Colloid and nanosized catalysts in organic synthesis: XII. Hydrogenation of carbonitriles catalyzed by nickel nanoparticles

Hydrogenation of carbonitriles catalyzed by nickel nanoparticles in isopropanol proceeds under atmospheric pressure of hydrogen within 6–15 h to yield mainly secondary amines. Hydrogenation of α-aminonitriles results in reductive decyanation. β-Aminonitriles undergo hydrogenolysis at the nitrogen–carbon bond.     

Colloid and nanosized catalysts in organic synthesis: XVII. Reductive amination of carbonitriles in the presence of supported nickel nanoparticles

Reductive amination of carbonitriles catalyzed by nickel nanoparticles applied onto a solid support in a plug flow reactor in the gas phase or the gas–liquid–solid catalyst system occurs at atmospheric pressure of hydrogen affording the nonsymmetrical secondary or tertiary amines. The effect of the support type on the target product yield and conversion of the substrate has been studied.     

Colloid and nanosized catalysts in organic synthesis: XI. Hydrogenation of alkynes catalyzed by nickel nanoparticles

The reaction of alkynes with hydrogen under atmospheric pressure in the presence of nickel nanoparticles as a catalyst led to the exhaustive hydrogenation of the triple bond.     

Colloid and nanosized catalysts in organic synthesis: XVI.<Superscript>1</Superscript> Continuous hydrogenation of carbonitriles catalyzed by nickel nanoparticles applied on a support

Conversion of the starting nitriles and selectivity of the products formation during continuous hydrogenation of various nitriles catalyzed by Ni⁰/Ceokar-2 have been studied as functions of temperature. Performing the process at temperature 120–260°С has led to the formation of a mixture of products containing di- and trialkylamines as well as the corresponding imines and enamines.     

Colloidal and nanosized catalysts in organic synthesis: XV. Gas-phase hydrogenation of alkenes catalyzed by supported nickel nanoparticles

Gas-phase hydrogenation of alkenes and their derivatives, catalyzed by nickel nanoparticles supported on zeolite or silica gel support occurs at 150–250°С and an atmospheric hydrogen pressure and results in a high conversion. The selectivity of the hydrogenation depends on the amount of hydrogen: at a low diene (triene)–hydrogen ratio, selective hydrogenation of one multiple bond in the substrate is possible.     

Colloid and nanosized catalysts in organic synthesis: IV. Reduction of nitroarenes with hydrazine hydrate catalyzed with metal nanoparticles

Reduction of a series of nitroarenes with hydrazine hydrate catalyzed with colloid iron, cobalt, nickel, and copper particles has been studied. High catalytic activity of nickel and iron nanoparticles has been demonstrated. Special features of nitrobenzene reduction in the presence of cobalt particles have been revealed.     

Colloid and nanosized catalysts in organic synthesis: XIII. Synthesis of 2-R-2-imidazolines catalyzed by copper and iron oxide nanoparticles

The reaction of carboxylic acids with ethylenediamine catalyzed by copper or iron oxide nanoparticles proceeds at 80°C with azeotropic water distilling off during 2–8 h to form 2-R-2-imidazolines. Acyl and diacyl derivatives of ethylenediamine are formed in the reaction as side products.     

Colloid and nanodimensional catalysts in organic synthesis: III. Alkylation of amines with primary alcohols catalyzed by colloidal nickel and cobalt

Alkylation of primary amines with primary alcohols has been performed under catalysis by colloidal nickel and cobalt particles. The synthesis of the catalyst and alkylation of amines have been carried out in a one-pot mode. The alkylation at 160–180°C in 6–12 h yields 55–90% of secondary amines.     

Colloid and nanodimensional catalysts in organic synthesis: VI. Hydrogenation and hydrogenolysis of carbonyl compounds

Aldehydes and ketones are found to be hydrogenated to alcohols with hydrogen at atmospheric pressure under the catalysis with nickel nanoparticles. The reaction under study may be used as technologically available and cheap method for hydrogenation of carbonyl groups. It is found that in the case of aromatic ketones hydrogenolysis of C=O bond with partial hydrogenation of aromatic groups takes place.     

Colloid and nanodimensional catalysts in organic synthesis: VIII. Hydrogenation of C=N bond with hydrogen in the presence of colloid nickel

Hydrogenation of azomethines with hydrogen at atmospheric pressure using nickel nanoparticles as catalyst was carried out. Reaction may be used for the preparation of secondary amines under mild conditions on an available catalyst. Continuation of studies will lead to development of a convenient method for the reductive amination of carbonyl compounds.     

Colloid and nanosize catalysts in organic synthesis: VII. Catalysis with copper colloid particles in Leucart-Wallach reaction

Modification of Leucart-Wallach reaction using catalytic amounts of copper colloid particles was developed. Reductive amination of a series of cyclic ketones proceeds at 100°C under a small excess of formamide or of alkyl(aryl)ammonium formate.     

pH-Dependent chemoselective synthesis of alpha-amino acids. Reductive amination of alpha-keto acids with ammonia catalyzed by acid-stable iridium hydride complexes in water

An acid-stable hydride complex [Cp*IrIII(bpy)H]+ {1, Cp* = eta5-C5Me5, bpy = 2,2'-bipyridine} serves as the active catalyst for the highly chemoselective synthesis of alpha-amino acids by reductive amination of alpha-keto acids with aqueous NH3 and HCOO- in water at pH 5-8. pH-dependent catalytic 15N- and 2H-double-labeling has also been accomplished by using 15NH3 and DCOONa, which are ideal amine and hydride ion sources, respectively.     

Colloid and nanodimensional catalysts in organic synthesis: II. The hydrogenation of alkenes with hydrogen at atmospheric pressure

Colloid particles of metals of varying valence are found to be relatively cheap and easily prepared catalyst permitting the the hydrogenation under mild conditions. Procedure of reduction of unsaturated compounds with gaseous hydrogen at atmospheric pressure and low temperaturehas been developed. Colloid solutions of metals from the series iron, nickel, cobalt, chromium, manganese or their mixtures were prepared in situ directly in the reaction mixture. Selective the hydrogenation of multiple carbon-carbon bonds without the reduction of a series of functional groups was observed.     

Reductive amination in the synthesis of azaheterocycles (review)

Methods for obtaining saturated five- and six-membered azaheterocycles based on the use of catalytic intra- and intermolecular hydroamination of dicarbonyl compounds and ketones and amines of the furan series, hydride amination of aldehydes and ketones, and the Leuckart reaction are examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 435–448, April, 1987.     

Polysilane-supported Pd and Pt nanoparticles as efficient catalysts for organic synthesis

Polysilane-supported Pd and Pt catalysts have been prepared for the first time, and used successfully in hydrogenation, Suzuki and Sonogashira reactions, and hydrosilylation respectively: the reactions proceeded in high yields, and the catalysts could be recovered almost quantitatively by simple filtration and reused.     

Colloid and nanodimensional catalysts in organic synthesis: I. Investigation of hydrogenation selectivity of unsaturated compounds with hydrazine hydrate and aluminum hydride

Results of investigation of selective hydrogenation of unsaturated carbon-carbon bonds with hydrazine hydrate or complex metal hydrides in the presence of metal nanoparticles are reported. Conditions of exhaustive and partial hydrogenation of some derivatives of norbornene, styrene, and unsaturated carboxylic acids are developed.     

Brevibacterium epidermidis催化酮不对称还原胺化合成(S)-手性胺

光学纯手性胺是一类非常重要的手性化学品,作为手性砌块和手性拆分剂广泛用于医药、农业化学品、精细化学品等产品的合成中.据统计,美国FDA近年来批准的约40％药物中都含有一个或多个手性胺结构单元.胺脱氢酶(AmDH)是由氨基酸脱氢酶改造而来的一类催化酮不对称还原胺化的新酶,其在手性胺的合成中展现出较强的潜力,已引起国内外学术界和工业界的广泛关注.这是因为该酶能够利用廉价的无机铵为胺供体,且具有催化效率高、原子经济性好和环境友好等优点.迄今为止已经有数个高效的胺脱氢酶被成功开发和报道,但是这些通过蛋白质工程改造的胺脱氢酶均为(R)-选择性,因此只能合成(R)-选择性的手性胺,遗憾的是还未见有(S)-选择性胺脱氢酶的报道.因此,本文主要目的是期望从自然环境中鉴定能够不对称还原胺化酮合成(S)-手性胺的微生物,进而从中分离得到能够以无机铵作为胺供体合成(S)-手性胺的(S)-选择性酶.本文首先利用苯乙胺作为唯一氮源,从土壤中筛选能够利用苯乙胺生长的菌株,进而利用苯乙酮作为初筛底物对得到的菌株进行胺化能力筛选,再利用(4-氟苯基)丙酮作为模式底物进行进一步的筛选.幸运的是,我们获得了能够利用无机铵作为胺供体催化(4-氟苯基)丙酮不对称还原胺化合成(S)-4-氟-α-甲基苯乙胺的菌株,经过16S RNA鉴定为表皮短杆菌,命名为B.epidermidis ECU1015.接下来,我们对B.epidermidis ECU1015催化的胺化反应中的关键参数如胺基供体及其最适浓度、反应温度、pH值和底物浓度等进行了优化,确定最佳反应条件:胺供体为NH4Cl(1.25 mol/L),反应温度为30°C,KPB缓冲液(200 mmol/L,pH 7.5),底物浓度10 mmol/L.最后,在最适的反应条件下,我们对B.epidermidis ECU1015催化的底物谱进行了研究.结果表明,该微生物不能催化大位阻芳香酮和链状酮的胺化,对位阻较小的苯乙酮及(4-氟苯基)丙酮具有较好的还原胺化能力,而且对苯环上带有吸电子取代基的酮化合物具有更好的转化效果.经手性分析,所有生成的手性胺均为(S)-构型,产品的光学纯度均>99％.B.epidermidis催化酮不对称胺化所形成的产物构型均为(S)-选择性,这不同于已报道的(R)-选择性胺脱氢酶.该菌株的发现为(S)-选择性胺脱氢酶的进一步鉴定奠定了一定的研究基础,相关蛋白的分离纯化工作正在进行.     

Synthesis of N-aryl imidazoles catalyzed by copper nanoparticles on nanosized silica-coated maghemite

A magnetically recoverable catalyst consisting of copper nanoparticles (CuNPs) on nanosized silica-coated maghemite is presented. The catalyst has been prepared under mild conditions by mixing the magnetic support with a freshly prepared suspension of CuNPs obtained by fast reduction of anhydrous CuCl₂ with lithium sand and a catalytic amount of DTBB (4,4′-di-tert-butylbiphenyl) as electron carrier. This copper-based catalyst has shown to be very efficient in the N-(hetero)arylation of imidazole using (hetero)aryl bromides and iodides as arylating agents under ligand-free conditions. The catalyst is easily recovered by means of an external magnet and can be reutilized in three N-arylation cycles without apparent loss of catalytic activity.