Selective N-alkylation Of Amines Research Articles

Activity enhancement of Ru/CeO2 for N-alkylation of amines with alcohols through tailoring metal-support interaction

Efficient and selective N-alkylation of amines with alcohols via transfer hydrogenation is of great significance but extremely challenging. Here, we report the production of N–benzylaniline (BZA) from benzyl alcohol and aniline over various fine-shaped Ru/CeO2 catalysts. The Ru/CeO2–R (rod) catalyst exhibits the highest catalytic activity among all catalysts, in which the yield of BZA reaches up to 88% with complete conversion, significantly higher than that of Ru/CeO2-C (cube, 52%) and Ru/CeO2-O (octahedron, 32%). Extensive experimental investigations disclose that Ru nanoparticles with a metallic state promote the dehydrogenation of the hydroxyl group and hydrogenation of imines, while the CeO2–R with rich oxygen vacancies facilitates the adsorption and activation of reactants. Furthermore, kinetic studies and time-resolved operando dual-beam Fourier transform infrared spectroscopy analysis confirms the transfer hydrogenation pathway, in which the benzyl alcohol is firstly dehydrogenated to benzaldehyde, followed by spontaneously reacting with aniline, and finally transforms into the N-benzylaniline rapidly.

N-Alkylation of Amines by C1-C10 Aliphatic Alcohols Using A Well-Defined Ru(II)-Catalyst. A Metal-Ligand Cooperative Approach.

A Ru(II)-catalyzed efficient and selective N-alkylation of amines by C1-C10 aliphatic alcohols is reported. The catalyst [Ru(L1a)(PPh3)Cl2] (1a) bearing a tridentate redox-active azo-aromatic pincer, 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline (L1a) is air-stable, easy to prepare, and showed wide functional group tolerance requiring only 1.0 mol % (for N-methylation and N-ethylation) and 0.1 mol % of catalyst loading for N-alkylation with C3-C10 alcohols. A wide array of N-methylated, N-ethylated, and N-alkylated amines were prepared in moderate to good yields via direct coupling of amines and alcohols. 1a efficiently catalyzes the N-alkylation of diamines selectively. It is even suitable for synthesizing N-alkylated diamines using (aliphatic) diols producing the tumor-active drug molecule MSX-122 in moderate yield. 1a showed excellent chemo-selectivity during the N-alkylation using oleyl alcohol and monoterpenoid β-citronellol. Control experiments and mechanistic investigations revealed that the 1a-catalyzed N-alkylation reactions proceed via a borrowing hydrogen transfer pathway where the hydrogen removed from the alcohol during the dehydrogenation step is stored in the ligand backbone of 1a, which in the subsequent steps transferred to the in situ formed imine intermediate to produce the N-alkylated amines.

Reusable Co-nanoparticles for general and selective N-alkylation of amines and ammonia with alcohols.

A general cobalt-catalyzed N-alkylation of amines with alcohols by borrowing hydrogen methodology to prepare different kinds of amines is reported. The optimal catalyst for this transformation is prepared by pyrolysis of a specific templated material, which is generated in situ by mixing cobalt salts, nitrogen ligands and colloidal silica, and subsequent removal of silica. Applying this novel Co-nanoparticle-based material, >100 primary, secondary, and tertiary amines including N-methylamines and selected drug molecules were conveniently prepared starting from inexpensive and easily accessible alcohols and amines or ammonia.

Selective N-Alkylation of Amines with DMC over Biogenic Cu-Zr Bimetallic Nanoparticles.

Herein, we report the green synthesis of copper–zirconium bimetallic nanoparticles (Cu–Zr BNPs) from aqueous solutions using Azadirachta indica leaf extract as a reducing and stabilizing agent. The CuO, ZrO2 NP, and Cu–Zr BNP samples were characterized by X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy, and the morphologies of the samples were analyzed by high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction analysis (SAED). The synthesized Cu–Zr BNPs have been employed as efficient catalysts for the selective N-methylation of aromatic and aliphatic amines with dimethyl carbonate. The effect of process conditions on the percentage conversion of benzylamine with dimethyl carbonate as a model reaction has been investigated. The Cu–Zr bimetallic nanoparticle catalytic system in a 1:2 molar ratio was able to convert amines into the corresponding N-methylated amines with a selectivity up to 91% at 180 °C in 4 h. The analysis of catalytic reusability confirmed that the reported heterogeneous catalyst can be used for five consecutive cycles without much loss in activity. Thus, the current protocol can be considered as a simpler, reproducible, and environmentally benign approach for N-methylation of amines.

Photocatalytic Water-Splitting Coupled with Alkanol Oxidation for Selective N-alkylation Reactions over Carbon Nitride.

Photocatalytic water splitting technology (PWST) enables the direct use of water as appealing "liquid hydrogen source" for transfer hydrogenation reactions. Currently, the development of PWST-based transfer hydrogenations is still in an embryonic stage. Previous reports generally centered on the rational utilization of the in situ generated H-source (electrons) for hydrogenations, in which photogenerated holes were quenched by sacrificial reagents. Herein, the fully-utilization of the liquid H-source and holes during water splitting is presented for photo-reductive N-alkylation of nitro-aromatic compounds. In this integrate system, H-species in situ generated from water splitting were designed for nitroarenes reduction to produce amines, while alkanols were oxidized by holes for cascade alkylating of anilines as well as the generated secondary amines. More than 50 examples achieved with a broad range scope validate the universal applicability of this mild and sustainable coupling approach. The synthetic utility of this protocol was further demonstrated by the synthesis of existing pharmaceuticals via selective N-alkylation of amines. This strategy based on the sustainable water splitting technology highlights a significant and promising route for selective synthesis of valuable N-alkylated fine chemicals and pharmaceuticals from nitroarenes and amines with water and alkanols.

Highly Efficient and Selective N-Alkylation of Amines with Alcohols Catalyzed by in Situ Rehydrated Titanium Hydroxide

Catalytic N-alkylation of amines by alcohols to produce desired amines is an important catalytic reaction in industry. Various noble-metal-based homogeneous and heterogeneous catalysts have been re...

Efficient and selective N-alkylation of amines with alcohols catalysed by manganese pincer complexes.

Borrowing hydrogen (or hydrogen autotransfer) reactions represent straightforward and sustainable C–N bond-forming processes. In general, precious metal-based catalysts are employed for this effective transformation. In recent years, the use of earth abundant and cheap non-noble metal catalysts for this process attracted considerable attention in the scientific community. Here we show that the selective N-alkylation of amines with alcohols can be catalysed by defined PNP manganese pincer complexes. A variety of substituted anilines are monoalkylated with different (hetero)aromatic and aliphatic alcohols even in the presence of other sensitive reducible functional groups. As a special highlight, we report the chemoselective monomethylation of primary amines using methanol under mild conditions.

Selective N‐Alkylation of Amines with Alcohols by Using Non‐Metal‐Based Acid–Base Cooperative Catalysis

Selective N‐Alkylation of Amines with Alcohols by Using Non‐Metal‐Based Acid–Base Cooperative Catalysis

Direct One‐Pot Reductive N‐Alkylation of Nitroarenes by using Alcohols with Supported Gold Catalysts

The formation of C N bonds is one of the most important transformations in chemistry because nitrogen-containing compounds, particularly amines and their derivatives, are versatile building blocks for various organic molecules and essential precursors to a variety of biologically active compounds. Although several methods are known for the synthesis of C N bonds, preparation under mild and wastefree conditions using simple, inexpensive, and readily available feedstock is still a challenging goal. The transitionmetal-catalyzed coupling of amines with alcohols by using a hydrogen-borrowing strategy (also known as a hydrogenautotransfer process) has proven to be an atom-economical and environmentally attractive method for the construction of C N bonds, especially for secondary amine preparation. Although many efficient catalysts for such transformations have been reported, 4] the development of easily recoverable and recyclable heterogeneous catalysts that can solve the problem of the homogeneous systems has attracted special attention. To the best of our knowledge, few heterogeneous catalyst systems have been reported that enable efficient and selective N-alkylation of amines with alcohols under simple, mild, and environmentally benign conditions. Nitroarenes are cheap and readily available organic compounds and the reduction of nitro compounds is a key step in the preparation of many pharmaceutical agents and fine chemicals. Despite numerous established procedures for the reduction of nitro compounds, the development of catalytic methodologies that afford high chemoand regioselectivity under mild reaction conditions is still a challenging problem. As for the synthesis of secondary amines, the direct use of commercially available and inexpensive nitroarenes and alcohols as starting materials is highly attractive, especially when a single catalyst system could be employed. In this valuable one-pot multistep transformation, the alcohol may conceivably serve two possible functions: as the hydrogen source for nitro reduction and as the alkylating reagent based on the catalytic hydrogen transfer. Although excess alcohol is required to ensure the completion of the reaction (see the Supporting Information for possible reaction stoichiometries), the operational simplicity of such transformations may have practical advantages for a concise synthesis of N-substituted amines in a more straightforward manner. Compared to the great progress being made in the amination of amines with alcohols, there are scarcely available reports dealing with the direct amination of nitroarenes with alcohols. To date, only three Ru-based homogeneous systems have been reported. However, these homogeneous catalysts are problematic in terms of the recovery/ recycling of the catalyst and the necessity of special handling of metal complexes. From a sustainable point of view, a more efficient reaction with a ligand-free heterogeneous catalyst is highly desired. Over the last five years, we have been interested in the unique catalytic properties of supported gold nanoparticles (NPs) and involved in their application to sustainable organic synthesis. Recently, we have shown that very small Au NPs (approx. 1.8 nm) deposited on TiO2 (Au/TiO2-VS; VS=very small) acts as an efficient heterogeneous catalyst for the clean and atom-efficient mono-N-alkylation of a range of amines with alcohols in excellent yields under hydrogen-borrowing conditions. In view of the prominent efficiency of the gold system for the amination of amines with alcohols, we envisioned that the Au-mediated hydrogen-borrowing strategy could afford a green and efficient protocol for the direct amination of nitroarenes with alcohols under mild conditions. Herein, we report for the first time that the simple Au/TiO2-VS system can catalyze the selective secondary or tertiary amine formation from the direct condensation of nitroarenes and alcohols. Notably, the reaction can proceed effectively under ligandand basefree conditions without any external hydrogen resources. To the best of our knowledge, this study also forms the first report of a one-pot selective preparation of imines from nitroarenes and alcohols by using a heterogeneous gold-mediated “catalytic hydrogen-transfer” procedure. Based on our previous results in heterogeneous Au-catalyzed amine/alcohol coupling chemistry, the optimization study was initiated with the direct amination of nitrobenzene (1a) with eight equivalents of benzyl alcohol (2a) in the presence of Au/TiO2-VS (0.5 mol% of Au, see the Sup[a] C.-H. Tang, L. He, Dr. Y.-M. Liu, Prof. Dr. Y. Cao, Prof. Dr. H.-Y. He, Prof. K.-N. Fan Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Department of Chemistry, Fudan University Shanghai 200433 (P.R. China) Fax: (+86)21-65643774 E-mail : yongcao@fudan.edu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201100393.

Selective N‐Alkylation of Amines with Alcohols over γ‐Alumina

AbstractFor Abstract see ChemInform Abstract in Full Text.