Selective Catalytic Reductions of Amides and Nitriles to Amines

This personal account summarizes our recent developments of catalytic hydrosilylations and hydrogenations of carboxylic amides and nitriles to selectively give amines. Special focus is given to highly chemoselective iron- and zinc-catalyzed reductions of amides.     

An Efficient and Improved Method for the Preparation of Nitriles from Primary Amides and Aldoximes†

The pivaloyl chloride‐pyridine system has been utilized as a novel and efficient reagent for the preparation of nitriles from primary amides and aldoximes. The reaction proceeds smoothly under mild reaction conditions and the products are obtained in excellent yields. This method is applicable to a wide range of substrates including aromatic, heterocyclic and aliphatic species. The dehydration takes place at room temperature in the case of primary amides and dichloromethane at reflux temperature is required for rapid conversion in the case of aldoximes.     

以偏铝酸钠为催化剂实现由芳香甲腈到芳香甲酰胺的转化

在水和乙醇混合溶剂中,以偏铝酸钠做催化剂,使芳香甲腈水解成芳香甲酰胺。偏铝酸钠的催化性能稳定,选择性高。该方法反应条件温和、成本低廉、产率较高、绿色环保,且具有较好的应用前景。     

Silver Nanoparticle Catalyzed Selective Hydration of Nitriles to Amides in Water Under Neutral Conditions

Abstract  

Ag NPs can efficiently catalyze hydration of nitriles to amide in water. This hydration method used water as solvent and Ag catalyst that can be recycled under neutral conditions, so it can make a great contribution settling the process that is environmentally better and industrially more satisfactory.     

Biocatalytic Synthesis of Nitriles through Dehydration of Aldoximes: The Substrate Scope of Aldoxime Dehydratases

Nitriles, which are mostly needed and produced by the chemical industry, play a major role in various industry segments, ranging from high‐volume, low‐price sectors, such as polymers, to low‐volume, high‐price sectors, such as chiral pharma drugs. A common industrial technology for nitrile production is ammoxidation as a gas‐phase reaction at high temperature. Further popular approaches are substitution or addition reactions with hydrogen cyanide or derivatives thereof. A major drawback, however, is the very high toxicity of cyanide. Recently, as a synthetic alternative, a novel enzymatic approach towards nitriles has been developed with aldoxime dehydratases, which are capable of converting an aldoxime in one step through dehydration into nitriles. Because the aldoxime substrates are easily accessible, this route is of high interest for synthetic purposes. However, whenever a novel method is developed for organic synthesis, it raises the question of substrate scope as one of the key criteria for application as a “synthetic platform technology”. Thus, the scope of this review is to give an overview of the current state of the substrate scope of this enzymatic method for synthesizing nitriles with aldoxime dehydratases. As a recently emerging enzyme class, a range of substrates has already been studied so far, comprising nonchiral and chiral aldoximes. This enzyme class of aldoxime dehydratases shows a broad substrate tolerance and accepts aliphatic and aromatic aldoximes, as well as arylaliphatic aldoximes. Furthermore, aldoximes with a stereogenic center are also recognized and high enantioselectivities are found for 2‐arylpropylaldoximes, in particular. It is further noteworthy that the enantiopreference depends on the E and Z isomers. Thus, opposite enantiomers are accessible from the same racemic aldehyde and the same enzyme.     

Supported Gold Nanoparticles‐Catalyzed Microwave‐Assisted Hydration of Nitriles to Amides under Base‐Free Conditions

Polystyrene‐supported gold (Au@PS) nanoparticles were synthesized by the reduction deposition approach and well characterized by UV‐visible, XRD, TEM, SAED, EDX, and XPS studies. The Au@PS was applied as catalyst for the hydration of nitriles to amides in water under microwave irradiation. Several functionalized aromatic, heterocyclic and aliphatic nitriles were found to be active for synthesis of the corresponding amides where no activation of water by base, ligand and support is needed. Easy recovery, negligible leaching and recyclability for up to eight runs are added advantages of the catalyst under water‐mediated reaction conditions.

     

A Practical Procedure for Reduction of Primary,Secondary and Tertiary Amides to Amines

A mild and general procedure for reduction of primary, secondary, and tertiary amides using catalytic triruthenium dodecacarbonyl and 1,1,3,3‐tetramethyldisiloxane as reductant is described. The reaction is tolerant of numerous functional groups, and the amine products can often be isolated by direct crystallization as hydrochloride salts. The catalyst and silane are commercially available, air stable, and inexpensive, making the procedure accessible for both laboratory and large‐scale applications.     

Oxidative Coupling between Methylarenes and Ammonia: A Direct Approach to Aromatic Primary Amides

A direct oxidative amidation between methylarenes and aqueous ammonia using a tert‐butyl hydroperoxide and tetrabutylammonium iodide (TBHP/TBAI) oxidation system with co‐catalysis of iron(III) chloride has been developed. Both coupling partners were used in their native form to render prior functionalization unnecessary and afford a facile approach to aromatic primary amides.

     

The Determination of Fatty Acid Primary Amides by Capillary Gas Chromatography

A method has been developed for the determination of 12 primary amides of long-chain fatty acids by capillary column gas chromatography. The method uses no derivatization or sample preparation other than extraction of the sample. A variety of commercial amidecontaining materials have been analyzed successfully. The amides, along with other soluble materials, are first separated from the host using refluxing 2-propanol containing an internal standard. The fatty acid amides are then identified and measured by gas chromatography over a programmed temperature range of 200 to 260 C. The chromatograms obtained show sharp peaks, unique retention times and acceptable reproducibility for quantitation.Cis- trans isomers of several of the fatty acid amides were tested and found to be resolved under the conditions employed.     

Selective Hydrogenation of Fatty Nitriles to Primary Fatty Amines: Catalyst Evaluation and Optimization Starting from Octanenitrile

In this contribution, an evaluation of the potential of various homogeneous and heterogeneous catalysts for a selective hydrogenation of fatty nitriles toward primary amines is reported exemplified for the conversion of octanenitrile into octane‐1‐amine as a model reaction. When using heterogeneous catalysts such as the ruthenium catalyst Ru/C, the palladium catalyst Pd/C, and the platinum catalyst Pt/Al₂O₃, low selectivities in the hydrogenation are observed, thus leading to a large portion of secondary and tertiary amine side‐products. For example, when using Ru/C as a heterogeneous catalyst, high conversions of up to 99% are obtained but the selectivity remains low with a percentage of the primary amine being at 60% at the highest. The study further reveals a high potential of homogeneous ruthenium and manganese catalysts. When also taking into account economical considerations with respect to the metal price, in particular, manganese catalysts turn out to be attractive for the desired transformation and their application in the model reaction leads to the desired primary amine product with excellent conversion, selectivity, and high yield. Practical Applications: This work describes an optimized hydrogenation process for transforming fatty nitriles to their corresponding primary amines. In general, fatty amines belong to the most applied fatty acid‐derived compounds in the chemical industry with an annual product volume exceeding 800 000 tons per year in 2011 and are widely required in the chemical industry since such compounds are either directly used in home products such as fabric softeners, dishwashing liquids, car wash detergents, or carpet cleaners or in a broad range of industrial products, for example, lubricating additives, flotation agents, dispersants, emulsifiers, corrosion inhibitors, fungicides, and bactericides, showing additional major applications, e.g., in the detergents industry. Among them primary amines play an important industrial role. However, a major concern of current processes is the lack of selectivity and the formation of secondary and tertiary amines as side‐products. By modifying a recently developed catalytic system based on manganese as economically attractive and environmentally benign metal component an efficient and selective access to fatty amines when starting from the corresponding nitriles is achieved. For example, hydrogenation of octanenitrile leads to a synthesis of octane‐1‐amine with >99% conversion and excellent selectivity with formation of secondary and tertiary amine side‐products being suppressed to an amount of <1%.     

Iron Nitrate/TEMPO: a Superior Homogeneous Catalyst for Oxidation of Primary Alcohols to Nitriles in Air

A highly practical, one‐step, facile synthesis of aromatic, heteroaromatic, allylic and aliphatic nitriles from primary alcohols catalyzed by ferric nitrate [Fe(NO₃)₃⋅9H₂O] in the presence of TEMPO, aqueous ammonia and air at room temperature is described.

     

脂肪腈催化氢化制伯胺工艺中常用抑制剂氨,氨水,碱水的作用性能的研究

本文叙述了脂肪腈催化氢化反应机理及常用抑制剂的作用机理,并用试验的方法对氨,氨水及碱水的作用性能进行了比较。     

乙醇脱水制乙烯的工业化应用

乙烯是石油化学工业中最重要的基础原料之一,乙烯工业是石油化学工业的龙头,在石油化学工业中乃至国民经济中占有重要地位,乙烯工业的发展与一个国家或地区的经济发展水平相联系。近十年来,世界乙烯工业仍处于快速发展期,乙烯生产和消费均处于良好态势之中。我国的乙烯工业自20世纪80年代以来获得了长足的发展,但从整体来看,我国的乙烯生产能力还远远不能满足国民经济发展的需求。特别是广西广维化工有限责任公司地处西南边陲,要想每年获得6000t乙烯,不仅运输困难,同时也找不到货源。随着石油价格的日益攀升,加上广西地区丰富的乙醇资源,乙醇脱水制乙烯在广西宜州有着良好的发展前景。     

Silver‐Catalyzed Cyclization of Propargylic Amides to Oxazolines

A ligand‐accelerated effect is observed in the cyclization of propargylic amides catalyzed by bis(pyridyl)silver(I) complexes, with an unexpected reversal of electronic demand to the analogous N H addition reaction. The catalyst was found to be effective for internal alkyne substrates, offering exclusive selectivity for the 5‐exo‐dig product. Differences in selectivity profile between gold‐ and silver‐catalyzed processes are highlighted and discussed.

     

微波辐射促进腈类化合物水解

采用微波辐射反应技术研究了苯乙腈、对羟基苯甲腈和吲哚-5-甲腈在氢氧化钠水溶液中的水解条件及辐射功率和辐射时间对收率的影响。结果表明，最适宜的功率为530W，辐射时间分别为4，4．5，7min，制备出苯乙酸、对羟基苯甲酸和吲哚-5-甲酸的收率分别为87．9％，85．8％，89．6％。     

Polymerization of Nitriles by Organotin Catalysts

The polymerization of the nitrile groups of polyacrylonitrile, polymethacrylonitrile and poly-α-cyanoethyl acrylate by organotin compounds was studied. The reaction, which was accompanied by color formation, was found to depend on the concentration and nature of the initiator, temperature, solvent and time of reaction. In the series Pb, Sn and Si, the organometallic derivatives of the former showed the strongest catalyst activity. A series of di- and higher nitriles, including benzal malononitrile, 1,1,3,3-tetracyanopropane, α-(2-cyanoethyl) acrylonitrile and Diels Alder adduct of tetracyanoethylene with anthracene, was also polymerized to dark colored polymers. The mechanism of the polymerization is thought to consist of the addition of the organotin compound to the nitrile groups followed by cyclization leading to the formation of conjugated C=N double bonds. Evidence for this mechanism was obtained from the reaction of model compounds, such as 1,3-dicyanobutane-1-carboxylic acid ester, with tributyltin methoxide.