Mechanistic studies on the <i>N</i>-alkylation of amines with alcohols catalysed by iridium(<scp>i</scp>) complexes with functionalised N-heterocyclic carbene ligands

Jiménez, M. Victoria; Fernández-Tornos, Javier; González-Lainez, Miguel; Sánchez-Page, Beatriz; Modrego, F. Javier; Oro, Luis A.; Pérez‐Torrente, Jesús J.

doi:10.1039/c7cy02488f

Cited by 32 publications

(19 citation statements)

References 96 publications

(36 reference statements)

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“…In accordance with the previous reports, [ 18,27,65,66 ] a plausible mechanism for the N‐ alkylation of amines with alcohols is proposed as shown in Scheme 3. The reaction initiated by the formation of I , which is formed via the elimination of HCl.…”

Section: Resultssupporting

confidence: 89%

Thiazoline‐Iridium (III) Complexes and Immobilized Nanomaterials as Selective Catalysts in N‐Alkylation of Amines with Alcohols

Denizalti

Dayan

Günnaz

et al. 2020

Applied Organom Chemis

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In this research, a new series of thiazoline‐iridium (III) complexes (4–7) derived from cysteine were prepared and fully characterized by conventional methods. The molecular structure of complex 5 was also determined by single‐crystal X‐ray diffraction. These complexes were evaluated as catalysts for hydrogen‐borrowing reactions of amines with alcohols. In particular, complex 5 showed the best activity as catalyst. Various amines have been alkylated with alcohols affording moderate to good yield (33–99%). Moreover, the immobilized nanomaterials (M1,2) were fabricated by sonication process from the best catalyst 5 with the multi‐walled carbon nanotubes (MWCNTs) and graphene oxide (GO), respectively, and characterized by X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) spectroscopy, field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray (EDX) spectroscopy, and inductively coupled plasma‐mass spectrometry (ICP‐MS). The M1,2 nanomaterials were also tested as catalysts in model catalytic reaction for N‐alkylation. The M1 nanomaterial showed significantly higher activity than the M2 nanomaterial. The M1 catalyst was recovered by filtration and reused for four catalytic cycles with high conversion (99%, 97%, 96%, and 86%).

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Section: Resultssupporting

confidence: 89%

Thiazoline‐Iridium (III) Complexes and Immobilized Nanomaterials as Selective Catalysts in N‐Alkylation of Amines with Alcohols

Denizalti

Dayan

Günnaz

et al. 2020

Applied Organom Chemis

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“…[ 53–55 ] Other authors have reported that this process is more favored by water [ 56 ] or alcohols [ 57 ] than by some metallic species. In contrast, other theoretical [ 21,58,59 ] and experimental [ 21 ] studies indicate that the condensation step takes place in the coordination sphere of the catalyst. In order to delve this question, we monitored by 1 H NMR the reaction of benzaldehyde and p ‐toluidine in a molar ratio 2:1 in TFE media in the absence of catalyst, and we found that this reaction was completed at room temperature in 5 min (see Figure S11).…”

Section: Resultsmentioning

confidence: 88%

“…The condensation reaction is promoted by acidic species and except in a few cases does not involve the participation of the metallic catalyst. [ 21 ] Nevertheless, the BH methodology requires the participation of metal complexes able to promote processes I and III. [ 22,23 ] During the last years, several groups have contributed to the development of this strategy with metal complexes, mainly of Ir, including highly active iridacyles, [ 13 ] Rh and Ru, [ 21,24–28 ] as well as other transition metals [ 29,30 ] and heterogeneous systems, [ 31–33 ] Catalysts active even in water and ionic liquids [ 34 ] or in solvent‐free conditions [ 35 ] have been reported, but the majority of catalysts are used in organic solvent media.…”

Section: Introductionmentioning

confidence: 99%

“…The ligands used in the metal complexes for BH processes are diverse although classical ligands such as phosphines are very common and half‐sandwich complexes with Cp or arene ligands are also used frequently. [ 17 ] NHC ligands, [ 21,42 ] or diamido ligands, [ 43 ] such as those developed by Noyori and Ikariya, have been reported as well. The derivative 5‐(pyridin‐2‐ylmethylene)hydantoin (Hpyhy) (see Scheme 2) has the appropriate conformation to form stable chelate complexes with transition metals, and, in fact, it has been used as proligand to synthesize nickel and copper complexes.…”

Section: Introductionmentioning

confidence: 99%

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Iridium complexes with a new type of N^N′‐donor anionic ligand catalyze the N‐benzylation of amines via borrowing hydrogen

Ruiz‐Castañeda

Rodrı́guez

Aboo

et al. 2020

Applied Organom Chemis

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The development of efficient and eco‐friendly methods for the synthesis of elaborate amines is highly desired as they are valuable chemicals. The catalytic alkylation of amines using alcohols as alkylating agents, through the so‐called borrowing hydrogen process, satisfies several of the principles of green chemistry. In this paper, four neutral half‐sandwich complexes of Ru(II), Rh(III), and Ir(III) have been synthesized and tested as catalysts in the N‐benzylation of amines with benzyl alcohol. The new derivatives contain a N^N′ anionic ligand derived from 5‐(pyridin‐2‐ylmethylene)hydantoin (Hpyhy) that has never been tested in metal complexes with catalytic applications. In particular, the Ir derivatives, [(Cp*)IrX(pyhy)] (X = Cl or H), exhibit high activity along with good selectivity in the process. Indeed, the scope of the optimized protocol has been proved in the benzylation of several primary and secondary amines. The selectivity towards monoalkylated or dialkylated amines has been tuned by adjusting the amine:alcohol ratio and the reaction time. Experimental results support a mechanism consisting of three consecutive steps, two of which are Ir catalyzed, and a favorable condensation step without the assistance of the catalyst. Moreover, an unproductive competitive pathway can operate when the reaction is performed in open‐air vessels, due to the irreversible release of H2. This route is hampered when the reaction is carried out in close vessels, likely because the release of H2 is reversed through metal‐based heterolytic cleavage. From our viewpoint, these results show the potential of the new catalysts in a very attractive and promising methodology for the synthesis of amines.

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“…N‐alkylation of aniline with benzyl alcohol was, initially, chosen as a model reaction (Figure 7), to examine the catalytic activity of Ir−PPy NPs.The results of the tests carried out by using the catalyst in the presence of different bases, and with bases or PPy alone, are reported for comparison in Table 1 and Table 2, Figures 8 and 10 and Figures S1–S11. The data show that the kinetic of imine formation is faster than that of hydrogenation to the secondary amine [13d] . In particular, in Table 1 and Table 2 the results of the tests performed with benzyl alcohol (1 mmol), aniline (1 mmol), catalyst (25 mg at 2 wt.% Ir), base (2 mmol), toluene (5 mL), at 100 °C and under N 2 were shown after 12 and 24 hours, respectively.…”

Section: Resultsmentioning

confidence: 94%

Easy and One‐Step Synthesis of Ir Single Atom Doped PPy Nanoparticles for Highly Active N‐Alkylation Reaction

et al. 2021

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Single atoms are nowadays considered new catalysts offering a lot of advantages such as reduced cost and use of noble metals. Here, we report the catalytic activity towards N‐alkylation reactions of single atoms (SACs) of iridium doped polypyrrole (Ir−PPy nanoparticles). The new nanocatalyst exhibits excellent behavior due to the combination of highly active SACs catalyst and the organic conductive support providing strong binding of single atoms and thus improved reusability and easiness to handle. In the presence of a low amount of Ir and of a suitable base, excellent activity (yield >99 %) and selectivity (>99 %) were obtained. In the optimized Ir condition (3 wt.% of Ir) an aniline conversion of about 99 %, with excellent selectivity, just after 600 min, was obtained. Recyclability tests show that the catalyst can be successfully recycled six times without significant catalyst activity loss.

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Mechanistic studies on the N-alkylation of amines with alcohols catalysed by iridium(i) complexes with functionalised N-heterocyclic carbene ligands

Abstract: Experimental and theoretical studies give support for an iridium-catalyzed C–N bond formation.

Cited by 32 publications

References 96 publications

Thiazoline‐Iridium (III) Complexes and Immobilized Nanomaterials as Selective Catalysts in N‐Alkylation of Amines with Alcohols

Thiazoline‐Iridium (III) Complexes and Immobilized Nanomaterials as Selective Catalysts in N‐Alkylation of Amines with Alcohols

Iridium complexes with a new type of N^N′‐donor anionic ligand catalyze the N‐benzylation of amines via borrowing hydrogen

Easy and One‐Step Synthesis of Ir Single Atom Doped PPy Nanoparticles for Highly Active N‐Alkylation Reaction

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