Cyclopentadienyl Ru<sup>II</sup> Complexes as Highly Efficient Catalysts for the <i>N</i>‐Methylation of Alkylamines by Methanol

Zotto, Alessandro Del; Baratta, Walter; Sandri, Mauro; Verardo, Giancarlo; Rigo, Pierluigi

doi:10.1002/ejic.200300518

Cited by 105 publications

(47 citation statements)

References 38 publications

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“…Most of them required very high reaction temperatures and the scope of applicable substrates was rather limited. To the present day, catalytic systems employing ruthenium, [7] rhodium, [8] platinum [9] and iridium, [8,10,11] complexes have been reported for the alkylation of primary amines with alcohols. In the last few years, research has mainly been focussed on ruthenium-catalyzed N-alkylation reactions and has helped to extend the applicability of this reaction towards a broad range of substrates.…”

Section: Introductionmentioning

confidence: 99%

An Efficient Method for the Selective Iridium‐Catalyzed Monoalkylation of (Hetero)aromatic Amines with Primary Alcohols

2008

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An efficient multi-gram scale synthesis protocol of a variety of P,N ligands is described. The synthesis is achieved in a two-step reaction. First, the amine is deprotonated and subsequently the chlorophosphine is added to yield the corresponding P,N ligand. Deprotonation of the amine is normally achieved with n-BuLi at low temperature, but for the preparation of ligands with a 2,2'-dipyridylamino backbone and phosphines with a high steric demand KH has to be employed in combination with reaction temperatures of 110 8C for the salt metathesis step. The reaction of two equivalents of a selected P,N ligand with one equivalent of the iridium complex [IrClA C H T U N G T R E N N U N G (cod)] 2 (cod = 1,5-cyclooctadiene) affords P,N ligand-coordinated iridium complexes in quantitative yield. X-Ray single crystal structure analysis of one of these complexes reveals a monomeric five-coordinated structure in the solid state. The iridium complexes were used to form catalysts for the N-alkylation of aromatic amines with alcohols. The catalyst system was optimized by studying 8 different P,N ligands, 9 different solvents and 14 different bases. Systematic variation of the substrate to base and the amine to alcohol ratios as well as the catalyst loading led to optimized catalytic reaction conditions. The substrate scope of the developed catalytic protocol was shown by synthesizing 20 different amines of which 12 could be obtained in isolated yields higher than 90%. A new efficient catalyst system for the selective monoalkylation of primary aromatic and heteroaromatic amines with primary aromatic, heteroaromatic as well as aliphatic alcohols has been established. The reaction proceeds with rather moderate catalyst loadings.

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Section: Introductionmentioning

confidence: 99%

An Efficient Method for the Selective Iridium‐Catalyzed Monoalkylation of (Hetero)aromatic Amines with Primary Alcohols

2008

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“…[12][13][14] Unfortunately, these methods are oen problematic from synthetic or environmental standpoints. A few catalytic systems [21][22][23][24] have been specially developed for the N-methylation of amines and nitro compounds using CH 3 OH as methylating reagent but they still require high temperatures and high pressures. Recently, considerable attentions had been paid on the N-alkylation of amines with alcohols as the alkylation reagents.…”

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confidence: 99%

Light-promoted N,N-dimethylation of amine and nitro compound with methanol catalyzed by Pd/TiO₂ at room temperature

Zhang

Deng

et al. 2015

RSC Adv.

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A series of TiO 2 supported nano-Pd catalysts (Pd/TiO 2 ) were prepared and used for the N,N-dimethylation of different amines and nitro compounds with methanol under UV irradiation at room temperature. A wide range of N,N-dimethyl amines were one-pot synthesized with up to 98% by applying aliphatic secondary amines, aromatic primary amines, aliphatic primary amines and aromatic nitro compounds as starting materials. It is noteworthy that up to 90% yield of 4-chloro-N,N-dimethylaniline was obtained by adjusting the Pd loadings on the TiO 2 and the dehalogenation reaction was inhibited. Finally, a reaction mechanism is discussed, involving PhN ¼ CH 2 and PhNHCH 3 as reaction intermediates.

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“…This effect fairly contrasts with that observed by using [RuCl(Cp)A C H T U N G T R E N N U N G (PPh 3 ) 2 ] complex as the catalyst: in fact, Del Zotto suggested in the N-methylation of amines the simultaneous dissociation of both phosphine and chloride in methanol and this was inferred from the slowing down effect of added chloride on the reaction rate. [15] The opposite effect observed in our case may be attributed to the higher polarity of the reaction medium in the presence of the ammonium salt. As a further comment on the mechanism, the effect of increasing the initial EDA concentration on its rate of disappearance is rather complex, so that, for example, maintaining constant…”

Section: Resultsmentioning

confidence: 73%

“…Remarkably, the presence of electronwithdrawing substituents in the olefin does not preclude by itself its reactivity towards diazo derivatives when using our catalyst (see also above). In fact, runs [14][15][16][17][18][19] show that a series of cyano olefins reacts very selectively with monoand diaryl diazo compounds to give mostly cyclization products, drastically minimizing also the product of diazo coupling. It seems that the cyano group can very efficiently coordinate to the metal centre, thereby favouring the formation of the crucial metallocyclic intermediate.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

Reactions of Diazo Compounds with Alkenes Catalysed by [RuCl(cod)(Cp)]: Effect of the Substituents in the Formation of Cyclopropanation or Metathesis Products

Basato

Tubaro

Biffis

et al. 2009

Chemistry A European J

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The reaction of diazo compounds with alkenes catalysed by complex [RuCl(cod)(Cp)] (cod = 1,5-cyclooctadiene, Cp = cyclopentadienyl) has been studied. The catalytic cycle involves in the first step the decomposition of the diazo derivative to afford the reactive [RuCl(Cp){=C(R(1))R(2)}] intermediate and a mechanism is proposed for this step based on a kinetic study of the simple coupling reaction of ethyl diazoacetate. The evolution of the Ru-carbene intermediate in the presence of alkenes depends on the nature of the substituents at both the diazo N(2)=C(R(1))R(2) (R(1), R(2) = Ph, H; Ph, CO(2)Me; Ph, Ph; C(R(1))R(2) = fluorene) and the olefin substrates R(3)(H)C=C(H)R(4) (R(3), R(4) = CO(2)Et, CO(2)Et; Ph, Ph; Ph, Me; Ph, H; Me, Br; Me, CN; Ph, CN; H, CN; CN, CN). A remarkable reactivity of the complex was recorded, especially towards unstable aryldiazo compounds and electron-poor olefins. The results obtained indicate that either cyclopropanation or metathesis products can be formed: the first products are favoured by the presence of a cyano substituent at the double bond and the second ones by a phenyl.

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Cyclopentadienyl Ru^II Complexes as Highly Efficient Catalysts for the N‐Methylation of Alkylamines by Methanol

Cited by 105 publications

References 38 publications

An Efficient Method for the Selective Iridium‐Catalyzed Monoalkylation of (Hetero)aromatic Amines with Primary Alcohols

An Efficient Method for the Selective Iridium‐Catalyzed Monoalkylation of (Hetero)aromatic Amines with Primary Alcohols

Light-promoted N,N-dimethylation of amine and nitro compound with methanol catalyzed by Pd/TiO₂ at room temperature

Reactions of Diazo Compounds with Alkenes Catalysed by [RuCl(cod)(Cp)]: Effect of the Substituents in the Formation of Cyclopropanation or Metathesis Products

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Cyclopentadienyl RuII Complexes as Highly Efficient Catalysts for the N‐Methylation of Alkylamines by Methanol

Cited by 105 publications

References 38 publications

An Efficient Method for the Selective Iridium‐Catalyzed Monoalkylation of (Hetero)aromatic Amines with Primary Alcohols

An Efficient Method for the Selective Iridium‐Catalyzed Monoalkylation of (Hetero)aromatic Amines with Primary Alcohols

Light-promoted N,N-dimethylation of amine and nitro compound with methanol catalyzed by Pd/TiO2 at room temperature

Reactions of Diazo Compounds with Alkenes Catalysed by [RuCl(cod)(Cp)]: Effect of the Substituents in the Formation of Cyclopropanation or Metathesis Products

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Cyclopentadienyl Ru^II Complexes as Highly Efficient Catalysts for the N‐Methylation of Alkylamines by Methanol

Light-promoted N,N-dimethylation of amine and nitro compound with methanol catalyzed by Pd/TiO₂ at room temperature