Catalyzed Friedel-Crafts Reaction Research Articles

Asymmetric Catalytic Friedel-Crafts Reactions of Unactivated Arenes.

Since its discovery more than a century ago, the Friedel-Crafts reaction has manifested itself as a powerful method for the introduction of carbon substituents to arenes. Despite its potential generality, the scope of the reaction is intrinsically limited by the arene's nucleophilicity, which has previously restrained the applicability of asymmetric variants to activated substrates. To overcome this fundamental limitation, we report herein an asymmetric Friedel-Crafts reaction of unactivated, purely hydrocarbon arenes, alkoxybenzenes, and heteroarenes with N,O-acetals to give enantioenriched arylglycine esters. Highly regio- and stereoselective C-C bond formation was achieved using strong and confined Brønsted acid organocatalysts, enabling the first asymmetric catalytic Friedel-Crafts reaction of simple alkylbenzenes.

Cyclotriphosphazene and tricarbazole based microporous hyper-crosslinked conjugated polymer for CCUS: Exceptional CO2 selectivity and high capacity CO2, CH4, and H2 capture

The most significant point in the synthesis of a hyper-crosslinked polymer with high CO2 adsorption and high selectivity properties to be used in carbon capture, utilization and storage (CCUS) is to choose the most compatible core and linker. These should allow the polymer to be synthesized in a single step under the mildest conditions with the highest yield. Here, the synthesis of microporous hyper-crosslinked conjugated polymer EBE-06 was achieved by a single step reaction of hexachlorocyclotriphosphazene and 1,3,5-tri(9H-carbazol-9-yl)benzene with an AlCl3 catalyzed Friedel-Crafts reaction. After being characterized using spectroscopic and analytical techniques, the gas uptake (CO2, CH4, O2, CO and H2) and selectivity properties (CO2/N2, CO2/CH4, CO2/O2 and CO2/CO) of EBE-06 were extensively tested at three different temperatures and up to 1.1 bar pressures. The hyper-crosslinked conjugated polymer EBE-06, formed by the bidirectional bonding of tricarbazole molecules to phosphazene, has a high surface area up to 1987 m2/g and a microporosity ratio up to 82%. In addition, 109 cm3/g CO2 adsorption and 33 cm3/g CH4 adsorption at 273 K and 220 cm3/g H2 adsorption was obtained at 77 K. Exceptional selectivity values were calculated for 05/95 CO2/N2 and reached 442 at 273 K. In addition, the calculation for 05/95 CO2/CH4 resulted in 121 at 273 K. Most importantly, 15/85 CO2/N2 selectivity reached 82 at 298 K, which shows that EBE-06 is an excellent candidate for CCUS processes.

Unlocking the Friedel-Crafts arylation of primary aliphatic alcohols and epoxides driven by hexafluoroisopropanol

Unlocking the Friedel-Crafts arylation of primary aliphatic alcohols and epoxides driven by hexafluoroisopropanol

Synthesis of difluoromethylated diarylmethanes via Fe(OTf)3-catalyzed Friedel-Crafts reaction of 2,2-difluoro-1-arylethyl phosphates.

The Fe(OTf)3-catalyzed Friedel-Crafts reaction of 2,2-difluoro-1-arylethyl phosphates with electron-rich (hetero)arenes afforded difluoromethylated diarylmethanes. Control experiments showed that Fe(OTf)3 behaves as the Lewis acid, and that the phosphate leaving group and o- or p-alkoxy substituents on the substrates are necessary for the Fe(OTf)3-catalyzed reaction to proceed under mild conditions.

Metal- and solvent-free synthesis of aniline- and phenol-based triarylmethanes via Brönsted acidic ionic liquid catalyzed Friedel-Crafts reaction.

A beneficial, scalable and efficient methodology for the synthesis of aniline-based triarylmethanes has been established through the double Friedel-Crafts reaction of commercial aldehydes and primary, secondary or tertiary anilines using Brönsted acidic ionic liquid as a powerful catalyst, namely [bsmim][NTf2]. This protocol was successfully performed under metal- and solvent-free conditions with a broad range of substrates, giving the corresponding aniline-based triarylmethane products in good to excellent yields (up to 99%). In addition, alternative aromatic nucleophiles such as phenols and electron-rich arenes were also studied using this useful approach to achieve a diversity of triarylmethane derivatives in high to excellent yields.

A comparative gas sorption study of dicarbazole-derived microporous hyper-crosslinked polymers

Tailoring selective gas uptake properties of porous organic polymers is very crucial for their future use in gas separation and storage, however, unraveling the impact of polymerization methods and linkers while fixing the core of the polymers remains a great challenge. Here, a comparative study of three microporous networks synthesized by linking dicarbazole (4,4′-di(9H-carbazol-9-yl)-1,1′-biphenyl, YBN) building blocks with dimetoxymethane, dimetoxybenzene, and cyanuric chloride. Linkers for giving hypercosslinked, hypercosslinked-covalent and covalent triazine frameworks through FeCl3 and AlCl3 catalyzed Friedel–Crafts reactions have been presented. The resulting microporous polymers, namely YBN-DMM, YBN-DMB, and YBN-CC were fully characterized by spectral and analytical methods then comparatively tested for gas uptake (CO2, CH4, O2, CO, and H2) and selectivity (CO2/N2, CO2/O2, for CO2/CO and CO2/CH4) under ambient pressure and three different temperature. These obtained polymers exhibit high BET specific surface area up to 968 m2 and predominantly ultramicroporous character, and remarkable thermal (up to 350 °C) and chemical stability in various solvents including concentrated hydrochloric acid. According to the linker, polymers have high gas uptake properties reaching 12.66 wt % CO2, 1.64 wt%. CH4, 1.04 wt% CO adsorption at 1 bar/273 K and 1.59 wt % H2 adsorption at 1 bar/77 K with interesting N2-phobia down to 0.04 wt% with relatively O2 phobia down to 0.22 wt% at 1 bar/320 K respectively. According to IAST calculations, it was observed that the selectivity properties, especially required for post-combustion processes at high pressures and temperatures, increase unusually by changing the linkers reaching up to 159 for CO2/N2, 63.5 for CO2/O2, 63.76 for CO2/CO, 7.47 for CO2/CH4.

Zeolite Catalyzed Friedel-Crafts Reactions: A Review

Friedel-Crafts reaction is one of the most useful synthetic tools in organic chemistry, mainly in the synthesis of aromatic ketones. The active catalysts for this reaction are modified zeolites and are preferable catalysts when shape selectivity affects the formation of the expected product. In this review, our aim is to corroborate recent literature available on zeolite catalyzed Friedel-Crafts alkylation and acylation reaction.

Recent Progress in Asymmetric Catalytic Friedel-Crafts Reaction of Pyrroles

Chiral pyrrolesare always found in many biologically active natural products.In recent years,asymmetriccatalytic Friedel-Crafts(F-C)reaction of pyrroles has become one of the research focuses.Asymmetric organo-catalysis and transition-metal catalysis are often used in asymmetric catalytic synthesis of chiral pyrroles.According to the classification of the catalyst,the research progress in the asymmetric catalytic F-C reaction of pyrroles is reviewed.

Short Synthesis of Oxetane and Azetidine 3-Aryl-3-carboxylic Acid Derivatives by Selective Furan Oxidative Cleavage.

Four-membered rings remain underexplored motifs despite offering attractive physicochemical properties for medicinal chemistry. Arylacetic acids bearing oxetanes, azetidines, and cyclobutanes are prepared in two steps: a catalytic Friedel-Crafts reaction from four-membered ring alcohol substrates, followed by mild oxidative cleavage. The suitability of the products as building blocks is reflected in their facile purification and amenability to derivatization. Examples include heteroaromatics and aryltriflates, as well as oxetane-derived profen drug analogues and a new endomorphin derivative containing an azetidine amino acid residue.

Fabrication of highly efficient thermal energy storage composite from waste polystyrenes

To high value-added utilization of waste polystyrene (PS) foam, an in-situ phase change material (PCM) encapsulation protocol was realized by using waste PS foam as a holding material for thermal energy storage with a shape-stabilization methodology. Mechanistic study suggested that the robust Lewis acid catalysed Friedel-Crafts reaction involved was the key to the success of this method owing to a simultaneous process of porous structure formation and PCM impregnation, by which the PCM encapsulation rate can attain to 68.7% without leakage. Lewis acid catalysts used in the process were able to be converted to their corresponding metal oxides via a simple alkali treatment, which not only diminished the tedious metal species isolation step but also made an external thermal conductivity enhancement that an utmost 61.0% thermal conductivity enhancement can be achieved compared with that of pristine paraffin wax. Additionally, the PCM composite preparation process can be facilely scaled up which strongly demonstrated its real application feasibility. Moreover, besides waste PS foam, other waste PS based materials were proven to be feasible towards PCM holding materials with the same approach.

Experimental and theoretical study on the cyclic(alkyl)(amino)carbene-copper catalyzed Friedel-Crafts reaction of N,N-dialkylanilines with styrenes.

The Friedel-Crafts reaction of alkalinous substrates is challenging because of the coordination between amines and traditional acid catalysts. Based on theoretical research, we designed a catalytic process for the Friedel-Crafts reactions of N,N-dialkylanilines in the presence of CAAC-CuCl [CAAC = cyclic(alkyl)(amino)carbene] and KB(C6F5)4. Experimental results show that the catalytic system is suitable for a series of N,N-dialkylanilines and styrenes with good to excellent yields of para-selectivity products. The results are comparable to those obtained in carbene-gold catalyzed processes.

Efficient Synthesis of Diarylmethylamines via Lewis Acid Catalyzed Friedel–Crafts Reactions of Donor–Acceptor Aziridines with N,N-Dialkylanilines

A method for efficient and mild synthesis of diarylmethylamine scaffold, via Lewis acid catalyzed Friedel–Crafts reaction of donor­–acceptor aziridines with N,N-dialkylanilines to afford a biologically important diarylmethylamine derivatives in high yields (up to 88%), is presented. This reaction is suitable for the synthesis of various diarylmethylamine derivatives and has a broad scope for electron-rich arenes, including dimethoxybenzene.

Catalytic Friedel‐Crafts Reactions on Saturated Heterocycles and Small Rings for sp3‐sp2 Coupling of Medicinally Relevant Fragments

gem‐Diarylheterocycles display a wide range of biological activity. Here we present a systematic study into the formation of 4‐ to 6‐membered O‐ and N‐heterocycles and cyclobutanes bearing the diaryl motif through a catalytic Friedel–Crafts reaction from the corresponding benzylic alcohols. 3,3‐Diaryltetrahydrofurans, 4,4‐diaryltetrahydropyrans, 3,3‐diarylpyrrolidines, 4,4‐diaryl‐piperidines, as well as diarylcyclobutanes are examined, with results for 3,3‐diaryloxetanes and 3,3‐diarylazetidines presented for comparison. Three catalytic systems are investigated for each substrate [Ca(II), Li(I) and Fe(III)], across preinstalled aromatic groups of differing electronic character. In most cases examined, the diaryl product is obtained directly from the alcohol with good yields using the most appropriate catalyst system. In the absence of a nucleophile, the olefins from the 5‐ and 6‐membered substrates by elimination of water are obtained under the same reaction conditions.

Synthesis of 3,3-Diarylazetidines by Calcium(II)-Catalyzed Friedel-Crafts Reaction of Azetidinols with Unexpected Cbz Enhanced Reactivity.

Azetidines are valuable motifs that readily access under explored chemical space for drug discovery. 3,3-Diarylazetidines are prepared in high yield from N-Cbz azetidinols in a calcium(II)-catalyzed Friedel-Crafts alkylation of (hetero)aromatics and phenols, including complex phenols such as β-estradiol. Electron poor phenols undergo O-alkylation. The product azetidines can be derivatized to drug-like compounds through the azetidine nitrogen and the aromatic groups. The N-Cbz group is crucial to reactivity by providing stabilization of an intermediate carbocation on the four-membered ring.

One-Pot Approach for the Synthesis of Bis-indole-1,4-disubstituted-1,2,3-triazoles.

A new strategy for the synthesis of bis-indoletriazoles was developed using a sequential one-pot four-step procedure via I2 and H2SO4-SiO2 catalyzed Friedel-Crafts reactions of indole with aldehyde followed by N-alkylation with propargyl bromide, azidation, and copper(I)-catalyzed azide alkyne cycloaddition (CuAAC). The reaction proceeded smoothly at room temperature in a short time, and a series of bis-indoletriazoles were obtained in good to excellent yields proving the generality of this one-pot methodology.

Ni(ClO4)2‐Catalyzed Friedel–Crafts Reaction of Coumarin‐Fused Donor–Acceptor Cyclopropanes with Indoles: Stereoselective Synthesis of trans‐3,4‐Disubstituted‐3,4‐dihydrocoumarins

A stereoselective synthesis of trans‐4‐(3‐indolylmethyl)‐3,4‐dihydrocoumarins has been developed. The method proceeds through a catalytic Friedel–Crafts reaction of coumarin‐fused donor–acceptor cyclopropanes with indoles. The use of Ni(ClO4)2 as a Lewis acid catalyst leads to the formation of a variety of 4‐(3‐indolylmethyl)‐3,4‐dihydrocoumarins in good yields with high diastereoselectivities.

Enantiospecific Total Syntheses of (+)-Hapalindole H and (-)-12-epi-Hapalindole U.

Enantiospecific total syntheses of (+)-hapalindole H and (-)-12-epi-hapalindole U as well as the formal syntheses of (+)-hapalindole Q and (+)-12-epi-fischerindole U isothiocyanate have been described. Key steps of our approach feature expedient, highly regio- and diastereoselective Lewis acid catalyzed Friedel-Crafts reaction of indole with cyclic allylic alcohols and intramolecular reductive Heck reaction. Efficiency of the synthetic route also relies on an alkynyl aluminate complex driven regioselective nucleophilic epoxide opening from a sterically hindered site.

Recent Advance in Catalytic Asymmetric Friedel-Crafts Reactions

Recent Advance in Catalytic Asymmetric Friedel-Crafts Reactions

A covalent triazine-based framework from tetraphenylthiophene and 2,4,6-trichloro-1,3,5-triazine motifs for sensing o-nitrophenol and effective I2 uptake

A covalent triazine-based framework with a tetraphenylthiophene (TTPT) backbone was prepared by the AlCl3 catalyzed Friedel–Crafts reaction of commercially available material 2,4,6-trichloro-1,3,5-triazine with tetraphenylthiophene in dichloromethane.

Extending the scope of the carbonyl facilitated triplet excited state towards visible light excitation.

A series of extended π-conjugated benzophenone analogs was synthesized through a facile Lewis-acid catalyzed Friedel-Crafts reaction in order to exploit the integral triplet state properties of benzophenone. Extending the π-conjugated plane of the phenyl ring of benzophenone allowed tuning of the excitation wavelength from the far-UV end (∼260 nm) to the visible spectrum (∼446 nm). Compared to benzophenone, significant red-shifts in the absorption (up to 450 nm in solution) with high photostability were observed for the synthesized benzophenone analogs. As is evident from the density functional theory calculations, expansion of the ring size of the aromatic part of the benzophenone analogs induces a decrease in the HOMO-LUMO gap. The considerable extension of the electron density to the carbonyl group in the LUMO substantiates the triplet nature associated with the benzophenone analogs. By virtue of the properties of the carbonyl functionality, an apparent increase in the triplet quantum yield (ΦT = 5.4% to 87.7%) was observed for the benzophenone analogs when compared to the corresponding bare polyaromatic hydrocarbon. The spin orbit coupling was computationally estimated for the benzophenone analogs to propose pathways for the observed intersystem crossing process. The plausibility to photoexcite the aromatic-ring-fused benzophenone frameworks for triplet activation in the visible range opens the door for a new class of materials for photonic application.