Practical One-Pot Synthesis of Secondary Amines by Zinc-Catalyzed Reductive Amination

Novel Enzymatic Method for Imine Synthesis via the Oxidation of Primary Amines Using D-Amino Acid Oxidase from Porcine Kidney

During studies on the oxidative cyanation reaction catalyzed by a variant of D-amino acid oxidase from porcine kidney (pkDAO) (Y228L/R283G), an unexpected formation of 1-phenyl-N-(1-phenylethylidene)ethanamine (PPEA) was detected. The optimal reaction conditions for the synthesis of PPEA and the reaction mechanism were investigated using the pkDAO variant. The highest PPEA synthesis was obtained in the reaction with 150 mM (R)-MBA at pH 9.0 and at 20 °C. Since PPEA synthesis proceeded by trapping the intermediate 1-phenylethanimine (1-PEI) by 15N-labeled n-hexylamine, which is not a substrate for the pKDAO variant, it was deduced that PPEA would be synthesized by a nucleophilic substitution of 1-PEI by another molecule of (R)-MBA. PPEA was further identified by its conversion to bis(1-phenylethyl)amine (BPEA) through reduction with NaBH4. Thus, a new enzymatic method of imine synthesis by oxidation of primary amine by the variant pkDAO was achieved for the first time.

Earth-abundant Metal-catalyzed Reductive Amination: Recent Advances and Prospect for Future Catalysis

Nitrogen-containing compounds, as an important class of chemicals, have been used widely in pharmaceuticals, materials synthesis. Transition metal-catalyzed reductive amination of an aldehyde or a ketone with ammonia or an amine has been proved to be an efficient and practical method for the preparation of nitrogen-containing compounds in academia and industry for a century. Given the above, several effective methods using transition metals have been developed in recent years. Noble transition metals like Pd, Pt, and Au-based catalysts have been predominately used in reductive amination. Because of their high prices, strict official regulations of residues in pharmaceuticals, and deleterious effects on the biological system, their industrial applications are severely hampered. With the increasing sustainable and environmental problems, the Earth-abundant transition metals including Ti, Fe, Co, Ni, and Zr have also been investigated for the reductive amination reaction and showed great potential to the advancement of sustainable and cost-effective reductive amination processes. This critical review will mainly summarize the work using Earth-abundant metals. The effects of different transition metals used in catalytic reduction amination were discussed and compared, and some suggestions were given. The last section highlights the catalytic activities of bi- and tri-metallic catalysts. Indeed, this latter family is very promising and simultaneously benefits from increased stability, and selectivity, compared to monometallic NPs, due to synergistic substrate activation. Few comprehensive reviews focusing on Earth-abundant transition metals catalyst has been published since 1948, although several authors reported some summaries dealing with one or the other part of this aspect. It is hoped that this critical review will inspire researchers to develop new efficient and selective earth-abundant metal catalysts for highly, environmentally sustainable reductive amination methods, as well as improve the pharmaceutical industry and related chemical synthesis company traditional method with the utilization of the green method widely.

Catalyst- and solvent-free efficient access to N-alkylated amines via reductive amination using HBpin

A sustainable approach which works under catalyst- and solvent-free conditions for the synthesis of structurally diverse secondary amines has been uncovered. This one-pot protocol works efficiently at room temperature and is compatible with a wide range of sterically and electronically diverse aldehydes and primary amines. Notably, this simple process offers scalability, excellent functional group tolerance, chemoselectivity, and is also effective at the synthesis of biologically relevant molecules.

Systematic Modification of Zingerone Reveals Structural Requirements for Attraction of Jarvis's Fruit Fly

Tephritid fruit flies are amongst the most significant horticultural pests globally and male chemical lures are important for monitoring and control. Zingerone has emerged as a unique male fruit fly lure that can attract dacine fruit flies that are weakly or non-responsive to methyl eugenol and cuelure. However, the key features of zingerone that mediate this attraction are unknown. As Jarvis's fruit fly, Bactrocera jarvisi (Tryon), is strongly attracted to zingerone, we evaluated the response of B. jarvisi to 37 zingerone analogues in a series of field trials to elucidate the functional groups involved in attraction. The most attractive analogues were alkoxy derivatives, with isopropoxy being the most attractive, followed by ethoxy and trifluoromethoxy analogues. All of the phenolic esters tested were also attractive with the response typically decreasing with increasing size of the ester. Results indicate that the carbonyl group, methoxy group, and phenol of zingerone are key sites for the attraction of B. jarvisi and identify some constraints on the range of structural modifications that can be made to zingerone without compromising attraction. These findings are important for future work in developing and optimising novel male chemical lures for fruit flies.

Imidazolium-based ionic liquid-catalyzed hydrosilylation of imines and reductive amination of aldehydes using hydrosilane as the reductant

Efficient imidazolium-based ionic liquid-catalyzed hydrosilylation of imines and reductive amination using a catalytic amount of [BMIm][FeCl₄].

Mechanism of Zn(OTf)2catalyzed hydroamination–hydrogenation of alkynes with amines: insight from theory

Zn(OTf)₂catalyzed hydroamination of alkynes with amines proceeds through an outer sphere mechanism which is contrary to other late transition metals.

Amine synthesis via transition metal homogeneous catalysed hydrosilylation

This review summarizes the preparation of amines involving homogeneous transition metal catalysed hydrosilylation including reductions of imines, amides, nitro and nitriles, reductive aminations and N-methylation of amines with CO₂.

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.

One-Pot Reductive Amination of Araldehydes by Aniline Using Borohydride with Cecl3·7H2O as Catalyst

A one-pot, two-step reductive amination of araldehydes or acetophenones with anilines using NaBH4 as a cheap hydride source and catalysed by CeCl3·7H2O has been achieved in EtOH at room temperature in good yields.

Lamellar Ni/Al-SBA-15 fibers: preparation, characterization, and applications as highly efficient catalysts for amine and imine syntheses

A novel lamellar Ni/Al-SBA-15 fiber catalyst was prepared and successfully utilized in one-pot syntheses of amines and imines.

Main group catalysed reduction of unsaturated bonds

This Perspective article reviews the recent developments in reduction reactions catalysed by main-group element compounds.

Reductive amination using a combination of CaH2 and noble metal

Amines were prepared by a reductive amination reaction in the presence of calcium hydride and Pt/C.

Direct catalytic N-alkylation of amines with carboxylic acids

A straightforward process for the N-alkylation of amines has been developed applying readily available carboxylic acids and silanes as the hydride source. Complementary to known reductive aminations, effective C-N bond construction proceeds under mild conditions and allows obtaining a broad range of alkylated secondary and tertiary amines, including fluoroalkyl-substituted anilines as well as the bioactive compound Cinacalcet HCl.

The first zinc-catalyzed oxidation of sulfides to sulfones using H2O2 as green oxidant

The first example of the zinc-catalyzed oxidation of sulfides to sulfones has been developed. By using a catalytic amount of zinc salt as the catalyst, DBU as the ligand, various sulfones were produced in good yields with hydrogen peroxide as the terminal green oxidant.

Non-redox-metal-catalyzed redox reactions: zinc catalysts

The advantages of zinc catalysts, such as their low toxicity, low cost, and environmentally benignity, are encouraging organic chemists to explore their applications in organic synthesis. As a non-redox metal, zinc catalysts have been investigated in redox reactions over the past few decades. Because of the importance of redox reactions, the interest in zinc catalysts, and the fact that no review on zinc-catalyzed redox reactions has been published, herein, I have collected and summarized the main contributions in this area. This review is divided into two parts: reduction reactions and oxidation reactions.