Stereospecific Palladium-Catalyzed Acylation of Enantioenriched Alkylcarbastannatranes: A General Alternative to Asymmetric Enolate Reactions

We report the development of a Pd-catalyzed process for the cross coupling of unactivated primary, secondary, and tertiary alkylcarbastannatrane nucleophiles with acyl electrophiles. Reactions involving optically active alkylcarbastannatranes occur with exceptional stereofidelity and with net retention of absolute configuration. Because the stereochemistry of the resulting products is entirely reagent-controlled, this process may be viewed as a general, alternative approach to the preparation of products typically accessed via asymmetric enolate methodologies. Additionally, we report a new method for the preparation of optically active alkylcarbastannatranes, which should facilitate their future use in stereospecific reactions.     

Cyclodextrin‐supported palladium complex: A highly active and recoverable catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous medium

A water‐soluble, cyclodextrin‐supported palladium complex (DACH‐Pd‐β‐CD) catalytic system was designed and synthesized, which can efficiently catalyze Suzuki–Miyaura cross‐coupling reactions between aryl halides and arylboronic acid in water under mild conditions. The catalyst was successfully characterized using the methods of transmission electron microscopy, energy‐dispersive X‐ray spectrometry, X‐ray diffraction, thermogravimetric analysis, and Fourier transform infrared and NMR spectroscopies. Furthermore, the catalyst can be easily separated from the reaction mixture and still maintain high catalytic activity after ten cycles. No leaching of palladium into the reaction solution occurred. The advantages of green solvent (water), short reaction times (2–6 h), low catalyst loading (0.001 mol%), excellent yields (up to 99%) and reusability of the catalyst mean it will have potential applications in green chemical synthesis.     

Modification of palladium–copper thin film by reduced graphene oxide or platinum as catalyst for Suzuki–Miyaura reactions

This study describes the synthesis of PdCu, PdCu/reduced graphene oxide and PtPdCu nanoparticle thin films via a simple reduction of organometallic precursors including [PtCl₂(cod)] and [PdCl₂(cod)] (cod = cis ,cis ‐1,5‐cyclooctadiene) complexes, in the presence of [Cu(acac)₂] (acac = acetylacetonate) complex at toluene–water interface. The structure and morphology of the thin films were characterized using energy‐dispersive analysis of X‐rays, X‐ray diffraction and transmission electron microscopy techniques. Our studies show that all of these nanoparticles are suitable for the Suzuki–Miyaura coupling (SMC) reaction in water. PtPdCu and PdCu thin films showed higher catalytic activity compared to Pd thin film in the SMC reaction due to the appropriate interaction among palladium, platinum and copper metals.     

Relationships between molecular structure and thermomechanical properties of bio‐based thermosetting polymers

Molecular dynamics simulations are used to study highly cross‐linked epoxy networks comprised of furanyl epoxy monomer, 2,5‐bis[(2‐oxiranylmethoxy)methyl]‐furan (BOF), that is cross‐linked by two furanyl amine hardeners, 5,5'‐methylenedifurfurylamine (DFDA) and 5,5'‐ethylidenedifurfirylamine (CH₃‐DFDA). Important properties of these fully furan‐based systems, including room temperature density, glass transition temperature, and Young's modulus are found to agree with previous experimental results. We also compare the simulated and experimental values of four fully furan‐based thermosetting materials to those using the conventional resin diglycidyl ether of bisphenol A (DGEBA) cured with the two furanyl hardeners. Our simulation results predict a slight decrease in density and Young's modulus, but no impact on the glass transition temperature, upon adding the methyl group in DFDA. Detailed analyses of the MD trajectories reveal the underlying mechanisms responsible for the observed structure/property relations, which center on the lack of collinear covalent bonds in the BOF molecular structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 285–292     

Dithienylmethanone‐Based Cross‐Conjugated Polymer Semiconductors: Synthesis,Characterization, and Application in Field‐Effect Transistors

Herein, we report the synthesis, characterization, and field‐effect properties of two cross‐conjugated dithienylmethanone (DMO)‐based alternating polymers, namely, PDMO‐S and PDMO‐Se . Both polymers possess high thermal stability, good solubility, and broad absorption spectra. Their electrochemical properties were investigated using cyclic voltammetry, indicating that PDMO‐Se has higher HOMO/LUMO energy levels of −5.49/−3.49 eV than −5.57/−3.58 eV of PDMO‐S . The two polymers exhibited promising charge transport properties with the highest hole mobility of 0.12 cm² V⁻¹ s⁻¹ for PDMO‐S and 0.025 cm² V⁻¹ s⁻¹ for PDMO‐Se . AFM and 2D‐GIXRD analyses demonstrated that the PDMO‐S formed lamellar, edge‐on packing thin film with close π‐π stacking. These findings suggest that cross‐conjugated polymers might be potential semiconducting materials for low‐cost and flexible organic electronics. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1012–1019     

运用CAFP教学提升学生化学意志素质的教学案例

鉴于当前学生化学意志素质缺乏的问题，探讨以认知、情绪唤醒、情感、意志为主控目标，在预习、尝试学习、交错搭配合作学习中，开展CAFP教学研究，以促成情意因素对认知的调动、动力、强化等功能。     

Redox‐responsive core cross‐linked micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) by Diels‐Alder reaction for doxorubicin release

Redox‐responsive core cross‐linked (CCL) micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) (PEO‐b‐PFMA) block copolymers were prepared by the Diels‐Alder click‐type reaction. First, the PEO‐b‐PFMA amphiphilic block copolymer was synthesized by the reversible addition‐fragmentation chain transfer polymerization. The hydrophobic blocks of PFMA were employed to encapsulate the doxorubicin (DOX) drug, and they were cross‐linked using dithiobismaleimidoethane at 60 °C without any catalyst. Under physiological circumstance, the CCL micelles demonstrated the enhanced structural stability of the micelles, whereas dissociation of the micelles took place rapidly through the breaking of disulfide bonds in the cross‐linking linkages under reduction environment. The core‐cross‐linked micelles showed fine spherical distribution with hydrodynamic diameter of 68 ± 2.9  nm. The in vitro drug release profiles presented a slight release of DOX at pH 7.4, while a significant release of DOX was observed at pH 5.0 in the presence of 1,4‐dithiothreitol. MTT assays demonstrated that the block copolymer did not have any practically cytotoxicity against the normal HEK293 cell line while DOX‐loaded CCL micelles exhibited a high antitumor activity towards HepG2 cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3741–3750     

DOSY NMR as a tool for predicting optimal conditions for hydrogel formation: The case of a hyperbranched polyglycidol cross‐linked with boronic acids

This article demonstrates the utility of DOSY NMR for the determination of the optimal conditions for the efficient covalent, reversible cross‐linking of macromolecules in water for hydrogel formation. The studied model system was hyperbranched polyglycidol (HbPGL) containing numerous diol groups in peripheral regions and two types of boronic acids, that is, B(OH)₄^? and benzene‐1,4‐boronic diacid, as cross‐linking agents. Diffusion coefficient changes of a polymer in solution, under the influence of various concentrations of cross‐linking agent and pH, which influences the equilibrium of the reaction between boronic acids and diols, were recorded. These data are consistent with the rheological properties, namely the G′_max(ω) of hydrogels prepared under analogous conditions, from more concentrated solutions of HbPGL. This approach appears to be promising as it facilitates avoiding the loss of a large amount of polymer that is necessary for the elaboration of appropriate conditions for network formation in aqueous media. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2171–2178     

Cross‐metathesis of biorenewable dioxalates and diols to film‐forming degradable polyoxalates

Starting from commonly available sugar derivatives, a single step protocol to access a small family of isohexide‐dioxalates ( 2a–c ) has been established. The synthetic competence of 2a–c has been demonstrated by subjecting them to condensation polymerization. Quite surprisingly, the proton NMR of poly(isomannide‐co‐hexane)oxalate revealed a 1:2 ratio between isomannide‐dioxalate ( 2a ) and 1,6‐hexanediol ( 3a ) in the polymer backbone. This intriguing reactivity was found to be an outcome of a cross metathesis reaction between 2a and 3a . The cross metathesis products 3a ”[2‐(2‐methoxyacetoxy)ethyl 2‐(2‐hydroxyethoxy)‐2‐(λ3‐oxydanylidene)acetate] and 2a ‘(3R,6R)‐6‐hydroxyhexahydrofuro[3,2‐b]‐furan‐3‐yl methyl oxalate were isolated in a control experiment. Based on direct and indirect evidence, and control experiments, an alternative polymerization mechanism is proposed. Polymerization conditions were optimized to obtain polyoxalates P1(2a‐3a)‐P9(2c‐3c) with molecular weights in the range of 14,000–68,000 g/mol, and narrow polydispersities. The identity of the polyoxalates was unambiguously established using 1‐2D NMR spectroscopy, MALDI‐ToF‐MS, and GPC measurements. The practical implication of these polymers is demonstrated by preparing transparent, mechanically robust films. The environmental footprint of the selected polyoxalates was investigated by subjecting them to solution and solid‐state degradation. The polyoxalates were found to be amenable to degradation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1584–1592