during reperfusion injury may be attributed, at least in part, to their ability to inhibit myoglobin-H2O2-mediated peroxidation reactions.     

T-cell-dependent popliteal lymph node reactions to platinum compounds in mice.

The requirements for sensitization to complex salts of platinum were investigated in a mouse model by means of the popliteal lymph node (PLN) assay. A single subcutaneous injection of dissolved hexachloroplatinates without adjuvant induced a vigorous primary immune reaction in the draining PLN. Dose-dependent lymph node activation was determined by an increase in both PLN weight and cellularity. In C57BL/6 mice, peak reactions were obtained around day 6 after administration of 90-180 nmol Na2[PtCl6] or (NH4)2[PtCl6] per animal. Mice primed to [PtCl6]2- mounted an enhanced response upon local restimulation with suboptimal doses of the same but not unrelated compounds, indicating a specific secondary response. T cells were required to elicit PLN reactions to [PtCl6]2-, because athymic nude mice completely failed to respond, in contrast to their +/nu littermates. Differences between various inbred strains of mice revealed that Pt-induced PLN responses are genetically controlled. Moreover, the immunogenicity of Pt salts in mice is not confined to hexachloroplatinates, but other compounds, such as the antineoplastic agent cis-dichlorodiamine platinum, are able to induce comparable PLN reactions.     

New thermo-crosslinking reactions of copolymers of phenyl methacrylates by use of polyfunctional epoxy compounds

Successful new thermo-crosslinking reactions of copolymers of various phenyl methacrylates by use of polyfunctional epoxy compounds were carried out in the film state at 100–150°C in presence of quaternary ammonium salts, quaternary phosphonium salts, tert-amines, or the crown ether dicyclohexyl-18-crown-6/potassium salt systems as a catalyst. Addition reactions of 4-nitrophenyl, 4-chlorophenyl or phenyl ester groups in the copolymers with ethylene glycol diglycidyl ether (EGGE) result in gel compounds without other side reactions. The rate of gel production of the copolymer having electron-attracting groups such as the 4-nitro group on phenoxide is faster than that of the other copolymers. It was also found that the rate of gel production of the copolymer is affected by the amount of phenyl methacrylate component in the copolymer, the glass transition temperature (T_g) of the copolymer, the structure of polyfunctional epoxy compounds as a crosslinking reagent, the length of alkyl chain in the catalyst, and the kind of counter anion of the catalysts, respectively.     

Addition reaction of multifunctional epoxides with silk fibroin

The reaction of di- and tri-functional epoxides with silk fibroin was investigated in the presence of various salts in different solvents at 45–75°C. The reaction rates depend on the nature of the salts and the solvents used. Large weight gains (to 28%) were obtained in the reactions with ethyleneglycol diglycidyl ether, glycerol triglycidyl ether, and vinylcyclohexene dioxide catalyzed by thiosulfate, thiocyanate, cyanide, or chloride ions in such solvents as carbon tetrachloride, toluene, ethanol, and isopropanol. The weight gains in the silk/epoxide reaction were obtained mainly by the reaction of epoxide with the phenolic hydroxyl groups of the tyrosine residues, although lysine, histidine, arginine, and serine residues were found to react. The silk fabrics reacted with the epoxides were imparted with low solubilities in aqueous NaOH and HCl solutions without an appreciable decrease of moisture regain and flexibility of the fabric, and had much improved creaseproof properties.     

Azo polymers — syntheses and reactions, 3. Photolysis of monomeric and polymeric azo compounds

Unsymmetrical azo compounds of the general structure m-R? C₆H₄? N?N? C(OCOCH₃) (R¹) (R²) ( 2–4 ), in which R stands for H, CH₃, CH?CH₂ or a polymeric residue, were irradiated with light of λ ≥ 330 nm. Depending on the substituents R¹ and R² and the reaction temperature trans-cis isomerization or/and decomposition was observed. Polymers containing azo groups and CC-double bonds can be crosslinked by irradiation.     

Fluorination of polymers containing COOH/COOR groups with SF4/HF, 1. Model reactions with low molecular weight compounds

Model studies with low molecular weight compounds are performed in order to evaluate the feasibility of synthesizing fluorine-containing polymers by modification of commercially available products. The conversion of ? COOH and ? COOR into ? CF₃ moieties by means of SF₄/HF is checked with the following low molecular weight models for poly(acrylic acid) and poly(acrylic ester)s: hexanoic acid ( 1 ), ethyl hexanoate ( 2 ), 2,4-dimethylglutaric acid ( 3 ), 4-carboxypimelic acid ( 4 ) and 2,2-diethylmalonic acid ( 5 ). For the model compounds, the reaction conditions have been optimized. The desired products are obtained in high yield and in high selectivity. Therefore, this type of reaction will be applied to the modification of polymers in the next step.     

Michael Addition Polymerizations of Trifunctional Amines with Divinyl Sulfone

Summary: The mechanisms of the Michael addition polymerization of N‐aminoethyl piperazine (AEPZ) with divinyl sulfone (DVS) were clarified based on the reactivity sequence of three different amines in AEPZ: 2° amine in piperazine ring > 1° amine ≫ 2° amine formed in situ. When the feed molar ratio of DVS to AEPZ was 1:1, the polymerization of AB intermediate formed proceeded, and the linear poly(sulfone amine) containing secondary and tertiary amines in the backbones were produced. The linear structure of the product was confirmed by NMR spectra, and the molecular weights, molecular weight distribution, and properties of poly(sulfone amine)s were characterized by GPC, DSC, and TGA.

Polymerization of linear poly(DVS‐AEPZ).