Base‐Catalyzed Cascade 1,3‐H Shift/Cyclization Reaction to Construct Polyaromatic Furans

A convenient new method was developed to prepare unfused polyaromatic furan derivatives from diynyl‐1,6‐diols through a novel base‐catalyzed cascade 1,3‐H shift/cyclization process. Deuterium experiments were performed to determine that the 1,3‐H shift was the rate‐determining step.     

Studies on thermoplastic polyurethanes based on new diphenylethane‐derivative diols. III. The effect of molecular weight and structure of soft segment on some properties of segmented polyurethanes

Two series of poly(ether urethane)s and one series of poly(ester urethane)s were synthesized, containing, respectively, poly(oxytetramethylene) diol (PTMO) of M _n = 1000 and 2000 and poly(ε‐caprolactone) diol of M _n = 2000 as soft segments. In each series the same hard segment, i.e., 4,4′‐(ethane‐1,2‐diyl)bis(benzenethiohexanol)/hexane‐1,6‐diyl diisocyanate, with different content (～ 14–72 wt %) was used. The polymers were prepared by a one‐step melt polymerization in the presence of dibutyltin dilaurate as a catalyst, at the molar ratio of NCO/OH = 1 (in the case of the polymers from PTMO of M _n = 1000 also at 1.05). For all polymers structures (by FTIR and X‐ray diffraction analysis) and physicochemical, thermal (by differential scanning calorimetry and thermogravimetric analysis), and tensile properties as well as Shore A/D hardness were determined. The resulting polymers were thermoplastic materials with partially crystalline structures (except the polymer with the highest content of PTMO of M _n = 2000). It was found that the poly(ether urethane)s showed lower crystallinity, glass‐transition temperature (T_g), and hardness as well as better thermal stability than the poly(ester urethane)s. Poly(ether urethane)s also exhibited higher tensile strength (up to 23.5 MPa vs. 20.3 MPa) and elongation at break (up to ～ 1950% vs. 1200%) in comparison with the corresponding poly(ester urethane)s. Among the poly(ether urethane)s an increase in soft‐segment length was accompanied by an increase in thermal stability, tensile strength, and elongation at break, as well as a decrease in T_g, crystallinity, and hardness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mg/Al水滑石催化合成聚碳酸酯二醇的研究

制备了Mg-Al水滑石,并将其进行了焙烧和再水合的处理,运用XRD,IR和BET对3种催化剂进行了表征,并对其应用于催化合成聚碳酸酯二醇(PCDL)的反应进行了研究.     

1-(4-安替比林)-3-(3-硝基苯胺)三氮烯的合成及其与金（Ⅲ）的显色反应

合成并鉴定了一种三氮烯试剂1-(4-安替比林)-3-(3-硝基苯胺)三氮烯(ANTA),研究了该试剂与Au（Ⅲ）的显色反应条件,并建立了一个测定Au（Ⅲ）的光度分析新方法。结果表明,在Triton X-100溶液存在下,ANTA与Au（Ⅲ） 在硼砂-氢氧化钠缓冲溶液中发生灵敏的显色反应,生成络合比为2∶1的橙红色络合物。该络合物的最大吸收峰位于515 nm,表观摩尔吸收系数为1.9×105 L·mol-1·cm-1,在10 mL溶液中,Au（Ⅲ）量在0.5～8.0 μg之间符合比尔定律,检出限为0.20 mg/L。共存干扰离子实验表明该显色反应具有较强的抗干扰能力。方法用于金矿石样品中Au（Ⅲ）的测定,结果与原子吸收光谱法一致,相对标准偏差(n=6)≤0.6%。     

Gold‐Catalyzed Regioselective Meyer–Schuster Rearrangement and Ring Expansion Cascade Leading to α‐Hydroxy‐α‐vinylcyclopentanones

Readily available cyclobutanols having a butyne‐1,4‐diol moiety underwent a sequential regioselective Meyer–Schuster rearrangement and 1,2‐shift, furnishing α‐hydroxy‐α‐vinylcyclopentanones. The reaction mechanism is consistent with the formation of an allenol intermediate that racemizes under the reaction conditions. Subsequent activation of the allenol leads to an enantio‐ and diastereoselective route to this scaffold.

     

Ce cooperated layered double oxide with enhanced base sites activity for the synthesis of polycarbonate diols

The development of highly efficient alkaline catalysts with abundant base sites is of paramount importance for the synthesis of polycarbonate diols (PCDLs). And the application of heterogeneous catalysts is an effective strategy to address the effect of residual catalysts on the quality of PCDLs. Here, Ce cooperated layered double oxide (LDO-Ce) was used as a catalyst for the preparation of PCDLs via transesterification between dimethyl carbonate (DMC) and 1,4-butanediol (BDO). CO₂ temperature-programmed desorption (CO₂-TPD) profiles demonstrated that the introduction of Ce led to an increase in strong base sites of LDO-Ce, thus endowing LDO-Ce with excellent catalytic performance. Besides, LDO-Ce possessed satisfactory specific surface area and pore size. A possible catalytic mechanism was proposed to illustrate the transesterification process. The effects of the reaction conditions on the hydroxyl value, yield, and BDO conversion were further investigated in detail. The yield of PCDLs with a hydroxyl value of 112.2 mg KOH/g (corresponding to a number average molecular weight [M_n] of 1000 g/mol) was 92.44% under its optimum reaction conditions (w (catalyst) = 0.5%, n(DMC)/n(BDO) = 1.25, T-_{transesterification} = 130°C, t-_{transesterification} = 5 h, T-_{polycondensation} = 170°C, t-_{polycondensation} = 4 h, P-_{polycondensation} = 10 kPa). Moreover, LDO-Ce was easily removed after the transesterification process (Step 1), ensuring the quality of PCDLs, and it was recycled three times without significant loss of catalytic activity.     

Silica Gel‐Supported Cinchona Alkaloid‐OsO4 Complex for Catalytic Heterogeneous Asymmetric Dihydroxylation of Olefins by H2O2 using a Titanium Silicalite‐Based Coupled Catalytic System

A triple catalytic system designed for asymmetric dihydroxylation of olefins, composed of NMM and two divergent heterogeneous catalysts, titanium silicalite and silica gel‐supported 1,4‐bis(9‐O‐dihydroquinidinyl)phthalazine [SGS‐(DHQD)₂PHAL)]‐OsO₄ complex relays the transport of two electrons from olefin to H₂O₂ used as a terminal oxidant to provide chiral diols with good yields and high enantiomeric excesses in a single pot.     

1-(2-苯并噻唑)-3-(4-溴苯)三氮烯与汞(Ⅱ)的显色反应研究

研究了1-(2-苯并噻唑)-3-(4-溴苯)三氮烯(BTBPT)与汞(Ⅱ)的显色反应。在非离子表面活性剂TritonX-100存在下,于pH10.9的Na2B4O7-NaOH缓冲介质中,Hg(Ⅱ)与BTBPT形成1∶2的稳定配合物。其最大吸收波长是465nm,表观摩尔吸光系数为:1.98×105L.mol-1.cm-1。汞(Ⅱ)在0~12μg/25mL范围内遵守比尔定律。此法应用于水样中Hg2+的测定,获得了较为满意的结果。     

过渡金属多相催化剂催化的分子氧选择性氧化邻二醇研究进展

邻二醇选择性氧化断键生成醛、酮和羧酸是重要和基本的有机反应,氧化剂通常采用化学计量的高碘酸盐或四乙酸铅,无论从经济还是环保的角度考虑,这些传统方法都有违绿色化工的发展理念。理论上以分子氧为氧化剂选择性氧化邻二醇断键的副产物只有水,而且分子氧廉价易得,因而具有环境友好和经济可行的双重优势。经过多年探索,人们已发展了多个基于不同过渡金属为活性组分的多相催化剂或催化体系用于分子氧选择性氧化邻二醇断键反应,如钌、金、锰、钴,为未来广泛应用奠定了基础。本文将按贵金属和非贵金属分类综述此类催化剂及相关反应工艺的研究进展,并指出该领域的发展方向     

Insight into the synthesis and thermomechanical properties of “short-long” type biobased aliphatic polyesters

A series of biobased “short-long” chain aliphatic polyesters having high molecular weight were successfully synthesized using dimethyl sebacate and diols with different carbon chain lengths via a two-step melt-polycondensation method by using titanium butoxide as a catalyst. The diols chain length and its odd-even effect on the structure–property relationship, crystallinity, and thermomechanical properties of the polyesters were systemically investigated. The synthesized polyesters displayed weight-average molecular weight between 23,600 to 72,900 g/mol and a maximum intrinsic viscosity of 0.933 dL/g. With increasing the diol chain length, the molecular weight of the polyesters increased linearly, except for poly(butylene sebacate) (PBS). Altogether, the “odd-even” effect of the diol chain on the crystalline (T_c)/melting temperature (T_m), and melting/ crystallization enthalpies of the polyester's were observed. Poly(pentylene sebacate) (PPeS) has the highest weight-average molecular weight of 72,900 Da, T_m of ∼55.4°C, degradation temperature (T_d,max) of about 404°C, and highest storage modulus (E′ at 25°C) of 661 MPa compared to other short-chain polyesters. PBS and PPeS showed the appearance of sharp intensity peaks from XRD diffraction patterns, indicating higher crystallinity in the material, in accordance with crystallization enthalpies (ΔH_c) values from the differential scanning calorimetry (DSC) thermograms. These fabricated biobased polymers with 100% bio-content, low melting temperature range, rapid crystallization, and high thermal stability suggest good processability and can offer an alternative option to nonrenewable thermoplastic polyesters for potential applications.