Formation Of Secondary Amines Research Articles

An efficient heterogeneous copper oxide nanocatalyst for N-alkylation of amines with carbonyl compounds under H2 atmosphere

The aim of this research is to investigate the potential of copper oxide nanoparticles (CuO NPs) as a catalyst for the reductive N-alkylation of amines with carbonyl compounds in order to synthesize secondary amines in an H2 environment. The synthesized CuO NPs were characterized using UV–vis DRS, XRD, FT-IR, and TEM techniques, which confirmed their spherical shape, monoclinic phase, and average diameter of 9 ± 2 nm. The results of the catalytic study indicate that the CuO NPs catalyst was able to produce various secondary amines with excellent yield. The study also explored the effects of reaction time, temperature, and catalyst weight under optimum reaction conditions. Additionally, the synthesized CuO NPs were shown to be highly stable and could be reused for three cycles without any loss of activity in the formation of secondary amines.

Ruthenium‐Catalyzed Secondary Amine Formation Studied by Density Functional Theory

AbstractAmines are a ubiquitous class of compounds found in a variety of functional organic building blocks. Within the past years, hydrogen autotransfer catalysis has evolved as a new concept for the synthesis of amines. A through understanding of the mechanism of these reactions is necessary to design optimal catalysts. We investigate secondary amine formation catalyzed by a NNNN(P)Ru‐complex and provide understanding on the three reaction steps involved. We find that the ligand has to open one coordination site in order to allow the formation of a metal hydride intermediate. In a second step, a condensation reaction, which could also happen uncatalyzed in solution, is significantly enhanced by the presence of the ruthenium complex. The back‐transfer of the hydride to the substrate in a third step regenerates the catalyst.

Electronic state regulation of supported Pt catalysts dictates selectivity of imines/secondary amines from the cascade transformation of nitroarenes and aldehydes

One-pot cascade transformations of nitroarenes and aldehydes are facile, cost-effective, and environmentally friendly processes for the synthesis of imines and secondary amines. However, these type of transformations generally suffer from serious problems regarding the selectivity towards imines and secondary amines. Herein, Pt nanoparticles anchored on various supports with strong electronic metal-support interactions facilitate unparalleled selectivity towards imines or secondary amines. The high selectivity derives from the adsorption strength of the imine intermediate, which has a strong correlation with the electron density of the supported Pt. High-electron-density Pt with a strong hydrogen activation ability exhibits a weak interaction with imines, accelerating the synthesis of imines. Pt nanoparticles with low electronic density benefit the formation of secondary amines owing to the strong adsorption of intermediate imines.

Enhanced Selectivity in the Hydrogenation of Anilines to Cyclo‐aliphatic Primary Amines over Lithium‐Modified Ru/CNT Catalysts

AbstractThe hydrogenation of aromatic amines to the corresponding cycloaliphatic primary amines is an important industrial reaction. However, secondary amine formation and other side reactions are frequently observed, resulting in reduced selectivity. The side products are formed mostly on the support, yet support effects are little understood at present. This study describes the facile modification of Ru/CNT catalysts with LiOH, by this means significantly improving catalyst selectivity in toluidine hydrogenation without decreasing the activity of the catalysts. The effect is explained by LiOH diminishing acidic sites on the catalyst support and enhancing the adsorption of the aromatic ring on the metallic ruthenium nanoparticles. With the LiOH‐modified Ru/CNT catalyst, other substrates, such as methylnitrobenzenes, are also converted efficiently. This study thus describes an improved catalyst for the preparation of cyclohexylamines and provides guidelines for future catalyst design.

Electronic Effect of Ruthenium Nanoparticles on Efficient Reductive Amination of Carbonyl Compounds.

Highly selective synthesis of primary amines over heterogeneous catalysts is still a challenge for the chemical industry. Ruthenium nanoparticles supported on Nb2O5 act as a highly selective and reusable heterogeneous catalyst for the low-temperature reductive amination of various carbonyl compounds that contain reduction-sensitive functional groups such as heterocycles and halogens with NH3 and H2 and prevent the formation of secondary amines and undesired hydrogenated byproducts. The selective catalysis of these materials is likely attributable to the weak electron-donating capability of Ru particles on the Nb2O5 surface. The combination of this catalyst and homogeneous Ru systems was used to synthesize 2,5-bis(aminomethyl)furan, a monomer for aramid production, from 5-(hydroxymethyl)furfural without a complex mixture of imine byproducts.

C–N Bond Formation of Secondary Amines with Cobalt/Alumina Catalyst

Key words cobalt - arylation - cross-coupling - heterogeneous catalysis - chloroarenes

ChemInform Abstract: One‐Pot Synthesis of Secondary Amines from Alcohols and Nitroarenes on TiO2 Loaded with Pd Nanoparticles under UV Irradiation.

Photoirradiation (λ > 300 nm) of TiO2 loaded with Pd nanoparticles (2 wt%, ca. 5 nm diameter) in water containing benzyl alcohol and nitrobenzene at room temperature successfully produces the corresponding secondary amine (N-benzylaniline) with 96% yield. This is achieved via three consecutive catalytic reactions: (i) photocatalytic oxidation of alcohol (aldehyde formation) and reduction of nitrobenzene (aniline formation); (ii) catalytic condensation of the formed aldehyde with aniline on the TiO2 surface (imine formation); and, (iii) photocatalytic hydrogenation of the formed imine (secondary amine formation). This catalytic system successfully produces several kinds of secondary amines, even those containing reducible substituents such as –CN, –COOH, or –CHO with >76% yields.

ChemInform Abstract: Copper(I) Carboxylate Catalyzed C—N Coupling of 2‐Amino Pyrimidines with Aryl Halides to Selectively Generate Secondary and Tertiary Amines.

AbstractIt is found that potassium phosphate used as base favors the formation of secondary amines (III), (VI), whereas tertiary amines (IV),(VII) are obtained when tBuONa is used.

Insight into O2‐Promoted Base‐Catalyzed N‐Alkylation of Amines with Alcohols

AbstractA highly efficient and practical transition‐metal‐free CsOH/O2 catalyst system was developed for the N‐alkylation of amines with alcohols under argon. This strategy was compatible with many alcohols and exhibits excellent functional group tolerance. More significantly, the selective formation of secondary amines was achieved in excellent yields. The detailed mechanistic study gave a clear understanding of the role of base and oxygen in the catalytic cycle.

Copper(I) carboxylate catalyzed C–N coupling of 2-amino pyrimidines with aryl halides to selectively generate secondary and tertiary amines

(2-Chlorobenzoyloxy)copper(I) exhibited high activity towards the challenging amination of 2-amino pyrimidines with aryl halides. Herein, secondary and tertiary amines were selectively produced by using potassium phosphate and sodium-t-butoxide. Potassium phosphate favored the formation of secondary amines, whereas tertiary amines were favored when sodium-t-butoxide was used.

Shape-and size-controlled Ag nanoparticles stabilized by in situ generated secondary amines

Silver amides such as AgNiPr2 and AgN(SiMe3)2 have been employed successfully as precursors for the yield synthesis of silver nanoparticles under mild conditions of dihydrogen gas reduction (2atm) in organic media. Transmission electron microscopy (TEM) showed the formation of silver nanoparticles with FCC structure, variously sized from 26 to 35nm for AgNiPr2 and from 14 to 86nm for AgN(SiMe3)2, the synthesis could take place in absence of added stabilizers due to the in situ formation of secondary amines from the reaction of dihydrogen gas with the amide ligands of the silver precursor. Indeed, the presence of HNR2 (R=iPr2, N(SiMe3)2) on the surface of the nanoparticle was confirmed by spectroscopic means.Finally, the addition of ethylenediamine as additional capping agent allowed not only the control of the structural characteristics of the resulting Ag nanoparticles (well-dispersed with spherical shape), but that regarding the nanoparticle size as it inhibited overgrowth, limiting it to ca. 25nm.

Straightforward access to cyclic amines by dinitriles reduction

1,1,3,3-Tetramethyldisiloxane (TMDS) and polymethylhydrosiloxane (PMHS), when associated with titanium(IV) isopropoxide, provide two convenient systems for the reduction of nitriles into the corresponding primary amines. Kinetics of the two systems have been studied by 1H NMR and demonstrated that reduction with PMHS occurs faster than with TMDS. These two titanium-based systems reduce both aromatic and aliphatic nitriles in the presence of Br, CC, NO2, OH, and cyclopropyl-ring. In the case of cyclopropyl-nitriles, the formation of secondary amines, which come from an intermolecular reductive alkylation reaction was observed. This result was exploited for the reduction of dinitriles, which led, in one-step, to azepane, piperidine, pyrrolidine, and azetidine derivatives through an intramolecular reductive alkylation reaction.

Determination of Rate Constants of N-Alkylation of Primary Amines by 1H NMR Spectroscopy

Macromolecules containing N-diazeniumdiolates of secondary amines are proposed scaffolds for controlled nitrogen oxide (NO) release medical applications. Preparation of these compounds often involves converting primary amine groups to secondary amine groups through N-alkylation. However, N-alkylation results in not only secondary amines but tertiary amines as well. Only N-diazeniumdiolates of secondary amines are suitable for controlled NO release; therefore, the yield of secondary amines is crucial to the total NO load of the carrier. In this paper, (1)H NMR spectroscopy was used to estimate the rate constants for formation of secondary amine (k1) and tertiary amine (k2) for alkylation reagents such as propylene oxide (PO), methyl acrylate (MA), and acrylonitrile (ACN). At room temperature, the ratio of k2/k1 for the three reactions was found to be around 0.50, 0.026, and 0.0072.

ZSM-5-Ln(Pc)2 catalyzed oxygen oxidation of thiophene

Abstract Direct oxidative desulfurization of thiophene with oxygen catalyzed by ZSM-5-Ln(Pc) 2 (NO 2 ) 6 (NH 2 ) 2 (Pc = phthalocyanine) was conducted. The precursor Ln(PcTn) 2 (Ln = Ce, Pr, Er, PcTn = tetra-substituted nitro phthalocyanine) was synthesized with programmed heating under nitrogen atmosphere. Then, the precursor was partially reduced by Na 2 S so the compound Ln(Pc) 2 (NO 2 ) 6 (NH 2 ) 2 (Ln = Ce, Pr, Er) was obtained, which was then anchored onto ZSM-5 zeolites through the formation of secondary amine. The catalyst was characterized by XRD, SEM, XPS, and N 2 adsorption–desorption. For the oxidation of thiophene with oxygen, the catalyst showed remarkable catalytic activity.

Disecondary amine synthesis and its reaction kinetics with epoxy prepolymers

Abstract3,3′‐Diaminodiphenyl sulfone (3,3′‐DDS) was reacted with acetaldehyde in the presence of sodium triacetoxy borohydride via reductive amination to yield a 3,3′‐DDS based secondary diamine, N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone. Near IR analysis indicated that the 5060 cm−1 peak for primary amine (NH2) in 3,3′‐DDS was absent in the reaction product spectrum. The NH2 proton peak at δ 5.66 ppm shifted to δ 6.16 ppm in the product. Methyl and methylene protons of CH3CH2NHPh group were observed at δ 3.01 and 1.12 ppm, respectively, in the product. The carbon NMR spectrum of the reaction product showed new peaks at δ 37.46 and 14.47 ppm that further confirmed secondary amine formation. The liquid chromatography coupled mass spectra peaks at 248–250 for 3,3′‐DDS and 304 for the reaction product further supported the formation of N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone. A blend of N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone with diglycidyl ether of bisphenol‐A (DGEBA) epoxy prepolymer started reacting at about 110–125°C surpassing an energy barrier of ∼ 66 kJ/mol as determined via differential scanning calorimetry analysis. Reaction kinetics were characterized via near IR spectroscopy specific to the reaction between secondary amine and DGEBA epoxy prepolymer. The results confirmed >97% conversion at a cure protocol of 5 h at 80°C, 5 h at 100°C, 11 h at 125°C, and 6 h at 185°C. N,N′‐diethyl‐3,3′‐diaminodiphenyl sulfone‐DGEBA thermoplastics displayed tensile and flexural modulii of 3.08 and 2.86 GPa, respectively, and glass transition temperature (Tg) of 120.77°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

ChemInform Abstract: Ruthenium‐Catalyzed One‐Pot Aromatic Secondary Amine Formation from Nitroarenes and Alcohols.

AbstractThe title reaction leads to aromatic secondary amines in high yields using an n excess of benzylic and aliphatic alcohols.

Ruthenium‐Catalyzed One‐Pot Aromatic Secondary Amine Formation from Nitroarenes and Alcohols

The title reaction leads to aromatic secondary amines in high yields using an n excess of benzylic and aliphatic alcohols.

Preparation and characterization of branched chitosans

Fully de- N-acetylated chito-oligomers were prepared by de-amination of chitosan using nitrous acid (HNO 2). The dimer to hexamer fractions of chitosan oligomers were fractionated with preparative size-exclusion chromatography (SEC) and characterized using 1H NMR spectroscopy. The purified oligomers were polymerized by reductive N-alkylation by the action of NaCNBH 3, in a reaction between the terminal 2,5-anhydro- d-mannofuranose ( M-unit) and the primary amines of the repeating units (1 → 4) bound β- d-glucosamine ( D-unit) resulting in a covalent bond and formation of secondary amines. The polymerized products were studied by SEC-RI and SEC-MALLS-RI and were confirmed to be branched reaching molecular weights of up to 10 000 g/mol. Analysis by 1H NMR spectroscopy confirmed that the chitosan oligomers had been branched by formation of secondary amines. Fully de- N-acetylated chitosan ( F A < 0.001) was degraded to various extents using nitrous acid resulting in degrees of scission ( α s ) in the range 0.01–0.10. The resulting chitosans, with the reactive M-unit on the reducing end, were branched by reductive N-alkylation using NaCNBH 3. Analysis by SEC-MALLS-RI-visc showed that the weight-average molecular weight ( M w ) and polydispersity ( M w / M n ) had increased, with a degree of branching in the range of 1.2–2.1. The structure in solution had become more compact compared to linear chitosan of the same molecular weight as demonstrated by a significant reduction of the radius of gyration and the intrinsic viscosity, with a corresponding change in the calculated viscosity contraction factor ( g′) and the geometric contraction factor ( g), respectively.

Spectroscopic and Quantitative Chemometric Analysis of the Epoxidised Oil/Amine System

The competitiveness between the oxirane functional group and the ester functional group present in a derivative epoxidised oil was studied by monitoring a model system which involved epoxidised oleic oil and aniline (1:1). The reaction was carried out under isothermal conditions at 95°C and monitored in situ by near infrared (NIR) spectroscopy. This system is taken as a model of the curing process in the manufacture of epoxy resins from triglycerides and diamines. Conventional spectroscopic analysis and generalised two-dimensional NIR correlation spectroscopy analysis have led to the conclusion that, even though the formation of secondary amines by ring-opening of the oxirane group as a consequence of the nucleophilic attack of the aniline is prior, the formation of amides as a consequence of the ester group reactivity is a competitive reaction. The presence of the two aforementioned reactions is also in accordance with the significant number of factors found when the spectra data matrix was analysed by evolving factor analysis. By applying multivariate curve resolution–alternating least squares to the NIR spectra obtained during the reaction, it has been possible to obtain the concentration and the spectra profiles of each chemical species involved in the reaction. The performance of the model was assessed by two parameters: alternating least squares lack of fit (lof = 1.67 %) and explained variance ( R2 = 99.68%). The recovered spectra of the generated products have the characteristic bands associated with the two postulated reactions.

Selective hydrogenation of amides using Rh/Mo catalysts

Rh/Mo catalysts formed in situ from Rh 6(CO) 16 and Mo(CO) 6 are effective for the liquid phase hydrogenation of CyCONH 2 to CyCH 2NH 2 in up to 87% selectivity, without the requirement for ammonia to inhibit secondary amine formation. Use of in situ HP-FTIR spectroscopy has shown that decomposition of metal carbonyl precursors occurs during an extended induction period, with the generation of recyclable, heterogeneous, bimetallic catalysts. Variations in Mo:Rh content have revealed significant synergistic effects on catalysis, with optimum performance at values of ca. 0.6, and substantially reduced selectivities at ⩾1. Good amide conversions are noted within the reaction condition regimes 50–100 bar H 2 and 130–160 °C. Ex situ characterization of the catalysts, using XRD, XPS and EDX-STEM, has provided evidence for intimately mixed (ca. 2–4 nm) particles that contain metallic Rh and reduced Mo oxides, together with MoO 3. Silica-supported Rh/Mo analogues, although active, perform poorly at <150 °C and deactivate during recycle.