Boronic Acid‐Catalyzed Selective Oxidation of 1,2‐Diols to α‐Hydroxy Ketones in Water

The activation of 1,2‐diols through formation of boronate esters was found to enhance the selective oxidation of 1,2‐diols to their corresponding α‐hydroxy ketones in aqueous medium. The oxidation step was accomplished using dibromoisocyanuric acid (DBI) as a terminal chemical oxidant or an electrochemical process. The electrochemical process was based on the use of platinum electrodes, methylboronic acid [MeB(OH)₂] as a catalyst and bromide ion as a mediator. Electro‐generated OH⁻ ions (EGB) at the cathode acted as a base and “Br⁺” ion generated at the anode acted as an oxidant. Various cyclic and acyclic 1,2‐diols as substrates were selectively oxidized to the corresponding α‐hydroxy ketones via their boronate esters by the two oxidative methods in good to excellent yields.

     

用于糖醇混合物氢解制低碳二元醇的镍锡/炭催化剂

针对C5和C6糖醇混合物氢解制低碳二元醇的反应,分别采用一步法和两步法制备了NiSn/C催化剂,考察了催化剂的氢解反应性能;并采用TEM和XPS方法对NiSn/C催化剂的微观结构进行了表征,推测了反应机理。实验结果表明,采用一步法制备的还原态NiSn/C催化剂进行氢解反应时,二元醇的收率可达44.11%、选择性达82.82%;而两步法制备的还原态NiSn/C催化剂基本无活性。TEM和XPS表征结果显示,一步法制备的NiSn/C催化剂表面粒子分布均匀,Ni粒子以氧化物形式分布在载体上,Sn以Sn2+或Sn4+的形式分布在载体表面;两步法制备的NiSn/C催化剂可能因Sn对Ni形成包围,因此无活性。     

Catalytic Asymmetric Dihydroxylation of Aliphatic Olefins with Reusable Resin‐Osmium Tetroxide

Asymmetric dihydroxylation of aliphatic olefins to chiral diols with good yields and ees by a heterogeneous Resin‐OsO₄ catalyst using ferricyanide as cooxidant is disclosed for the first time. The catalyst was recovered quantitatively by simple filtration and reused for several times without significant loss of activity.     

Bifunctional Catalysts Stabilized on Nanocrystalline Magnesium Oxide for One‐Pot Synthesis of Chiral Diols

New bifunctional catalysts composed of PdCl₄²⁻, OsO₄²⁻ and OsO₄²⁻, WO₄²⁻ designed and prepared by a counterionic stabilization technique involving the reactions of Na₂PdCl₄‐K₂OsO₄ and K₂OsO₄‐Na₂WO₄ with nanocrystalline MgO are well characterized. These bifunctional catalysts, NAP‐Mg‐PdOs and NAP‐Mg‐OsW perform tandem Heck asymmetric dihydroxylation and asymmetric dihydroxylation‐N‐oxidation reactions, respectively, in the presence of the chiral ligand 1,4‐bis(9‐o‐dihydroquinidinyl)phthalazine [(DHQD)₂PHAL] in a single pot. It is quite impressive to note that H₂O₂ is used as a terminal oxidant to provide N‐methylmorpholine N‐oxide (NMO) in situ by the oxidation of N‐methylmorpholine (NMM) in the asymmetric dihydroxylation‐N‐oxidation catalyzed by NAP‐Mg‐OsW.     

聚碳酸酯二元醇及其在聚氨酯材料中的应用

本文论述了聚碳酸酯二元醇及聚碳酸酯型聚氨酯材料的发展概况，并分别简述了聚碳酸酯二元醇的合成方法、应用及聚碳酸酯型聚氨酯材料的性能与特点。     

杂环三氮烯显色剂BTNPT的合成及其在分析中的应用研究

合成一种新的杂环三氮烯显色荆：1-(2-苯并噻唑)-3-(4-硝基苯)-三氮烯(BTNPT)．研究试剂的结构、光度性质和在Na2B4O7-NaOH缓冲介质及有非离子表面活性剂Triton-X 100存在下，试剂与Hg的显色反应．该方法应用于废水样中Hg^2 的测定，获得了较为满意的结果。     

New polyurethane cationomers with naphthyl and phenyltriazene pendants: Synthesis and properties

Two new diols bearing triazene moiety, 1‐(α‐naphthyl)‐3,3‐di(2‐hydroxyethyl) triazene‐1 (NT‐D) and 1‐phenyl‐3,3‐di(2‐hydroxyethyl) triazene‐1 (PT‐D), were synthesized from aromatic amines and diethanolamine. These monomers were used as chain coextenders in the two‐step addition reaction between poly(tetramethylene oxide) diol, 2,4‐tolylene diisocyanate, and N‐methyldiethanolamine to obtain photosensitive polyurethanes of elastomer type. Triazene polyurethane cationomers with chlorine counterions were prepared via a quaternization reaction of the above polymers with benzyl chloride. All polyurethanes had a quantity of triazene units between 7.02 and 8.93 wt % polymer, and the content of ammonium quaternary groups in the cationic ones was of 30.56 meq/100 g naphthyl triazene polyurethane cationomer (PUC‐NT) and 30.19 meq/100 g phenyl triazene polyurethane cationomer (PUC‐PT), respectively. Photobehavior of the triazene units in all polymers under continuous Hg‐lamp irradiation was similar to that found for monomers, when both chromophores were transformed during UV irradiation. It is concluded that the PT‐D acts as a more efficient sensitizer in the UV light‐induced reaction but the photolysis in elastomeric films was lower than that observed in solution. The presence of quaternary ammonium structure on the same polymer backbone decreases the constant rates of photolysis. Because the triazene polyurethanes become crosslinked during UV irradiation could be assessed as potential negative‐resist polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2599–2605, 2004     

Mercury(II) selective membrane electrode based on 1,3-bis(2-methoxybenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-methoxybenzene)triazene (MBT) for highly selective determination of mercury(II) has been developed. The electrode showed a good Nernstian response (30.2 ± 0.3 mV decade^− 1) over a wide concentration range (1.0 × 10^− 7−1.0 × 10^− 2 mol L^− 1). The limit of detection was 5.0 × 10^− 8 mol L^− 1. The electrode has a response time about 15 s and can be used for at least 1 month without observing any deviation from Nernstain response. The proposed electrode revealed an excellent selectivity toward mercury(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.6–4.2. The electrode was used in the determination of Hg²⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Hg(II) ions.     

Organocatalytic Asymmetric Michael Addition/Carbon‐Carbon Bond Cleavage of Trifluoromethyl α‐Fluorinated gem‐Diols to Nitroolefins

A new organocatalytic asymmetric Michael addition reaction by cleavage of carbon‐carbon bonds through a mild release of trifluoroacetate has been developed. The reported method generates the decarboxylated γ‐nitro‐α‐fluorocarbonyl products with excellent enantioselectivies (up to 98% ee) and good diastereoselectivies (up to 20:1 dr).     

有机钛酸酯催化制备聚碳酸酯二元醇的工艺研究

以有机钛酸酯（Ti（OBu）4）为催化剂,考察了反应物碳酸二乙酯（DEC）和1,4-丁二醇（BDO）摩尔比、减压时间及温度、精馏柱塔板数等对酯交换反应的影响,制备出了相对分子质量在2000左右的聚碳酸酯二元醇（PCDL）。采用IR和1H—NMR表征了产物PCDL的分子结构,气相色谱法分析了馏分的组成。结果表明,常压阶段馏分为乙醇,与反应物的摩尔比无关;减压阶段,当反应物摩尔比〉1．0时,DEC与乙醇形成共沸物一起被蒸出。当反应物摩尔比≥1．0时,所得产物的相对分子质量能够稳定地控制在2000左右。随着减压反应时间的延长和温度的升高,PCDL的相对分子质量诼渐增大．羟值则逐渐降低。