Absorption and reaction of CO2 with 2,3-epoxypropyl phenyl ether using aliquat 336 AS catalyst

A kinetic study on the absorption and reaction of carbon dioxide with 2,3-epoxypropyl phenyl ether (phenyl glycidyl ether, PGE) in benzene solution has been carried out at room temperature in the presence of tricaprylylmethyl ammonium chloride (Aliquat 336) as catalyst. A simple method of measuring the absorbed volume of CO₂ was proposed to obtain the reaction rate constant, and it was based on the film theory accompanied by a chemical reaction. The enhancement factor (β-N_CO2/N_CO2 ^o) increased with increasing bulk concentration of PGE and Aliquat 336. The flux of CO₂ was proportional to the agitation speed.     

Synthesis of poly(silyl ether)s containing pendant chloromethyl groups by the polyaddition of bis(oxetane)s with dichlorosilanes

The polyaddition of bis(3‐ethyl‐3‐oxetanylmethyl) terephthalate (BEOT) with dichlorodiphenylsilane (CPS) using tetrabutylammonium bromide (TBAB) as a catalyst proceeded under mild reaction conditions to afford a polymer containing silicon atoms in the polymer main chain. A poly(silyl ether) (P‐1) with a high molecular weight (M_n = 53,200) was obtained by the reaction of BEOT with CPS in the presence of 5 mol % of TBAB in toluene at 0 °C for 1 h and then at 50 °C for 24 h. The structure of the resulting polymer was confirmed by IR and ¹H NMR spectra. Furthermore, it was proved that the polyaddition of certain bis(oxetane)s with dichlorosilanes proceeds smoothly to give corresponding poly(silyl ether)s with TBAB as the catalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2254–2259, 2000     

Anionic polymerization of styrene in the presence of different anisoles

The butyllithium-initiated polymerization of styrene has been studied in toluene solution at 20°C in the presence of anisole, o-ethylanisole, and p-ethylanisole. The concentration of styrene was 0.16 mole/1.; the concentration of ether varied from 0.8 to 0.33 mole/1. The rates of initiation were followed spectrophotometrically at γ_max 330 mμ; they increased with increasing concentration of ether. The rates of propagation were measured dilatometrically. In the presence of anisole and p-ethylanisole, the rate expression is R_p = [M][PLi]^1/2(k₁ + k₂ [ether]), where k₁ is the propagation rate constant in pure hydrocarbon, k₂ that of the ether solvated chain end, and [PLi] denotes the concentration of polystyryllithium. On the contrary, o-ethylanisole did not affect the rate of propagation of styrene, possibly on account of the steric hindrance of the o-ethyl group. The apparent first-order termination rate constants were also determined spectrophotometrically at 20°C and compared to those of poly-o- and p-methoxystyryllithium. The following decreasing order of rate constant was found: poly-p-methoxystyryllithium > polystyryllithium-anisole > polystyryllithium–4-ethylanisole > polystyryllithium-2-ethylanisole > poly-o-methoxystyryllithium.     

Modification of olefin polymerization catalysts. I. Mechanism of the interaction between AIEt3 and silyl ethers

The interaction between AlEt₃ and silyl ethers, Ph_nSi(OMe)_4-n (n = 0–3), was followed by ¹³C- and ²⁹Si-NMR techniques in conditions close to those typical for an olefin polymerization reaction with supported Ziegler–Natta catalysts (A1Et₃:silyl ether ratios from 1 to 10, temperature range 25–75°C). A1Et₃ and silyl ethers form instantaneously at ambient temperature a donor-acceptor complex, which is stable at a 1:1 molar ratio. In the presence of excess A1Et₃ the complex decomposes via a mechanism consisting, in the case of PhSi(OMe)₃, of five consecutive steps: alternating complexation and ether reductions with the formation of alkylated silyl ethers, Ph(Et)_nSi(OMe)_3-n (n = 1,2), and dialkyl-aluminum alkoxides, (Et₂A1OMe₃)_n (n = 2,3). The rate of decomposition was enhanced by the increasing number of methoxy groups present in the silyl ether, heating, or a high A1Et₃:silyl ether ratio. The decomposition was not inhibited by the presence of 1-hexene.     

Stereoelective cationic polymerization of propenyl ether by asymmetric catalysts

In order to elucidate the possibility of stereoelective cationic polymerization (asymmetric selective polymerization) of olefinic monomers, racemic cis- and trans-1-methylpropyl propenyl ether and racemic 1-methylpropyl vinyl ether were polymerized by asymmetric alkoxyaluminum dichlorides. In the polymerization of racemic cis-1-methylpropyl propenyl ether with (?)-menthoxyaluminum dichloride in toluene at ?78°C, the polymer obtained showed a positive optical activity, and the residual monomers were converted by BF₃OEt₂ into a polymer having a negative optical activity. Thus, the stereoelective polymerization of racemic cis-1-methylpropyl propenyl ether was beyond any doubt attained in homogeneous cationic polymerization. In the polymerization of the trans isomer by the same catalyst, an optically active polymer was hardly formed. In the polymerization of racemic 1-methylpropyl vinyl ether which has no β-methyl group, stereoelectivity was not observed at all. The cis-1-methylpropyl propenyl ether did not produce an optical active polymer in the polymerization catalyzed by (S)-1-methylpropoxyaluminum dichloride or (S)-2-methylbutoxyaluminum dichloride under the same polymerization conditions.     

Stereospecific polymerization of isobutyl vinyl ether. III. Polymerization with VCl3 • LiCl

The polymerization of isobutyl vinyl ether by vanadium trichloride in n-heptane was studied. VCl₃ ? LiCl was prepared by the reduction of VCl₄ with stoichiometric amounts of BuLi. This type of catalyst induces stereospecific polymerization of isobutyl vinyl ether without the action of trialkyl aluminum to an isotactic polymer when a rise in temperature during the polymerization was depressed by cooling. It is suggested that the cause of the stereospecific polymerization might be due to the catalyst structure in which LiCl coexists with VCl₃, namely, VCl₃ ? LiCl or VCl₂ ? 2LiCl as a solid solution in the crystalline lattice, since VCl₃ prepared by thermal decomposition of VCl₄ and a commercial VCl₃ did not produce the crystalline polymer and soluble catalysts such as VCl₄ in heptane and VCl₃ ? LiCl in ether solution did not yield the stereospecific polymer. It was found that some additives, such as tetrahydrofuran or ethylene glycol diphenyl ether, to the catalyst increased the stereospecific polymerization activity of the catalysts. Influence of the polymerization conditions such as temperature, time, monomer and catalyst concentrations, and the kind of solvent on the formed polymer was also examined.     

Domino Mukaiyama-Michael reactions in the synthesis of polycyclic systems

Good results were obtained in the Mukaiyama-Michael reaction of the silyl enol ether of cyclohexanone with 2-methyl-2-cyclopentenone and carvone, with transfer of the silyl group to the receiving enone and with TrSbCl₆ as catalyst. A second Mukaiyama-Michael reaction of this new silyl enol ether with methyl vinyl ketone and cyclization of the resulting adduct leads to tricyclic compounds in one-pot domino sequences. The scope and limitations of this domino reaction have been investigated.     

The matrix-isolation IR spectrum of the o-quinonoid intermediate in the photolysis of 2-nitrobenzyl methyl ether

Photolysis of 2-nitrobenzyl methyl ether in Ar and N₂ matrices at 12 K generated an intermediate with λ_max at 430 nm, and which was itself photolabile at 430–460 nm. Matrix IR spectra, as well as the UV-visible absorption, were obtained for this species. An analogous intermediate had previously been observed in flash-photolysis studies of 2-nitrobenzyl 4-cyanophenyl ether, and had been assigned an o-quinonoid structure on the basis of its kinetic behaviour and the position of its UV-visible absorption. In the matrix studies with 2-nitrobenzyl methyl ether, the IR spectra confirmed the o-quinonoid structure.     

Quenching of metal‐catalyzed living radical polymerization with silyl enol ethers

Various silyl enol ethers were employed as quenchers for the living radical polymerization of methyl methacrylate with the R Cl/RuCl₂(PPh₃)₃/Al(Oi–Pr)₃ initiating system. The most effective quencher was a silyl enol ether with an electron‐donating phenyl group conjugated with its double bond [CH₂C(OSiMe₃)(4‐MeOPh) ( 2a )] that afforded a halogen‐free polymer with a ketone terminal at a high end functionality [F̄_n ∼ 1]. Such silyl compounds reacted with the growing radical generated from the dormant chloride terminal and the ruthenium complex to give the ketone terminal via the release of the silyl group along with the chlorine that originated from the dormant terminal. In contrast, less conjugated silyl enol ethers such as CH₂C(OSiMe₃)Me were less effective in quenching the polymerization. The reactivity of the silyl compounds to the poly(methyl methacrylate) radical can be explained by the reactivity of their double bonds, namely, the monomer reactivity ratios of their model vinyl monomers without the silyloxyl groups. The lifetime of the living polymer terminal was also estimated by the quenching reaction mediated with 2a . © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4735–4748, 2000     

Selective vinyl polymerization of 4-vinyl-1-cyclohexene with ziegler–natta catalyst

The polymerization of 4-vinyl-1-cyclohexene (4VCHE) with Ziegler–Natta catalysts was studied. The polymerization of 4VCHE by the vinyl group took place with TiCl₃–aluminum alkyls catalysts, while vinylene group of 4VCHE did not participate in the reaction, but it affected the polymerization rate of 4VCHE. The effects of aluminum alkyl and type of TiCl₃ on the polymerization were examined. The overall activation energy for the polymerization was estimated to be 41.9kJ/mol. Monomer-isomerization copolymerization of 4VCHE and trans-2-butene occurred with the TiCl₃-(i-C₄H₉)₃Al catalyst to give copolymers consisting of 4VCHE and 1-butene units.     

Synthesis of dimethyl ether from CO and H<Subscript>2</Subscript>

Thermodynamic conditions for synthesizing dimethyl ether from synthesis gas are determined. The optimum conditions of the process are as follow: T ∼ 300°C at p = 3 MPa for two catalysts loaded into the reactor: methanol synthesis catalyst (Katalco-58) and catalyst of methanol dehydration to dimethyl ether (γ-Al₂O₃). The changes that occur with the catalysts during this process are demonstrated by electron scanning microscopy.     

Stereoregularity of poly(vinyl ether)

α-Methylvinyl isobutyl and methyl ethers were polymerized cationically and the structure of the polymers was studied by NMR. Poly(α-methylvinyl methyl ether) polymerized with iodine or ferric chloride as catalyst was found to be almost atactic, whereas poly(α-methylvinyl isobutyl ether) polymerized in toluene with BF₃OEt₂ or AlEt₂Cl as catalyst was found to be isotactic. In both cases, the addition of polar solvent resulted in the increase of syndiotactic structure as is the case with polymerization of alkyl vinyl ether. tert-Butyl vinyl ether was polymerized, and the polymer was converted into poly(vinyl acetate), the structure of which was studied by NMR. A nearly linear relationship between the optical density ratio D₇₂₂/D₇₃₆ in poly(tert-butyl vinyl ether) and the isotacticity of the converted poly(vinyl acetate) was observed.     

Anionic polymerization of propylene oxide: Isomerization of allyl ether to propenyl ether end groups

The isomerization of allyl ether to propenyl ether end group in anionically-polymerized poly (propylene oxide) was monitored by ¹H NMR spectroscopy. It was confirmed that the reaction followed a simple second-order rate law: ?d[allyl]dt = k₂[allyl] [O^?]. Values of k₂ determined over the 90–130°C temperature range, indicated an activation energy of 116 kJ mol^?1. © 1994 John Wiley & Sons, Inc.     

Hydrogenation of substituted nitroarenes by a polymer-bound palladium(II) Schiff base catalyst

The catalytic activity of a polymer-bound palladium Schiff base catalyst was investigated toward the reduction of aryl nitro compounds under ambient temperature and pressure. The dependence of the rate of hydrogenation of o-nitroaniline and o-nitrotoluene on substrate concentration, catalyst concentration and temperature has been determined. Based on the results obtained a plausible mechanism for the hydrogenation reaction is proposed and a rate expression is deduced. The energy and entropy of activation have been evaluated from the kinetic data. The polymer-bound catalyst was found to be better than its homogeneous analog PdCl₂(NSBA) [NSBA = N-salicylidene benzylamine] for both stability and reusability. Recycling studies revealed that the catalyst could be used six times without metal leaching or significant loss in activity.     

Some aspects of the polymerization of n-butyl vinyl ether by chromyl chloride

The rate of n-butyl vinyl ether polymerization by chromyl chloride is first order in [catalyst] and second order in [monomer]. Added H₂O (after a certain concentration) and HCl increase the rate, thiophene retards the rate, while pyridine inhibits the rate. DP is independent of [chromyl chloride] and increases with increasing [monomer] up to 1M, thereafter becoming independent of it. Both rate and DP increase over the range 10?32°C and decrease at higher temperatures.     

Polysiloxane microspheres functionalized with imidazole groups as a palladium catalyst support

Polysiloxane microspheres containing a large number of silanol groups were obtained by an emulsion process of modified polyhydromethylsiloxane. N‐substituted imidazole groups were grafted on these microspheres by the silylation of their silanol groups with N‐[γ‐(dimethylchlorosilyl)propyl]imidazole hydrochloride. The progress of the reaction was monitored using ²⁹Si and ¹³C magic angle spinning (MAS) NMR and its impact on microsphere morphology was studied using scanning electron microscopy (SEM). The usefulness of the imidazole‐functionalized microspheres as a support for a metal catalyst was demonstrated by their reaction with PdCl₂(PhCN)₂. In this way a new heterogenized catalyst, Pd(II) complex with imidazole ligands supported on polysiloxane microspheres, was generated. This catalyst, MPd , was characterized using ¹³C and ²⁹Si MAS NMR, X‐ray photoelectron, Fourier transform infrared and far‐infrared spectroscopies, X‐ray diffraction, SEM–energy‐dispersive X‐ray spectroscopy and wide‐angle X‐ray scattering. The catalyst appears in two structures, as Pd(II) complex and Pd(0) nanoclusters. Its catalytic activity was tested using a model reaction, the hydrogenation of cinnamaldehyde, and compared with that of an analogous complex operating in a homogeneous system. MPd showed a high activity in the promotion of hydrogenation of cinnamaldehyde. The activity in the substrate conversion was stable at least in five cycles of this reaction. The main product was hydrocinnamaldehyde which could be obtained with a yield above 70%. A mechanism of the reaction is proposed. Copyright © 2016 John Wiley & Sons, Ltd.     

Polymerization of cyclohexene oxide with aluminum complex-silanol catalyst. IV. Photopolymerization with Ph3SiCOPh-Al complex-alcohol catalyst system

A new catalyst system (Ph₃SiCOPh-aluminum complex-alcohol) was investigated for photopolymerization of cyclohexene oxide. Polymer conversion and molecular weight increased with polymerization time. When a Ph₃SiCOPh-Al (n-Praa)₃-alcohol catalyst system was used the catalyst activity decreased, depending on the alcohol: i-PrOH > n-PrOH > i-BuOH > MeOH > t-BuOH > H₂O. When the Ph₃SiCOPh-Al complex-i-PrOH catalyst system was used the catalyst activity decreased, depending on the ligand of the Al complex: ß-ketoester > orthocarbonyl phenol > ß-diketone. Benzophenone derivatives were effective for catalyst activation as a photosensitizer.     

NMR studies on the stereospecific polymerization of methyl vinyl ether. Part II. Polymerization by sulfuric acid–aluminum sulfate complex: Enantiomorphic catalyst sites model

Highly crystalline poly(methyl vinyl ether) (PMVE) was produced in toluene in a temperature range of 0 to ?20°C. with the use of sulfuric acid–aluminum sulfate complex (SA catalyst). It was found from the NMR spectra that these polymers contained more than 50% of the triad isotactic fraction and the melting point of the unfractionated polymer was about 130°C. However, PMVE containing a large amount of the isotactic fraction was insoluble in nitromethane, so the triad tacticity of highly crystalline PMVE could not be quantitatively determined. The molecular weight of PMVE increased with increasing conversion and increasing polymerization temperature. This behavior is different from that in metal halide catalysts. Also, the stereoregularity of PMVE decreased with increasing monomer concentration. However, addition of a polar solvent and increasing the polymerization temperature had little effect on the stereoregularity of the polymer. The increase in the isotactic fraction at high catalyst concentration and the difference in the monomer composition in the copolymerization of methyl vinyl ether with 2-chloroethyl vinyl ether by SA catalyst from that obtained by BF₃·O(C₂H₅)₂ suggest that the absorption of MVE on a catalyst surface is an important step in the propagation step by SA catalyst. The fraction of the triad tacticity calculated from the enantiomorphic catalyst sites model⁸ coincided with the experimental results. This fact shows that the steric structure of the adding monomer is determined only by the nature of the catalyst irrespective of the nature of a growing chain end. It is concluded, on considering also the results of the previous paper, that completely different factors can control the steric structure of a polymer even for the same monomer when different catalysts are used.     

Cationic iridium complex is a new and efficient Lewis acid catalyst for aldol and Mannich reactions

A cationic iridium complex [Ir(cod)₂]SbF₆ was found to be a new and efficient Lewis acid catalyst for Mukaiyama aldol and Mannich reactions. Aldehydes react smoothly with silyl enol ethers to give β-siloxy ketones in the presence of 0.5 mol % of [Ir(cod)₂]SbF₆. The reaction of N-alkyl arylaldimines with ketene silyl acetals in the presence of 5 mol % [Ir(cod)₂]SbF₆/P(OPh)₃ gave β-amino esters. After Mannich reaction was complete, stirring of the reaction mixture for 24 h led to cyclization to give β-lactam. The reaction of N-aryl benzaldimine with silyl enol ether derived from acetophenone gave a tetrahydroquinoline derivative as a single diastereomer.     

Polymerization of propylene with TiCl3–AlEt2Cl–polymeric electron donor catalyst

Polymeric donors having ether or carbonyl groups were added to the TiCI₃–AlEt₂CI catalyst system as the third component, and the effects on the polymerization of propylene were investigated in comparison with the effect of the electron donors with low molecular weight. The polymeric donors were effective in making the catalyst more active, but the donors of low molecular weight depressed the catalyst activity. In the case of poly(propylene glycol dimethyl ether) (PPG-DME), PPG–DME with a number of propylene oxide units (n) of more than 6.7 was effective in enhancing the catalyst activity. These effects were considered to be due to the different reactivities between TiCI₃ and AlEt₂CI-polymeric donor complexes having various chain lengths.