Reductive Amination Of Aromatic Aldehydes Research Articles

Hydrogen Bond‐Assisted Macrocyclic Synthesis: An Extended Application For 4‐Hydroxybenzylamine Derivatives

AbstractThis work involved synthesizing three N‐benzyl‐4‐hydroxybenzylamines using indirect reductive amination of aromatic aldehydes and 4‐hydroxybenzylamine. Such benzylamines’ reaction with formaldehyde produced tricyclic azacyclophanes formed by two benzylamine units joined by methylene bridges. Computational calculations established that macrocyclization was promoted by template formation stabilized by hydrogen bonds and π‐stacking.

Switchable reductive amination of aldehydes over metal-encapsulated S-1 zeolites with tunable acid-base properties

Catalytic reductive amination of aldehydes is a valuable strategy to synthesize nitrogen-containing compounds but often suffers from low selectivity and complex reaction mechanisms. This study aims to develop a selective control method for the syntheses of primary amines and secondary imines, which are widely used in fine and bulk chemicals, materials, and pharmaceuticals. Metal-encapsulated zeolite is a special type of catalyst that combines the advantages of metal nanoparticles and zeolites, such as high activity and selectivity. Herein, metal-encapsulated zeolites (Pd-M@S-1, M=Ni, Mn, Co) were applied as catalysts for the reductive amination of aromatic aldehydes. Results showed that the reductive amination of aldehydes over Pd-M@S-1 catalysts can be selectively switched between primary amines over Pd0.6@S-1 and secondary imines over Pd0.6Ni@S-1 by tuning the acid-base properties of the catalysts. The effect of acid-base properties of catalysts on selectivity control was claimed by conducting control experiments, time-dependent curves, and detailed characterizations.

Catalytic Reductive Amination of Aromatic Aldehydes on Co-Containing Composites

The performance of a series of cobalt-based composites in catalytic amination of aromatic aldehydes by amines in the presence of hydrogen as well as hydrogenation of quinoline was studied. The composites were prepared by pyrolysis of CoII acetate, organic precursor (imidazole, 1,10-phenantroline, 1,2-diaminobenzene or melamine) deposited on aerosil (SiO2). These composites contained nanoparticles of metallic Co together with N-doped carboneous particles. Quantitative yields of the target amine in a reaction of p-methoxybenzaldehyde with n-butylamine were obtained at p(H2) = 150 bar, T = 150 °C for all composites. It was found that amination of p-methoxybenzaldehyde with n-butylamine and benzylamine at p(H2) = 100 bar, T = 100 °C led to the formation of the corresponding amines with the yields of 72–96%. In the case of diisopropylamine, amination did not occur, and p-methoxybenzyl alcohol was the sole or the major reaction product. Reaction of p-chlorobenzaldehyde with n-butylamine on the Co-containing composites at p(H2) = 100 bar, T = 100 °C resulted in the formation of N-butyl-N-p-chlorobenzylamine in 60–89% yields. Among the considered materials, the composite prepared by decomposition of CoII complex with 1,2-diaminobenzene on aerosil showed the highest yields of the target products and the best selectivity in all studied reactions.

One‐Pot Reductive Amination of Aromatic Aldehydes in [Et3NH][HSO4] using Sodium Borohydride and A Mechanistic Investigation using Computational Method

AbstractThe reductive amination of aromatic aldehydes and aromatic amines, performed in the Brønsted acidic ionic liquid [Et3NH][HSO4], using sodium borohydride as a reducing agent is reported. In this protocol, the ionic liquid plays a crucial role in efficiently converting aromatic aldehydes to amines in excellent yields, without the formation of side products. In the presence of [Et3NH][HSO4], the imine was generated in situ from the reaction between the aromatic aldehydes and aromatic amines, and underwent smooth reduction with sodium borohydride. This one‐pot synthesis is practically simple and sustainable. The catalyst [Et3NH][HSO4] also has a demonstrably wide applicability, in that it can be used with a variety of aromatic aldehydes and aromatic amines substituted by various electron‐withdrawing and electron‐donating groups. The role of IL [Et3NH][HSO4] in catalytic reductive amination is validated with the help of density functional theory (DFT)‐based computational studies.

Cu‐Al mixed oxide derived from layered double hydroxide as an efficient catalyst for continuous‐flow reductive amination of aromatic aldehydes

AbstractBACKGROUNDSecondary amines are important intermediates in the manufacture of pharmaceuticals and other valuable chemicals. Hence, there is a continuing interest in cost‐effective and environmentally friendly methods for producing these compounds. Reductive amination of aldehydes or ketones with primary amines over heterogeneous metal catalysts is an attractive approach due to the use of inexpensive and environmentally benign molecular hydrogen as a reducing agent.RESULTSVarious secondary amines were obtained by two‐step reductive amination of benzaldehyde derivatives and furfural with primary amines. The condensation of aromatic aldehydes with amines at room temperature in low water methanol gives imines, which are then hydrogenated in a flow reactor over CuAlOx catalyst derived from layered double hydroxide. This process does not require isolation and purification of intermediate imines and can be utilized to obtain several secondary amines in good to excellent yield. The time‐dependent study showed that CuAlOx catalyst demonstrates excellent stability in imine hydrogenation.CONCLUSIONAn environmentally friendly procedure has been developed for the synthesis of secondary amines through a reductive amination of aromatic aldehydes with primary amines over Cu‐based catalyst. This procedure presents a novel way for the sustainable production of secondary amines. © 2020 Society of Chemical Industry

Photoredox-catalyzed Direct Reductive Amination of Aldehydes without an External Hydrogen/Hydride Source

The direct reductive amination of aromatic aldehydes has been realized using a photocatalyst under visible light irradiation. The single electron oxidation of an in situ formed aminal species generates the putative α-amino radical that eventually delivers the reductive amination product. This method is operationally simple, highly selective, and functional group tolerant, which allows the direct synthesis of benzylic amines by a unique mechanistic pathway.

Synthesis of new daunorubicin N-derivatives by one-step reductive amination

One-step reductive amination of aromatic aldehydes using an anthracycline antibiotic daunorubicin resulted in the preparation of its new N-derivatives, which are of interest as potential antitumor drugs.

ChemInform Abstract: A Rapid and Additive‐Free Ruthenium‐Catalyzed Reductive Amination of Aromatic Aldehydes.

The ruthenium complex [(η6-cymene)Ru(Cl)(dpmpy)]+ {dpmpy = 2-[2-(dimethylamino)pyrimidin-4-yl]pyridine} is highly reactive in catalyzing the reductive amination of aromatic aldehydes through in situ generated imines with 2-propanol as the hydrogen source following a transfer-hydrogenation mechanism. This transformation does not require any activating additives and is applicable to a broad variety of aldehydes.

A Rapid and Additive‐Free Ruthenium‐Catalyzed Reductive Amination of Aromatic Aldehydes

The ruthenium complex [(η6‐cymene)Ru(Cl)(dpmpy)]+ {dpmpy = 2‐[2‐(dimethylamino)pyrimidin‐4‐yl]pyridine} is highly reactive in catalyzing the reductive amination of aromatic aldehydes through in situ generated imines with 2‐propanol as the hydrogen source following a transfer‐hydrogenation mechanism. This transformation does not require any activating additives and is applicable to a broad variety of aldehydes.

ChemInform Abstract: Catalyst‐Free Reductive Amination of Aromatic Aldehydes with Ammonium Formate and Hantzsch Ester.

AbstractThe novel direct reductive amination of aromatic aldehydes furnishes both symmetric and asymmetric secondary benzyl amines in a mild, convenient, acid‐ and catalyst‐free system.

Catalyst-free reductive amination of aromatic aldehydes with ammonium formate and Hantzsch ester

The protocol of the reductive amination of aromatic aldehydes using ammonium formate and Hantzsch ester is described. It is a mild, convenient, acid- and catalyst-free system applied for the synthesis of both symmetric and asymmetric aromatic secondary amines.

ChemInform Abstract: Efficient and Chemoselective Direct Reductive Amination of Aromatic Aldehydes Catalyzed by Oxo—Rhenium Complexes Containing Heterocyclic Ligands.

Abstract This work describes the catalytic activity of 17 oxo–rhenium complexes containing heterocyclic ligands in the direct reductive amination of 4-nitrobenzaldehyde with 4-chloroaniline, using phenylsilane as reducing agent. In general, all of the catalysts tested gave excellent yields of the secondary amine, although, the best result was obtained with the catalytic system PhSiH3/ReOBr2(Hhmpbta)(PPh3) (2.5 mol %). This system was also applied to the synthesis of a large variety of secondary amines in good to excellent yields and tertiary amines in moderate yields, with tolerance of different functional groups.

Efficient and chemoselective direct reductive amination of aromatic aldehydes catalyzed by oxo–rhenium complexes containing heterocyclic ligands

This work describes the catalytic activity of 17 oxo–rhenium complexes containing heterocyclic ligands in the direct reductive amination of 4-nitrobenzaldehyde with 4-chloroaniline, using phenylsilane as reducing agent. In general, all of the catalysts tested gave excellent yields of the secondary amine, although, the best result was obtained with the catalytic system PhSiH3/ReOBr2(Hhmpbta)(PPh3) (2.5 mol %). This system was also applied to the synthesis of a large variety of secondary amines in good to excellent yields and tertiary amines in moderate yields, with tolerance of different functional groups.

ChemInform Abstract: Palladium‐Mediated Intramolecular Buchwald—Hartwig α‐Arylation of β‐Amino Esters: Synthesis of Functionalized Tetrahydroisoquinolines.

AbstractThe three‐step strategy involves reductive amination of aromatic aldehydes, addition of the resulting secondary amines to ethyl acrylate and final Buchwald—Hartwig cyclization.

ChemInform Abstract: Direct Reductive Amination of Aromatic Aldehydes Catalyzed by Gold(I) Complex under Transfer Hydrogenation Conditions.

AbstractAn efficient method is elaborated for the gold‐catalyzed reductive amination of aldehydes (I) and ketones (IV) with an equimolar amount of anilines in the presence of Hantzsch ester as reducing agent.

ChemInform Abstract: A Fast and Highly Efficient Protocol for Reductive Amination of Aromatic Aldehydes Using NaBH4 and Isoxazole Amines in an Ionic Liquid Medium.

AbstractThe Broensted acidic ionic liquid acts as both solvent and catalyst.

A Fast and Highly Efficient Protocol for Reductive Amination of Aromatic Aldehydes Using NaBH4 and Isoxazole Amines in an Ionic Liquid Medium

Reductive amination of aromatic aldehydes using NaBH4 and isoxazole amines is carried out in a Brønsted acidic ionic liquid 1-methylimidazolium tetrafluoroborate [(HMIm)BF4]. The ionic liquid plays dual roles of solvent as well as catalyst for the efficient transformation of aromatic aldehydes to heterocyclic substituted amines in excellent yields without any undesired side product formation. The newly synthesized compounds (3, 6 and 7) were characterized by IR, 1H NMR and mass spectral techniques.

Solvent-free reductive amination of aromatic aldehydes catalyzed by CeCl3·7H2O

CeCl3·7H2O is found to be an efficient catalyst in the one-pot reductive amination of aromatic aldehydes under solvent-free conditions. Selectivity is observed in the reaction of cinnamaldehyde with aromatic amines, providing an alternative green route to the synthesis of N-cinnamyl anilines. The reaction conditions are mild and the desired product is obtained in good yields.

Direct reductive amination of aromatic aldehydes catalyzed by gold(i) complex under transfer hydrogenation conditions

The direct reductive amination of aromatic aldehydes has been achieved with excellent isolated yields (89-96%) using readily accessible Ph(3)PAuCl/AgOTf catalyst along with ethyl Hantzsch ester as hydrogen source under mild reaction conditions.

ChemInform Abstract: Reductive Amination of Aromatic Aldehydes and Ketones with Nickel Boride.

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