纳米尺度氧化石墨烯层作为高效碳催化剂用于苄醇与芳香醛的绿色氧化

合成了纳米尺度氧化石墨烯(NGO)层,用作碳催化剂高效催化苄醇与芳香醛的氧化反应.对于醇氧化反应,当80℃时H2O2存在下,NGOs(20 wt％)可高效催化醇选择性生成醛,其反应速率和产率取决于醇上取代基的性质.对于4-硝基苄醇,反应24 h后,只有10％可转换为相应羧酸.相反,4-甲氧基苄醇和二苯基甲醇分别反应仅9和3h则可完全转化为对应的羧酸和酮.NGO碳催化剂上芳香醛氧化速率高于醇氧化速率.对于所有的醛,采用7 wt％ NGO作催化剂,在70℃反应2-3 h后,就可完全转化为相应羧酸.我们讨论了NGO催化剂结构对苄醇和芳香醛氧化反应影响的可能机理.     

Heterogenized polymetallic catalysts: Part III. Catalytic air oxidation of alcohols by Pd(II) complexed to a polyphenylene polymer containing β-di- and tri-ketone surface ligands

This paper describes further studies on mono- and bi-metallic catalysts attached to a polymer support by β-di- and tri-ketone surface ligands. The previous two papers described the oxidation of catechol by the heterogeneous catalysts using Cu(II), Fe(III) and Pd(II) as the metal species. The present study expands these studies to a series of mono- and polyfunctional alcohols using Pd(II) as the metal species. The final catalytic surfaces were prepared by treatment of the modified polymer with a very reactive form of Pd(II), [Pd(CH₃CN)₄]²⁺. The simple alcohols gave increases in rates of up to 5-fold for the bimetallic systems. As might be expected glycols and - -glucose gave even higher increases in rate in going from the mono- to the bi-metallic catalyst. For ethylene glycol the factor was 30. Unsaturated alcohols gave the most dramatic results. With the monometallic catalyst, the products from allyl alcohol consisted of 25% acrolein resulting from direct alcohol oxidation and 75% 3-hydroxypropanal resulting from Wacker-type oxidation of the double bond. With the bimetallic catalyst the overall rate increased by a factor of 10 and the products consisted of 80% acrolein and 20% 3-hydroxypropanal. The actual rate increase for the direct alcohol oxidation is calculated to be a factor of 32. 4-Penten-2-ol and 4-penten-1-ol gave rates that were lower than the monofunctional alcohols. This is attributed to inhibition by olefin π-complex formation with the Pd(II).     

Unique hydrogenation activity of supported tin catalyst: Selective hydrogenation catalyst for unsaturated aldehydes

Selective hydrogenation of unsaturated aldehydes, crotonaldehyde (CH₃CH=CHCH=O) and cinnamaldehyde (C₆H₅CH=CHCH=O), has been studied over SiO₂-supported monometallic Sn and bimetallic Rh---Sn catalysts in the liquid phase. Over a silica-supported monometallic Rh catalyst, Rh/SiO₂, no unsaturated alcohol (crotyl alcohol or cinnamyl alcohol) was formed, whereas considerable amounts of the corresponding saturated aldehyde and saturated alcohol were obtained. The selectivity to the unsaturated alcohol was improved over the Rh---Sn bimetallic catalyst. The selectivity to the corresponding unsaturated alcohol attained ca. 65% over the Rh---Sn bimetallic catalysts. On the other hand, The supported Sn catalyst showed markedly high selectivity to the unsaturated alcohols. The selectivity of the Sn/SiO₂, attained 95% to crotyl alcohol and 100% to cinnamyl alcohol, respectively. Although the conversion of each unsaturated aldehyde over Rh---Sn/SiO₂ catalysts was greater than that over Sn/SiO₂ catalysts, the selectivity of Sn/SiO₂ catalysts to the corresponding unsaturated alcohols was superior to that over Rh---Sn/SiO₂. The selectivity of Sn/SiO₂ was also compared with that of Rh---Sn/SiO₂ at a similar conversion of the unsaturated aldehydes. The selectivity of Sn/SiO₂ was significantly greater than that of the Rh---Sn bimetallic catalyst. These results indicate that the high selectivity over Sn/SiO₂ was ascribed not to low conversion but to intrinsic selectivity of the Sn catalyst.     

A rugged lead-ruthenate pyrochlore membrane catalyst for highly selective oxidation of alcohols

A rugged lead-ruthenate pyrochlore (Py, Pb₂Ru₂O₇) Nafion 417 membrane catalyst (|NPy|) has been demonstrated for highly efficient and fully selective oxidation of primary and secondary alcohols to aldehydes and ketones. Under a triphasic condition of CH₂Cl_2(org)//|NPy|_(s)//NaOCl-pH 11_(aq), the |NPy| can be recycled and reused effectively on oxidations of alcohols. Using a same piece of |NPy|, similar reaction yields were obtained by repeating benzyl alcohol oxidation reaction for 20 times. Electrochemical mechanistic investigation indicated that the perruthenate ion (RuO₄⁻) intermediate was responsible for selective mediation of the alcohol oxidation.     

CuI/2,2'-联吡啶/2,2,6,6-四甲基哌啶氧化物催化氧化醇生成腈的工艺

以高压反应釜为反应装置,采用CuI/Bipy(2,2'-联吡啶)/TEMPO(2,2,6,6-四甲基哌啶氧化物)催化体系,以氨水作氮源,分子氧作氧化剂,对醇催化氧化生成相应腈的方法进行了优化。 以苯甲醇的催化氧化反应为模型反应,考察了催化剂及其用量、溶剂、反应温度以及时间对催化性能的影响。 实验表明:在高压釜中,120 ℃、40×10⁵ Pa的氮氧混合气(φ(O₂)=8%)条件下,将催化剂摩尔分数降低至1%(脂肪醇催化剂摩尔分数为5%),反应时间缩短至8 h时,催化效果最佳。同时,该反应系统对于不同的芳香醇和脂肪醇的氧化均取得了90%以上的转化率和90%以上的产品收率。     

Performance of Pt/SnO2 catalyst in the gas phase hydrogenation of crotonaldehyde

Selective hydrogenation of crotonaldehyde was performed on 5% Pt/SnO₂ catalysts, in gaseous phase, at atmospheric pressure, at 353 K. Two types of catalyst were prepared using H₂PtCl₆ and Pt(NH₃)₄(NO₃)₂ as metallic precursors. Their performances were compared as a function of the reduction temperature and both catalysts were characterised by X-ray diffraction after different reduction treatments. Using the ex-chloride catalyst, the selectivity values to the unsaturated alcohol (UOL) resulted into a maximum of 45% while a selectivity as high as 70–77%, in 0–25% conversion range, was achieved by using ex-nitrate catalyst reduced at 443 K. The formation of Pt–Sn alloy on the metal particles of platinum was thought to be necessary to improve the activity and the selectivity on these catalysts. In the contrast, a presence of PtSn₂ formed at a reduction temperature higher than 473 K led to a decrease of activity and selectivity.     

不饱和一元醇、乙酸酯和醛的合成

大多数鳞翅目昆虫性信息素是不饱和长碳链(C_(12)～C_(16))醇、乙酸酯或醛,双键位置一般在5、7、8、9、10和11位。它们的差别主     

非过渡金属催化体系NHPI/DDQ/NaNO2催化分子氧选择氧化醇

考察了N-羟基邻苯二甲酰亚胺(NHPI),2,3-二氯-5,6-二氰基-1,4-苯醌(DDQ)与NaNO2组成的非金属催化体系,催化分子氧选择氧化醇的反应性能.结果表明,该体系可有效地催化芳香醇等生成相应的醛(酮).在80℃反应6h,苯甲醇转化率达到65%,苯甲醛选择性为99%.此外,该催化体系也能有效地催化其它醇的选...     

Catalytic oxidation of alcohols with allyl diethyl phosphate and palladium acetate

Allyl diethyl phosphate (ADP) was found to function as a stoichiometric hydrogen acceptor in a catalytic oxidation reaction of alcohols with Pd(OAc)₂. A variety of acyclic primary and secondary alcohols were oxidized in good yields and under mild conditions to the corresponding aldehydes and ketones, in the presence of Na₂CO₃ or K₂CO₃. Simple aliphatic primary alcohols yielded esters, exclusively. Polar ligand solvents (DMF, DMSO) were found to accelerate the reaction. Slow, but high yield reactions were encountered in THF and acetonitrile as solvents. The reactivity of several other allyl systems serving as H-acceptors, and several Pd compounds serving as catalysts, in the above oxidation reaction, was evaluated. It has been experimentally demonstrated (H-NMR) that ADP is capable of generating a π-allyl-Pd complex using a Pd(0) complex. Consequently, a catalytic cycle was proposed for the above oxidation reaction.     

Liquid-phase Oppenauer oxidation of primary allylic and benzylic alcohols to corresponding aldehydes by solid zirconia catalysts

Hydrous zirconia and grafted zirconium 1-propoxide catalysts were found active in the Oppenauer oxidation of cinnamyl alcohol, geraniol and 4-tert-butylcyclohexanol (cis- and trans-). The most active hydrous zirconia catalysts were formed by calcining at 250–300 °C. Grafted zirconium 1-propoxide on silica gel and MCM-41 were active in the Oppenauer oxidation of geraniol with high selectivity to the desired citral product. However, over an acidic support such as AlMCM, the grafted zirconium 1-propoxide catalysed the dehydration and isomerisation of the alcohol, leading to low yield to citral. Also, furfural was found to be an efficient oxidant for the titled Oppenauer oxidation. Other solid catalysts such as γ-Al₂O₃, Na–Al₂O₃, zeolite beta and Mg/Al hydrotalcite showed only moderate catalytic activity and selectivity in the Oppenauer oxidation of geraniol. As compared to other solid catalysts, hydrous zirconia solid catalysts used in this work are active and selective towards the formation of desired carbonyl oxidation products; additionally, these solid zirconia catalysts are easy to prepare and recycle, and applicable to different alcohol substrates.

Graphical abstract

Hydrous zirconia calcined at 250–300 °C and grafted zirconium 1-propoxide solid catalysts were found to be efficient for the Oppenauer oxidation of cinnamyl alcohol, geraniol and 4-tert-butylcyclohexanol in toluene when furfural was used as the oxidant.

Full-size image (4K)

     

Kinetics of catalytic Meerwein-Ponndorf-Verley reduction of aldehydes and ketones using boron triethoxide

Catalytic Meerwein-Ponndorf-Verley (MPV) reduction of various aliphatic, aromatic, and unsaturated aldehydes and ketones to corresponding alcohols (analyzed by GC-MS) in the presence of boron triethoxide (B(OEt)₃) were studied. Kinetics of this reduction reaction was also studied and the respective rate constants were determined. It was found that B(OEt)₃ catalyzes the reduction of aliphatic aldehydes and ketones to alcohols at room temperature while aromatic aldehydes and ketones were not reduced under the same conditions. In addition, MPV reduction using B(OEt)₃ was found to be chemoselective as unsaturated aldehydes and ketones afforded the corresponding alcohols without affecting unsaturated groups. The mechanism proposed involves a six-membered transition state in which both the alcohol and the carbonyl are coordinated to the same boron centre of a boron alkoxide catalyst.     

Catalytic air oxidation of ambient temperature hydrocarbons

Catalytic air oxidation of the aliphatic hydrocarbons n-decane, hexanes, gasoline and diesel fuel was conducted at ambient temperature with novel iron catalysts. The concentration of n-decane in water was reduced from 1.42 g in 100 ml to 0.07 g in 100 ml in 5 h at room temperature forming carbon monoxide and water by means of intermediate aldehydes. Results of FT–IR and GC–MS analyses demonstrated formation of aldehydes and unsaturated alcohols. Carbon monoxide was detected on catalyst residues and in the vapor phase. The indicated catalytic reaction mechanisms are discussed.     

Kinetics and mechanism of oxidation of allyl,crotyl and cinnamyl alcohol by chromium(V)

Summary The kinetics of oxidation of unsaturated alcoholsviz. allyl, crotyl and cinnamyl alcohol by sodium bis[2-ethyl-2-hydroxy butanoato (2–)] oxochromate(V) Cr^v, has been investigated in 25% (v/v) aq. HOAc:HClO₄. The order in [oxidant] and [substrate] was 1.0 and 0.7 respectively. The oxidation rate increased with increase in [2-ethyl-2-hydroxybutyric acid] (EHBA) and decreased with increase in the percentage of HOAc. The rate decreases slightly with increase in [H^_]. The unsaturated alcohols exhibited higher reactivity compared to their saturated analogues. A mechanism involving the formation of a complex between Cr^v and alcohol which in turn disproportionates into products in a slow step is advanced to explain the kinetic results.     

Oxidation of alcohols by TBHP in the presence of sub-stoichiometric amounts of MnO2

Commercially available activated MnO₂ has been investigated as a catalyst for the oxidation of alcohols (phenylethanol, 4-methyl- and 4-methoxybenzyl alcohol, trans-cinnamyl alcohol, cyclohexanol, menthol, perillyl alcohol and myrtenol) by TBHP/decane or TBHP/water in MeCN. The activity is highest for benzylic and allylic alcohols. Secondary alcohols yield ketones with good selectivities, while the aldehydes generated from primary alcohols are further oxidized. The process competes with the TBHP catalyzed decomposition. It thus requires the use of excess TBHP and high catalyst loadings to achieve high conversions. However, the low cost of the reagents makes this new protocol convenient for the oxidation of reactive secondary alcohols. The study also suggests that MnO₂ should be proscribed as a reagent to quench excess TBHP in oxidative processes when the synthetic target contains easily oxidizable alcohol functions and when carrying our detailed kinetic monitoring of oxidation processes.     

溴酸钠和氯化铁为助催化剂2,2,6,6-四甲基-N-氧化哌啶催化醇的氧化

建立了溴酸钠和氯化铁为助催化剂2,2,6,6-四甲基-N-氧化哌啶(NaBrO₃-FeCl₃-TEMPO)新型催化体系,以苯甲醇的氧化为研究对象,得出各成分与底物的最佳物质的量比为:2%TEMPO、35%NaBrO₃、3.7%H₂SO₄、2%FeCl₃·6H₂O。该体系在室温下可有效实现芳香醇、脂肪醇及杂环醇的氧化,收率高(99%)、选择性强(99%),在无氧条件下,仍表现出较好的催化活性。     

离子液体负载的TEMPO/离子液体聚合物/碳黑三元复合材料在醇的电化学氧化中的应用

以4-羟基-2,2,6,6-四甲基哌啶氧基自由基（4-OH-TEMPO）为原料合成了负载有TEMPO结构单元的咪唑四氟硼酸盐离子液体 (TEMPO-IL-BF₄),以双三氟甲磺酰亚胺锂 (LiTFSI) 和聚二烯丙基二甲基氯化铵 (PDDA) 为原料合成了聚合物离子液体 PDDA(Tf₂N),将上述两种物质和碳黑（CB）按照一定比例制备得到一种三元复合材料. 以此三元复合材料为支持电解质和电催化剂,研究了其在乙腈溶液中电化学氧化对甲氧基苯甲醇等各类醇的能力及其循环使用效果. 结果表明：在电化学条件下,此三元复合材料不仅可以有效地氧化对甲氧基苯甲醇等各类醇,生成的醛的产率都在80%以上,并且经过4次循环使用,该三元复合材料的回收率均在95%以上.     

Synthesis of Quinolines via a Metal‐Catalyzed Dehydrogenative N‐Heterocyclization

Efficient ruthenium‐, rhodium‐, palladium‐, copper‐ and iridium‐catalysed methodologies have been recently developed for the synthesis of quinolines by the reaction of 2‐aminobenzyl alcohols with carbonyl compounds (aldehydes and ketones) or the related alcohols. The reaction is assumed to proceed via a sequence involving initial metal‐catalysed oxidation of 2‐aminobenzyl alcohols to the related 2‐aminobenzaldehydes, followed by cross aldol reaction with a carbonyl compound under basic conditions to afford α,β‐unsaturated carbonyl compounds. These aldehydes or ketones can be also generated in situ via dehydrogenation of the related primary and secondary alcohols. In the final step cyclodehydration of the α,β‐unsaturated carbonyl compound intermediates gives quinolines. Good yields of quinolines were also obtained by reacting 2‐nitrobenzyl alcohols and secondary alcohols in the presence of a ruthenium catalyst. Finally, aniline derivatives afforded also a useful access to quinolines by the reaction with 1,3‐propanediol or 3‐amino‐1‐propanol, or in a three‐component reaction with benzyl alcohol and aliphatic alcohols.     

Highly stereoselective reduction of methyl ketone complexes of the chiral Lewis acid [(η-C5H5)Re(NO)(PPh3)] by K(s-C4H9)3BH; synthesis of optically active secondary alcohols and derivatives

Reaction of optically active ketone complexes (+)-(R)-[(η⁵-C₅H₅)Re(NO)-(PPh₃)(η¹-O=C(R)(CH₃)]⁺ BF₄⁻ (R = CH₂CH₃, CH(CH₃)₂m C(CH₃)₃, C₆H₅) with K(s-C₄H₉)₃BH gives alkoxide complexes (+)-(RS)-(η⁵-C₅H₅)Re(NO)(PPh₃)-(OCH(R)CH₃) (73–90%) in 80–98% de. The alkoxide ligand is then converted to Mosher esters (93–99%) of 79–98% de.     

Vapor–liquid equilibria and excess properties for methyl tert-butyl ether (MTBE) containing binary systems

Methyl tert-butyl ether (MTBE) is recently widely used in the chemical and petrochemical industry as a non-polluting octane booster for gasoline and as an organic solvent. The isobaric or isothermal vapor–liquid equilibria (VLE) were determined directly for MTBE+C₁–C₄ alcohols. The excess enthalpy (H^E) for butane+MTBE or isobutene+MTBE and excess volume (V^E) for MTBE+C₃–C₄ alcohols were also determined. Besides, the infinite dilute activity coefficient, partial molar excess enthalpies and volumes at infinite dilution (γ^∞, H^E,∞, V^E,∞) were calculated from measured data. Each experimental data were correlated with various g^E models or empirical polynomial.     

负载型二乙酰氧碘苯与功能离子液体协同氧化醇为醛酮

将聚苯乙烯树脂(PS)先碘化再乙酰基化,制得了负载型二乙酰氧碘苯(PS-DIB)作为氧化剂。2,2,6,6-四甲基-N-氧自由基哌啶醇(TeMPO)与1,4-二溴丁烷反应生成4-溴丁氧基-2,2,6,6-四甲基-哌啶-1-氧化物,再与N-甲基咪唑发生季铵化反应,生成的溴化季铵盐与四氟硼酸钠进行离子交换制得氟硼酸型2,2,6,6-四甲基-N-氧自由基哌啶负载离子液体(TeMPO-IL)。室温下,以离子液体1-甲基-3-丁基咪唑四氟硼酸盐([bmim]BF4)为溶剂,PS-DIB为氧化剂,TeMPO-IL为催化剂,选择性协同氧化各种醇为相应的醛或酮。在实验条件范围内未检测到羧酸副产物。氧化剂、催化剂和溶剂均可循环使用,在苯甲醇的氧化中,循环使用5次,反应的转化率和收率均保持基本不变。