Alkylation Reactions Research Articles

Acidity Quantification and Structure Analysis of Amide-AlCl3 Liquid Coordination Complexes for C4 Alkylation Catalysis

Liquid coordination complexes (LCCs), which are formed between metal halides and donor molecules, represent promising catalysts. Six amide-AlCl3 LCCs were successfully synthesized, followed by their characterization through NMR, Raman, and UV-visible spectroscopy. The acidity of these LCCs was quantified by performing computational modelling of fluoride ion affinities (FIA) and experimental Gutmann–Beckett measurements. Spectroscopic analysis indicated bidentate coordination between amide ligands and Al, which induced asymmetric splitting of Al2Cl6 into diverse ions such as [AlCl2L2]+, [AlCl4]−, [AlCl3L], and [Al2Cl6L]. The computed FIA was found to align well with the experimental acidity trends, thereby confirming the proposed structure of the LCC. In the alkylation tests, the LCC with a high acidity demonstrated an increase in the yields of C5-C7 alkylates. These results provide an in-depth understanding of the tuneable structures of amide-AlCl3 LCCs. The acidity of LCCs can be controlled by tuning the ratio of the organic ligand to AlCl3, which allows bidentate coordination to facilitate asymmetric splitting of Al2Cl6. The LCCs demonstrate a high degree of potential as versatile and sustainable acid catalysts in alkylation reactions. These findings may advance the foundational knowledge of LCCs for the purpose of targeted acid catalyst design.

Impact of ionic liquid's cation alkyl chain length and reaction time on cellulose nanocrystals preparation

Traditional methods to obtain cellulose nanocrystals typically involve mechanical and chemical processes and develop an improved process in terms of efficiency, sustainability, and the quality of CNCs produced are interesting. In this sense, we aimed to prepare cellulose nanocrystals (CNCs) from the hydrolysis of microcrystalline cellulose using protic ionic liquids (PILs), named 3-diethylamino-propylammonium hexanoate ([DEAPA][Hex]), 3-dimethylamino- 1-propylammonium hexanoate ([DMAPA][Hex]), and propylammonium hexanoate ([PA][Hex]) at different reaction times. The PILs demonstrated efficiency in producing cellulose nanocrystals, regardless of the cation size and reaction times. However, as expected the properties of the CNCs varied depending on the studied condition. The highest yield was observed in DMAPA[Hex], with a 34 % conversion. Crystalline indices decreased independent of the cation sizes and reaction times. Thermal stabilities were shifted to higher temperatures up to 92 ºC probably due to PILs cation sizes. In contrast, increasing reaction times decreased nanocrystals’ thermal stabilities up to 51ºC. So, protic ionic liquids (PILs) can be considered more environmentally friendly or sustainable solvents compared to traditional organic solvents for preparing cellulose nanocrystals. In the present work, it is reported an alternative method for obtaining CNCs and additionally provide the best preparation conditions for achieving important properties of this nanomaterial, with the potential for various applications.

High heat Resistance, Strength, and toughness of epoxy resin with cellulose nanofibers and structurally designed ionic liquid

This study investigates the synergistic effects of ionic liquid (IL) and nanofillers on the properties of epoxy resin, aiming to address the issues of brittleness commonly associated with commercial epoxy resins. Starting from molecular structural design, a novel ionic liquid containing amino and phenylboronic acid groups is synthesized via a one-step alkylation reaction. The newly synthesized IL is then synergistically combined with cellulose nanofibers (CNFs) to fabricate a series of IL/CNFs epoxy resin composites. The influence of IL/CNFs content on the thermal properties, mechanical performance, glass transition temperature, and transparency of the composite materials is investigated. Compared to pure epoxy resin (EP), the epoxy composite material with 0.5IL-1.0CNFs exhibits a 50.72 % increase in flexural strength, a 126.94 % increase in elongation at break, and a 97.51 % increase in impact strength. In comparison, both the initial and maximum decomposition temperatures increased (T5% was 374 °C, and Tmax was 400 °C), showing an increase of 6 °C and 4 °C, respectively. Additionally, the epoxy composite material maintains high transparency, with a relatively high level of transmittance in the visible light range (400 nm-760 nm). The transmittance at T500nm increases to 86.8 %, and at T400nm it increases to 69.54 % compared to the pure epoxy resin.

A green route of isobutane-butene alkylation catalyzed by Y zeolite modified with synergistic F-containing solution

Fast deactivation is a long-standing problem for zeolite catalyzed isobutane-butene alkylation that hinders its massive industrialization, and the optimization of the zeolites' acidity and pore structure is the key problem. A synergistic F-containing solution modification method was proposed to improve the diffusion performance without damaging the zeolites’ acidity. The low-temperature ammonium fluoride treatment precise partly opened the cage windows of the zeolites to increase the acidity accessibility and diffusion performance. And the following acid treatment of ammonium fluosilicate effectively removed the extra-framework aluminum generated by the former treatment to achieve a high acidity and Brönsted acid amount to Lewis acid amount ratio. The best modified zeolite Y-11 has a lifetime of 60 h, which is 32% higher compared to that of the reference zeolite. Our primary results provide a promising strategy for designing superior zeolite catalysts for alkylation reactions.

Construction of Unique Spiro[dibenzo[a,f]azulene-6,2'-indenes] via Unprecedented Annulation of ortho-C-H Bond of Benzylidene Group.

The domino reaction of alkyl and aryl isocyanides with two molecules of 2-arylidene-1,3-indanediones in acetonitrile at 80 °C resulted in unique functionalized spiro[dibenzo[a,f]azulene-6,2'-indenes] in good yields, in which the two 2-arylidene-1,3-indanediones acted as different building blocks to construct the polycyclic system. More importantly, the unprecedented anticipation of the ortho-position of benzylidene group to form a novel dibenzo[a,f]azulene ring through a formal [5 + 2] cycloaddition process was first observed. On the other hand, DABCO-promoted reaction of the isocyanides with two molecules of 2-arylidene-1,3-indanediones in acetonitrile at 80 °C afforded functionalized spiro[cyclopenta[a]-indene-2,2'-indene] derivatives.

Polyaniline-Supported Tungsten-Catalyzed α-H Alkylation Reaction of Ketone with Alcohol.

α-H alkylation of carbonyls is a significant reaction in the pharmaceutical industry because it can directly form a C-C bond in an environmentally benign manner. Thus, developing a novel catalyst for this reaction is a hot and practical topic in catalysis, organic synthesis, and materials science. In this paper, we found that polyaniline-supported tungsten could catalyze the α-H alkylation reaction of ketone with alcohol generating water as the only byproduct. Polyaniline support is the key for promoting the catalytic activity of tungsten, which is relatively cheaper than the traditionally employed noble metals. The reaction occurred under mild conditions with a wide substrate scope. The substrate initial concentration was enhanced to 1 mol/L, while the reaction speed was accelerated to reduce the reaction time to only 6 h; these improvements could significantly enhance the production capacity. The advantages make this reaction practical for synthesis with industrial purposes.

Ultra-high-throughput mapping of the chemical space of asymmetric catalysis enables accelerated reaction discovery

The discovery of highly enantioselective catalysts and elucidating their generality face great challenges due to the complex multidimensional chemical space of asymmetric catalysis and inefficient screening methods. Here, we develop a general strategy for ultra-high-throughput mapping of the chemical space of asymmetric catalysis by escaping the time-consuming chiral chromatography separation. The ultrafast ( ~ 1000 reactions/day) and accurate (median error < ±1%) analysis of enantiomeric excess are achieved through the ion mobility-mass spectrometry combines with the diastereoisomerization strategy. A workflow for accelerated asymmetric reaction screening is established and verified by mapping the large-scale chemical space of more than 1600 reactions of α-asymmetric alkylation of aldehyde with organocatalysis and photocatalysis. Importantly, a class of high-enantioselectivity primary amine organocatalysts of 1,2-diphenylethane-1,2-diamine-based sulfonamides is discovered by the accelerated screening, and the mechanism for high-selectivity is demonstrated by computational chemistry. This study provides a practical and robust solution for large-scale screening and discovery of asymmetric reactions.

Probing the kinetic sensitization effect of NO2 on ethylene oxidation

Exhaust gas recirculation (EGR) has been widely equipped in modern engines for pollutant emission abatement. NOx present in EGR can greatly influence fuel combustion properties in engine operation. Ethylene (C2H4) is well-known a critical intermediate formed via β-scission reactions of alkyl radicals in the pyrolysis and oxidation of hydrocarbons, thus investigating the mutual effects of C2H4 and NOx is beneficial to engine design as well as hierarchically developed strategy of the chemical kinetic model. This study investigated the auto-ignition behavior of C2H4/air mixtures containing different levels of NO2 (0 ppm, 200 ppm, 500 ppm, 3000 ppm) in a high-pressure shock tube at pressures of 1 atm and 24 atm, temperatures of 820–1300 K and different equivalence ratios of 0.5, 1.0 and 2.0. The results showed that the addition of NO2 significantly promoted auto-ignition at high pressure, while only limited effects at low pressure. A detailed kinetic mechanism was proposed based on a hierarchically developed strategy, and it successfully reproduced the experimental data over the entire test conditions. Flux and sensitivity analyses were implemented to explore the sensitization effect of NO2 addition on the ignition kinetics of C2H4. The analysis revealed that NO2 mainly affects the reaction pathway of ĊH2CHO radical, leading to the formation of HONO. The additional generation of ȮH radicals through HONO = NO + ȮH and NO + HȮ2 = NO2 + ȮH accelerate the auto-ignition of C2H4. At low pressure, the decrease in the rate constant of HONO decomposition weakens the role of NO2.

Reactions of Alkyl β‐Nitroacrylates with Arenes in Triflic Acid: Synthesis of Oximes of Alkyl 2,3‐Diaryl‐3‐oxopropanoates

AbstractMethyl or ethyl 3‐nitropropenoates (β‐nitroacrylates) AlkO(O)C1−C2H=C3H−NO2 in reaction with arenes ArH in triflic acid CF3SO3H (TfOH) at room temperature in 1 h give rise to oximes of alkyl 2,3‐diaryl‐3‐oxopropanoates AlkO(O)C−CH(Ar)−C(Ar)=NOH in yields of 42–92 %. The obtained oximes bearing ortho‐methyl substituents in the aryl ring exist as atropoisomers in solutions. The study of protonated forms of β‐nitroacrylates by NMR and DFT calculations has revealed that the reactive electrophiles are species AlkO(HO+)C1−C2H=C3H−N+(O)(OH) protosolvated on the acceptor groups NO2 and CO2R. Plausible reaction mechanism is based on the primary interaction of aromatic nucleophiles with these electrophilic species onto their carbon C2.

Origin of Enantio- and Chemoselectivity in the Synthesis of Spirocycles via Palladium/Xu-Phos-Catalyzed Cascade Heck/Remote C(sp2)-H Alkylation: A Computational Mechanistic Study.

Density functional theory (DFT) calculations were performed to study the mechanism and factors affecting the enantio-, regio-, and chemoselectivities in the palladium/Xu-Phos-catalyzed cascade Heck/remote C(sp2)-H alkylation reaction. The active catalyst is found to be able to sustain coordination with P and S atoms and can adapt its coordination mode to accommodate the significant steric hindrance between the ligand and substrate, unlike previous findings that showed coordination with P and O atoms. The reaction is established to occur in sequence through the oxidative addition of the aryl iodide to Pd(0), intramolecular alkene insertion, C(sp2)-H bond activation, and C(sp2)-C(sp3) bond reductive elimination. The C(sp2)-C(sp3) bond reductive elimination is identified as the rate-determining step, and the intramolecular alkene insertion as the enantioselectivity-determining step. The high enantioselectivity originates from the stronger electronic interaction between the catalyst and substrate; the exclusive 5-exo-regioselectivity is due to the stronger nucleophilicity of the terminal alkene carbon atom, and the chemoselectivity of C-H activation over carboiodination is driven by thermodynamics.

Experimental and Computational Studies on Cobalt(I)‐Catalyzed Regioselective Allylic Alkylation Reactions

AbstractHere, we report the development of cobalt(I)‐catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3‐dicarbonyl compounds. A family of well‐defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh3)Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh3)Cl] (dppp=1,3‐Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt‐catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.

Experimental and Computational Studies on Cobalt(I)-Catalyzed Regioselective Allylic Alkylation Reactions.

Here, we report the development of cobalt(I)-catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3-dicarbonyl compounds. A family of well-defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh3 )Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh3 )Cl] (dppp=1,3-Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt-catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.

Polyethylene glycol-based halogen-free acidic deep eutectic solvents for removal of olefins from aromatics

In this study, seven novel green acidic deep eutectic solvents (ADESs) based on polyethylene glycol (PEG) was successfully synthesized. Organic acids containing carboxylic acid and sulfonic acid functional groups were utilized as hydrogen bond donors (HBDs) for the synthesis. The formation mechanism of ADESs was elucidated through 1H NMR and FTIR spectroscopy, as well as density functional theory (DFT) calculations. Acetonitrile-IR spectroscopy was employed to investigate the acidity of the prepared ADESs, revealing the superior Lewis acidity of ADESs derived from carboxylic acid functional groups. The generation of Lewis acidic sites can be attributed to the hydrogen bonding interaction between the hydroxyl groups of PEG and the carboxylic acid functional groups, promoting the dissociation of carboxylic acid molecules. The obtained DES [PEG:2FA] and [PEG:2AA], with formic acid (FA) and acetic acid (AA) as HBDs, exhibited remarkable efficiency in removing olefins from aromatics under mild reaction conditions. GC–MS analysis of the reaction products confirmed the formation of alkylbenzenes, indicating the occurrence of alkylation reactions. Furthermore, a rational reaction mechanism was proposed to elucidate the reaction process of aromatics and olefins on acidic sites.

4-Octyl itaconate reduces influenza A replication by targeting the nuclear export protein CRM1.

Itaconate derivates, as well as the naturally produced metabolite, have been proposed as antivirals against influenza virus. Here, the mechanism behind the antiviral effects of exogenous 4-octyl itaconate (4-OI), a derivative of itaconate, against the influenza A virus replication is demonstrated. The data indicate that 4-OI targets the cysteine at position 528 of the CRM1 protein, resulting in inhibition of the nuclear export of viral ribonucleoprotein complexes in a similar manner as previously described for other selective inhibitors of nuclear export. These results postulate a mechanism not observed before for this immuno-metabolite derivative. This knowledge is helpful for the development of derivatives of 4-OI as potential antiviral and anti-inflammatory therapeutics.

Functions of local structural surrounding in activity of Ca-containing catalysts for vapor upgrading during biomass thermal decomposition

The catalytic activity of calcium-containing complex oxides with perovskite structure (CaTiO3), brownmillerite structure (Ca2Fe2O5 and Ca2FeAlO5), spinel structure (CaAl2O4), and pseudowollastonite structure (CaSiO3) was compared to CaO for the upgrading of Oakwood fast pyrolysis vapors. Initial catalyst particle sizes range between 0.61 and 3.21 μm, while the BET surface area is between 0.2 and 8.7 m2/g. In contrast to CaO, the complex oxides compounds demonstrated negligible CO2 and H2O chemisorption during catalytic fast pyrolysis, thereby a low deactivation of catalysts, good structural and morphological stability and thus high reusage feasibility. Due to their unique features, Ca-containing catalysts were found to promote specific reaction pathways, such as the conversion of guaiacol to 3-methyl phenol, 4-ethenyl-2-methoxyphenol to 4-ethyl-2-methoxyphenol, 1-(4-hydroxy-3,5-dimethoxyphenyl)ethanone to 3,5-dimethoxy acetophenone and long chain carboxylic acids to acetic acid through a multitude of reaction routes including demethylation/demethoxylation, hydrogenation and hydrodeoxygenation, oxidative cleavage, and dehydration reactions. CaO and Ca2Fe2O5 promoted the alkylation reactions within the methoxy phenolics, whilst CaSiO3 promoted hydrogenation reactions. The formation of acetic acid was promoted over Ca2FeAlO5, CaAl2O4, and CaSiO3, while acetone, 2-butanone, new cyclic C5 ketones were revealed over CaO. The resulting ketonic fraction was noticeably affected by the use of Ca2Fe2O5 and CaAl2O4 catalysts.

Discovery of novel cannabidiol derivatives with augmented antibacterial agents against methicillin-resistant Staphylococcus aureus

Drug-resistant bacterium infections are a severe threat to public health and novel antimicrobial agents combating drug-resistant bacteria are an unmet medical need. Although cannabidiol (CBD) has been reported to show antibacterial effects, whether its antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) can be improved remains unclear. Herein, a series of novel CBD derivatives were designed and synthesized using various chemical approaches including amidation, Friedel-Crafts alkylation, and Negishi cross-coupling reaction for the modifications at the C-7, C-2′, C-4′, and C-6′ positions of CBD skeleton. Derivative 21f showed augmented antibacterial activity against MRSA with a minimum inhibitory concentration of 4 μM without cytotoxic effect in microglia BV2 cells. Further mechanistic studies suggested that 21f inhibited the formation of biofilms, induced excess reactive oxygen species, and reduced bacterial metabolism, which collectively led to the acceleration of bacterial death. Findings from this study expand the understanding of CBD derivatives as promising antibacterial agents, which provides useful information for the development of cannabinoid-based antibacterial agents.

A new strategy for facile and rapid separation of astatine-211 from nitric acid medium

Developing fast and efficient separation avenues can promote either fundamental study or practical application of astatine-211(211At). This work presents a new solid-phase extraction (SPE) separation strategy based on functional resin for recovering 211At from the irradiated bismuth (Bi) target mildly and rapidly, without switching HNO3 medium into HCl system. Four functional resins containing acyl-resin, thioether, sulfonate- and sulfonate-groups had been prepared via Friedel-Crafts acylation and alkylation reactions successfully, and subsequently characterized by FTIR, EA, SEM etc. Acyl-resin from these functional materials have shown good retention towards 211At but low binding affinity to all possible metal impurities (Zn2+, Cu2+, Ga3+and Bi3+) in simulated separation experiments. Static batch sorption experiments indicate that the pseudo-second-order kinetic model is more suitable for describing the binding behavior of 211At on Acyl-resin. This reveals that chemisorption dominates the reaction between the target radionuclide and functional material. During several practical separations in medically-used scale, over 98.5 % of 211At can be well retained on SPE column with metal impurities removed in the process of loading target solution and removing non-target radionuclides. More importantly, 60.03 %∼79.05 % of 211At on the Acyl-resin SPE column is recoverable by NH2OH-NH3·H2O-CH3OH elution process, and over 60 % of the radioactivity distributes in volatile organic solvent (CH3OH). The whole SPE separation process can be completed within 20 min, giving 211At product with high radionuclidic purity (≥ 99 %), low metal impurities (Bi3+≤ 17.37 μg and Cu2+≤ 2.91 μg) and high radiolabeling availability. This work implies that acyl-groups can act as potential binding motifs not only for developing new 211At separation methods but also designing bifunctional conjugate agents for astatinated compounds based on coordination bonds.

COMPLEXES OF p-METHOXYPHENYLTELLURIUM TRICHLORIDE WITH ALLYL THIOETHERS OF 5-ARYL-1,3,4-OXADIAZOLE

1,3,4-Oxadiazole and its functional derivatives have a wide spectrum of biological activity. There are well-known examples of the use of oxadiazoles in materials science as high-energy molecules. Therefore, the synthesis of new functional derivatives based on them is an urgent problem. This paper describes the synthesis of allylic thioethers of 5-nitrophenyl-1,3,4-oxadiazole by the alkylation reaction of the corresponding thiones with allyl bromide in an alcohol-alkaline medium. Such thioethers were studied in reactions with phenylselentrihalides, as a result of which oxadiazolo[2,3-d][1,3,4]thiaselenazinium halides were synthesized. We investigated the interaction of the tellurium-containing analogue p-methoxyphenyltellurium trichloride with allylic thioethers of 5-nitrophenyl-1,3,4-oxadiazole. It was established that the reaction between p-methoxyphenyl tellurium trichloride and the investigated alkenyl thioethers within 8 hours occurs with the formation of adducts of the substrate-electrophile composition 1:1, regardless of the ratio of reagents. Attempts to change the polarity of the solvent, increase the reaction time, and change the temperature regime did not change the direction of the reaction. Based on the obtained experimental spectral data and elemental analysis data, the structure of the obtained complexes is proposed.&#x0D; Keywords: p-methoxyphenyltellurium trichloride; 1,3,4-oxadiazole; allyl thioethers; organotellurium compounds; molecular complexes.

Recent Advancements in Typical Friedel–Crafts Alkylation Reactions Focused on Targeting Arene Nucleophiles

AbstractThis review delves into recent advances and significant breakthroughs in the field of the catalytic Friedel–Crafts alkylation of targeted arenes or heteroarenes. Though a few earlier literatures are referenced, the main emphasis of this review focuses on the literature mainly published between 2015 and March 2023.1 Introduction2 History and Background3 Alcohols as Alkylating Agents4 Aldehydes and Ketones as Alkylating Agents5 Alkyl Fluorides as Alkylating Agents6 Epoxides as Alkylating Agents7 Cyclopropanes as Alkylating Agents8 Conclusion and Outlook

Ligand-Controlled Diastereodivergency in Propargylic Alkylation of Vinylogous Aza-Enamines: Construction of 1,3-Stereocenters.

The first diastereodivergent propargylic alkylation reaction is developed. This Cu(I)-catalyzed formal decarboxylative [4+2] cycloaddition between ethynyl benzoxazinanone and vinylogous aza-enamine delivers each diastereomer of tetrahydroquinoline derivatives, bearing 1,3-stereocenters, using either i-Pr-Pybox or BINAP as the ligand under otherwise identical reaction conditions. This is the first application of vinylogous aza-enamines in a transition metal-catalyzed transformation and the first example of the creation of 1,3-stereocenters in a propargylic substitution reaction.