Catalyst In Toluene Research Articles

Dibutyltin Oxide Catalyzed Allyl-Transfer Reaction from Tertiary ­Homoallylic Alcohols to Aldehydes

A catalytic allyl-transfer reaction from tertiary homo­allylic alcohols to aldehydes was achieved using dibutyltin oxide as a catalyst in toluene under reflux conditions. Various secondary ­homoallylic alcohols were prepared in high yield (up to 99%). When β-alkylated tertiary homoallylic alcohols were used, branched products were exclusively obtained.

Stereocontrolled Synthesis of gem-Difluoromethylenated Goniodiols and Goniothalamin Epoxides Based on Ring-Closing Metathesis

An efficient and general method to stereoselectively synthesize gem-difluoromethylenated goniodiols and goniothalamin epoxides has been developed. The introduction of a gem-difluoro­methyl-containing group was achieved by the reaction of aldehydes with 3-bromo-3,3-difluoropropene in the presence of indium. The gem-difluoromethylenated α,β-unsaturated-δ-lactone moiety was constructed through the ring-closing metathesis of highly electron-deficient gem-difluoromethylenated acryloyl esters by Grubbs’ II catalyst in toluene at reflux.

Study of enantioselective hydrogenation of bulky esters of phenylglyoxylic acid on Pt-CD and Pt- β-ICN chiral catalysts: Steric effect of ester groups and inversion of enantioselectivity

Enantioselective hydrogenation of seven different esters of phenylglyoxylic acid was investigated by variation of the bulkiness at ester side of the substrates [Ph C(O) C(O)OR, R = Me ( l), cyclohexyl ( 2), adamantyl ( 3), cis-decahydro-1-naphthyl ( 4), phenyl ( 5), 1-naphthyl ( 6), 2-naphthyl ( 7)] on Pt-alumina-cinchonidine (CD) and Pt-alumina- β-isocinchonine ( β-ICN) chiral catalysts using mild experimental conditions (273 K and room temperature, hydrogen pressure of 1–25 bar) in solvents of AcOH and toluene. Hydrogenation on Pt-alumina-CD chiral catalyst produced high values of ee for all but the 5 and 7 compounds. The formation of ( R)-mandelic acid esters was 86–91% in AcOH and 79–94% in toluene. The experiments verified the general applicability of the Orito reaction in the preparation of enantiomers of α-hydroxyesters. Under the experimental conditions applied, the magnitude of ee is affected by the steric size of α-ketoesters and by solvents. In the enantioselective hydrogenation of substrates over a Pt-alumina- β-ICN catalyst in toluene, inversion of enantioselectivity occurred; ( R)-mandelic acid esters formed with a medium ee of 30–54%. The conformation of the adsorbed modifier plays a more determining role than the bulkiness of the substrate in the formation of the intermediate complex responsible for enantioselection.

Synthesis of liquid crystalline poly(1‐pentyne)s and fabrication of polyacetylene–perovskite hybrids

AbstractPoly(1‐pentyne)s containing biphenyl and phthalimido pendant groups with different spacer lengths {P1(m); [HCC(CH2)3OBiphOCO(CH2)mN(CO)2C6H4]n, Biph4,4′biphenylyl; m = 7, 10} are synthesized in satisfactory yields by WCl6‐Ph4Sn catalyst in toluene at elevated temperatures. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, DSC, POM, and XRD analyses. Both of the polymers are thermally stable (Td ≥ 300 °C) and exhibit nematicity at high temperatures. Their phthalimido groups are converted into amino groups by hydrolysis, which can, after acidification, complex with lead(II) bromide to furnish polyacetylene–perovskite hybrids in high yields. The organic components contribute good solubility to the hybrids, while the perovskite framework induces the polyacetylene chains to align within the inorganic sheets. The hybrids emit a strong UV light of 374 nm upon photoexcitation, whose quantum yield increases with an increase in the spacer length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3538–3550, 2006

Synthesis and properties of polyacetylenes with directly attached bis(4‐alkoxyphenyl)terephthalate mesogens as pendants

AbstractLiquid‐crystalline, monosubstituted polyacetylenes containing lateral pendants of bis(4‐alkoxyphenyl)terephthalate with no flexible spacers and alkoxy tails {RO, where R is CH3 [P(1)] or C6H13 [P(6)]} were synthesized, and the effects of the backbone structure and alkoxy tails on the properties of the polymers were investigated. The polymerizations of acetylene monomers were carried out with chloronorbornadiene rhodium(I) dimer as a 1,2‐insertion catalyst in toluene. The structures and properties of the monosubstituted polyacetylenes were characterized and evaluated with nuclear magnetic resonance, infrared spectroscopy, thermogravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet spectroscopy, and photoluminescence analyses. The molecular weights of the polymers were measured by gel permeation chromatography. The polymer with long tails (p‐hexyloxy), that is, P(6), formed a smectic mesophase upon heating above the melting temperature, but the other one with short tails (p‐methoxy), that is, P(1), could not exhibit liquid crystallinity at elevated temperatures. The steric effect of bulky, liquid‐crystalline mesogens and a direct connection with the main chain prevented the planar conformation of the polyene backbone and, therefore, led to the lower absorption and emission wavelength of the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2499–2509, 2006

Ind2TiMe2‐Catalyzed Addition of Methyl‐ and Ethylamine to Alkynes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Ind2TiMe2‐Catalyzed Addition of Methyl‐ and Ethylamine to Alkynes

AbstractWe describe a very simple hydrogenation‐like experimental protocol for the addition of gaseous methyl‐ and ethylamine to alkynes in the presence of Ind2TiMe2 as the catalyst. For efficient hydroamination reactions it is sufficient to stir a mixture of the alkyne and the catalyst in toluene at temperatures between 80 °C (terminal alkynes) and 105 °C (internal alkynes) under a constant pressure of 1 atm of the corresponding amine. After subsequent reduction of the initially formed imines, methyl‐ and ethylamine derivatives are the final products of the described one‐pot reaction sequences. In the case of 2‐alkyl‐1‐phenylalkynes as starting materials, biologically interesting 2‐phenylethylamine derivatives possessing a small methyl or ethyl substituent at the N atom are easily accessible by the new reaction protocol. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis of new photoresponsive polyesters containing norbornadiene moieties by the ring‐opening copolymerization of donor–acceptor norbornadiene dicarboxylic acid anhydride with donor–acceptor norbornadiene dicarboxylic acid monoglycidyl ester derivatives

AbstractThe ring‐opening copolymerization of donor–acceptor norbornadiene (D–A NBD) dicarboxylic acid monoglycidyl ester derivatives with D–A NBD dicarboxylic acid anhydride was performed with tetraphenylphosphonium bromide as a catalyst in toluene to produce new norbornadiene (NBD) polyesters containing D–A NBD moieties in the main chain and in the side chain in one step in good yields. The photoisomerization of the D–A NBD moieties in these polyesters proceeded very smoothly to give the corresponding quadricyclane groups. Because these NBD polyesters contained many NBD moieties in the polymer chain, they had the highest capacity for heat storage in the D–A NBD polymers reported so far. The stored thermal energy of the irradiated polyesters was evaluated by differential scanning calorimetry analysis to be approximately 150–190 J/g. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4412–4421, 2005

What Can a Metal Catalyst Do with Allenes? One‐Step Formation of Steroid Scaffolds from Readily Available Starting Materials

The beauty and power of transition-metal-catalyzed reactions has been demonstrated by the one-step synthesis of steroid scaffolds from readily available allenes. The best results (57–73 % yield) were obtained using trans-[RhCl(CO)(PPh3)2] as the catalyst in toluene (see scheme; E=CN, CO2Me, SO2Ph, Ts=toluene-4-sulfonyl).

Modeling of Ethylene‐Norbornene Copolymer Microstructure in Solution Polymerization with Homogeneous Metallocene Catalysts

AbstractSummary: The microstructure of ethylene‐norbornene copolymer produced in solution polymerization is analyzed through kinetic modeling and experiments using homogeneous rac‐Et(1‐indenyl)2ZrCl2/methylaluminoxane catalyst in toluene at 70 °C. The sequence distribution function and average chain length equations are derived for terminal model and penultimate model. The model simulations show that both models provide similar predictions of average copolymer composition, especially at low norbornene concentration in the copolymer. However, at higher norbornene concentrations the penultimate model yields much better predictions of norbornene sequence length distribution than the terminal model. The terminal model has been inadequate in describing the copolymerization rate, whereas the penultimate model yields excellent predictions of rate behavior. The model calculations also indicate that at norbornene concentration in the copolymer larger than about 10 mol‐%, the maximum ethylene block length is smaller than 70, prohibiting the formation of crystalline copolymer.Ethylene sequence distribution curves at different mol‐% of norbornene in copolymer.magnified imageEthylene sequence distribution curves at different mol‐% of norbornene in copolymer.

Palladium‐Catalyzed Functionalization of Indoles with 2‐Acetoxymethyl‐Substituted Electron‐Deficient Alkenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Influences of Electronic Effects and Anions on the Enantioselectivity in the Oxazaborolidine‐Catalyzed Asymmetric Borane Reduction of Ketones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Lipase catalyzed transesterification of methyl acetoacetate with n-butanol

Keto esters represent an important class of organic building blocks which are used for efficient synthesis of a number of complex natural products. Keto esters are normally produced by chemical catalysis necessitating use of higher temperatures. Alternatively they can be synthesized in non-aqueous media using enzyme catalysis under milder conditions. n-Butyl acetoacetate is an important β-keto ester and its synthesis was studied by transesterification of methyl acetoacetate with n-butanol using supported lipases such as Novozym 435, Lipozyme RM IM and Lipozyme TL IM. Among these enzymes, Novozym 435 was found to be the most active catalyst in toluene as a solvent. The effects of various parameters on conversion and rates of reaction were studied in the absence of mass transfer limitations. A model based on ping-pong bi-bi mechanism was found to fit the initial rate data very well and the kinetic parameters were evaluated by non-linear regression analysis.

Biphasic hydroformylation catalysis in ionic liquid media

The ionic liquids 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF 4]), 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF 6]) and 1,2-dimethyl-3-butyl-imidazolium hexafluorophospate ([bdmim][PF 6]) were investigated as potential media for hydroformylation catalysis in a liquid–liquid biphase reaction environment. The study used the known rhodium/tppti* (tppti* = tri( m-sulfonyl) triphenyl phosphine 1,2-dimethyl-3-butyl-imidazolium salt) system as the catalyst and hexene-1 as the substrate, which enabled the produced heptanal to be conveniently isolated from the ionic liquid by phase separation. All catalyst evaluations were carried out in high-purity ionic liquids to avoid any decomposition of the catalyst, substrate and/or ionic liquid. The activity of the biphasic ionic liquid system containing the Rh/tppti* catalyst was approximately one order of magnitude lower than that observed for the conventional Rh/PPh 3 catalyst in toluene. The Rh/tppti* catalyst system showed a decrease of activity in the semicontinuous hydroformylation of hexene-1 due to catalyst deactivation and/or metal loss. The n/ i ratio of the produced heptanal only slightly increased after changing the Rh/P ratio from 1:3 to 1:100 in [bmim][PF 6]. The loss of rhodium metal from the ionic liquid phases appears to be correlated to the solubility characteristics of the ionic liquid and the concentration of the aldehyde in the organic phase. In support of this theory, the ionic liquid [bmim][PF 6] gave the best results due to its very low miscibility with polar substances. A high-pressure NMR (HP-NMR) study revealed that the solution structure of HRh( 13CO)(tppts) 3 (tppts = tri( m-sulfonyl)triphenyl phosphine sodium salt) in [bmim][BF 4] was similar to that of HRh( 13CO)(PPh 3) 3 in toluene-d 8. The HP-NMR investigation at elevated syngas pressures showed that HRh( 13CO)(tppts) 3 lies in equilibrium with HRh( 13CO) 2(tppts) 2.

Influences of electronic effects and anions on the enantioselectivity in the oxazaborolidine-catalyzed asymmetric borane reduction of ketones.

The influence of electronic effects on the enantioselectivity of the oxazaborolidine-catalyzed asymmetric borane reduction of ketones has been observed and investigated with use of para-substituted acetophenones and propiophenones with a variety of functional groups and B-unsubstituted and B-methoxyoxazaborolidines derived from (S)-2-(diphenylhydroxymethyl)pyrrolidine with borane and trimethyl borate as catalysts in toluene and THF. The results indicate that Hammett linear free energy electronic effects on the enantioselectivity in the asymmetric reduction were observed and rationalized. Tuning electronic effects of the catalyst can improve the enantioselectivity in the reduction. Another interesting finding to be noted is that anions heavily affect the enantioselectivity, especially for the B-methoxy catalyst, because of their coordination with the boron atom in the catalysts.

Synthesis of graft copolymer from copolymerization of styrene‐terminated poly(ethylene oxide) macromonomer and styrene with CpTiCl3/methylaluminoxane catalyst

AbstractCopolymerization of styrene (St) and St‐terminated poly(ethylene oxide) macromonomer (SEOM) with CpTiCl3/methylaluminoxane (MAO) catalyst in toluene was investigated. The copolymerization of St and SEOM proceeded easily to give a graft copolymer consisting of syndiotactic polystyrene as the main chain and hydrophilic poly(ethylene oxide) as the side chain. A number of side chains in the graft copolymer could be controlled by the amount of SEOM in the feed. The reactivity of SEOM was determined from copolymerization of St and SEOM with the CpTiCl3/MAO catalyst, and the reactivity of SEOM depended on the molecular weight of SEOM. The thermal properties of the graft copolymer such as the melting temperature were influenced by the introduction of SEOM. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2904–2910, 2004

Efficiency of ligands in atom transfer radical polymerization of lauryl methacrylate and block copolymerization with methyl methacrylate

Atom transfer radical polymerization of lauryl methacrylate (LMA) was carried out in the presence of various ligands using ethyl-2-bromoisobutyrate as initiator and CuBr as catalyst in toluene at 95 °C. The ligands used were 2,2′-bipyridyl,4,4′-dimethyl-2,2′-bipyridyl, N, N, N′, N′, N″-pentamethyldiethylenetriamine (PMDETA) and N-( n-propyl)-2-pyridylmethanimine (PPMI). Controlled polymerization was observed with PMDETA and PPMI ligands and poly(LMA)s with narrow molecular weight distribution (MWD) ( M w/ M n≤1.2) were obtained. The first-order time-conversion plot showed the presence of termination in the presence of PMDETA. A linear first-order time-conversion plot with a small induction period (∼10 min) was observed in the presence of PPMI ligand. Di-block copolymers of LMA and methylmethacrylate with controlled molecular weight and narrow MWDs were synthesized via sequential monomer addition.

Synthesis and characterization of a brush-like copolymer of polylactide grafted onto chitosan

A brush-like poly( dl)-lactide grafted onto chitosan as the backbone was investigated. The graft copolymerization was carried out with triethylaluminum as catalyst in toluene at 70 °C. It was found that a greater lactide content in the feeding ratio results in a higher grafting percentage. FTIR spectrometry, 1H NMR, DSC scanning, and wide-angle X-ray scattering, respectively, are used to characterize these branch copolymers. A copolymer has a definite melting point when the molar feeding ratio of lactide to chitosan is more than 10:1, and the Δ H of the copolymers increases with the feed ratio of lactide to chitosan in feeding.

Alkylation of N-substituted 2-phenylacetamides: Benzylation of N-(4-chlorophenyl)-2-phenylacetamide

Benzylation of N-(4-chlorophenyl)-2-phenylacetamidewith benzyl chloride in the presence of powdered potassium hydroxide under various reaction conditions was performed in order to establish the possible reaction products. Different temperatures and ratios of reactants and solvents were used. The reactions were also carried out in the presence of different phase-transfer catalysts in toluene as a solvent. The formation of the reaction products was followed using gas chromatography. On the basis of the obtained results, the reactivity and the orientation in the alkylation reaction of the investigated amide is discussed.

Photo-Induced Chromiumcarbonyl Catalyzed Hydrosilylation of Conjugated Dienes with Triethylsilane: The Solvent Effect

Photocatalytic hydrosilylation of conjugated dienes (1,3-butadiene, 2-methyl-1,3-butadiene, 2,3- dimethyl-1,3-butadiene, trans-1,3-pentadiene) with triethylsilane was studied by using Cr(CO)5L (L = CO, P(CH3)3, P(OCH3)3, P(C6H5)3, P(C6H11)3, NC5H5) in two very different solvents, toluene and tetrahydrofuran, for comparison with the results found in n-hexane. In toluene, the photocatalytic hydrosilylation yields the same products as those in n-hexane, with the exception of trans- 1,3-pentadiene which gives cis-1-triethylsilyl-2-pentene as the sole product. However, each of the precursor complexes shows different catalytic activities in toluene and n-hexane. The hydrosilylation of 1,3-butadiene in toluene is, in general, significantly faster than that in n-hexane. By using Cr(CO)6, Cr(CO)5[P(CH3)3] or Cr(CO)5[P(OCH3)3] in toluene, the conversion of triethylsilane increases almost linearly as the reaction proceeds, indicating the stability of the active catalyst throughout the reaction, similar to that in n-hexane. While no hydrosilylation of 1,3-butadiene could be achieved with Cr(CO)5[P(C6H5)3] or Cr(CO)5(NC5H5) in n-hexane, the same precursor complexes appear to be active in toluene, though the conversion occurs at much lower rate compared to that obtained using Cr(CO)5[P(CH3)3] or Cr(CO)5[P(OCH3)3]. The precursor complex Cr(CO)5[P(C6H11)3] shows catalytic activity neither in toluene nor in n-hexane. No photocatalytic hydrosilylation of 1,3-butadiene with triethylsilane was observed in tetrahydrofuran by using any of the precursor complexes. The relative reactivity of conjugated dienes in the hydrosilylation was investigated by using triethylsilane in the presence of Cr(CO)5[P(OCH3)3] as catalyst in toluene, and the same reactivity order was obtained as in n-hexane solution: 1,3-butadiene > 3-methyl-1,3-butadiene > 2,3-dimethyl-1,3-butadiene > trans-1,3-pentadiene. For all of the dienes, one obtains higher conversion to hydrosilylated product in toluene than in n-hexane.