- Efficient methylation of anilines with methanol catalysed by cyclometalated ruthenium complexes
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Cyclometalated ruthenium complexes4-10allow the effective methylation of anilines with methanol to selectively giveN-methylanilines. This hydrogen autotransfer procedure proceeds under mild conditions (60 °C) in a practical manner (NaOH as base). Mechanistic investigations suggest an active homogenous ruthenium complex and β-hydride elimination of methanol as the rate determining step.
- Piehl, Patrick,Amuso, Roberta,Spannenberg, Anke,Gabriele, Bartolo,Neumann, Helfried,Beller, Matthias
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p. 2512 - 2517
(2021/04/22)
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- Simple RuCl3-catalyzed N-Methylation of Amines and Transfer Hydrogenation of Nitroarenes using Methanol
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Methanol is a potential hydrogen source and C1 synthon, which finds interesting applications in both chemical synthesis and energy technologies. The effective utilization of this simple alcohol in organic synthesis is of central importance and attracts scientific interest. Herein, we report a clean and cost-competitive method with the use of methanol as both C1 synthon and H2 source for selective N-methylation of amines by employing relatively cheap RuCl3.xH2O as a ligand-free catalyst. This readily available catalyst tolerates various amines comprising electron-deficient and electron-donating groups and allows them to transform into corresponding N-methylated products in moderate to excellent yields. In addition, few marketed pharmaceutical agents (e. g., venlafaxine and imipramine) were also successfully synthesized via late-stage functionalization from readily available feedstock chemicals, highlighting synthetic value of this advanced N-methylation reaction. Using this platform, we also attempted tandem reactions with selected nitroarenes to convert them into corresponding N-methylated amines using MeOH under H2-free conditions including transfer hydrogenation of nitroarenes-to-anilines and prepared drug molecules (e. g., benzocaine and butamben) as well as key pharmaceutical intermediates. We further enable one-shot selective and green syntheses of 1-methylbenzimidazole using ortho-phenylenediamine (OPDA) and methanol as coupling partners.
- Sarki, Naina,Goyal, Vishakha,Tyagi, Nitin Kumar,Puttaswamy,Narani, Anand,Ray, Anjan,Natte, Kishore
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p. 1722 - 1729
(2021/04/19)
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- Tandem Transformation of Aldoximes to N-Methylated Amides Using Methanol
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Tandem conversion of aldoximes to N-methylated amides with methanol in presence of a single Ru(II) catalyst is accomplished through the Ru(II)-mediated rearrangement followed by the reductive N-methylation. Employing this protocol, several aldoximes were directly transformed to the N-methylated amides using methanol. Kinetic experiments with H218O advocated that the aldoxime is acted as the nucleophile during the aldoxime to amide rearrangement process. Involvement of nitrile intermediate during this transformation is realized from the kinetic study. (Figure presented.).
- Paul, Bhaskar,Maji, Milan,Panja, Dibyajyoti,Kundu, Sabuj
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supporting information
p. 5357 - 5362
(2019/11/14)
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- Ruthenium-Catalyzed Synthesis of N-Methylated Amides using Methanol
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An efficient synthesis of N-methylated amides using methanol in the presence of a ruthenium(II) catalyst is realized. Notably, applying this process, tandem C-methylation and N-methylation were achieved to synthesize α-methyl N-methylated amides. In addition, several kinetic studies and control experiments with the plausible intermediates were performed to understand this novel protocol. Furthermore, detailed computational studies were carried out to understand the mechanism of this transformation.
- Paul, Bhaskar,Panja, Dibyajyoti,Kundu, Sabuj
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supporting information
p. 5843 - 5847
(2019/08/26)
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- Highly Selective N-Monomethylanilines Synthesis from Nitroarene and Formaldehyde via Kinetically Excluding of the Thermodynamically Favorable N,N-Dimethylation Reaction
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The synthesis of N-monomethylamine remains a challenging topic because the N,N-dimethylation reaction is thermodynamically favorable. In this work, the kinetically controlled N-monomethylamine synthesis from nitroarene and paraformaldehyde/H2 is reported to have superhigh N-monomethylamine selectivity in the presence of a Pd/TiO2 catalyst. The superior selectivity should be attributed to the preferential adsorption of the primary amine over N-monomethylamine on the Pd/TiO2 surface, as elucidated by NH3/Me2NH-TPD, while the excellent catalytic activity could be associated with the good H2 activation ability and high amine adsorbing capacity of the catalyst, as elucidated by NH3-TPD and H2-TPR tests. Good results were obtained with a variety of nitroarenes containing methyl, methoxyl, hydroxyl, fluoride, trifluoromethyl, ester, and amide substituents as starting materials, and the potential synthetic utility of this protocol in pharmaceutical is illustrated by N-monomethylation of drug molecules, such as clinidipine, nimesulide, procaine, and methyl aminosalicylate.
- Wang, Hongli,Yuan, Hangkong,Yang, Benqun,Dai, Xingchao,Xu, Shan,Shi, Feng
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p. 3943 - 3949
(2018/05/23)
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- Acetic Acid Accelerated Visible-Light Photoredox Catalyzed N-Demethylation of N,N-Dimethylaminophenyl Derivatives
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N,N-Dimethylaminophenyl moiety is a common fragment in medicinal chemistry as several pharmaceuticals bearing this privileged motif are on the market and under clinical evaluation. Oxidative N-demethylation is generally regarded as the major metabolic pathway. However, pharmacokinetics, metabolites studies as well as the further structural modification are precluded by the impracticality of chemical synthesis. Here we report that acetic acid can significantly accelerate visible-light photoredox catalyzed N-demethylation of N,N-dimethylaminophenyl derivatives. This approach is easy for large scale reaction and even for potential industrial manufacture. (Figure presented.).
- Wu, Guolin,Li, Yazhen,Yu, Xuemei,Gao, Yu,Chen, Haijun
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supporting information
p. 687 - 692
(2017/02/23)
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- Improved and General Manganese-Catalyzed N-Methylation of Aromatic Amines Using Methanol
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A novel lutidine-based manganese PNP-pincer complex has been synthesized for the selective N-methylation of aromatic amines with methanol. Using borrowing hydrogen methodology, a selection of differently functionalized aniline derivatives is selectively methylated in good yields.
- Neumann, Jacob,Elangovan, Saravanakumar,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
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supporting information
p. 5410 - 5413
(2017/04/27)
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- Mono-N-methylation of anilines with methanol catalyzed by a manganese pincer-complex
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The selective mono-N-methylation of anilines derivatives was achieved under mild conditions using inexpensive methanol as C1 source. Under hydrogen borrowing conditions, using a tridentate PN3P manganese pre-catalyst (5?mol%), a catalytic amount of base (20?mol%), for 24?h at 120?°C, a large variety of anilines derivatives was methylated in good to excellent yield. Mechanistic investigations allowed us to isolate and characterize by X-ray diffraction studies a de-aromatized manganese intermediate.
- Bruneau-Voisine, Antoine,Wang, Ding,Dorcet, Vincent,Roisnel, Thierry,Darcel, Christophe,Sortais, Jean-Baptiste
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- Efficient ruthenium-catalyzed N-methylation of amines using methanol
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An in situ-generated complex from [RuCpCl2]2 and dpePhos ligand is reported as an efficient catalyst in the presence of 5 mol % of LiOtBu for the N-methylation of amines using methanol as the methylating agent at moderate conditions, following hydrogen borrowing strategy. This simple catalyst system provides selective N-monomethylation of substituted primary anilines and sulfonamides as well as N,N dimethylation of primary aliphatic amines in excellent yields at 40-100 °C with good tolerance to reducible functional groups. The catalytic intermediate CpRu(dpePhos)H was isolated and was shown to be active for methylation in the absence of base.
- Dang, Tuan Thanh,Ramalingam, Balamurugan,Seayad, Abdul Majeed
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p. 4082 - 4088
(2015/11/11)
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- Aminocarbonylation of (Hetero)aryl bromides with ammonia and amines using a palladium/dalphos catalyst system
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Variants of the DalPhos [2-aminophenylbisadamantyl)phosphine] ligand family were examined in a palladium-catalyzed carbonylative amination reaction using inexpensive carbon monoxide and ammonia as reagents. As a result of this survey, the Pyr-DalPhos ligand was identified as being effective for the selective aminocarbonylation of aryl bromides with ammonia, as well as primary and secondary alkylamines. A variety of primary aromatic, heteroaromatic and N-substituted benzamides were formed in moderate to good yields. As part of this study, a (Mor-DalPhos)Pd-benzoyl complex was prepared and crystallographically characterized, thereby showing the viability of the carbonyl insertion step. Copyright
- Alsabeh, Pamela G.,Stradiotto, Mark,Neumann, Helfried,Beller, Matthias
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supporting information
p. 3065 - 3070
(2013/01/15)
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- Mono-N-methylation of functionalized anilines with alkyl methyl carbonates over NaY faujasites. 4. Kinetics and selectivity
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(Chemical Equation Presented) In the presence of NaY faujasite as the catalyst, the reaction of bifunctional anilines (1-4: XC6H 4-NH2; X = OH, CO2H, CH2OH, and CONH2) with methyl alkyl carbonates [MeOCO2R′: R′ = Me or MeO(CH2)2O(CH2)2] proceeds with a very high mono-N-methyl selectivity (XC6H 4NHMe up to 99%), and chemoselectivity as well, with other nucleophilic functions (OH, CO2H, CH2OH, CONH2) fully preserved from alkylation and/or transesterification reactions. Aromatic substituents, however, modify the relative reactivity of amines 1-4: good evidence suggests that, not only steric and electronic effects, but, importantly, direct acid-base interactions between substituents and the catalyst are involved. Weakly acidic groups (OH, CH2OH, CONH2, pKa ≥ 10) may help the reaction, while aminobenzoic acids (pK a of 4-5) are the least reactive substrates. The solvent polarity also affects the reaction, which is faster in xylene than in the more polar diglyme. The mono-N-methyl selectivity is explained by the adsorption pattern of reagents within the zeolite pores: a BAl2 displacement of the amine on methyl alkyl carbonate should occur aided by the geometric features of the NaY supercavities. Different factors account for the reaction chemoselectivity. Evidence proves that the polarizability of the two nucleophilic terms (NH 2 and X groups) of anilines is relevant, although adsorption and confinement phenomena of reagents promoted by the zeolite should also be considered.
- Selva, Maurizio,Tundo, Pietro,Foccardi, Tommaso
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p. 2476 - 2485
(2007/10/03)
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- Synthesis of mono-N-substituted functionalized anilines
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The present invention relates to a process for direct and selective synthesis of mono-N-substituted functionalized anilines by using alkylating agents selected from the class of organic carbonates, preferably of the dialkyl, dibenzyl and diallyl types, in the presence of suitable catalysts that are chemically related to the class of aluminosilicates.
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- Synthesis of mono-N-substituted functionalized anilines
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The present invention relates to a process for direct and selective synthesis of mono-N-substituted functionalized anilines by using alkylating agents selected from the class of organic carbonates, preferably of the dialkyl, dibenzyl and diallyl types, in the presence of suitable catalysts that are chemically related to the class of aluminosilicates.
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- Reaction of functionalized anilines with dimethyl carbonate over NaY faujasite. 3. Chemoselectivity toward mono-N-methylation
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In the presence of NaY faujasite, dimethyl carbonate (MeOCO2Me, DMC) is a highly chemoselective methylating agent of functionalized anilines such as aminophenols (1), aminobenzyl alcohols (2), aminobenzoic acids (3), and aminobenzamides (4). The reaction proceeds with the exclusive formation of N-methylanilines without any concurrent O-methylation or N-/O-methoxy carbonylation side processes. Particularly, only mono-N-methyl derivatives [XC6H4NHMe, X = o-, m-, and p-OH; o- and p-CH 2OH; o- and P-CO2H; o- and p-CONH2] are obtained with selectivity up to 99% and isolated yields of 74-99%. DMC, which usually promotes methylations only at T > 120 °C, is activated by the zeolite catalyst and it reacts with compounds 1, 2, and 4, at 90 °C. Aminobenzoic acids (3) require a higher reaction temperature (≥130 °C).
- Selva, Maurizio,Tundo, Pietro,Perosa, Alvise
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p. 7374 - 7378
(2007/10/03)
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