Preparation of Sulphur-containing Aromatic Amines by Reduction of the Corresponding Aromatic Nitro Compounds with Hydrazine Hydrate over Iron Oxide Hydroxide Catalyst

The sulphur-containing aromatic amines are an important class of compounds frequently used as key intermediates in the synthesis of pharmaceutical products1,2, dyestuffs3-6 and polymers7. The usual methods for preparing sulphur-containing aromatic amines …     

D296树脂分散钯催化氢转移反应的研究──Ⅰ.取代芳香硝基化合物的还原

首次报道用离子交换树脂D296为载体,制备的D296树酯分散把催化剂／甲酸铵还原体系,催化氢转移还原取代芳香硝基化合物成芳胶的方法．该法反应条件温和,操作简便,催化剂可重复使用,收率可达83～94％。     

Co/Cu bimetallic ZIF as New heterogeneous catalyst for reduction of nitroarenes and dyes

Nowadays one of the great challenges is to design new bimetallic catalysts with enhanced catalytic activity, selectivity and recycling properties. In this work, the preparation of new Co/Cu bimetallic Zeolitic Imidazolate Framework (Co-Cu/ZIF) as an efficient catalyst for the reduction of nitro compounds and organic dyes is described. Co-Cu/ZIF was characterized with different techniques such as SEM, TEM, XRD, XPS, TGA, FT-IR and UV–vis absorption indicating formation of entirely uniform cubic particles. Using this catalyst, structurally different aromatic nitro compounds were reduced efficiently to corresponding amines in excellent yields. Kinetic studies revealed that the reduction rates of nitrophenol isomers follow 3-NP > 4-NP > 2-NP order. The catalytic activity of Co-Cu/ZIF was further investigated in the reduction of organic dyes such as methyl orange (MO) and rhodamine B (RhB). This catalyst was recycled for at least ten runs in the reduction of 4-nitrophenol without a noticeable decrease in activity and reused catalyst was characterized.     

Preparation of Aromatic Amines by Reduction of Aromatic Nitro Compounds with Metallic Tellurium in Near-Critical Water

Aromatic amines were prepared in good yields by a novel reduction of aromatic nitro compounds with tellurium metal in near-critical water at 275 ℃。     

钯催化甲酸为氢源的芳硝基化合物直接加氢和一锅法酰胺化

Pd/C催化剂实现了甲酸为氢源的芳硝基化合物的直接加氢及甲酸为氢源和羰基源的一锅法芳硝基化合物的酰胺化.在芳硝基化合物的直接加氢过程中,该体系体现了很好的催化活性,实现了对同时带有其它可还原官能团的芳硝基化合物的选择性加氢,得到较高收率的胺类化合物.同时,通过提高反应温度和增加甲酸的量,实现了芳硝基化合物的加氢和甲酰化的串联反应,该体系体现了较高的催化活性.     

Catalyst‐Free Reductive Coupling of Aromatic and Aliphatic Nitro Compounds with Organohalides

A rare reductive coupling of nitro compounds with organohalides has been realized. The reaction is initiated by a partial reduction of the nitro group to a nitrenoid intermediate. Therefore, not only aromatic but also aliphatic nitro compounds are efficiently transformed into monoalkylated amines, with organohalides as the alkylating agent. Given the innate reactivity of the nitrenoid, a catalyst is not required, resulting in a high tolerance for aryl halide substituents in both starting materials.     

One pot synthesis of N-ethylaniline from nitrobenzene and ethanol

A novel method for the one pot synthesis of N-alkyl arylamines from nitro aromatic compounds and alcohols is proposed through the combination of the aqueous-phase reforming of alcohol for hydrogen production, the reduction of nitro aromatic compounds for the synthesis of aromatic amine and the N-alkylation of aromatic amine for the production of N-alkyl arylamine over an identical catalyst under the same conditions of temperature and pressure in a single reactor. In this process, hydrogen generated from the aqueous-phase reforming of alcohols was used in-situ for the hydrogenation of nitro aromatic compounds for aromatic amine synthesis, followed by N-alkylation of aromatic amine with alcohols to form the corresponding N-alkyl arylamines at a low partial pressure of hydrogen. For the system composed of nitrobenzene and ethanol, under the conditions of 413 K and PN2 = 1 MPa, the conversion degrees of nitrobenzene and aniline were 100%, the selectivity to N-ethylaniline and N, N-diethylaniline were 85.9% and 0%-4%, respectivity, after reaction for 8 h at the volumetric ratio of nitrobenzene:ethanol:water = 10:60:0. The selectivity for N, N-diethylaniline production is much lower than that through the traditional method. In this process, hydrogen and aromatic amines generated from the aqueous-phase reforming of alcohols and hydrogenation of nitro aromatic compounds, respectively, could be promptly removed from the surface of the catalyst due to the occurrence of in-situ hydrogenation and N-alkylation reactions. Thus, this may be a potential approach to increase the selectivity to N-alkyl arylamine.     

Selective N-alkylation of amines using nitriles under hydrogenation conditions: facile synthesis of secondary and tertiary amines

Nitriles were found to be highly effective alkylating reagents for the selective N-alkylation of amines under catalytic hydrogenation conditions. For the aromatic primary amines, the corresponding secondary amines were selectively obtained under Pd/C-catalyzed hydrogenation conditions. Although the use of electron poor aromatic amines or bulky nitriles showed a lower reactivity toward the reductive alkylation, the addition of NH(4)OAc enhanced the reactivity to give secondary aromatic amines in good to excellent yields. Under the same reaction conditions, aromatic nitro compounds instead of the aromatic primary amines could be directly transformed into secondary amines via a domino reaction involving the one-pot hydrogenation of the nitro group and the reductive alkylation of the amines. While aliphatic amines were effectively converted to the corresponding tertiary amines under Pd/C-catalyzed conditions, Rh/C was a highly effective catalyst for the N-monoalkylation of aliphatic primary amines without over-alkylation to the tertiary amines. Furthermore, the combination of the Rh/C-catalyzed N-monoalkylation of the aliphatic primary amines and additional Pd/C-catalyzed alkylation of the resulting secondary aliphatic amines could selectively prepare aliphatic tertiary amines possessing three different alkyl groups. According to the mechanistic studies, it seems reasonable to conclude that nitriles were reduced to aldimines before the nucleophilic attack of the amine during the first step of the reaction.     

Reductive Molybdenum‐Catalyzed Direct Amination of Boronic Acids with Nitro Compounds

The synthesis of aromatic amines is of utmost importance in a wide range of chemical contexts. We report a direct amination of boronic acids with nitro compounds to yield (hetero)aryl amines. The novel combination of a dioxomolybdenum(VI) catalyst and triphenylphosphine as inexpensive reductant has revealed to be decisive to achieve this new C?N coupling. Our methodology has proven to be scalable, air and moisture tolerant, highly chemoselective and engages both aliphatic and aromatic nitro compounds. Moreover, this general and step‐economical synthesis of aromatic secondary amines showcases orthogonality to other aromatic amine syntheses as it tolerates aryl halides and carbonyl compounds.     

Cu nanoparticles: a highly efficient non-noble metal catalyst for rapid reduction of nitro compounds to amines with NaBH<Subscript>4</Subscript> in water

The purely aqueous-phase reduction of a wide range of nitro compounds to the corresponding amines has been carried out with NaBH₄ in the presence of inexpensive Cu nanoparticles as catalyst. The reactions were taken place in water (80 °C) within 4–15 min to give amines in high to excellent yields.     

The formation of amines in the analytical pyrolysis of nitro and azo compounds

The analytical pyrolysis of aromatic nitro and azo compounds on metal supports yields the corresponding amines, which are the major volatile products. This reduction is mainly due to effects of the support. The origin of the hydrogen under high vacuum conditions is established. It is shown that the sample preparation can be of great importance.     

高分子微凝胶负载镍催化剂及催化还原芳硝基化合物

以高分子微凝胶为载体, 先通过浸渍法在载体上引入少许的镍金属种子, 再通过化学法镀镍, 在种子载体上镀上大量镍, 制备出微凝胶负载Ni催化剂。 以水合肼为氢给体, 使用此类催化剂催化还原芳香族硝基化合物呈现出较高的活性。 经动态光散射法检测, 这种微凝胶催化剂的流体力学直径为411.9 nm。 高分辨透射电子显微镜和X射线光电子能谱分析表明, 所制得的催化剂中Ni主要是以NiO的形式存在。 以硝基苯为原料考察了水合肼的用量对反应的影响, 结果表明, 底物与水合肼的摩尔比为1:15最佳。 在优化条件下, 硝基苯衍生物的还原均能得到高产率的芳香胺。 动力学研究结果表明, 硝基苯氢转移反应的活化能为133.7 kJ/mol, 焓变为130.9 kJ/mol, 熵变为102.8 J/(mol·K)。     

A General Method for N‐Methylation of Amines and Nitro Compounds with Dimethylsulfoxide

DMSO methylates a broad range of amines in the presence of formic acid, providing a novel, green and practical method for amine methylation. The protocol also allows the one‐pot transformation of aromatic nitro compounds into dimethylated amines in the presence of a simple iron catalyst.     

A constructive synthetic approach for reduction of nitro heterocyclics- characterization and degradation studies

A novel synthetic approach was proposed for a metal free reduction of nitro aromatic compounds to the resultant amines by sodium dithionite. A series of nitro compounds containing various reducible functional groups were chemoselectively reduced in good to excellent yield. Instantaneously some of the products are chemically degraded and all are characterized by spectral methods.     

Reduction with Metal Borohydride-Transition Metal Salt System. I. Reduction of Aromatic Nitro Compounds with Potassium Borohydride-Copper(I) Chloride

Upon treatment with potassium borohydride-copper(I) chloride, aromatic nitro compounds afforded cleanly primary amines in high yields. Similarly, nitroso-, azoxy- and azobenzene were reduced by the same reagent system to give aniline.     

Convenient and mild synthesis of nitroarenes by metal-free nitration of arylboronic acids

A novel methodology for the direct nitration of arylboronic acids has been developed. By using inexpensive tert-butyl nitrite various aromatic nitro compounds are produced in moderate to good yields (45-87%) without the need of any catalyst.     

First and Efficient Method for Reduction of Aliphatic and Aromatic Nitro Compounds with Zinc Borohydride as Pyridine Zinc Tetrahydroborato Complex: A New Stable Ligand‐Metal Borohydride

Pyridine zinc tetrahydroborate, [(Py)Zn(BH₄)₂], as a new stable ligand‐metal borohydride, is prepared quantitatively by complexation of 1:1 zinc borohydride and pyridine at room temperature. This reagent efficiently reduces different aromatic and aliphatic nitro compounds to their primary amines in refluxing THF. In addition, the reduction shows chemoselectivity for aliphatic nitro compounds over the aromatic nitro compounds.     

Liquid phase hydrogenation and hydrodenitrogenation of aromatic nitrogen-containing environmental pollutants

Carcinogenic aromatic nitro-compounds are hydrogenated at 80–140 °C in the presence of a silica sol–gel entrapped combined palladium-[Rh(cod)Cl]₂ catalyst to give hydroaromatic amines and nitrogen-free hydrocarbons. The process involves initial transformation of the nitro to an amino function. Further hydrogenation causes denitrogenation and saturation of the aromatic moieties. Using 1-aminonaphthalene as a model substrate reveals simultaneous formation of 1- and 5-aminotetralin. While the former amine is readily converted into tetralin and 1-aminodecalins, the 5-aminotetralin gives, in a slow process, only the aminodecalins. The latter compounds are slowly denitrogenated to decalins. The catalytic hydrogenation of the aromatic compounds is accompanied by NH₃ elimination by which secondary amines are formed in a reversible fashion. The entrapped catalyst is leach-proof and recyclable. However, its catalytic activity in the different steps changes during the recycling. The high activity of the combined catalyst results from synergism between the two different metal nuclei.     

Alternative method for the reduction of aromatic nitro to amine using TMDS-iron catalyst system

The system 1,1,3,3-tetramethyldisiloxane (TMDS)/Fe(acac)₃ is reported here as a new method to obtain amines from aromatic nitro compounds. Amines are synthetized in a straightforward step and are isolated as hydrochloride salts with good to excellent yields. This system has shown a good selectivity toward aryl-chloride, aryl-bromide, ester, carboxylic acid, and cyano groups.The reduction of alkylnitro compounds was unfortunately not possible using this method, only a mixture of mono and dialkylated amine was obtained.     

One pot synthesis of <Emphasis Type="Italic">N</Emphasis>-ethylaniline from nitrobenzene and ethanol

A novel method for the one pot synthesis of N-alkyl arylamines from nitro aromatic compounds and alcohols is proposed through the combination of the aqueous-phase reforming of alcohol for hydrogen production, the reduction of nitro aromatic compounds for the synthesis of aromatic amine and the N-alkylation of aromatic amine for the production of N-alkyl arylamine over an identical catalyst under the same conditions of temperature and pressure in a single reactor. In this process, hydrogen generated from the aqueous-phase reforming of alcohols was used in-situ for the hydrogenation of nitro aromatic compounds for aromatic amine synthesis, followed by N-alkylation of aromatic amine with alcohols to form the corresponding N-alkyl arylamines at a low partial pressure of hydrogen. For the system composed of nitrobenzene and ethanol, under the conditions of 413 K and P _N2 = 1 MPa, the conversion degrees of nitrobenzene and aniline were 100%, the selectivity to N-ethylaniline and N, N-diethylaniline were 85.9% and 0%–4%, respectivity, after reaction for 8 h at the volumetric ratio of nitrobenzene:ethanol:water = 10:60:0. The selectivity for N, N-diethylaniline production is much lower than that through the traditional method. In this process, hydrogen and aromatic amines generated from the aqueous-phase reforming of alcohols and hydrogenation of nitro aromatic compounds, respectively, could be promptly removed from the surface of the catalyst due to the occurrence of in-situ hydrogenation and N-alkylation reactions. Thus, this may be a potential approach to increase the selectivity to N-alkyl arylamine. Supported by the Program for New Century Excellent Talents in University (Grant No. NCET-04-0557), and the Specialized Research Fund for the Doctoral Program of High Education (Grant No. SRFDP-20060337001)