树脂法分离纯化邻硝基苯甲醛

本文报道树脂法从混合物中分离纯化邻硝基苯甲醛的方法。研究说明，通过伯胺树脂与醛的反应对邻硝基苯甲醛进行化学吸附，可以将邻硝基苯甲醛从含有邻硝基甲苯、邻硝基苯甲醛、邻硝基溴苄、邻硝基－α，α─二溴苄、以及邻硝基苄醇的混合物中有效地分离出来。     

Sc(Ⅲ)催化硫醇对邻亚甲基苯醌的亲核加成反应合成邻羟基苄硫醚衍生物

以2-[羟基(苯基)甲基]苯酚类化合物和简单的硫醇为原料, 1,2-二氯乙烷为溶剂, 在Sc(Ⅲ)促进下原位生成邻亚甲基苯醌, 并发生亲核加成反应构建邻羟基苄硫醚. 该反应在50 ℃下搅拌2 h即可完成, 目标产物产率82%95%. 反应可放大至克级规模.     

邻羟基苄醇与邻羟基苯乙烯的催化不对称[4+2]环加成反应——手性色满骨架的立体选择性构建

研究了手性磷酸催化下邻羟基苄醇和邻羟基苯乙烯的不对称［4+2］环加成反应,立体选择性地一步构建了手性2,4-二取代四氢色满骨架,该反应具有较高的收率、中等到较高的对映选择性和很好的非对映选择性（最高产率为78%,最高ee值为72%,dr值基本都大于95∶5）.带有不同取代基的多种邻羟基苄醇和邻羟基苯乙烯均适用于该反应,电子效应对于该反应的对映选择性有一定影响,其中连有供电子基的底物具有更高的反应活性和对映选择性.由邻羟基苄醇原位生成的邻亚甲基苯醌中间体和邻羟基苯乙烯可以同时与催化剂手性磷酸形成双重氢键,对于促进反应的进行和控制该反应的对映选择性起着至关重要的作用.     

有机相中α-氰基-3-苯氧基苄醇乙酯的酶促醇解反应

研究了有机相中脂肪酶催化α-氰基-3-苯氧基苄醇乙酯的醇解化反应。制备α -氰基-3-苯氧基苄醇。考察了酶、溶剂、醇、醇用量、溶剂水含量以及底物浓度等 因素对反应的影响，结果表明Novozym435脂肪酶催化活性最高，经实验确定的最佳 条件为：脱水甲苯为溶剂，正辛醇为酰基受体，正辛醇、酯的摩尔比为1.5:1，酶 量为8 mg/mL时的最佳底物浓度为108.13 mmol/L，在上述条件下反应30 h酯的转化 率 > 96%。     

溶剂和酰基受体对α-氰基-3-苯氧基苄醇乙醇的酶促对映体选择性转酯化反应的影响

研究了在有机溶剂中固定化Alcaligenes sp.脂肪酶催化α-氰基-3-苯氧基苄醇乙酯的对映体选择性转酯化反应，考察了不同性质的溶剂和酰基受体对酶的催化活性和选择性以及对产物稳定性的影响．结果发现在弱极性溶剂如正己烷中酶具有较高的催化活性但产物e．e．％值低，而且容易分解；在四氢呋喃等溶剂中酶催化活性相对低，但产物e．e．％值高，也较为稳定；但反应时间太长，会导致产物分解及纯度下降；不同酰基受体对酶反应无显著影响，甲醇为最佳酰基受体，太多醇会导致反应速率下降；溶剂水含量大于2．0％时对酶活性和产物稳定性产生明显不利影响．在优化条件下，酶反应可得到（S）-α-氰基-3-苯氧基苄醇产率＞48％，纯度＞99％e．e．     

N-(末端三甲基硅苄基甘氨酸肽链)邻苯二甲酰亚胺的光诱导单电子转移成环反应

以苄基甘氨酸为起始原料合成N-(末端三甲基硅苄基甘氨酸肽链)邻苯二甲酰亚胺(1).1在甲醇溶剂中光照发生单电子转移反应,生成分子内双自由基10,自由基偶合生成环聚甘氨酸肽化合物2.此反应产率好,区域选择性高.所有新化合物结构均经NMR和质谱验证.     

乙酸中碘催化氧化苄醇为相应醛或酮(英文)

本文报道了用I2/NaNO2/4-OH-TEMPO为催化剂,空气为氧化剂,在冰乙酸中催化氧化苄醇的方法.文中考察了催化剂各组分和温度对催化氧化反应的影响,在催化过程中碘替代过渡金属作为4-OH-TEMPO的共催化剂,在选择条件下苄醇氧反应的产物产率达到90%,在反应过程中生成醛或酮.     

气相色谱法同时测定邻氯甲苯的氯化气物

提出用气相色谱（ＧＣ）同时测定邻氯甲苯氯化产物中的邻氯苄基氯，邻氯苄叉二氯，邻氯苄川三氯以及邻氯甲苯含量的方法。相对标准偏差小于１５％（ｎ＝５）。     

对硝基氯苄与活性亚甲基化合物的反应

对硝基苄基衍生物可以与许多阴离子起单电子转移的亲核取代反应。Kornblum等以对硝基氯苄为底物,2-乙氧羰基香豆满-3-酮的钠盐为阴离子,作了深入的研究,得出对硝基氯苄与2-乙氧羰基香豆满-3-酮钠盐的C-烷化反应机理为自由基链式亲核取代反应。同时,Russell等提出对硝基氯苄与2-     

季铵盐催化氧化法合成硝基苯甲酸

研究了季铵盐A－1催化KMnO4分别氧化邻、对硝基甲苯合成邻、对硝基苯甲酸的反应。考察了不同相转移催化剂的催化活性及催化剂用量、反应温度、反应时间、KMnO4用量和反应体系酸碱性对反应的影响。在优化反应条件下，即以季铵盐A－1为相转移催化剂，KMnO4与硝基甲苯摩尔比为2．5：1，反应温度为95℃，反应时间为3h，在中性条件下进行反应，邻位、对位产物收率分别可达95%和92%。实验表明，季铵盐A－1对于KMnO4氧化硝基甲苯合成硝基苯甲酸的反应是一种优良的相转移催化剂。     

Benzylic bromination catalyzed by triphenylphosphine selenide via Lewis basic activation

The synthesis of benzyl bromides was achieved under mild reaction conditions using N-bromosuccinimide as a bromine source and triphenylphosphine selenide as a catalyst. These conditions were compatible with a variety of substrates including boronic esters, protected amines to give imines, and carboxylic acids (to give phthalides when ortho to the benzylic center). A preliminary mechanistic investigation utilizing calculated bond dissociation energies (BDE) is employed to rationalize how a Lewis base can activate a radical mechanism.     

Synthesis of diarylcyclopropyl spirocyclic ketones

A facile one-pot synthetic route for preparing a series of functionalized diarylcyclopropyl spirocyclic ketones 4 is developed. The efficient cyclopropanation route of the conjugated cyclic ketones 2 with sulfones 1 in the presence of NaH shows interesting molecular diversities. The reaction mechanism of the stereocontrolled cyclopropanations has been discussed.     

Rapid Dihydrogen Cleavage by Persistent Nitroxide Radicals under Frustrated Lewis Pair Conditions

Persistent radicals undergo hydrogen atom abstraction reactions with a great variety of substrates, but not with dihydrogen. It has now been found that the TEMPO radical splits dihydrogen under mild conditions in the presence of the strong bulky B(C₆F₅)₃ boron Lewis acid. The reaction is thought to proceed by a typical frustrated Lewis pair mechanism with the TEMPO radical acting as the active Lewis base. The reaction was analyzed by DFT, which indicates that no significant spin density on the hydrogen atoms is accumulated along the H₂ splitting reaction path.     

Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Electrochemical oxidation of trolox on carbon electrodes was investigated by means of some voltammetric techniques in methanol and ethanol solutions in the presence of an excess of acid or base. The oxidation occurs according to EEC mechanism, i.e. in two quasireversible one‐electron steps yielding the corresponding phenoxyl radical and, subsequently, phenoxonium cation. Phenoxonium ion decays because of a pseudo‐first order follow‐up chemical reaction with nucleophiles. The electrochemical behavior of trolox is strongly influenced by the surrounding environmental conditions. In acidic solutions, a single two‐electron anodic wave was observed. The presence of a strong base drastically improves the stability of the intermediate, phenoxyl radical. Under these conditions, the two‐electron wave was found to split into its one‐electron components over a range of scan rates. The resolution is much distinct in ethanol. Simulations with DigiSim software were used to fit the cyclic voltammograms in order to estimate thermodynamic and kinetic data for the reaction mechanism studied.     

Selective cleavage of the linear ether bond in benzyl glycidyl ether and triphenylmethyl glycidyl ether by potassium alkalide as two-electron-transfer reagent

The linear ether bond was exclusively cleaved in benzyl glycidyl ether and triphenylmethyl glycidyl ether under the influence of K⁻, K⁺(15-crown-5)₂ (1), whereas the strongly strained three-membered oxacyclic ring remained undisturbed. Potassium glycidoxide and benzylpotassium were found as the primary reaction products of benzyl glycidyl ether with 1. Subsequently, benzylpotassium reacted with benzyl glycidyl ether giving the next potassium glycidoxide molecule and bibenzyl. Benzyl phenyl ether was used as a model compound to explain the mechanism of bibenzyl formation. The reaction of triphenylmethyl glycidyl ether with 1 resulted in potassium glycidoxide and stable triphenylmethylpotassium. After treating with a quenching agent a new glycidyl ether or glycidyl ester was obtained from potassium glycidoxide. These results were found when the reaction occurred at the excess of glycidyl ether. In another case, i.e. at the excess of 1 further reactions took place with the participation of potassium anions and various new compounds were observed in the reaction mixture after benzylation or methylation. Thus, the method of substrates delivery influences the course of studied processes in a decisive way.     

Electrochemical reduction of 2-hydroxypyrimidine in dimethylsulfoxide: Influence of the father-son reaction

In DMSO (0.1 M TEAP), 2-hydroxypyrimidine (2-HP) is reversibly reduced (1e process) to a radical anion, whose dimerization is slower than its attack (it is a strong base) on unreduced 2-HP to abstract a proton (father-son reaction), producing the neutral free radical, which dimerizes more rapidly than the radical anion, and the anion of 2-HP, which can be involved in a Hg(I)?Hg(0) couple; the apparent faradaic n is less than one. On addition of strong base to a 2-HP solution, the 2-HP is converted to the anion and the only electrochemical activity seen is that due to the mercury couple. On strong acid addition, the protonated 2-HP formed is more easily reduced than neutral 2-HP; the resulting current considerably exceeds that for 2-HP itself (faradaic n equals one); the anion-mercury reaction couple is not seen. The neutral free radical formed rapidly dimerizes. Weak acid addition produces an adduct due to hydrogen bridging between acid anion and pyrimidine reduction site; reduction to the neutral free radical is facilitated; the weak acid anion is involved in a Hg(I)?Hg(0) couple at a potential characteristic for the acid used; the mercury-pyrimidine anion couple occurs at a potential characteristic for 2-HP.     

Electrochemical activation of chain radical processes by radical organophosphorus cations

It is found that electrochemically generated radical cations of organophosphorus compounds react with substrates that are capable of homolytic cleavage of the element-hydrogen bond via a radical detachment of the hydrogen atom, thus initiating the chain radical addition of the substrates over the double bond of alkenes. The presence of a strong base that is capable of deprotonating intermediate phosphonium salts in electrolyte allows one to set up an electrocatalytic cycle and use organophosphorus compounds in catalytic quantities. The main side reaction in the studied processes is the interaction between radical cations of organophosphorus compounds and olefin which leads to the formation of phosphorylated alkenes.     

A fast radical chain mechanism in the polyfluoroalkoxylation of aromatics through NO2 group displacement. Mechanistic and theoretical studies

Introduction of polyfluoroalkoxy and polyfluoroalkylthio substituents in aromatic rings can be achieved with mild conditions and short times thorough reaction of concentrated solutions of dinitrobenzenes in DMF with polyfluoro alcohols and polyfluoro thiols in moderate excess, in the presence of excess tetrabutylammonium fluoride as a base. Mechanistic studies suggest that under these conditions a fast radical chain mechanism operates. This mechanism is elicited by oxidation of a Meisenheimer complex and proceeds through a radical aromatic substitution with the polyfluoroalkoxy or the polyfluoroalkylthio radicals as key intermediates. At low concentrations, entrainment can be achieved with superoxide anion. A rationale for this effect is discussed. Answers to particular questions about the proposed mechanism are achieved through a theoretical study at the B3LYP/6-31+G(d,p) level. Specifically, the competition between the radical mechanism and the corresponding polar one (classical S(N)Ar reaction) is studied in that way, with the conclusion that the key steps of the radical mechanism in our reaction conditions (polar aprotic solvent) are at least as efficient as the ones of the polar one, thus justifying the observed kinetic advantage for the chain reaction in the conditions where an efficient initiation occurs.     

对甲苯磺酰胺电还原过程的电化学-ESR研究

对一些含硫的镀镍光亮剂电还原反应曾提出过两种反应机理，一种是生成硫酸的机理，一种是脱磺酸（酞）基团的机理．Brook和Crossleyu］认为这类反应是按后一种机理进行的自由基反应，但未对中间产物作出检测．因此目前对反应机理尚无定论．为了阐明还原中间产物与反应本性，本文利用自旅捕集技术与UV光谱研究了对甲基磺欧胺在汞电机上的电还原过程．1实验1．1仪器HDVI－xFD｛－x－Y仅组装CV图测量系统；日本JE巳FElxG波谱仪；xJP七ZI新极谱仪阳春应化所）2751G紫外分光光度计．1．2主要试剂苯亚甲基叔丁基氮氧化物（PBN，由中科…     

自由基-氟代烯烃加成反应活性的理论研究

利用AMI半经验量化方法对一系列自由基-氟取代烯烃加成反应进行了计算，并用软硬酸碱规则的理论基础-广义微扰理论对计算结果进行了处理．发现该类烯烃与自由基加成的反应活性（以活化能来表示）可由该理论得到很好的解释、同时发现影响反应活性的主要因素是路易斯酸碱对之间的共价作用，而静电作用的影响则非常小。另外还发现，对于本文讨论的烯烃分子，两不饱和碳原子间存在有强的相互作用．