Methylation Of Amines Research Articles

Targeted valorization of waste polycarbonate into bisphenol A dimethyl ether

The chemical recycling of waste polycarbonate (PC) plastic to produce high value-added chemicals represents a sustainable and economical approach to its management. Facile methods that utilize the unique structure of the bisphenol A (BPA) unit are expected to be more low-carbon and cost-effective. However, there are few established routes for converting BPA into valuable derivatives while preserving its structure. In this work, we developed a new pathway for the targeted valorization of PC waste into a multifunctional value-added chemical, bisphenol A dimethyl ether (BPAME). Using ionic liquids as catalysts, low-toxicity and environmentally friendly dimethyl carbonate (DMC) as a methyl source, and N-methylpyrrolidone as a co-solvent, we successfully achieved 100 % depolymerization of PC and an impressive 99 % yield of BPAME under mild conditions (150 °C, 6 h). Kinetic studies indicated that the methylation of BPA is the rate-determining step. Moreover, this innovative pathway not only transformed commercial PC waste into BPAME with exceptional selectivity (99 %) and high yield (≥92 %), but also facilitated the efficient methylation of aromatic phenols and amines. This valorization strategy for PC waste disposal offers a promising option for industrial applications.

Polyoxymethylene Upcycling into Methanol and Methyl Groups Catalyzed by a Manganese Pincer Complex.

Polyoxymethylene (POM) is a commonly used engineering thermoplastic, but its recycling by conventional means, i.e., mechanical recycling, is not practiced to any meaningful extent, due to technical limitations. Instead, waste POM is typically incinerated or disposed in landfills, where it becomes a persistent environmental pollutant. An attractive alternative to mechanical recycling is upcycling, namely, the conversion of waste POM into value-added chemicals, but this has received very little attention. Herein, we report the upcycling of POM into useful chemicals through three different reactions, all of which are efficiently catalyzed by a single pincer complex of earth-abundant manganese. One method involves hydrogenation of POM into methanol using H2 gas as the only reagent, whereas another method converts POM into methanol and CO2 through a one-pot process comprising acidolysis followed by Mn-catalyzed disproportionation. The third method utilizes POM as a reagent for the methylation of ketones and amines.

“Anion-Switchable” Pincer-Mn(I) Catalyst for the Reductive N-Methylation of Amines with Formic Acid and CO2

“Anion-Switchable” Pincer-Mn(I) Catalyst for the Reductive <i>N</i>-Methylation of Amines with Formic Acid and CO₂

First row transition metal catalyzed small molecule activation for sustainable organic transformation: Synergy between nature and chemist’s toolbox

In this review we have tried to present our view on the synergy between nature and chemists’ toolbox toward discovery of new reactions. Toward the search for new chemical reactivity, not only chemists learn from nature but nature’s evolutionary pathway perhaps has footprints of chemist’s innovative discoveries and beyond. Taking CO2 as a representative example of an abundant energy rich small molecule resource, we have tried to explore the probable strategies of activating the molecule using first row transition metal catalysts for sustainable organic transformation. Our study has tried to unfold nature’s strategy of CO2 activation and recycling which eventually motivated chemists toward discovery of new chemical reactions and further inspired to expand their toolbox for discovering new reactivities beyond the natural enzyme repertoire. The basic chemical CO2 activation strategy which have been focused in this review are using CO2 as a C1 building block in organic synthesis; catalytic reductive formylation and methylation of amines; carboxylation reactions via CO2 insertion. Additionally, carbonylation reactions with CO2 as CO surrogate has also been discussed. The focus of this review is to correlate nature’s chemical strategies with chemist’s approach to understand the concept involved in the chemical activation and utilization process of CO2 for unlocking new reaction paradigm, both for chemists’ and for nature’s catalytic repertoire.

One-pot two-step reduction of CO2 with amines and NaBH4 to N-substituted compounds at atmospheric pressure

In this paper, the reductive N-formylation, methylation and cyclization of amines with carbon dioxide (CO2) using sodium borohydride (NaBH4) at atmospheric pressure, via a one-pot two-step procedure, is presented. Formato borohydride (NaBHn(OCHO)4-n), in situ formed in the reaction of NaBH4 with CO2, as an efficient agent to promote the corresponding reaction, and the mechanism is proposed on the basis of experiments. This wide substrate scope and simple operational methodology also facilitates the effective synthesis of formamides, methylamines, benzimidazoles and other heterocyclic compounds avoiding high temperature and pressure.

Simplified Version of the Eschweiler-Clarke Reaction.

The traditional Eschweiler-Clarke reaction is a three-component process involving formaldehyde, amine, and formic acid. In this work, we showed that the reductive potential of formaldehyde was sufficient to provide methylation of secondary amines in the absence of acidic additives. Various acid-sensitive moieties remain intact under developed conditions. The scalability of the elaborated approach was shown for several products. Synthesis of the antifungal agent butenafine demonstrated the preparative utility of the developed approach.

Modeling Amine Methylation in Methyl Ester Cavitand.

Methylation of amines inside an introverted resorcinarene-based deep methyl ester cavitand is investigated by means of molecular dynamics simulations and quantum chemical calculations. Experimentally, the cavitand has been shown to bind a number of amines and accelerate the methylation reaction by more than four orders of magnitude for some of them. Eight different amines are considered in the present study, and the geometries and energies of their binding to the cavitand are first characterized and analyzed. Next, the methyl transfer reactions are investigated and the calculated barriers are found to be in generally good agreement with experimental results. In particular, the experimentally-observed rate acceleration in the cavitand as compared to the solution reaction is well reproduced by the calculations. The origins of this rate acceleration are analyzed by computational modifications made to the structure of the cavitand, and the role of the solvent is discussed.

Tuneable reduction of CO2 – organocatalyzed selective formylation and methylation of amines

The selective N-formylation and N-methylation of amines with carbon dioxide (CO2) catalyzed by methyltriphenylphosphonium methylcarbonate and tuned by polymethylhydrosiloxane or trimethoxysilane as reducing agents is reported.

Quantitative Peptidomics Using Reductive Methylation of Amines.

A number of different approaches have been used for quantitative peptidomics. In this protocol, we describe the method in which peptides are reacted with formaldehyde and sodium cyanoborohydride, which converts primary and secondary amines into tertiary amines. By using different combinations of regular reagents, deuterated reagents (2H), and reagents containing deuterium and 13C, it is possible to produce five isotopically distinct forms of the methylated peptides, which can be quantified by mass spectrometry. Peptides with free N-termini that are primary amines incorporate two methyl groups using this procedure, which differ by 2Da for each of the five isotopic combinations. Peptides that contain unmodified lysine residues incorporate additional pairs of methyl groups, leading to larger mass differences between isotopic forms. The reagents are commercially available, relatively inexpensive, and chemically stable.

Tuning and Coupling Irreversible Electroosmotic Water Flow in Ionic Diodes: Methylation of an Intrinsically Microporous Polyamine (PIM-EA-TB).

Molecularly rigid polymers with internal charges (positive charges induced by amine methylation) allow electroosmotic water flow to be tuned by adjusting the charge density (the degree of methylation). Here, a microporous polyamine (PIM-EA-TB) is methylated to give a molecularly rigid anion conductor. The electroosmotic drag coefficient (the number of water molecules transported per anion) is shown to increase with a lower degree of methylation. Net water transport (without charge flow) in a coupled anionic diode circuit is demonstrated based on combining low and high electroosmotic drag coefficient materials. The AC-electricity-driven net process offers water transport (or transport of other neutral species, e.g., drugs) with net zero ion transport and without driver electrode side reactions.

Selective mono-N-methylation of amines using methanol as a methylating reagent over heterogeneous Ni catalysts

Mixed oxide (ZnAlOx) supported heterogeneous Ni nanoparticle catalysts (Ni/ZnAlOx-600) for the direct synthesis of mono-N-methylamines from amines and methanol.

DIC–borane-catalyzed selective methylation of primary amines with CO2 using boranes as reducing agents

The highly selective N-methylation and N,N-dimethyaltion of primary amines using 1 atm CO2 in the presence of DIC-BH3∙piperazine and DIC-BH3∙NMe3 catalytic systems, respectively, were developed.

N-Methylation of Amines with Methanol Catalyzed by Iridium(I) Complexes Bearing an N,O-Functionalized NHC Ligand

A set of neutral [IrBr(L2)(κC-tBuImCH2PyCH2OMe)] and cationic [Ir(L2)(κ2C,N-tBuImCH2PyCH2OMe)]PF6 (L2 = cod, (CO)2) Ir(I) compounds featuring a flexible lutidine-derived polydentate ligand having NHC and −OMe as donor functions have been evaluated as catalyst precursors for the N-methylation of aniline using methanol both as a reducing agent and a C1 source. The carbonyl complexes are somewhat more active than the related diene compounds with the neutral compound [IrBr(CO)2(κC-tBuImCH2PyCH2OMe)] being the more active. A range of aromatic primary amines, including heterocyclic amines, have been selectively transformed into the corresponding N-methylamino derivatives using this catalyst at a low catalyst loading (0.1 mol %) and substoichiometric amounts of Cs2CO3 (half equiv) as a base, in methanol at 423 K. For aliphatic primary amines, selective N,N-dimethylation was achieved under the same catalytic conditions. The unselective deprotonation of the methylene linkers in [IrBr(CO)2(κC-tBuImCH2PyCH2OMe)] affords two isomeric neutral complexes featuring a coordinated dearomatized pyridine core, which were converted into [Ir(OMe)(CO)2(κC-tBuImCH2PyCH2OMe)] upon addition of methanol. This compound undergoes thermal activation of a C–H bond of the tert-butyl group to give the cyclometalated iridium(I) complex [Ir(CO)2{κ2C,C-(-CH2Me2C-ImCH2PyCH2OMe)}] featuring a bidentate C,C-coordinated NHC ligand. Mechanistic investigations support a borrowing hydrogen mechanism proceeding through iridium(I) intermediates with the methoxo complex as the catalytic active species and the cyclometalated complex as the catalyst resting state. Deuterium labeling experiments have demonstrated that both species are in equilibrium under catalytic conditions, which is consistent with the exhibited catalytic activity of the cyclometalated complex.

Boosting Mass Exchange between Pd/NC and MoC/NC Dual Junctions via Electron Exchange for Cascade CO2 Fixation.

Merging existing catalysts together as a cascade catalyst may achieve "one-pot" synthesis of complex but functional molecules by simplifying multistep reactions, which is the blueprint of sustainable chemistry with low pollutant emission and consumption of energy and materials only when the smooth mass exchange between different catalysts is ensured. Effective strategies to facilitate the mass exchange between different active centers, which may dominate the final activity of various cascade catalysts, have not been reached until now, even though charged interfaces due to work function driven electron exchange have been widely observed. Here, we successfully constructed mass (reactants and intermediates) exchange paths between Pd/N-doped carbon and MoC/N-doped carbon induced by interfacial electron exchange to trigger the mild and cascade methylation of amines using CO2 and H2. Theoretical and experimental results have demonstrated that the mass exchange between electron-rich MoC and electron-deficient Pd could prominently improve the production of N,N-dimethyl tertiary amine, which results in a remarkably high turnover frequency value under mild conditions, outperforming the state-of-the-art catalysts in the literature by a factor of 5.9.

Platinum nanoparticles as recyclable heterogeneous catalyst for selective methylation of amines and imines with formic acid: Indirect utilization of CO2

N-methylation of amines and imines with formic acid as C1 source by easily prepared Pt NPs as heterogeneous catalyst is reported here. Primary, secondary amines and imines were successfully methylated in good to excellent yields under mild conditions. Both aromatic and aliphatic amines could be applied as substrates. Meanwhile, the heterogeneous Pt NPs were capable to be recylcled and reused for 7 times without significant decrease of reactivity. This protocol provided an indirect utilization pathway of CO2 by using formic acid as C1 source.

Additive-free selective methylation of secondary amines with formic acid over a Pd/In2O3 catalyst

Formic acid is the sole carbon and hydrogen source in the additive-free catalytic methylation of amines.

Palladium-catalyzed enantioselective (2-naphthyl)methylation of azaarylmethyl amines

A method for the synthesis of enantioenriched azaarylmethyl amine derivatives, which are useful building blocks is presented.

Sample Preparation and Relative Quantitation using Reductive Methylation of Amines for Peptidomics Studies

Sample Preparation and Relative Quantitation using Reductive Methylation of Amines for Peptidomics Studies

Sample Preparation and Relative Quantitation using Reductive Methylation of Amines for Peptidomics Studies.

Peptidomics can be defined as the qualitative and quantitative analysis of peptides in a biological sample. Its main applications include identifying the peptide biomarkers of disease or environmental stress, identifying neuropeptides, hormones, and bioactive intracellular peptides, discovering antimicrobial and nutraceutical peptides from protein hydrolysates, and can be used in studies to understand the proteolytic processes. The recent advance in sample preparation, separation methods, mass spectrometry techniques, and computational tools related to protein sequencing has contributed to the increase of the identified peptides number and peptidomes characterized. Peptidomic studies frequently analyze peptides that are naturally generated in cells. Here, a sample preparation protocol based on heat-inactivation is described, which eliminates protease activity, and extraction with mild conditions, so there is no peptide bonds cleavage. In addition, the relative quantitation of peptides using stable isotope labeling by reductive methylation of amines is also shown. This labeling method has some advantages as the reagents are commercially available, inexpensive compared to others, chemically stable, and allows the analysis of up to five samples in a single LC-MS run.

Green and chemo selective amine methylation using methanol by an organometallic ruthenium complex

Herein a green and convenient catalytic N-methylation of aniline and n-hexylamine using methanol as a dual methylation agent and solvent has been investigated. A new ruthenium carbonyl complex was synthesized and applied as a homogeneous catalyst in methylation reaction. The solid-state structure of the complex was determined by X-ray crystallographic analysis which indicate xantphos ligand bonded to ruthenium (II) as a tridentate pincer ligand by two P donor and one O atom. The catalytic system showed excellent conversion and selectivity toward N-methylaniline, and N,N-hexyldimethylamine at 140°C.