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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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 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. 相似文献
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.
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. 相似文献
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%. 相似文献
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.
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.
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. 相似文献