Highly Efficient and Versatile Acetalization of Glycol Catalyzed by Cupric p-Toluenesulfonate

Acetalization of glycol with carbonyl compounds was carded out catalyzed by cupric p-toluenesulfonate. These carbonyl compounds included cyclohexanone, propionoaldehyde, n-butyraldehyde, /so-butyraldehyde, n-valeraldehyde, benzaldehyde and butanone. Satisfactory results were obtained： the conversions of these carbonyl compounds were more than 90%, the selectivities were higher than 99.1%, only 0.1% mole ratio of catalyst to substrate and 90 min were sufficient in most cases. The catalyst and products were separated easily by phase separation.     

Visible‐light induced RAFT polymerization of styrenic monomers with aromatic aldehydes as organophotoredox catalysts

A photoinduced electron transfer‐reversible addition‐fragmentation chain transfer (PET‐RAFT) polymerization of p‐methylstyrene (p‐MS) and styrene (St) with 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid as the chain transfer agent (CTA) and aromatic aldehydes, including 4‐cyanobenzaldehyde (PC1), 2,4‐dimethoxy benzaldehyde, and 4‐methoxy benzaldehyde, as organic photocatalysts has been demonstrated via irradiation with 23 W compact fluorescent lamps. The kinetics of the polymerizations shows first order with respect to monomer conversions. Linear evolution of the M_n of the produced polymers with the monomer conversion is observed. Meanwhile, the as‐prepared polymers are of relatively narrow polydispersity (PDI = M_w/M_n). For instance, the polymerization of p‐MS shows living polymerization features using PC1 within a range of solvents. Especially, the M_n of PpMS increased from about 2100 to 12,700 g/mol with the monomer conversion from 8% to 52% in tetrahydrofuran. The controlled polymerization of St is also observed under optimal reaction conditions. However, the M_n discrepancy between the experimental readings and theoretical calculations is greater at the monomer conversions greater than 40% and the PDI increased gradually over the monomer conversion. This is probably because that CTA is strongly sensitive to the light irradiation with wave range around its characteristic absorption wavelength, leading to significant decomposition of CTA moieties during the RAFT polymerization. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2072–2079     

Highly renewable,thermoplastic tetrapolyesters based on hydroquinone,p‐hydroxybenzoic acid or its derivatives,phloretic acid,and dodecanedioic acid

A series of tetrapolyesters were obtained by polymerizing phloretic acid, hydroquinone, p‐hydroxybenzoic acid, or its derivatives, that is, vanillic acid or syringic acid, and dodecanedioic acid. Each monomer was polymerized in its acetylated form, except for the diacid to undergo polymerization by acidolysis. Initial polymerizations had shown that the use of phloretic acid resulted in better polymer properties than with p‐coumaric acid. The predominantly renewable polymers were obtained by melt polymerization using a two‐stage condensation process whereby antimony(III) oxide was applied as catalyst. Monomer conversions were typically close to 90%. ¹H and ¹³C NMR, DSC, TGA, solution viscometry, and GPC were applied, as well as polarized microscopy to determine polymer microstructure and composition, transition temperatures, decomposition temperatures, intrinsic viscosities, and other molecular weight properties, and when applicable the liquid crystalline behavior of the polymers. All peaks, including end group peaks in the ¹³C NMR spectra were assigned, the monomer sequence distribution was verified to be random, and a complete dyad analysis involving nine dyads and eight peaks was performed. By using p‐hydroxybenzoic acid and its derivatives without any, one or two methoxy groups and varying the copolymer compositions, melting temperatures could be tuned between 106 and 181 °C. The tetrapolyesters, which included residues of p‐hydroxybenzoic acid, formed nematic liquid crystals. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1498–1507     

Kinetic investigation of the RAFT polymerization of p‐acetoxystyrene

The kinetics of the RAFT polymerization of p‐acetoxystyrene using a trithiocarbonate chain transfer agent, S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate, DDMAT, was investigated. Parameters including temperature, percentage initiator, concentration, monomer‐to‐chain transfer agent ratio, and solvent were varied and their impact on the rate of polymerization and quality of the final polymer examined. Linear kinetic plots, linear increase of M_n with monomer conversion, and low final molecular weight dispersities were used as criteria for the selection of optimized polymerization conditions, which included a temperature of 70 or 80 °C with 10 mol % AIBN initiator in bulk for low conversions or in 1,4‐dioxane at a monomer‐to‐solvent volume ratio of 1:1 for higher conversions This study opens the way for the use of DDMAT as a chain transfer agent for RAFT polymerization to incorporate p‐acetoxystyrene together with other functional monomers into well‐defined copolymers, block copolymers, and nanostructures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2517–2524, 2010     

A Nano‐Fibrillated Mesoporous Carbon as an Effective Support for Palladium Nanoparticles in the Aerobic Oxidation of Alcohols “on Pure Water”

A novel nano‐fibrillated mesoporous carbon (IFMC) was successfully prepared via carbonization of the ionic liquid 1‐methyl‐3‐phenethyl‐1H‐imidazolium hydrogen sulfate ( 1 ) in the presence of SBA‐15. The material was shown to be an efficient and unique support for the palladium nanoparticle (PdNP) catalyst Pd@IFMC ( 2 ) in aerobic oxidation of heterocyclic, benzylic, and heteroatom containing alcohols on pure water at temperatures as low as 40 °C for the first time and giving almost consistent activities and selectivities within more than six reaction runs. The catalyst has also been employed as an effective catalyst for the selective oxidation of aliphatic and allylic alcohols at 70–80 °C. The materials were characterized by X‐ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption analysis, transmission electron microscopy (TEM), and electron tomography (ET). Our compelling XPS and ET studies showed that higher activity of 2 compared to Pd@CMK‐3 and Pd/C in the aerobic oxidation of alcohols on water might be due to the presence of nitrogen functionalities inside the carbon structure and also the fibrous nature of our materials. The presence of a nitrogen heteroatom in the carboneous framework might also be responsible for the relatively uniform and nearly atomic‐scale distribution of PdNPs throughout the mesoporous structure and the inhibition of Pd agglomeration during the reaction, resulting in high durability, high stability, and recycling characteristics of 2 . This effect was clearly confirmed by comparing the TEM images of the recovered 2 and Pd@CMK‐3.     

Esterification of caprylic acid with alcohol over nano-crystalline sulfated zirconia

The catalytic activity of nano-crystalline sulfated zirconia catalyst, prepared by sol–gel method and characterized by various analytical tools, was evaluated for the esterification of caprylic acid with different short chain alcohols. The lower concentration of catalyst (0.5 wt%) exhibited 96–98% conversion of caprylic acid with methanol and 100% selectivity for methyl caprylate at 60 °C. The conversion was decreased with increasing carbon chain of alcohols namely with ethanol, n-propanol and n-butanol at 60 °C but increased significantly (91–98%) at higher reaction temperature. The selectivity for respective alkyl caprylate was observed to be 100% irrespective of the alcohol used. The activity of the catalyst was slightly decreased with successive five reaction cycles due to the water formed during the reaction.     

Synthesis of gold nanocomposite via chemisorption of gold nanoparticles with poly(p‐methylstyrene) containing multiple bonding groups on the chain side

Styrenic nanocomposite containing gold nanoparticles (AuNPs) has been synthesized by anchoring polymer molecules containing multiple functional groups onto the gold surface. p‐Methylstyrene was first anionically polymerized and the resulting polymer was chlorinated with sodium hypochlorite in the presence of a phase transfer catalyst. The chlorinated poly(p‐methylstyrene) was next reacted with methylthiomethyllithium, which had been prepared via a metalation reaction of dimethyl sulfide with n‐butyllithium, to form a styrenic polymer containing thioether groups on the sides of the molecule. These thioether groups on the chain sides afforded more chemisorption sites per molecule to AuNPs. The nanocomposite was analyzed using NMR, TEM, UV‐VIS, TGA, and XPS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4710–4720, 2005     

Preparation of N‐n‐Octyl‐D‐glucamine by the catalytic hydrogenation with palladium complex of MgO‐supported melamine‐formaldehyde polymer

The palladium complex of MgO‐supported melamine‐formaldehyde polymer catalyst was prepared and characterized by X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The preparation of N‐n‐octyl‐D ‐glucamine was investigated by using this complex as the catalyst. It was found that the palladium complex of MgO‐supported melamine‐formaldehyde polymer has a good catalytic activity for the hydrogenation of n‐octylamine with D ‐glucose to produce N‐n‐octyl‐D ‐glucamine. The effects of additive, solvent, temperature, hydrogen pressure, Pd content in the catalyst and the amount of catalyst on the preparation of N‐n‐octyl‐D ‐glucamine have all been studied. Under the optimum experimental conditions—D ‐glucose, 37.2 mmol; n‐octylamine, 31 mmol; triethylamine, 1.0 ml; ethanol, 60 ml; temperature, 333 K; hydrogen pressure, 1.5 MPa; the amount of the catalyst (Pd content 3.55%, N/Pd molar ratio 12), 0.7 g—the highest yield of N‐n‐octyl‐D ‐glucamine (57.6%) was obtained. XRD results show that melamine‐formaldehyde polymer changed the structure of MgO, and XPS results suggest that coordination bonds were formed between the hexatomic ring and metal atom, and palladium particles were immobilized on the polymer. Copyright © 2004 John Wiley & Sons, Ltd.     

Ruthenium Complexation in an Aluminium Metal–Organic Framework and Its Application in Alcohol Oxidation Catalysis

A ruthenium trichloride complex has been loaded into an aluminium metal–organic framework (MOF), MOF‐253, by post‐synthetic modification to give MOF‐253‐Ru. MOF‐253 contains open bipyridine sites that are available to bind with the ruthenium complex. MOF‐253‐Ru was characterised by elemental analysis, N₂ sorption and X‐ray powder diffraction. This is the first time that a Ru complex has been coordinated to a MOF through post‐synthetic modification and used as a heterogeneous catalyst. MOF‐253‐Ru catalysed the oxidation of primary and secondary alcohols, including allylic alcohols, with PhI(OAc)₂ as the oxidant under very mild reaction conditions (ambient temperature to 40 °C). High conversions (up to >99 %) were achieved in short reaction times (1–3 h) by using low catalyst loadings (0.5 mol % Ru). In addition, high selectivities (>90 %) for aldehydes were obtained at room temperature. MOF‐253‐Ru can be recycled up to six times with only a moderate decrease in substrate conversion.     

Perfluorocyclobutyl-containing Amphiphilic Block Copolymers Synthesized by RAFT Polymerization

Amphiphilic block copolymers containing hydrophobic perfluorocyclobutyl‐based (PFCB) polyacrylate and hydrophilic poly(ethylene glycol) (PEG) segments were prepared via reversible addition‐fragmentation chain transfer (RAFT) polymerization. The PFCB‐containing acrylate monomer, p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)‐phenyl acrylate, was first synthesized from commercially available compounds in good yields, and this kind of acrylate monomer can be homopolymerized by free radical polymerization or RAFT polymerization. Kinetic study showed the 2,2′‐azobis(isobutyronitrile) (AIBN) initiated and cumyl dithiobenzoate (CDB) mediated RAFT polymerization was in a living fashion, as suggested by the fact that the number‐average molecular weights (M_n) increased linearly with the conversions of the monomer, while the polydispersity indices kept less than 1.10. The block polymers with narrow molecular weight distributions (M_w/M_n≦1.21) were prepared through RAFT polymerization using PEG monomethyl ether capped with 4‐cyanopentanoic acid dithiobenzoate end group as the macro chain transfer agent (mPEG‐CTA). The length of the hydrophobic segment can be tuned by the feed ratio of the PFCB‐based acrylate monomer and the extending of the polymerization time. The micellization behavior of the block copolymers in aqueous media was investigated by the fluorescence probe technique.     

吸附NOx的功能化硅胶用于催化温和条件下醇的选择性氧化

利用接枝方式将2,2,6,6-四甲基哌啶(TEMPO)固载到SPE柱填料硅胶上制备了功能化硅胶,其吸附NO_x应用于催化醇的选择性氧化反应中. 并利用元素分析、红外光谱、N₂吸附-脱附和NO_x程序升温脱附对催化剂进行了考察. 结果表明,所制备催化剂中TEMPO固载量为0.292 mmol/g,NO_x吸附量为0.749 mmol/g; 常温常压下1 mmol芳香醇在0.5g该催化剂作用下进行选择性氧化反应2h,原料转化率和产物选择性均高达99%. 该催化剂提高了醇分子在孔道内部与TEMPO和NO_x接触几率,促进了反应进行,根据反应现象,对该体系催化机理进行了推测.     

Synthesis and characterization of functional polyethylene with regularly distributed thioester pendants via ring‐opening metathesis polymerization

Four kinds of functional polyethylene carrying thioester pendants were synthesized via ring‐opening metathesis polymerization (ROMP) of alkyl cyclopent‐3‐enecarbothioate catalyzed by a ruthenium‐based commercial catalyst and subsequent hydrogenation of the ROMP products (alkyl = ethyl, n‐butyl, n‐octyl, or n‐dodecyl). In these polymers the pendant alkyl thioester groups are precisely distributed along the backbone on every five methylene carbons. Chain structure, molecular weight and molecular weight distribution of the polymers were characterized by ¹H and ¹³C NMR, and GPC. The ROMP reactions all reached high monomer conversions, and hydrogenation of the ROMP products were exhaustive. Thermal transitions and side chain crystallization behaviors of the polymer were investigated and characterized by DSC and TGA. Glass transition temperature and melting temperature of these polymers were higher than the counterparts containing ester pendants. TGA analysis indicated that all the thioester‐containing polymers exhibited moderate thermal stability, and the sulfur‐containing polymers show slightly lower thermal stability than their counterparts without sulfur. The new family of functionalized polyethylenes could be used as models of ethylene‐thioacrylate copolymers, and find applications as novel functional materials. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 4027–4036     

Chiral Phosphoric Acid Dual‐Function Catalysis: Asymmetric Allylation with α‐Vinyl Allylboron Reagents

We report a dual function asymmetric catalysis by a chiral phosphoric acid catalyst that controls both enantioselective addition of an achiral α‐vinyl allylboronate to aldehydes and pseudo‐axial orientation of the α‐vinyl group in the transition state. The reaction produces dienyl homoallylic alcohols with high Z‐selectivities and enantioselectivities. Computational studies revealed that minimization of steric interactions between the alkyl groups of the diol on boron and the chiral phosphoric acid catalyst influence the orientation of α‐vinyl substituent of the allylboronate reagent to occupy a pseudo‐axial position in the transition state.     

Preparation and characterization of biodegradable poly(lactic acid)‐ block‐poly(ε‐caprolactone) multiblock copolymer

Biodegradable copolymers of poly(lactic acid)‐block‐poly(ε‐caprolactone) (PLA‐b‐PCL) were successfully prepared by two steps. In the first step, lactic acid monomer is oligomerized to low molecular weight prepolymer and copolymerized with the (ε‐caprolactone) diol to prepolymer, and then the molecular weight is raised by joining prepolymer chains together using 1,6‐hexamethylene diisocyanate (HDI) as the chain extender. The polymer was carefully characterized by using ¹H‐NMR analysis, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The results of ¹H‐NMR and TGA indicate PLA‐b‐PCL prepolymer with number average molecular weights (M_n) of 4000–6000 were obtained. When PCL‐diols are 10 wt%, copolymer is better for chain extension reaction to obtain the polymer with high molecular weight. After chain extension, the weight average molecular weight can reach 250,000 g/mol, as determined by GPC, when the molar ratio of –NCO to –OH was 3:1. DSC curve showed that the degree of crystallization of PLA–PCL copolymer was low, even became amorphous after chain extended reaction. The product exhibits superior mechanical properties with elongation at break above 297% that is much higher than that of PLA chain extended products. Copyright © 2009 John Wiley & Sons, Ltd.     

Visible light‐induced RAFT polymerization of methacrylates with benzaldehyde derivatives as organophotoredox catalysts

The benzaldehyde derivatives, such as 2,4‐dimethoxy benzaldehyde (PC1) and p‐anisaldehyde (PC2), were successfully used as photoredox catalysts (PCs) in combination with typical RAFT agent 4‐cyano‐4‐(phenylcarbonothioylthio)pentanoic acid (CTP) for the controlled photoinduced electron transfer RAFT polymerization (PET‐RAFT) of methyl methacrylate (MMA) and benzyl methacrylate (BnMA) at room temperature. The kinetics of the polymerizations showed first order with respect to monomer conversions. Besides, the average number molecular weights (M_n) of the produced polymers increased linearly with the monomer conversions and kept relatively narrow polydispersity (PDI = M_w/M_n). For example, the M_n of PMMA increased from about 3400 to 17,300 g mol⁻¹ with the increasing in monomer conversion from 11% to 85%, and the PDI maintained around 1.36. The living features of polymerizations with the PC1 and PC2 as catalysts have also been further supported by chain extension and synthesis of PMMA‐b‐PBnMA diblock copolymer. As a result, the simplicity and efficiency of benzaldehyde derivatives catalyzed PET‐RAFT polymerization have been demonstrated under mild conditions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 229–236     

Synthesis,characterization, and curing kinetics of novel ladder‐like polysilsesquioxanes containing side‐chain maleimide groups

Two ladder‐like polysilsesquioxanes (LPS) containing side‐chain maleimide groups have been synthesized successfully by reacting N‐(4‐hydroxyphenyl)maleimide (HPM) with LPS containing 100 mol % of chloropropyl groups (Ladder A ) and 50 mol % of each methyl and chloropropyl group (Ladder B ). HPM was synthesized by reacting maleic anhydride with 4‐aminophenol, and the resulting amic acid was imidized using p‐toluenesulfonic acid as a catalyst (Scheme 1 ). The LPSs were characterized by Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (NMR), proton‐decoupled ¹³C NMR, ²⁹Si NMR, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Characterization indicated that these polymers had ordered ladder‐like structures with possible defects. These polymers were soluble in common solvents at ambient temperature, which suggested that they were not crosslinked. Both the polymers and the HPM were cured, and their kinetics were followed by dynamic DSC. The Ozawa and Kissinger methods were used to calculate activation energies for curing. Curing increased the temperature at which both 5% weight loss and maximum rate of weight loss were observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4036–4046, 2004     

Use of a Catalytic Chiral Leaving Group for Asymmetric Substitutions at sp3‐Hybridized Carbon Atoms: Kinetic Resolution of β‐Amino Alcohols by p‐Methoxybenzylation

A catalytic strategy was developed for asymmetric substitution reactions at sp³‐hybridized carbon atoms by using a chiral alkylating agent generated in situ from trichloroacetimidate and a chiral phosphoric acid. The resulting chiral p‐methoxybenzyl phosphate selectively reacts with β‐amino alcohols rather than those without a β‐NH functionality. The use of an electronically and sterically tuned chiral phosphoric acid enables the kinetic resolution of amino alcohols through p‐methoxybenzylation with good enantioselectivity.     

Thermoreversible covalent crosslinking of maleated ethylene/propylene copolymers with diols

The objective of this study is the thermoreversible crosslinking of maleated ethylene/propylene copolymer (MAn‐g‐EPM) using the equilibrium reaction with diols. Covalent hemi‐ester crosslinks are formed via the reaction of anhydrides with alcohols, while an equilibrium shift at elevated temperatures may result in their removal. High conversions to hemi‐ester are obtained at low temperatures in the presence of p‐toluenesulfonic acid, whereas conversions are low at high temperatures. The presence of microphase‐separated aggregates acting as physical crosslinks was demonstrated for MAn‐g‐EPM and all crosslinked materials. The covalent crosslinks were only formed within the aggregates, resulting in stronger aggregates that persisted to higher temperatures. The tensile strength and elasticity were significantly improved upon increasing level of crosslinking, whereas the type of diol has less influence. The covalently crosslinked MAn‐g‐EPM was reprocessable via compression molding at temperatures above 175 °C. Irreversible diester formation occurred for the longer diols, but did not prevent reprocessing, while short diols evaporated. Both effects lowered the level of crosslinking, resulting in significantly changed mechanical properties. The reprocessability does not originate from an equilibrium shift, but from a dynamic exchange between crosslinked and non‐crosslinked functional groups, which allows crosslinks to disconnect and the corresponding chain segments to diffuse between aggregates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1810–1825, 2008     

Synthesis of ethylene/vinyl ester copolymers with pendent linear branches via ring‐opening metathesis polymerization of fatty acid‐derived cyclooctenes

Fatty acid‐derived cyclooctenes, including n‐hexanoic acid ( M1 ), n‐octanoic acid ( M2 ), lauric acid ( M3 ), and palmitic acid ( M4 ), were prepared as monomers and polymerized by ring‐opening metathesis polymerization (ROMP) using Grubbs second‐generation catalyst ( G2 ). In all the cases, the regio‐irregular unsaturated polymers with pendent linear branches were obtained, which could be saturated by chemical hydrogenation with TSH/TPA in high conversion, yielding ethylene/vinyl ester copolymers with pendent linear branches on precisely every eighth backbone carbon. Both unsaturated and saturated polymers were amorphous, and their structures were characterized by FTIR, ¹H and ¹³C NMR spectra, and elemental analysis. Differential scanning calorimetry (DSC) and thermo‐gravimetric analysis (TGA) were used to study their thermal properties. The chain length of branches greatly affected the thermal properties of polymers. After hydrogenation, the thermal degradation stability of polymers was relatively improved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2211–2220     

Catalytic Regioselective Isomerization of 2,2‐Disubstituted Oxetanes to Homoallylic Alcohols

The selective isomerization of strained heterocyclic compounds is an important tool in organic synthesis. An unprecedented regioselective isomerization of 2,2‐disubstituted oxetanes into homoallylic alcohols is described. The use of tris(pentafluorophenyl)borane (B(C₆F₅)₃)_, a commercially available Lewis acid was key to obtaining good yields and selectivities since other Lewis acids afforded mixtures of isomers and substantial polymerization. The reaction took place under exceptionally mild reaction conditions and very low catalyst loading (0.5 mol %). DFT calculations disclose the mechanistic features of the isomerization and account for the high selectivity displayed by the B(C₆F₅)₃ catalyst. The synthetic applicability of the new reaction is demonstrated by the preparation of γ‐chiral alcohols using iridium‐catalyzed asymmetric hydrogenation.