Friedel-Crafts Research Articles

Highly para-selective alkylation of toluene by methyl mercaptan over silylated ZSM-5 zeolite

Friedel-Crafts alkylation of toluene with methyl mercaptan has been investigated in the presence of H-ZSM-5 and SiO2/H-ZSM-5 catalysts. The silica layers have been built on H-ZSM-5 zeolite by chemical liquid deposition of tetraethyl orthosilicate. The passivation with silica of the external surface of H-ZSM-5 zeolite has been confirmed by FT-IR spectroscopy and mesitylene isomerization, used as a model reaction. All catalysts exhibited notable behavior in the alkylation of toluene to xylenes. Efficiencies higher than 98 % in alkylation for both toluene and methyl mercaptan were obtained at 375 °C. In terms of para-selectivity, outstanding performance was revealed by the silylated zeolites. Thus, over 12 % SiO2/H-ZSM-5, at 375 °C and WHSV = 9.4 gtoluene+CH3SH gcat-1h−1, the para-xylene selectivity was close to 100 %. The experimental apparent activation energy for the toluene alkylation with methyl mercaptan catalyzed by H-ZSM-5 was 80 kJ/mol.

The embedding of 1,8-diazabicyclo[5.4.0]undec-7-ene into hyper-crosslinked ionic polymers for efficient CO2 conversion at atmospheric pressure

The preparation of cyclic carbonates via CO2 cycloaddition reaction was crucial for the lithium industry. Herein, a series of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) based hyper-crosslinked ionic polymers with different ionic site densities were prepared by simultaneously Friedel-Crafts alkylation and quaternization reactions. The obtained P[DBU]DCX(1:1) with a high ionic site density (1.45 mmol g−1), prepared by the equimolar ratio of 1,8-diazabicyclo[5.4.0]undec-7-ene and α,α′-dichloro-p-xylene, exhibiting excellent catalytic performance with a chloropropylene carbonate (CPC) yield of 98.8 % and selectivity of 99.3 % at atmospheric pressure. Meanwhile, the conversion capacity was comparable with other catalysts. Moreover, the CO2 cycloaddition reaction over P[DBU]DCX(1:1) catalyst followed pseudo-first-order kinetics, and the activation energy (Ea) was obtained to be 28.7 kJ/mol by performing kinetic experiments at different temperatures. In addition, it also had a good reusability and universality for different epoxides. The synergistic effects of abundant quaternary nitrogen cations derived from DBU and chlorine anions on the activation of CO2 and epoxide were explored based on density functional theory calculation. This study offers a new approach for the design and application of hyper-crosslinked ionic polymers for efficient CO2 conversion at atmospheric pressure.

Porous calix[4]pyrrole-based polymers with high surface area for efficient removal of polar organic micropollutants from water

Herein, effort was made to construct innovative adsorbent for the removal of polar organic micropollutants (OMPs) from water. Tetra-meso resorcinol-functionalized calix[4]pyrrole (CP) featured with endo-functionalized attribute and polyphenol hydroxyl structure was crosslinked by π-electron-rich 4,4′-bis(chloromethyl)biphenyl (BCMBP) through Friedel-Crafts reaction to generate porous calix[4]pyrrole-based polymers (PCPPs) with high surface area. The porosity of the PCPPs could be tuned by adjusting the molar ratio of hydrophilic CP to hydrophobic BCMBP, and diversified binding sites were integrated together. Based on adsorption kinetics and isotherm studies, PCPP(1–16) showed rapid adsorption rate and high removal efficiency (RE) as well as advanced adsorption capacity. The REs towards the tested polar OMPs by PCPP(1–16) were all above 95% in 30 min. Compared with granular activated carbon (GAC), the rate constant of pseudo-second-order model (k2) and adsorption capacity upon PCPP(1–16) were 8–230 times and 1.3–3.1 times greater than those by GAC. Adsorption mechanism studies confirmed the presence of multiple interactions and thermodynamic investigation revealed the spontaneous and physical adsorption nature. Besides, PCPP(1–16) showed excellent adsorption performance in real water samples at environmental levels and exhibited advanced absorption ability in flow-through mode. Accompanied by facile regeneration under eluting with methanol and cost-effective preparation, PCPP(1–16) demonstrated great potential as promising adsorbent for water treatment.

Iron, cobalt embedded nitrogen-doped carbon derived from conjugated macrocyclic polymers as electrocatalysts for oxygen reduction reaction

The synthesis of earth-abundant metal-based electrocatalysts for deploying electrochemical energy devices has become an area of considerable interest. Herein, we have illustrated a facile Friedel-Crafts reaction for designing a metalloporphyrin polymer followed by its calcination to synthesize cauliflower-like nitrogen-doped iron-cobalt bimetallic electrocatalyst (FeCoTpp-900-2) and its satisfactory performance toward reducing oxygen. The bimetallic FeCoTpp-900-2 catalyst exhibits a half-wave potential (E1/2) of 0.84 V (vs. reversible hydrogen electrode (RHE)) and an onset potential (Eonset) of 0.95 V (vs. RHE). The notable electrocatalytic activity for oxygen reduction reaction (ORR) of FeCoTpp-900-2 is attributed to the presence of ORR active nitrogen species along with the Fe-Nx/Co-Nx sites. In addition, FeCoTpp-900-2 possesses an appreciable amount of mesopores responsible for the ORR behavior. Notably, the zinc-air battery consisting of FeCoTpp-900-2 as the catalyst for the air cathode presents a maximal power density of 127.53 mW cm−2 and robust durability for 24 hours (h). Therefore, this work can contribute to the facile synthesis of bimetallic electrocatalysts with non-noble metals to explore their applications in ORR.

Synthesis of poly(terphenyl-co-dibenzo-18-crown-6 methylimidazole) copolymers for high-performance high temperature polymer electrolyte membrane fuel cells

This study focuses on the development of high temperature polymer electrolyte membranes (HT-PEMs), which are essential components for HT-PEM fuel cells (HT-PEMFCs). While phosphoric acid (PA) doped polybenzimidazole (PBI) has been recognized as a successful HT-PEM, it faces several challenges, including the use of carcinogenic monomer, complex synthesis processes, and poor solubility in organic solvents. To produce more cost-effective, easily synthesized, and high-performance alternatives, this study utilizes a straightforward superacid-catalyzed Friedel-Crafts reaction to synthesize a series of poly(terphenyl-co-dibenzo-18-crown-6 methylimidazole) copolymers, referred to as Co-x%TP-y%CE-Im, using p-terphenyl, dibenzo-18-crown-6 and 1-methyl-1H-imidazole-2-formaldehyde as monomers. The copolymerized hydrophilic and bulky crown ether units introduce substantial free volume and multiple interaction sites with PA molecules, as indicated by theoretical calculations. Additionally, the formation of microphase separation structures, confirmed by atomic force microscope (AFM) and transmission electron microscope (TEM), contributes to the enhanced performance of these membranes. For instance, after immersion in 85 wt% and 75 wt% PA solutions, the Co-90%TP-10%CE membrane achieves PA doping contents of 200 % and 169 %, achieving high conductivities of 0.092 S cm−1 and 0.054 S cm−1 at 180 °C, while maintaining tensile strengths of 6.5 MPa and 7.5 MPa at room temperature. Without the need for humidification or backpressure, the peak power density of an H2-O2 cell equipped with Co-90%TP-10%CE/169%PA membrane with a thickness of 79 μm reaches an impressive 1018 mW cm−2 at 210 °C. These results demonstrate new materials and insights for the development of high-performance HT-PEMs.

An Efficient Multi‐Component Double Friedel‐Crafts Alkylation of Isatin: Access to Unsymmetrical and Symmetrical 3, 3‐Diaryl oxindoles

AbstractAcetic acid‐mediated three‐component double Friedel–Crafts alkylation reaction for the synthesis of α, α‐diaryl oxindole derivatives is demonstrated. The reaction is successful with various isatin, indole, and N, N‐disubstituted aniline derivatives. The efficiency of the reaction is further enhanced by a four‐component reaction of isatin, electrophiles and acetic anhydride for the synthesis of N‐acylated 3,3‐diaryl oxindole derivatives facilitated by dual activation of C3 and N1 acetylation in a single‐step. Various unsymmetrical and symmetrical 3,3‐diaryl oxindoles were prepared in single‐step MCR reaction under easy to operate reaction conditions.

Efficient bis(indoyl)methanes synthesis enabled by SnO2/SiO2 nanocomposite

This study focuses on the synthesis of SnO2/SiO2 nanocomposite materials using sol-gel method and investigates their role in the synthesis of bis(indoyl)methanes via the Friedel–Craft alkylation route. The results, based on TON and TOF, show that 15 wt % SnO2/SiO2 exhibits high production efficiency and greater stability, with yields reaching 91–93% within 80–93 min. The prepared catalysts were characterized using various analytical techniques. The XRD revealed a crystalline size of 25.05 nm. The TEM analysis indicated a reduced particle size of about 25–30 nm. The SEM reflected the porous nature of the material and EDS showed the constituent elements Sn, O and Si with 3.65, 54.93, and 41.44 atomic %, respectively. FT-IR identified the composite framework with bands at 3408, 1620, 1093, 806 and 631 cm−1. The NH3-TPD indicated the presence of both Lewis acidic and Bronsted acidic sites in the composite materials. The BET method revealed a specific surface area and average pore diameter of 331.5814 m2/g. The developed method offers several advantages, such as a simple workup procedure, high yield, nontoxicity, cleanliness, and the ability to recycle and reuse the catalytic materials three times without loss in catalytic activity. These findings demonstrate the potential of SnO2/SiO2 nanocomposites as efficient and environmentally friendly catalysts for the synthesizing bis(indoyl)methane derivatives.

Advances in Chiral Pincer Complexes: Insights and Applications in Catalytic Asymmetric Reactions.

Chiral pincer complexes, characterized by their rigid tridentate coordination framework, have emerged as powerful catalysts in asymmetric synthesis. This review provides a comprehensive overview of recent advancements in the development of chiral pincer-type ligands and their corresponding transition metal complexes. We highlight the latest progress in their application across a range of catalytic asymmetric reactions, including the (transfer) hydrogenation of polar and non-polar bonds, hydrophosphination, alkynylation, Friedel-Crafts reactions, enantioselective reductive cyclization of alkynyl-tethered cyclohexadienones, enantioselective hydrosilylation, as well as Aza-Morita-Baylis-Hillman reactions. The structural rigidity and tunability of chiral pincer complexes enable precise control over stereoselectivity, resulting in high enantioselectivity and efficiency in complex molecular transformations. As the field advances, innovations in ligand design and the exploration of new metal centers are expected to expand the scope and utility of these catalysts, bearing significant implications for the synthesis of enantioenriched compounds in pharmaceuticals, materials science, and beyond.

Post-crosslinking knitting strategy for triazine-functionalized ionic hypercrosslinked polymers: Enhanced CO2 adsorption and conversion

Pore engineering has gained significant recognition as a pivotal strategy to tailor the structure and functionality of porous materials. In this study, a post-crosslinking knitting strategy was employed to fabricate a series of triazine-functionalized ionic hypercrosslinked polymers (IHCPs) using low specific surface area ionic polymers as precursors and external crosslinkers α,α′-dichloro-p-xylene (DCX) and α,α′-dibromo-p-xylene (DBX) through the Friedel Crafts alkylation reaction. This post-crosslinking knitting methodology increases the specific surface area of the resulting IHCPs, leading to enhanced CO2 adsorption capabilities (reaching 1.92 mmol·g−1 at 1 bar and 273 K), enhanced a remarkable 5.6-fold increase in CO2 uptake compared to the original ionic polymers. Of particular interest, inclusion of –NH– groups in PTA-2-DBX exhibits a synergistic catalytic effect facilitated by hydrogen bonding interactions that enable efficient conversion of CO2 into various cyclic carbonates under solvent- and cocatalyst-free conditions with yields exceeding 99 %. Furthermore, PTA-2-DBX demonstrates excellent recyclability while maintaining its activity even after five consecutive cycles. This study offers an effective approach for modulating pores in ionic polymers while highlighting the promising applications of triazine-functionalized IHCPs as dual-functional materials for both CO2 capture and conversion.

Developing three-dimensional hydrophobic photocatalysts to enhance mass transfer for promoting hydrogen peroxide production

Photocatalytic oxygen reduction reaction (ORR) is a promising approach for hydrogen peroxide (H2O2) production to alternative conventional anthraquinone process. However, the slow O2 diffusion and low-efficiency water oxidation reaction (WOR, limitation of protons) pathways have restricted the H2O2 production efficiency of organic photocatalysts. Therefore, a promising strategy to develop photocatalysts with three-dimensional (3D) architectures possessing high O2 diffusion, high-efficiency WOR pathway, and quick H2O2 desorption is desirable. Herein, a hydrophobic two-dimensional porous organic polymer (2D-POP) based on tetraphenylethylene (TPE) was synthesized as the building block. 3D-POPs (TPE-2 and TPE-3) were subsequently developed through the Friedel-Crafts alkylation reaction to regulate the O2 adsorption and optical properties. The 3D architectures allow O2 to diffuse into the interlayers, leading to efficient extraction of O2 from air, thus an excellent H2O2 production rate of 2.57 mmol g−1 h−1has been achieved by TPE-2 in air and without sacrificial agents, which only decreases by 4% compared to that in O2 due to a suitable specific surface area, good photoelectric properties, and excellent mass transfer of O2, H+, and H2O2. Furthermore, the H2O2 production rate of TPE-2 reaches 2.67 mmol g−1 h−1 in a triphasic system in air, which is higher than that in a traditional diphasic system, and the concentration of H2O2 reaches 1.80 mmol L−1 h−1. Additionally, by adding external Fe2+ or Fe3+ to make the utmost of photogenerated H2O2 and trigger the in-situ Fenton reaction for the formation of ·OH, TPE-2 exhibits extraordinary photodegradation efficiency toward representative organic pollutants, reaching > 99% removal within 60 min for bisphenol A and 2,4-dichlorophenoxyacetic acid with high concentrations (200 ppm).

Mass transfer-enhanced platform for heterogeneous dual organocatalysis to boost yield and diastereoselectivity in enantioselective Michael/benzoin cascade reaction

Mass transfer limitation and tedious anchoring of multiple expensive chiral organocatalysts are the key bottlenecks in heterogeneous asymmetric cascade/tandem reactions, leading to high-cost processes with low catalytic performances. In this paper, two chiral organocatalysts, including (S)-diphenylprolinoltrimethylsilyl ether (ProTMS) and N-heterocyclic carbenes (NHC), are simultaneously immobilized to hollow mesoporous polystyrene nanospheres (HMPNs) in one-pot via Friedel-Crafts alkylation to afford supported dual organocatalysts (ProTMS&NHC@HMPNs) at low cost. The catalyst possesses the spherical morphology with a hollow interior and a thin mesopore-abundant shell, providing suitable environments for reactants to quickly access to the catalytic sites of NHC and ProTMS. The side reactions caused by limited mass transfer are effectively suppressed, and superior yields (70–92 %) and diastereoselectivities (dr = 3:120:1) to homogeneous catalysis are achieved in heterogeneous Michael/benzoin cascade reaction. Overall, the mass transfer-enhanced platform for efficient heterogeneous dual organocatalysis is developed to boost yield and diastereoselectivity in asymmetric cascade reactions.

The N,N,N′,N′-tetraphenylbenzidine-based conjugated hypercrosslinked polymers for adsorping iodine and fluorescence sensing 2,4-dinitrophenol, iodine

Although progress has been made in the development of hypercrosslinked polymers (HCPs) for iodine uptake, their fluorescence performance and fluorescence sensing performance are rare due to the lack of conjugated behavior in common HCPs. Herein, the N,N,N′,N′-tetraphenylbenzidine-based conjugated hyper-crosslinked polymers (conjugated TPB-based HCPs) were efficiently fabricated via a one-step Friedel-Crafts arylation reaction by selecting N,N,N′,N′-tetraphenylbenzidine (TPB) and N,N′-diphenyl-N,N′-di(m-tolyl)benzidine (DPDB) as the basic building blocks and p-dimethoxybenzene (DMB) as an external crosslinker which will lead to the formation of the conjugated structures. The derived TPB-based HCPs (denoted as, TPB-DMB and DPDB-DMB) possessed excellent stability and high surface areas, Their iodine adsorption capacities are up to 4.25 and 3.56 g·g−1. The high iodine adsorption is caused by chemical adsorption. The fully conjugated structure and the 3D aryl network give the conjugated TPB-based HCPs excellent luminescence properties and fluorescence sensing properties for 2,4-dinitrophenol and iodine. The fluorescence sensing mechanisms of the conjugated TPB-based HCPs for DNP and I2 includes photo-induced electron process and the resonance energy transfer process. This study provides a viable approach for the development of highly efficient iodine sorbents and fluorescence sensors of DNP and iodine for addressing environmental issues.

Construction of controlled hyper-crosslinked nanofibrous tubes for Cr(VI) removal: Response surface, kinetics, and isotherm

Porous organic polymers (POPs) exhibit significant potential for adsorbing toxic metal ions in wastewater. Developing POPs with controlled morphologies is a pivotal direction in this field. This study synthesized a series of novel hyper-crosslinked nanofibrous tubes designated HCNT-Cn (n = 4, 8, 12, 16) via Friedel-Crafts alkylation and quaternization reactions. These reactions were fine-tuned through a post-synthetic strategy involving varying alkyl chain lengths. These materials were characterized using FT-IR, SEM, N₂ adsorption-desorption isotherms, among others, and they were specifically evaluated for their ability to adsorb Cr(VI). Among the variants, HCNT-C₄ exhibited the highest specific surface area (495.26 m2 g−1), superior hydrophilicity (CA = 48.7°), and optimal adsorption performance. The adsorption kinetics of HCNT-C₄ conformed to a pseudo-second-order model, while its adsorption isotherm aligned with the Langmuir model. An investigation into the impact of Cr(VI) removal was conducted using three independent variables in a Central Composite Design (CCD) response surface model, revealing that under optimal conditions, the Cr(VI) removal efficiency reached 98%. Additionally, a mechanism for Cr(VI) adsorption on HCNT-C₄ was proposed. It was also found that HCNT-C₄ could be reused up to four times, maintaining a removal efficiency of 70%. This study suggests potential applications for removing Cr(VI) from contaminated wastewater.

Enantioselective Friedel-Crafts alkylation of 1,3,5-trimethoxybenzene with trans-β-nitrostyrenes catalysed by [Cp*Rh{(R)-Prophos}(H2O)][SbF6]2 (Prophos = propane-1,2-diyl-bis(diphenylphosphane)

The aqua complex (SRh,RC)-[Cp*Rh{(R)-Prophos}(H2O)][SbF6]2 (Prophos = propane-1,2-diyl-bis(diphenylphosphane) catalyses the asymmetric Friedel-Crafts (FC) alkylation of 1,3,5-trimethoxybenzene with trans-β-nitrostyrenes. Only the monoalkylated adduct was obtained in all cases with enantioselectivities of up to 93/7 e.r. Solution NMR measurements have allowed us to detect and characterise catalytic intermediates such as metal-trans-β-nitrostyrene and metal‑aci-nitro complexes, as well as free aci‑nitro compound. Based on these studies, a Michael-type Friedel-Crafts mechanism is proposed.

Bis(imidazolidine)-Derived NCN Nickel-Pincer-Catalyzed Asymmetric Reactions.

A bis(imidazolidine)-derived NCN nickel-pincer complex (tBu-PhBidine-Ni-OTf: NCN-Ni-OTf) was synthesized by the oxidative addition of imidazolidine-containing aryl triflate to Ni(cod)2 in MeCN. NCN-Ni-OTf exhibited asymmetric induction in three reactions. In the Friedel-Crafts reaction of indoles with N-Boc imines, 3-indolylmethanamine products were obtained in 79% yield with 99% ee. In a conjugate addition reaction of malononitrile to nitroalkenes, products were obtained in 95% yield with 75% ee. In iodolactonization, the pincer-Ni complex showed catalytic activity superior to that of tBu-PhBidine-Pd-OTf.

Imidazolium and pyridine bifunctionalized hypercrosslinked polymers as efficient and recyclable catalysts for CO2 cycloaddition

Converting CO2 into precious chemicals is considered to be a fundamental and effective tool for controlling the abundant CO2 emitted. One of the most compelling methods for CO2 conversion is the synthesis of cyclic carbonates by cycloaddition of CO2 with epoxides. However, the development of materials with specific functionalities for CO2 capture and conversion is still considered to be a significant challenge. Herein, a novel imidazolium salts and pyridine skeleton bifunctionalized hypercrosslinked polymers were prepared by FeCl3-catalyted Friedel-Crafts alkylation reaction. Various analytical techniques were used to investigate the properties of the catalysts. The bifunctionalized heterogeneous catalysts exhibited outstanding catalytic performances for CO2 cycloaddition under mild conditions with an excellent yield of up to 99 %. Besides, the catalyst could bear various epoxides and no significant loss of activity after 6 cycles. The properties of metal-free, solvent-free, cocatalyst-free, easy-to-prepare, mild conditions, facility separation and recyclability make the bifunctionalized hypercrosslinked polymers useful for CO2 cycloaddition.

Site-Specific Radical Alkylation of Aryl Cyanide: Visible-Light, Photoredox-Catalyzed, Three-Component Arylalkylation of [1.1.1]Propellane.

We report herein a three-component radical arylalkylation of [1.1.1]propellane toward the synthesis of aryl-substituted bicyclo[1.1.1]pentane derivatives. The use of electron-deficient aryl cyanide as an aryl group source not only reduces the energy barrier of the arylation of the nucleophilic alkyl radical species, but also suppresses the electrophilic Friedel-Crafts alkylation process, enabling the present site-selective arylalkylation.

Friedel–crafts alkylations of indoles, furans, and thiophenes with arylmethyl acetates promoted by trimethylsilyl trifluoromethanesulfonate

Various indoles undergo Friedel–Crafts alkylation at the 3-position when treated with secondary arylmethyl acetates in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,6-lutidine. Tertiary benzylic alcohols are also effective alkylating agents, undergoing TMSOTf-promoted activation to yield alkylated indoles that feature quaternary centers. A related study shows that benzofuran reacts under similar conditions to yield 2-alkylated benzofurans when treated with similar alkylating agents, and the reaction has been extended to include other representative heteroarenes. Yields for these Friedel–Crafts alkylation products range from 43%–99% over a wide range of substrate combinations.

Chemistry of Thieno [2,3-h]-/[3,2-h] Quinoline and Thieno [2,3-f]-/[3,2-f] Quinoline Derivatives Part (x), Reactivities, and Biological Activities

Abstract: Several thieno [2,3-h] /[3,2-h] quinolines and thieno [2,3-f] /[3,2-f] quinolines (TQs) are discussed in this review from a few perspectives, including various preparation and processing methods employing cutting-edge machinery. The preparation of (TQs), from 4-(5)aminobenzothiophene, 2(3)chloromethylthiophene, 2(3)thienylboric acid, and other chemical reagents is illustrated via a number of chemical procedures in this review. The formation of (TQs) was clarified using the Michael addition, Photocyclization, Skraup reaction, Ullmann-Fetvadjian process, Suzuki-Miyaura and Sonogashira reaction, aza-Diels-Alder reaction, and Friedel-Crafts reaction.

The Intra- and Intermolecular Friedel-Crafts Acylation of Amino Acid Derivatives in Stereo-retarded Manner

: The Friedel-Crafts acylation of natural or unnatural amino acids in stereoretarded manner is willing to prescribed here. Depending on its main skeleton, the typical intra- and intermolecular Friedel-Crafts reaction of amino acids can be differentiated. The unique amino acid’s general structure can contribute to the reaction between its carboxyl group and the side chain. Depending on the Friedel-Crafts reaction condition, the amino acid’s optical retention can be retarded. This perspective can contribute to the development of this one-century reaction in the field of organic chemistry.