Borrowing Hydrogen in the Activation of Alcohols

Alcohols can be temporarily converted into carbonyl compounds by the metal‐catalysed removal of hydrogen. The carbonyl compounds are reactive in a wider range of transformations than the precursor alcohols and can react in situ to give imines, alkenes, and α‐functionalised carbonyl compounds. The metal catalyst, which had borrowed the hydrogen, then returns it to the transformed carbonyl compound, leading to an overall process in which alcohols can be converted into amines, compounds containing C C bonds and β‐functionalised alcohols.     

Propheromones that release pheromonal carbonyl compounds in light

Pheromonal carbonyl compounds; (Z)-11-hexadecanal, (E)-citral, and 2-heptanone were treated with six alcohols to give acetals or ketals, some of which acted as propheromones by releasing the pheromonal carbonyl compounds in ultraviolet or simulated sunlight. Highest yields of pheromone were obtained from adducts prepared witho-nitrobenzyl alcohol ando-nitrophenylethane-1,2-diol. Adducts from (Z)-11-hexadecenal and these two alcohols were employed in lures to catch diamondback moths,Plutella xylostella (L.).     

Reactivity of t-butyl chromate resins with substituted α-phenylethanols: A kinetic study

Polystyrene and polyacenaphthylene supports were functionalized to generate a t-butyl chromate function and the resulting polymer-supported reagents were used for the oxidation of alcohols. They were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in quantitative yields. Oxidation of differently substituted α-phenylethanols was attempted for this purpose and the kinetics of oxidation reactions was studied. The reaction was found to be first order with respect to the substrate, the reaction being carried out with an excess of the t-butyl chromate reagent. The rate of oxidation was also found to be dependent on the nature of the substrate, concentration of the reagent function, and the nature and concentration of the acid catalyst used. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 799–804, 1998     

N-烷基芳胺合成的研究进展

N-烷基芳胺是非常重要的有机原料和精细化工中间体,广泛应用于染料、塑料、医药和农药等领域。介绍了芳胺与烷基化试剂如卤代烃、羰基化合物、醇等进行的取代烷基化反应合成N-烷基芳胺的反应机理及烷基化工艺;重点阐述了以芳香硝基化合物为原料一锅法合成N-烷基芳胺的生产工艺,分别讨论了以羰基化合物、腈、醇作为烷基化试剂的优劣,认为以醇为烷基化试剂的反应条件温和、不需要添加任何配体,具有较好的应用前景。指出开发适合以醇为烷基化试剂的选择性高的催化剂是以后的研究方向。     

TEMPO‐Copper(II) Diimine‐Catalysed Oxidation of Benzylic Alcohols in Aqueous Media

In situ generated copper(II)‐diimine complexes combined with TEMPO (2,2,6,6‐tetramethylpiperidinyl‐1‐oxyl radical) were studied in the oxidation of benzylic alcohols, the focus being on enviromentally benign reaction conditions. In this respect, reactions were studied in aqueous alkaline solutions and dioxygen was used as an end oxidant. This simple catalytic system turned out to be highly efficient and selective in the oxidation of primary and secondary benzylic alcohols to their corresponding carbonyl compounds. Under optimised reaction conditions [5 mol % of TEMPO, 3 mol % of copper(II ) diimine, pH 12.6–13.5, 80 °C, 10 bar O₂] benzyl alcohol was quantitatively and selectively oxidised to benzaldehyde. According to ESI‐MS studies, coordination of TEMPO, as well as deprotonated benzyl alcohol to the parent copper‐diimine complex in aqueous solutions is feasible. Supported by these observations a plausible reaction mechanism is proposed for the oxidation reaction.     

Oxidation of primary and secondary alcohols to the corresponding carbonyl compounds with molecular oxygen using 1,1-diphenyl-2-picrylhydrazyl and WO3/Al2O3 as catalysts

The oxidation of primary and secondary alcohols to their corresponding carbonyl compounds proceeds with high efficiency under molecular oxygen in the presence of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tungsten oxide/alumina (WO₃/Al₂O₃). The method is environmentally benign, because the reaction requires only molecular oxygen as the terminal oxidant and gives water as a side product. Various aromatic, alicyclic, and aliphatic alcohols can be converted to their corresponding carbonyl compounds in excellent yields. It is noteworthy that the oxidative transformation of the alcohols proceeds chemoselectively in the presence of other functional groups. In addition, a plausible catalytic pathway is proposed.     

氢氟醚的合成和应用研究进展

第三代氯氟烃替代品之一——氢氟醚类化合物（HFEs）的合成方法分为两类,第一类是醚类化合物的氟化,包括直接氟化法和电化学氟化法;第二类是通过含氟化合物与其他化合物的反应制备氢氟醚,反应类型主要包括不饱和烃与醇的加成反应、含氟羰基化合物的烷基化反应和卤代烷与醇的分子间消除反应。其中,碱催化不饱和烃与醇加成制备氢氟醚操作简便,反应条件相对温和,产物易分离提纯,是一具有工业化前景的氢氟醚合成方法。氢氟醚物化性能优良,且环境友好,在制冷、清洗等行业有着广阔的应用前景。     

综述与展望 醇氧化反应研究进展

醇氧化反应是重要的有机化学反应,产物广泛应用于医药和化学工业生产,如何有效使醇氧化为相应的羰基化合物是研究的热点。讨论醇氧化反应的意义,探讨醇在均相催化氧化反应和非均相催化氧化反应的研究进展,介绍近年来醇的绿色氧化方法。     

The reduction of α,β-unsaturated carbonyl compounds by the meerwein—ponndorf—verley method: The cause of low yields

The main cause of low yields in the formation of allylic alcohols from unsaturated carbonyl compounds by the Meerwein—Ponndorf—Verley reaction has been found to be polymerisation of the product by acidity arising from small amounts of chloroalkoxides which occur in most alkoxides. Hot alkaline processing of crude reduction products effectively removes chloroalkoxides and leads to high yields of the allylic alcohols. The present work relates to the preparation of cinnamyl alcohol but it is applicable to other α,β-unsaturated carbonyl compounds.     

Deep eutectic solvents (DES) as green reaction media for the redox isomerization of allylic alcohols into carbonyl compounds catalyzed by the ruthenium complex [Ru(η3:η3-C10H16)Cl2(benzimidazole)]

The bis-allyl Ru(IV) complex [Ru(η³:η³-C₁₀H₁₆)Cl₂(benzimidazole)] (1c) is an active catalyst in the redox isomerization of allylic alcohols into saturated carbonyl compounds using, for the first time, Deep eutectic solvents (DES) as reaction media. A series of primary and secondary allylic alcohols could be isomerized into the corresponding carbonyl compounds in the absence of base. Although high activities and selectivities were reached at short reaction times and with low catalyst loadings (0.2 mol% in Ru) for monosubstituted allylic alcohols, for their disubstituted counterparts, high catalyst loading and longer reaction times were always required. It is important to note that the catalytic system: i) is active in a large-scale experiment, and ii) could be recycled up to four consecutive runs.     

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.     

One-pot three-component Mannich reaction catalyzed by sucrose char sulfonic acid

Sucrose char sulfonic acid efficiently catalyzed the one-pot three-component Mannich reaction of ketones, aromatic aldehydes and amines in ethanol to afford the corresponding β-amino carbonyl compounds in good to excellent yields. A series of heteroaromatic β-amino carbonyl compounds can be obtained when using 2-acetylpyrazine as substrate. This reaction can be performed under mild reaction conditions with clean reaction profiles and a simple workup procedure.     

Chemoenzymatic Asymmetric Synthesis of Pyridine-Based α-Fluorinated Secondary Alcohols

Fluoro-substituted and heteroaromatic compounds are valuable intermediates for a variety of applications in pharma- and agrochemistry and synthetic chemistry. This study investigates the chemoenzymatic preparation of chiral alcohols bearing a heteroaromatic ring with an increasing degree of fluorination in α-position. Starting from readily available picoline derivatives prochiral α-halogenated acyl moieties were introduced with excellent selectivity and 64–95 % yield. The formed carbonyl group was subsequently reduced to the corresponding alcohols using the alcohol dehydrogenase from Lactobacillus kefir, yielding an enantiomeric excess of 95–>99 % and up to 98 % yield.     

Polyhalide Derivatives of Polystyrene-based Benzyltriethylammonium Resins as Oxidizing Reagents: Synthetic and Reactivity Correlations

The oxidation of alcohols using polystyrene-based benzyltriethylammonium dichloroiodate, tetrachloroiodate and dichlorobromate reagents is described. On reaction with different alcohols, the polymeric polyhalide reagents afforded the respective carbonyl compounds in high yields. The insoluble spent reagents could be regenerated and reused without significant loss in reactivity. The reactivities of the polymeric polyhalides were investigated as a function of the nature of solvents, effective molar concentration of the reagent, temperature and by varying the polarity of the macromolecular support, and the results are discussed. © of SCI.     

31P NMR Spectroscopy in Wood Chemistry. I. Model Compounds

The quantitative reaction in an NMR tube of 1,3,2-dioxaphospholanyl chloride (I) with compounds bearing active hydrogens was explored as a simple method for derivatizing the labile centres known to occur in lignins. Derivatives of phenols, alcohols and carboxylic acids with (I) gave ³¹P chemical shifts which appeared in different ranges of the NMR spectra. Any ortho substitution onto the aromatic ring of phenols significantly affected the magnitude of the ³¹P NMR chemical shifts, while para and/or meta substituents had a much smaller effect. A clear distinction between guaiacyl, syringyl and unsubstituted phenolic hydroxyls can thus be made in mixtures of model compounds. Primary alcohols were clearly distinguished from secondary and tertiary alcohols in their derivatives with (I), while different ³¹P NMR signals for derivatives of erythro and threo forms of lignin-like model compounds were identified. While alcohols, phenols and simple carboxylic acids on reaction with (I) gave derivatives that were substitution products, aldehydes reacted via a distinctly different addition mechanism; ketones did not react at all.     

Study on quantitative analyses of hydroperoxides and alcohols by NMR shift reagent

Recently, much literature concerning the effects of NMR shift reagents upon compounds with Lewis’s basic functional groups have been reported. These literatures have shown the effects of NMR shift reagents upon hydroxyl, amino, carbonyl, ether, ester carbonyl, cyano, and epoxy compounds but not hydroperoxyl compounds. Chemical and paramagnetic shifts of protons in t-butyl and cumene hydroperoxides, t-butyl and 2-phenyl-2-propyl alcohols, and autoxidized methyl linoleate with incremental additions of an NMR shift reagent were determined. These experimental results indicated that each alcohol and hydroperoxide could be determined separately and quantitatively even in their mixtures. Moreover, this method can be recommended to obtain information about the structures of hydroperoxides, as well as alcohols.     

氢氟醚合成进展

介绍了氢氟醚（HFEs）的物性及应用，叙述了国内外制备HFEs方法，如醚类化合物的氟化、含氟醇（或酚）与卤代烃分子间消除、含氟醇与烯烃的加成、合氟羰基化合物的烷基化、含氟醇与多聚甲醛的加成、叔丁醇盐与烷基硫酸酯反应，以及含羟基和双键HFEs的合成方法。通过比较其合成路线．认为采用的碱催化不饱和烃与醇加成制备HFEs的方法操作简便，反应条件相对温和，产物易分离提纯，是一具有工业化前景的方法。     

Electrochemical Oxidation of Alcohols Using Halogen Mediators

The high importance of carbonyl compounds in organic synthesis and fine chemical industries has let the development of efficient and environmentally benign methods for the oxidation of alcohols be an important research field. Electrochemistry would be one of the ideal strategies to achieve green redox processes avoiding the use of chemical oxidants/reductants. Due to the relatively high oxidation potential of alcohols, indirect methods using redox mediators have often been employed for the electrochemical alcohol oxidation. Halide salts would be one of the most traditional but still common mediators owing to the advantage of wide commercial availability and cost-efficiency. This review summarized the electrogenerated active halogen-mediated transformations of prim- sec-, and tert-alcohols from the pioneering works to the recent examples. In addition, recent advances in the direct oxidation of alcohols are also presented.     

Low-valent ruthenium and iridium hydride complexes as alternatives to Lewis acid and base catalysts

The discovery of a new chemical reaction often leads to new applications and new chemical principles. Low-valent ruthenium and iridium hydride complexes are highly useful redox Lewis acid and base catalysts. Nitriles are activated by these catalysts and undergo reactions with either nucleophiles or electrophiles under neutral conditions. Hydration of nitriles, esterification of nitriles with alcohols, and amidation of nitriles with amines can be performed catalytically together with formation of ammonia. The catalytic reactions of pronucleophiles such as nitriles and carbonyl compounds with electrophiles such as alkenes, alkynes, carbonyl compounds, imines, and nitriles take place generally.     

Aerobic oxidation of alcohols over novel crystalline MoVO oxide

Novel crystalline MoVO oxide was employed as the catalyst in the aerobic oxidation of alcohols to the corresponding carbonyl compounds. Reactions were mainly conducted at 353 K in pure oxygen or air (1 atm). The selectivities for benzaldehydes were more than 95% in all cases. The conversions of benzyl alcohols varied from 10% to 99% depending on the substituent. A Hammett plot gave a moderate ρ-value of −0.249 (r² = 0.98), suggesting that the reaction processes may involve hydride abstraction. The oxidation of primary alkanols afforded aldehydes, and secondary alcohols were mainly dehydrated to olefins. It was found that the conversion of linear alkanols decreased with the length of alkanols. Kinetic analysis showed that catalytic reaction rate was first-order dependent on the concentrations of substrate and of catalyst. The apparent activation energy was estimated to be 45.7 kJ mol⁻¹. Catalytic reactions took place on the 6- or 7-member rings on the a–b basal plane, where highly dense unsaturated metal cation centers and oxygen anion might serve as catalytic active sites.