Oxone/CaCl2/TEMPO体系在温和条件下对醇的氧化反应

Oxone/TEMPO/CaCl₂ (TEMPO＝2,2,6,6-Tetramethyl-1-piperidinyloxy)是一种稳定安全和易得的氧化催化体系, 在室温条件下, 可以氧化苄基或烷基醇生成醛或酮. 苄基伯醇很容易被氧化成相应的醛, 有较高的反应收率(90%～96%), 仲醇氧化成相应的酮, 收率在81%～85%之间, 1,4-丁二醇环氧化生成γ-丁内酯得到了94%的收率.     

氮氧自由基TEMPO：选择氧化醇的高效有机小分子催化剂*

醇被氧化为相应的醛或酮是有机合成中重要的官能团转换反应之一。自从Anelli法（TEMPO/NaBr/NaOCl）发现以来,由于所具有的醇被氧化为相应的醛或酮是有机合成中重要的官能团转换反应之一。自从Anelli法（TEMPO/NaBr/NaOCl）发现以来,由于所具有的高活性和高选择性, 有机小分子催化剂2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)催化醇的氧化反应成为温和条件下醇选择氧化的一个重要方法,并在实验室和工业生产中广泛应用。最近有关TEMPO催化醇氧化反应的研究,主要集中在开发用于分子氧对醇绿色氧化的催化体系和目的在于实现催化剂回收再用的TEMPO固载化研究两个领域上。本文以此为重点,综述了TEMPO催化醇氧化反应的发展和最近研究进展。     

以Saccharin/TEMPO高效催化氧化醇制备醛酮的研究

采用Saccharin/TEMPO共催化剂并在次氯酸钠NaClO作用下高效地催化氧化醇合成了醛或酮。筛选了溶剂及SAC/TEMPO用量等条件获得了最优工艺。以一系列的醇作为底物进行了研究,结果表明,高效地实现了对醇的氧化转化,产率可达95%,并且有良好的选择性。应用此共催化体系对醛或酮的制备具有广泛的适用性,是一种较好的方法。     

功能离子液体催化分子氧氧化醇为醛酮

2,2,6,6-四甲基-N-氧自由基哌啶醇(2,2,6,6-tetramethyl-piperidin-4-ol-N-oxyl,TEMPO)与氯乙酰氯反应生成2-氯乙酸-2,2,6,6-四甲基-1-氧-4-哌啶醇酯,该酯与N-甲基咪唑发生季铵化反应后再与六氟磷酸钾进行离子交换制得2,2,6,6-四甲基-N-氧自由基哌啶醇负载离子液体TEMPO-IL。温和条件下以离子液体1-甲基-3-丁基咪唑六氟磷酸盐(1-butyl-3-methylimidazolium hexafluorophosphate,[bmim]PF6)为溶剂,TEMPO-IL和CuCl为催化剂,分子氧氧化各种醇为相应的醛或酮。研究发现,该氧化体系对苄醇和烯丙醇有较好的氧化效果,65℃下反应10h左右,转化率可达99%,收率可达80%~90%。氧化体系对醛酮有高度的选择性,在实验所采用的条件范围内未检测到有羧酸生成。溶剂和催化剂可循环使用,在苯甲醇的氧化中,溶剂和催化剂循环使用6次,反应转化率和苯甲醛的收率保持不变。     

锚定基团对HKUST-1/TEMPO共催化体系催化性能的影响

用异烟酸(Iso-NTA)为桥接分子, 将有机小分子自由基4-氨基-2,2,6,6-四甲基哌啶-1-氧自由基(4-NH₂-TEMPO)与异烟酸缩合, 合成出含吡啶官能团的TEMPO自由基(Iso-NTA-TEMPO). 与TEMPO相比, Iso-NTA-TEMPO具有较高的氧化电位, 在无Cu(Ⅱ)辅助时, Iso-NTA-TEMPO对苯甲醇的氧化效率高于TEMPO. 在与HKUST-1组成的复合催化体系中, Iso-NTA-TEMPO可通过吡啶基团与HKUST-1孔道中的Cu(Ⅱ)相互作用, 从而在催化过程中(部分)锚定在HKUST-1孔道内部. 与TEMPO/HKUST-1体系相比, Iso-NTA-TEMPO/HKUST-1体系表现出对芳香醇更加高效的催化活性. 采用模板辅助溶剂诱导结晶法合成的HKUST-1晶体表面具有较多缺陷, 更有利于Iso-NTA-TEMPO自由基分子扩散进入HKUST-1孔道内部, 也有助于提高Iso-NTA-TEMPO/HKUST-1体系的催化效率. Iso-NTA-TEMPO/HKUST-1体系可将各种取代基(苄醇、 杂环醇以及二级脂肪醇)高效、 高选择性地氧化成相应的醛或酮.     

将醇控制氧化成醛或酮的催化体系

介绍一种有效催化醇氧化成醛或酮反应的新型催化剂(TEMPO/CuCl),涉及醇的氧化、配位、电负性等高中化学知识,供一线教师用于新课标高中“有机化学基础”模块课程教学。     

CuBr/1,8-二氮杂双环[5.4.0]十一碳-7-烯催化苄醇的选择性空气氧化反应（英文）

发展了一种新型、实用性的以溴化亚铜为催化剂,以1,8-二氮杂双环[5.4.0]十一碳-7-烯(DBU)为添加剂,在空气条件下进行氧气氧化苄醇的催化体系.各种一级或二级苄醇及烯丙醇可以以高的产率及选择性转换为相应的醛和酮.该过程为无溶剂反应,同时不需要使用四甲基哌啶氧化物(TEMPO)类助氧化剂.     

α-硝基酮的合成

醛与硝基烷烃发生Henry反应合成了硝基仲醇(2);2经氧化制得α-硝基酮,总收率72%～93%,其结构经1H NMR和MS表征.     

金刚烷负载高价碘试剂的合成及氧化反应活性

以1,3,5,7-四氨基金刚烷与4-碘苯基酰氯为原料,经酰化、氧化反应,制备了新型金刚烷负载的高价碘试剂(1a-1c)。 酰化反应以CH₂Cl₂为溶剂,首先,0 ℃,反应4 h,然后室温反应2 h,投料比n(1,3,5,7-四氨基金刚烷)∶n(4-碘苯基酰氯)∶n(三乙胺)=1∶4.4∶5.2。 氧化反应以CH₂Cl₂/醋酸(体积比1∶1)为溶剂,间氯过氧苯甲酸(m-CPBA)为氧化剂,室温反应12 h,投料比n(2)∶n(m-CPBA)=1∶12。 化合物1a,1b和1c的总收率分别为86.4%、85.4%和85.3%。 以化合物1a-1c为氧化剂,在四甲基哌啶氮氧化物(TEMPO)催化下各类醇被氧化成相应的醛或酮,产物收率87%~100%。 负载碘苯2a-2c可以被方便地分离和回收,平均回收率98%,可再经氧化,高收率转化成化合物1a-1c,循环利用。     

氟烷磺酰氟/双氧水/碱/丙酮体系与苄醇衍生物的氧化反应

研究了氟烷磺酰氟/双氧水/氢氧化钠/丙酮体系与6个苄醇衍生物的氧化反应, 其中氟烷磺酰氟包括HCF₂CF₂OCF₂CF₂SO₂F, n-C₄F₉SO₂F和n-C₈F₁₇SO₂F. 最优反应条件为n(苄醇衍生物): n(氟烷磺酰氟): n(双氧水): n(氢氧化钠)=1: 4: 8: 8, 溶剂为丙酮, 反应温度为20℃, 反应时间为24 h. 产物酮的收率为23% ~92%. 探讨了该氧化反应的机理, 原位生成的氟烷基过氧磺酸中间体可将丙酮氧化为二甲基二氧杂环丙烷, 进而将反应体系中共存的苄醇衍生物氧化成相应的产物酮. 氟烷磺酰氟/双氧水/氢氧化钠/丙酮体系原位生成的二甲基二氧杂环丙烷氧化苄位羟基的能力和传统的Oxone/CH₃COCH₃体系相当. 本研究提供了一种新颖的原位制备二甲基二氧杂环丙烷的方法.     

Mild and selective oxidation of alcohols to aldehydes and ketones using NaIO4/TEMPO/NaBr system under acidic conditions

A TEMPO-catalyzed selective oxidation of alcohols to the corresponding aldehydes and ketones using NaIO₄ as the terminal oxidant is reported. The NaIO₄/TEMPO/NaBr system provides a mild and efficient method for the oxidation of alcohols that are sensitive to basic conditions. Furthermore, the recoverable ionic liquid immobilized TEMPO-catalyzed oxidation of benzyl alcohol in ionic liquid-H₂O medium is also developed.     

CuI/TPA/4-乙酰胺基-TEMPO催化的苄醇与烯丙基醇氧化反应的研究

CuI/TPA(tris(pyridin-2-ylmethyl)amine)/4-乙酰胺基-TEMPO(2,2,6,6-Tetramethylpiperidyl-1-oxyl)催化体系能够在室温下,以氧气作氧化剂,乙腈作溶剂,高效、高选择性地催化一系列苄醇,烯丙基醇和含杂原子伯醇的氧化,且在体系中无需添加任何碱作助催化剂.     

Catalytic Oxidation of Alcohols to Corresponding Aldehydes or Ketones with TEMPO-Mediated Iodosobenzene in Water in the Presence of a Surfactant

An efficient, facile, and rapid oxidation of alcohols to the corresponding aldehydes or ketones with a stoichiometric amount of iodosobenzene (PhIO) in the presence of catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl free radical (TEMPO), KBr, and a surfactant, such as SDS (sodium dodecylsulfate), was reported. The oxidation proceeded in water at room temperature to afford aldehydes or ketones in excellent yields and high selectivity without overoxidation to carboxylic acids. Selective oxidation of primary alcohols in the presence of secondary alcohols was also achieved with the catalytic system of PhIO/TEMPO/KBr/SDS. A possible mechanism for the oxidation was supposed.     

Room temperature Fe(NO3)3·9H2O/TEMPO/NaCl-catalyzed aerobic oxidation of homopropargylic alcohols

A practical and eco-friendly aerobic oxidation of homopropargylic alcohols using Fe(NO₃)₃·9H₂O/TEMPO/NaCl as catalysts at room temperature under atmospheric pressure was developed affording corresponding homopropargylic ketones with moderate to good yields. Aryl, heteroaryl as well as alkyl 1,2-allenic ketones were obtained by the isomerization of corresponding terminal homopropargylic ketones through column chromatographic workup on silica gel.     

离子液体-水介质中离子液体负载TEMPO催化选择氧化合成脂肪醇羟基芳香醛和酮

由于脂肪醇羟基和苄醇羟基具有相同的氧化反应活性,所以当分子内同时含有脂肪醇羟基和苄醇羟基时,很难选择氧化苄醇羟基合成含脂肪醇羟基的芳香醛或酮。本文报道了在离子液体-水介质中,NCS/NaBr/IL-TEMPO（离子液体负载TEMPO）催化氧化合成含有脂肪醇羟基的芳香醛、酮的方法,反应条件温和,选择性好,收率高,且离子液体和催化剂可以循环使用。     

Selective aerobic oxidation of alcohols catalyzed by iron chloride hexahydrate/TEMPO in the presence of silica gel

An environmentally friendly and efficient process whereby FeCl₃?6H₂O/2,2,6,6‐tetramethylpiperidine N‐oxyl (TEMPO)‐catalyzed oxidation of alcohols to the corresponding aldehydes and ketones is accomplished in the presence of silica gel using molecular oxygen or air as the terminal oxidant. The electron‐deficient benzyl alcohol was smoothly oxidized to the corresponding aldehydes with up to 99% isolated yield. It was found that silica gel not only could enhance the catalytic reaction rate but also increase the selectivity for the product. The high performance of FeCl₃?6H₂O/TEMPO catalyst system in the presence of silica gel might be attributed to the surface silanol groups. UV–visible spectra analysis showed that the Fe (III)–TEMPO complex could serve as the active intermediate species in the present catalytic system. A plausible mechanism of the catalytic system is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

Lewis acid-catalyzed oxidative rearrangement of tertiary allylic alcohols mediated by TEMPO

Two methods for the oxidative rearrangement of tertiary allylic alcohols have been developed. Most of tertiary allylic alcohols studied were oxidized to their corresponding transposed carbonyl derivatives in excellent to fair yields by reaction with TEMPO in combination with PhIO and Bi(OTf)₃ or copper (II) chloride in the presence or not of oxygen. Other primary oxidants of TEMPO such as PhI(OAc)₂, mCPBA, and Oxone^® were unsatisfactory giving the enone in modest to low yields.     

Comparison of TEMPO and its derivatives as mediators in laccase catalysed oxidation of alcohols

A series of TEMPO (2,2′,6,6′-tetramethylpiperidinyl-1-oxy) derivatives were studied as mediators of laccase (from Trametes versicolor) in the oxidation of benzyl alcohol and 1-phenylethyl alcohol. TEMPO (1), 4-hydroxy-TEMPO (2) and 4-acetylamino-TEMPO (4) turned out to be the most active mediators for laccase. In addition, 4-acetylamino-TEMPO and 4-hydroxy-TEMPO were more active in the oxidation of 1-phenylethanol compared to TEMPO. For these mediators kinetic isotope effects in the range of 2.1-3.2 were observed for α-monodeutero-p-methylbenzyl alcohol oxidation. These values are consistent with a mechanism involving oxoammonium intermediacy. Competition experiments between benzyl alcohol and 1-phenylethanol showed that TEMPO and its derivatives react faster with primary alcohols than with secondary alcohols, also in line with the proposed mechanism.     

Metal‐Free 2,2,6,6‐Tetramethylpiperidin‐1‐yloxy Radical (TEMPO) Catalyzed Aerobic Oxidation of Hydroxylamines and Alkoxyamines to Oximes and Oxime Ethers

TEMPO‐Mediated oxidation of hydroxylamines (=hydroxyamines) and alkoxyamines to the corresponding oxime derivatives is reported (TEMPO=2,2,6,6‐tetramethylpiperidin‐1‐yloxy radical; Scheme 2). These environmentally benign oxidations proceed in good to excellent yields (Table 1). For alkoxyamines, oxidation to the corresponding oxime ethers can be performed by using dioxygen as a terminal oxidant in the presence of 5–10 mol‐% of TEMPO or 4‐substituted derivatives thereof as a catalyst (Scheme 3 and Table 2). Importantly, benzyl bromides can directly be transformed to oxime ethers via in situ alkoxyamine formation by a nucleophilic substitution followed by TEMPO‐mediated oxidation (Scheme 4 and Table 3).