Iron Chloride/4‐Acetamido‐TEMPO/Sodium Nitrite‐Catalyzed Aerobic Oxidation of Primary Alcohols to the Aldehydes

A variety of 4‐substituted 2,2,6,6‐tetramethylpiperidyl‐1‐oxy (TEMPO) derivatives has been screened for their ability in the oxidation of primary alcohols to the aldehydes with dioxygen under mild conditions. An evaluation of the efficiency of these 4‐substituted TEMPO derivatives in the alcohol oxidation may allow an insight into the effect of the structural variations of TEMPO on the oxidation of alcohols, which should facilitate catalyst design and screening efforts. Based on the screening results of 4‐substituted TEMPO derivatives, the catalyst comprised of 4‐acetamido‐TEMPO, iron chloride and sodium nitrite, has been developed for the highly efficient oxidation of a wide range of primary alcohols including primary aliphatic alcohols to the corresponding aldehydes under mild conditions.     

亚硝酰自由基及其选择性氧化多糖类物质研究进展

亚硝酰自由基能选择性氧化天然多糖类高分子,如纤维素,淀粉,甲壳质,壳聚糖等,从而为制备这些天然高分子的氧化产物或进一步制备氧化产物的衍生物,对环境友好高分子,可生物降解高分子,医用高分子的开发具有较大的应用前景。本文在简介亚硝酰自由的基础上,对其选择性氧化多糖类物质的研究进展作了综述。     

Efficient and Selective Aerobic Alcohol Oxidation Catalyzed by Copper(II)/2,2,6,6,‐Tetramethylpiperidine‐1‐oxyl at Room Temperature

A simple and efficient copper(II)/2,2,6,6,‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐catalyzed aerobic oxidation of both primary and secondary benzylic, allylic, and aliphatic alcohols to their corresponding aldehydes and ketones at room temperature using the copper(II) complex [Cu(μ‐Cl)(Cl)(phen)]₂ as the Cu(II) source is reported. The conversion of both electron‐rich and electron‐neutral benzyl alcohols is smooth and faster than those of electron‐deficient ones. The chemoselectivity of a primary benzyl alcohol over the secondary alcohol is also observed. Alcohols regarded as difficult substrates for oxidation due to their coordinating ability with transition metal catalyst such as 4‐(methylthio)benzyl alcohol and 3‐pyridinemethanol are also oxidized easily. In addition, a lignin model alcohol is oxidized to the corresponding aldehyde in excellent yield. Conversions of benzylic and allylic alcohols are faster as compared to those of aliphatic alcohols in accordance with their C_α H bond strengths. A plausible mechanism of the TEMPO‐based catalytic cycle is proposed.     

Biodegradable poly(ester amide)s – A remarkable opportunity for the biomedical area: Review on the synthesis,characterization and applications

Poly(ester amide)s have emerged in the last years as an important family of biodegradable synthetic polymers. These polymers present both ester and amide linkages in their structure and they gather in the same entity the good degradability of polyesters with the good thermo-mechanical properties of polyamides. Particularly, poly(ester amide)s containing α-amino acids have risen as important materials in the biomedical field. The presence of the α-amino acid contributes to better cell–polymer interactions, allows the introduction of pendant reactive groups, and enhances the overall biodegradability of the polymers.     

Activation of Dioxygen by Cobaloxime and Nitric Oxide for Efficient TEMPO‐Catalyzed Oxidation of Alcohols

The aerobic oxidation of alcohols to their corresponding carbonyl compounds could be efficiently accomplished by using the combination of cobalt nitrate, dimethylglyoxime and 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO) as a novel catalytic system, and various alcohols including primary and secondary benzylic, allylic and aliphatic alcohols could be quantitatively converted to the corresponding aldehydes or ketones at 70 °C under 0.4 MPa dioxygen pressure in dichloromethane. During the oxidation, the in situ generated cobaloxime and nitric oxide (NO) were responsible for the activation of dioxygen, respectively, thereby, two concerted catalytic routes exist: cobaloxime‐activating‐dioxygen TEMPO‐catalyzed and NO‐activating‐dioxygen TEMPO‐catalyzed aerobic oxidation of alcohols.     

Nitroxide‐mediated ‘living’ free radical synthesis of novel rod–coil diblock copolymers with polystyrene and mesogen‐jacketed liquid‐crystal polymer segments

The synthesis of rod–coil diblock copolymers with narrow polydispersity was achieved for the first time by TEMPO‐mediated ‘living’ free radical polymerization of styrene and 2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene. The block architecture of the two diblock copolymers thus prepared, MPCS‐block‐St (5400/2400) and MPCS‐block‐St (10 800/8700), was confirmed by GPC, ¹H and ¹³C NMR and DSC studies. The liquid‐crystalline behaviour of the copolymers was studied by DSC and polarized optical microscope. It was observed that both copolymers showed two distinct glass transitions, corresponding to polystyrene and poly(‐2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene). Above the glass transition temperature of rigid block, liquid‐crystalline phase was formed. The clearing point of the phase is higher than the polymer decomposition temperature. © 2000 Society of Chemical Industry     

The electrochemistry of TEMPO-mediated oxidation of alcohols in ionic liquid

The detailed electrochemistry of TEMPO-mediated oxidation of alcohols to carbonyl compounds in ionic liquid medium is presented. It is shown that TEMPO diffusion currents are suppressed in IL medium, relative to acetonitrile solvent, due to the high viscosity of the IL medium; however, the presence of substrate and base reagent significantly reduces IL viscosity, improving performances significantly. Cyclic voltametry shows that the kinetics of the reaction between electrooxidized TEMPO and the alcohol are similar in both media. It was also observed that in the case where the oxidation product is non-enolizable, electrolyses (diaphragm cell) with catalytic quantities of TEMPO, and in the presence of base (2,6-lutidine), results in close to 100% Faradaic and 100% chemical efficiencies. In contrast, prolonged electrolysis of alcohols yielding enolizable products results in catalyst deactivation due to the irreversible reaction between the active form of the catalyst and the product, which ultimately leads to low product yields and catalyst loss. Under these circumstances, reasonable Faradaic and chemical selectivities can only be obtained with partial electrolyses (to ≤1F/mol).     

TOCNF与磁性羧甲基壳聚糖纳米粒子复合物的制备及吸附Pb2+的特性

水体中铅污染对环境及人的健康安全造成了极大的危害。本文将四甲基呱啶（TEMPO）氧化的纤维素纳米纤维（TEMPO-oxidized cellulose nanofibers,TOCNF）与磁性羧甲基壳聚糖纳米粒子（magnetic carboxymethyl chitosan nanoparticles,MCCN）交联复合制备一种经济高效且对环境无毒害的Pb²⁺吸附剂,对复合前后的材料进行结构表征。通过单因素实验研究pH、Pb²⁺初始浓度、吸附时间及温度对Pb²⁺吸附效率的影响,确定最优吸附条件后比较TOCNF/MCCN及TOCNF对Pb²⁺的吸附效果,研究复合材料对Pb²⁺的吸附特性。研究结果表明,Fe₃O₄成功被羧甲基壳聚糖纳米粒子包裹并与TOCNF交联复合,在最优吸附条件（pH=5,Pb²⁺初始浓度为100mg/L,吸附时间为240min,常温下进行实验）下,TOCNF/MCCN吸附Pb²⁺的饱和容量为193.5mg/g,比TOCNF高了近一倍。复合吸附剂吸附Pb²⁺的过程更符合准二级动力学方程,说明决定吸附速率的主要是化学吸附。等温吸附方程的相关系数R²表明,Langmuir方程能更好地拟合吸附过程,说明复合吸附剂对Pb²⁺的吸附主要是表面基团的单分子层吸附。通过线性方程的斜率计算得到的理论饱和吸附量为201.1mg/g,与实际值差3.8%,经过5次解吸再吸附的过程,吸附剂的吸附效率仅下降了13%,表明该吸附剂有良好的可再生性,具有很好的应用前景。     

Copper‐Catalyzed α‐Aminoxylation of Ketones with 2,2,6,6‐Tetramethylpiperidine‐1‐oxyl (TEMPO)

An efficient copper‐catalyzed α‐aminoxylation of ketones with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) is presented for the synthesis of 2‐aryloxy‐1‐aryl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethanones in moderate to excellent yields. It is noteworthy that the copper/iron (Cu/Fe) catalyst can be recovered and reused several times with high catalytic reactivity.

     

羧基化改性纤维素凝胶球的制备和表征

以微晶纤维素为原料,利用NaOH/尿素体系对微晶纤维素进行溶解,得到再生纤维素溶液。采用滴定悬浮的方法制备纤维素水凝胶球,采用2,2,6,6-四甲基哌啶-1-氧基自由基（TEMPO）/NaBr/NaClO选择性氧化体系对纤维素水凝胶球进行氧化处理,获得羧基化改性纤维素水凝胶球,冷冻干燥得到羧基化改性纤维素气凝胶球。研究结果表明：羧基化改性纤维素水凝胶球的含水量为95.64%,吸附4h,亚甲基蓝的吸附量达到6.97mg/g。对羧基化改性纤维素气凝胶球进行傅里叶变换红外光谱（FT-IR）和扫描电子显微镜（SEM）表征分析,在1600cm^-1处出现了CO的伸缩振动峰,TEMPO的选择性氧化对样品起到羧基化改性作用,羧基化改性纤维素气凝胶增加了球形气凝胶的表面通透性,内部仍呈现网络结构,羧基化改性纤维素气凝胶球的密度为0.038g/cm³。