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This article provides an overview of photoredox-catalyzed C(sp2)–H bond functionalization reactions, which use low-energy photons to enable reactions under mild conditions. It discusses the contributions of researchers in advancing the field and explores the potential of using organic photocatalysts. The article focuses on the author's group's work in utilizing these reactions for C–H bond functionalizations, specifically in the context of enamides. The researchers explored various reactions, including the functionalization of enamide β-C(sp2)-H bonds, phosphorylation of alkenyl C(sp2)-H bonds, and bromination and alkylation of (hetero)arene C(sp2)-H bonds. These reactions have applications in the synthesis of natural products and pharmaceuticals, and further research is needed to develop new transformations and expand their applications. [Extracted from the article]

The Friedel‐Crafts reaction stands as a powerful synthetic tool for C−H functionalization of aromatic feedstocks, which is conventionally realized through electrophilic alkylation and acylation. The burgeoning interests in axially chiral compounds across diverse fields have spurred extensive exploration of this classic transformation for catalytic atroposelective synthesis. Consequently, the past decade has witnessed the rapid expansion of various non‐canonical Friedel‐Crafts reactions, including electrophilic arylation, alkenylation, halogenation, sulfenylation, and amination of aryl C−H bonds, thereby delving into new chemical spaces. A range of catalytic atroposelective synthetic methods have been devised for these significant arene C−H functionalization. This review provides a comprehensive overview of the cutting‐edge catalytic synthesis of atropoisomers through non‐canonical Friedel‐Crafts reactions, categorized into three parts based on the type of bond formation on the aromatics: C(sp2)−C(sp3) bond formations, C(sp2)−C(sp2) bond formations and C(sp2)−heteroatom bond formations. The richness of electrophiles and the modulation of atroposelectivity by diverse chiral organocatalysts, particularly chiral Brønsted acids, are elucidated. We anticipate that the repertoire of asymmetric Friedel‐Crafts reaction will continue to flourish and to be demonstrated in not only scientific researches but also industrial organic synthesis. [ABSTRACT FROM AUTHOR]

Pillar[n]arenes can be constructed using a Friedel–Crafts alkylation process. However, due to the reversible nature of the alkylation, mixture of large pillar[n]arenes (n≥7) are obtained as minor products, and thus laborious purification are necessary to isolate the larger pillar[n]arenes. Moreover, inert methylene bridges are introduced during the alkylation process, and the multi‐functionalization of the bridges has never been investigated. Herein, an irreversible Friedel–Crafts acylation is used to prepare pillar[n]arenes. Due to the irreversible nature of the acylation, the reaction of precursors bearing carboxylic acids and electron‐rich arene rings results in a size‐exclusive formation of pillar[n]arenes, in which the ring‐size is determined by the precursor length. Because of this size‐selective formation, laborious separation of undesired macrocycles is not necessary. Moreover, the bridges of pillar[n]arenes are selectively installed with reactive carbonyl groups using the acylation method, whose positions are determined by the precursor used. The carbonyl bridges can be easily converted into versatile functional groups, leading to various laterally modified pillar[n]arenes, which cannot be accessed by the alkylation strategy. [ABSTRACT FROM AUTHOR]

Hierarchical ZSM5 and Y zeolites were prepared through a surfactant-mediated strategy with NH4OH changing the duration of the treatment and the amount of CTAB surfactant and taking as reference multiples of the critical micellar concentration (CMC). The materials were characterized using powder X-ray diffraction, N2 adsorption isotherms at −196 °C, and SEM and TEM microscopy. The catalytic performance was evaluated in Friedel–Crafts acylation of furan with acetic anhydride at 80 °C. The alkaline surfactant-mediated treatment had different effects on the two zeolites. For ZSM5, the CTAB molecular aggregates can hardly diffuse inside the medium-size pores, leading mainly to intercrystalline mesoporosity and increased external surface area, with no positive catalytic impact. On the other hand, for large-pore Y zeolite, the CTAB molecular aggregates can easily diffuse and promote the rearrangement of crystal units around micelles, causing the enlargement of the pores, i.e., intracrystalline porosity. The optimized Y-based sample, treated for 12 h with a CTAB amount 32 times the CMC, shows an increase in product yield and rate constant that was not observed when a higher amount of surfactant was added. The reuse of spent catalysts upon thermal treatment at 400 °C shows a regeneration efficiency around 90%, showing good potentialities for the modified catalysts. [ABSTRACT FROM AUTHOR]

The Friedel‐Crafts acylation reaction between activated amides and arenes was carried out by employing [Pd(cinnamyl)Cl]2 and Cu(OTf)2 as catalysts. A range of N‐phenyl‐N‐tosylbenzamides, which were substituted at the phenyl ring of the benzamide moiety, underwent reaction with various arenes, such as mesitylene, toluene, anisole, 4‐tert‐butylbenzene, o‐xylene, m‐xylene, and p‐xylene, affording the corresponding diaryl ketones with yields ranging from 49% to 89%. [ABSTRACT FROM AUTHOR]

The reaction of 4,5-dichlorocyclopent-4-en-1,3-dione with 1,3,5-trimethoxybenzene under Friedel–Crafts reaction conditions gave, along with the expected 5-(2,4,6-trimethoxyphenyl)-4-chlorocyclopent-4-ene-1,3-dione, a disubstituted product―3,4-bis-(2,4,6-trimethoxyphenyl)-2-chlorocyclopent-2-en-1-one. [ABSTRACT FROM AUTHOR]

The Friedel–Crafts acylation reaction, which belongs to the class of electrophilic aromatic substitutions is a highly valuable and versatile reaction in synthesis. Regioselectivity is predictable and determined by electronic as well as steric factors of the (hetero)arene substrate. Herein, a radical approach for the acylation of arenes and heteroarenes is presented. C−H acylation is achieved through mild cooperative photoredox/NHC radical catalysis with the cross‐coupling of an arene radical cation with an NHC‐bound ketyl radical as a key step. As compared to the classical Friedel–Crafts acylation, a regiodivergent outcome is observed upon switching from the ionic to the radical mode. In these divergent reactions, aroyl fluorides act as the acylation reagents in both the ionic as well as the radical process. [ABSTRACT FROM AUTHOR]

Friedel‐Crafts alkylation and acylation reactions are important methodologies in synthetic and industrial chemistry for the construction of aryl‐alkyl and aryl‐acyl linkages that are ubiquitous in bioactive molecules. Nature also exploits these reactions in many biosynthetic processes. Much work has been done to expand the synthetic application of these enzymes to unnatural substrates through directed evolution. The promise of such biocatalysts is their potential to supersede inefficient and toxic chemical approaches to these reactions, with mild operating conditions ‐ the hallmark of enzymes. Complementary work has created many bio‐hybrid Friedel‐Crafts catalysts consisting of chemical catalysts anchored into biomolecular scaffolds, which display many of the same desirable characteristics. In this Review, we summarise these efforts, focussing on both mechanistic aspects and synthetic considerations, concluding with an overview of the frontiers of this field and routes towards more efficient and benign Friedel‐Crafts reactions for the future of humankind. [ABSTRACT FROM AUTHOR]

An efficient PCl3‐promoted Friedel‐Crafts reaction using esters as both alkylating and acylating reagents has been developed. By using a PCl3/I2 combination, various esters underwent Friedel‐Crafts alkylation and acylation reactions with arenes in one‐pot, readily producing two kinds of products aromatic ketones and alkyl aromatics by one step in good yields. The Friedel‐Crafts alkylation and acylation of arene with 4‐formylbenzoate derivatives in one‐pot have also been achieved. This novel strategy features high step economy, low‐cost, metal‐free and simple reaction conditions. [ABSTRACT FROM AUTHOR]

Functionalizing and derivatising organic molecules is a centerpiece in organic synthesis. Succinctly manipulating and installing acyl moieties in organic molecules spurred the interest of chemists owing to its occurrence in natural products, bioactive molecules, pharmaceuticals, and advanced materials. Traditionally, access to acylation reaction was achieved by Friedel‐Crafts reaction, Schotten‐Baumann, and Vilsmeier‐Haack acylation, however, these protocols own pitfalls. Further to make the acylation process attractive and environmentally friendly, toluene, aldehydes, alcohols, α‐keto acids, amines, amides, esters, ethers, nitriles, alkynes, alkenes, ketenes, N‐acylbenzotriazoles, ketones, thioacids, oximes, thiazolium carbinols, PIDA, diacyl disulfides and acyl salts were used as an acyl surrogates/reagents. Amusingly, these acylating reagents are considered uncommon and alternative to carboxylic acids, acid chlorides and acetic anhydrides. This short review aims to encompass the usage of acylating agents in transition‐metal, metal‐free, light‐driven and other demanding conditions, and thus reveals their practicality. [ABSTRACT FROM AUTHOR]

Bismuth SBA-16 catalyst was synthesized by the hydrothermal method. Four kinds of p-toluenesulfonic acid functionalized imidazole ionic liquids were prepared by a two-step method and their molecular structures were characterized by 1H NMR and MS. The post-synthesis impregnation method was used to functionalize the Bi(10)-SBA-16 silicon mesoporous material with the ionic liquids and the obtained materials were characterized by FT-IR, XRD, BET, XPS, and TG. The results show that the volume and pore size of SBA-16 were changed by loading Bi and ionic liquids, while the three-dimensional cubic pore structure of SBA-16 was not destroyed. The composite catalyst was evaluated in Friedel–Crafts acylation of anisole with acetic anhydride. The effects of reaction temperature and the ratio of anisole and acylating agent on the acylation of anisole were investigated by experimental design. The results showed that 1.2ILc@Bi(10)-SBA-16 was used as the catalyst, the conversion of anisole was 85.41% and the yield of aromatic ketone was 69.19% under the conditions of a reaction temperature of 100 °C, a catalyst dosage of 0.5 g, a time period of 4 h and a molar ratio of 1 : 1.5. After 5 recycling runs, the reduction in the overall ratio of reactant conversion and product yield did not exceed 7.5%, indicating that 1.2ILc@Bi(10)-SBA-16 has good stability and reusability. [ABSTRACT FROM AUTHOR]

A concise and convergent stereoselective synthesis of curvulone B is described. The synthesis utilized a tandem isomerization followed by C–O and C–C bond-forming reactions following Mukaiyama-type aldol conditions for the construction of the trans -2,6-disubstituted dihydropyran ring system as the key steps. Other important features of this synthesis are a cross-metathesis, epimerization, and Friedel–Crafts acylation. [ABSTRACT FROM AUTHOR]

A new and autocatalytic method was developed for Friedel‐Crafts acylation of arenes without additional catalyst and additive. A series of electron‐rich arenes underwent the acylation to give the targeted product in low to high yields by using aryl, alkyl and vinyl acyl chlorides as the acylating reagent, which gave an effective method for the preparation of diaryl ketones, alkyl aryl ketones and α,β‐unsaturated ketones. Preliminary mechanistic investigation suggested that the present acylation displayed an induction period and a sigmoid kinetic profile characteristic of autocatalytic systems, and the resulting H+ played a role of the catalyst. [ABSTRACT FROM AUTHOR]

Cyclic ketones, anhydrides, lactams and lactones are a particular class of molecules that are often used in synthesis, wherein their electrophilic properties are leveraged to enable facile Friedel–Crafts ring openings through nucleophilic attack at the carbonyl sp2 centre. The use of electron-rich alkoxybenzenes as nucleophiles has also become important since the discovery of the Friedel–Crafts reaction. As a result, various isomeric alkoxybenzenes are used for preparing starting materials in target-oriented syntheses. This review covers the instances of different alkoxybenzenes that are used as nucleophiles in ring-opening acylations with carbonyl-containing cyclic electrophiles, for the construction of important building blocks for multistep transformations. This review summarizes the ring-opening functionalization of three- to seven-membered molecular rings with alkoxybenzenes in a Friedel–Crafts fashion. Sometimes the rings need subtle or considerable activation by the help of Lewis acid(s), followed by nucleophilic attack. This review is aimed to be a summary of the important acylations of electron-rich alkoxybenzenes by nucleophilic ring-opening of cyclic molecules. The works cited employ a wide range of conditions and differently substituted substrates for target-oriented syntheses. 1 Introduction and Scope 2 Arenes for Acylative Ring Opening 2.1 Three-Membered Rings: Ring Opening of Oxirane-2,3-dione 2.2 Four-Membered Rings 2.2.1 Ring Opening of Cyclobutanones 2.2.2 Ring Opening of β-Lactams 2.2.3 Ring Opening of β-Lactone 2.3 Five-Membered Rings 2.3.1 Ring Opening of Phthalimides 2.3.2 Ring Opening of γ-Lactones 2.3.3 Ring Opening of Anhydrides 2.4 Six-Membered Rings 2.5 Seven-Membered Rings 3 Conclusion [ABSTRACT FROM AUTHOR]

A series of highly diversified 3‐aroylmenadiones was prepared by a new Friedel–Crafts acylation variant/oxidative demethylation strategy. A mild and versatile acylation was performed between 1,4‐dimethoxy‐2‐methylnaphthalene and various activated/deactivated benzoic and heteroaromatic carboxylic acids, in the presence of mixed trifluoroacetic anhydride and triflic acid, at room temperature and in air. The 1,4‐dimethoxy‐2‐methylnaphthalene‐derived benzophenones were isolated in high yield, and submitted to oxidative demethylation with cerium ammonium nitrate to produce 3‐benzoylmenadiones. All 1,4‐naphthoquinone derivatives were investigated as redox‐active electrophores by cyclic voltammetry. The electrochemical data recorded for 3‐acylated menadiones are characterized by a second redox process, the potentials of which cover a wide range of values (500 mV). These data emphasize the ability of the generated structural diversity at the 3‐aroyl chain of these electrophores to fine‐tune their corresponding redox potentials. These properties are of significance in the context of antimalarial drug development and understanding of the mechanism of bioactivation/action. [ABSTRACT FROM AUTHOR]

This work highlights how the treatment of ZSM-5 (parent Zeolite Socony Mobil-5, Si/Al = 23) with different surfactant templates and alkaline solution, improved the catalytic performance in the Friedel-Crafts acylation of anisole with a propionic anhydride to obtain p-methoxypropiophenone. Themodifiedmicroporous tomesoporous zeolite catalystswere characterized using different analytical techniques, including X-ray diffraction (XRD), nitrogen porosimetry, Fourier-transform infrared spectroscopy (FT-IR), temperature-programmed desorption (ammonia-TPD) and field emission scanning electron microscopy (FE-SEM) to analyze the crystallographic structure, surface acidity, surface area, porosity, morphology, and particle size. The results showed that the formed mesoporous zeolite by NaOH solution had smaller mesopores (ca. 3.7 nm) as compared to the mesoporous zeolites obtained by surfactant templates, such as, CTAB (ca. 14.9 nm), TPAOH (ca. 11.1 nm) and mixture of CTAB/TPAOH (ca. 15.2 nm). The catalytic acylation reaction was conducted in a batch glass reactor at various temperatures and the products were analyzed using off-line gas chromatography-mass spectrometry (GC-MS). It was found that the activity of treated ZSM-5 withmixed surfactant templates (CTAB/TPAOH) exhibited enhanced selectivity towards the main product (p-methoxypropiophenone) by a factor 1.7 or higher than unmodified ZSM-5 due to its increased surface area by 1.5 times and enhanced acid sites. [ABSTRACT FROM AUTHOR]

A concise and highly stereoselective total synthesis of the Daphniphyllum alkaloids (−)‐daphenylline has been accomplished. The synthesis was started from (S)‐carvone and proceeded via a stereoselective Mg(ClO4)2‐catalyzed intramolecular amide addition cyclization, an intramolecular Diels–Alder reaction to construct the ABCD tetracyclic core architecture, and a Robinson annulation coupled with an oxidative aromatization sequence. Finally, the DF ring system was installed through an intramolecular Friedel–Crafts cyclization. The total synthesis of (−)‐daphenylline is achieved in 19 steps in the longest reaction sequence and in 7.6 % overall yield. Round, round, get around: A concise and highly enantioselective total synthesis of (−)‐daphenylline was accomplished in 19 steps and 7.6 % overall yield from (S)‐carvone. It features an Mg(ClO4)2‐catalyzed intramolecular amide cyclization and a Diels–Alder cycloadditon to construct the tetracyclic motif, a tandem Robinson annulation with oxidative aromatization, and an intramolecular Friedel–Crafts acylation and Nazarov‐type cyclization to construct the DF rings. [ABSTRACT FROM AUTHOR]

H‐β Zeolites, doped with various metal salts, were investigated as heterogeneous catalysts for continuous‐flow Friedel‐Crafts acylation reactions. It was found that Zr‐β zeolites possessed excellent catalyst activity and stability, which enabled its use as a catalyst, up to 5 days, for Friedel‐Crafts reactions between various activated arenes and acid anhydrides. Challenging substrates, such as toluene and m‐xylene, were also successfully applied for the continuous‐flow process. H‐β zeolite, doped with zirconium, was found to be an excellent heterogeneous catalyst for the continuous‐flow Friedel‐Crafts acylation reaction of arenes with acid anhydrides. Control experiments and characterization studies of the used H‐β and Zr‐β zeolites revealed that the metal dopant improves the stability of the catalyst. [ABSTRACT FROM AUTHOR]

Functionalization of aromatic compounds by acylation has considerable significance in synthetic organic chemistry. As an alternative to chemical Friedel‐Crafts acylation, the C‐acyltransferase from Pseudomonas protegens has been found to catalyze C−C bond formation with non‐natural resorcinol substrates. Extending the scope of acyl donors, it is now shown that the enzyme is also able to catalyze C−S bond cleavage prior to C−C bond formation, thus aliphatic and aromatic thioesters can be used as acyl donors. It is worth to mention that this reaction can be performed in aqueous buffer. Identifying ethyl thioacetate as the most suitable acetyl donor, the products were obtained with up to >99 % conversion and up to 88 % isolated yield without using additional base additives; this represents a significant advancement to prior protocols. New tool available: As an alternative to chemical Friedel‐Crafts acylation, the C‐acyltransferase from Pseudomonas protegens catalyzes C−C bond [ABSTRACT FROM AUTHOR]

A bis-acylation strategy to access functionalized anthraquinones via one-pot relay process, is presented. The first acylation was feasible under [Pd]-catalyzed intermolecular direct acylation reaction, while, the second acylation was accomplished by using intramolecular Friedel–Crafts acylation. Notably, benchtop aldehydes have been utilized as non-toxic acylation agents in the key [Pd]-catalyzed acylation. [ABSTRACT FROM AUTHOR]

A series of bimetallic Zn-Co catalysts before and after calcination were prepared by simple MOFs template methods. The effects of calcination on their structures were investigated by XRD, FT-IR, TPD, XPS and EPR characterization methods, and their catalytic performances were compared in the cycloaddition reactions of CO 2 and propylene oxide and acylation reactions of anisole and acetyl chloride, respectively. The results show that uncalcined ZnCo2-MOFs catalyst has excellent catalytic performance for cycloaddition reaction due to the presence of acid-base synergism, whereas the strong acidity of calcined ZnCo2O X catalyst is very favorable for acylation reaction. This is due to the fact that calcination changes the structure of ZnCo2-MOFs catalyst, causes charge migration on the surface and results in the conversion of lattice oxygen to oxygen vacancies, which brings a large difference in the acidity and basicity of catalysts. [Display omitted] • A series of Zn-Co bimetallic catalysts via a simple MOFs template method were obtained. • These catalysts before and after calcination exhibit excellent results for two different reactions. • Before calcination, acidity comes from metal sites and basicity comes from imidazole N as well as lattice oxygen. • After calcination, strong Lewis acidity derived from metal sites as well as oxygen vacancies. • Innovative linking of changes in acidity and basicity to structural differences brought about by calcination. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Decarbonylation occurs in Friedel-Crafts acylation of glyoxylic acid chlorides. • 7,7′-Diindolylketones can be formed by acylation reactions. • Novel cyclisation of indolyl N atoms on aromatic ring. • New and effective formation of acridones. Abstract Acylation reactions of 4,6-dimethoxyindoles with glyoxyloyl chlorides were achieved by the use of graphite powder in 1,2-dichloroethane at reflux. The products were monoketones as a result of decarbonylation, rather than the expected 1,2-diketones. Treatment of these monoketones with base led to their cyclisation and elimination of methanol to afford the novel dipyrrolo[ 2. 3 - a : 1′ , 2′ , 3′ - fg ]acridin-12(1 H)-ones. [ABSTRACT FROM AUTHOR]

Abstract This paper reports the synthesis of five acylated derivatives of the polyetherimide (PEI) by means of Friedel-Crafts acylation. PEI derivatives containing acetyl, butanoyl, hexanoyl, decanoyl and benzoyl side groups were synthesized and characterized by means of 1H NMR, FTIR and UV–vis spectroscopy, as well as by DSC and TGA. It was observed that, under the conditions reported herein, the acylation takes place at two different rings, in degrees ranging from 4.0 to 55%, and that the acyl groups have a significant influence on the processes of intermolecular and intramolecular charge transfers, on the thermal stability and on the glass transition temperature of the polymer. Graphical abstract Image 1 Highlights • Acylated PEI can be easily prepared by means of Friedel-Crafts acylation. • Two different rings can be acylated in different degrees. • The T g is linearly related to the degree of modification. [ABSTRACT FROM AUTHOR]

Abstract: As the most important method to prepare pharmaceutical and chemical intermediate aromatic ketones, Friedel-Crafts (F-C) acylation is used to seek a novel catalytic system which is imminently consistent with the concept of green chemistry. In this study, six deep eutectic solvents (DES) were synthesized for the Friedel-Crafts acylation reaction as a catalytic solvent. Among the six DES, choline chloride-zinc chloride ([ChCl][ZnCl2]2) proved to be the most competent candidate of electron-rich arenes with acylation reagent. It got the highest yield when 1.0 equivalent of [ChCl][ZnCl2]2 used with acyl halides at 70 °C. Recycled DES was reused directly without any extra process. After five cycles, the catalytic activity did not decrease significantly (80-85%). Finally, according to experimental validation, the possible mechanism of this reaction was considered.Graphical Abstract: [ABSTRACT FROM AUTHOR]

An improved, short and efficient synthesis of vinylferrocene is reported. This three-step synthesis includes Friedel-Crafts acylation, reduction, and a one-pot mesylation/elimination step to afford the target compound in 62% yield over three steps. [ABSTRACT FROM AUTHOR]

Amides, ketones, Friedel-Crafts acylation, palladium, copper Cover Picture: Palladium and Copper-Catalyzed Friedel-Crafts Acylation with Activated Amides (Adv. Keywords: amides; ketones; Friedel-Crafts acylation; palladium; copper EN amides ketones Friedel-Crafts acylation palladium copper 2990 2990 1 09/25/23 20230919 NES 230919 The inside cover picture illustrates a new approach that was devised for the Friedel-Crafts acylation reaction, involving the combination of an activated amide and an arene. [Extracted from the article]

A series of supported CuCl/γ-AlO with different Cu content (2, 6, 10, 13, 16 and 17 wt%) were prepared by the method of wet impregnation and spontaneous monolayer dispersion techniques. These co-catalysts were analyzed by XRD, BET, SEM, XPS and ICP techniques and were found to inhibit the formation of defluorination byproducts during the phenylacetylation of fluorobenzene catalyzed by AlCl, allowing the using of fluorobenzene as the reaction solvent that could be easily recycled. The best inhibitor was 10 wt% Cu supported CuCl/γ-AlO, which still had good catalytic performance after being recycled for five times. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The Friedel-Crafts acylation is commonly used for the synthesis of aryl ketones, and a biocatalytic version, which may benefit from the chemo- and regioselectivity of enzymes, has not yet been introduced. Described here is a bacterial acyltransferase which can catalyze Friedel-Crafts C-acylation of phenolic substrates in buffer without the need of CoA-activated reagents. Conversions reach up to >99 %, and various C- or O-acyl donors, such as DAPG or isopropenyl acetate, are accepted by this enzyme. Furthermore the enzyme enables a Fries rearrangement-like reaction of resorcinol derivatives. These findings open an avenue for the development of alternative and selective C−C bond formation methods. [ABSTRACT FROM AUTHOR]

The mechanism of electrophilic aromatic substitution (SAr) is still matter of debate and interest in the literature. In this work, the Friedel-Crafts alkylation and the acylation in the gas phase were investigated in the context of the unified mechanism for SAr. In this unified proposal three kinds of intermediates can potentially be formed: oriented and unoriented π-complexes, intimate single electron transfer (SET) intermediates and σ-complexes. Quantum chemical calculations at M06-2X/6-311++G(d,p) level were carried out for the investigation of the reaction of benzene with acetyl and tert-butyl ions as model non-oxidant electrophiles for acylation and alkylation, respectively, in the gas phase. It was found that both the tert-butyl and the acetyl cations prefer to form oriented π-complexes. Both electrophiles do not react through a SET pathway with benzene. The π-complex between tert-butyl cation and benzene can evolve to a σ-complex, while in the case of the acetyl cation and benzene the σ-complex was not found as a minimum on the potential energy surface. Instead, it corresponds to a transient species or a very shallow minimum. The outcome of this is that the π-complex would only react with the aromatic ring evolving to the product with nucleophilic assistance by a species of the reaction medium, in either through a concerted mechanism or a specific interaction. This is also observed for aromatics with low ionization energies/nucleophilicities. However, very electron rich aromatic systems afford σ-complexes, and as their ionization energies increases (i.e., less nucleophilic), the more the resulting complex resembles a π-complex, more or less continuously. This suggests out that electrophilic aromatic substitution reactions cannot be rationalized within a single mechanistic framework. Instead, a continuum of mechanistic possibilities may be involved. [ABSTRACT FROM AUTHOR]

Biologically active phenyl[3-(3,7-dimethyl-2,6-octadienyl)-2,4,6-trihydroxyphenyl]methanone (2) and phenyl[2,4,6-trihydroxy-3-(3-methyl-2-butenyl)phenyl]methanone (3) were synthesized by an efficient and convenient synthetic sequence. The reaction steps of this synthesis included methylation, Friedel-Crafts acylation, demethylation and geranylation steps. [ABSTRACT FROM PUBLISHER]

A facile synthetic method to chromenones and thiochromenones has been developed using a one-pot Friedel-Crafts acylation of alkynes with suitably substituted benzoyl chlorides. This unified approach to (thio)chromenones is readily applicable to aryl- and alkylalkynes where the stereochemically well-defined β-chlorovinyl ketone intermediates undergo distinctively different cyclization pathways. The ready availability of both starting materials, alkynes and benzoyl chlorides, coupled with the experimental simplicity makes the current synthetic method to (thio)chromenones fast, efficient, and practical. [ABSTRACT FROM AUTHOR]

[(2-Ferrocenylvinyl)methyl]dimethylamine ( 2) was obtained in good yields and with perfect regio- and stereoselectivity by reaction of dimethylmethylideneammonium salts with vinylferrocene. After methylation of amine 2, [(2-ferrocenylvinyl)methyl]trimethylammonium iodide ( 4) was obtained in high yields and used to transfer the ferrocene-containing allyl group to various amines. By controlling reaction conditions, various linear and branched ferrocenyl-substituted allylamines could be obtained with good yields and selectivities. When anilines were used as substrates against ammonium salt 4, compounds originating from Friedel-Crafts reactions were also obtained, with complete regioselectivity towards the para position. [ABSTRACT FROM AUTHOR]

Acid catalysts including Ni, Ag and Fe-loaded zeolites of different structures were prepared either via cationic exchange or impregnation techniques from pristine H-zeolites (BEA, and MFI). Their catalytic activity was evaluated in the liquid-phase Friedel–Crafts acylation of anisole with propanoic acid. It turned out that, whatever the doping procedure was, the zeolite loaded with transition metals led to considerable decrease in propanoic acid conversion, regardless of the nature or the metal content. However, the extent of this detrimental effect followed the order: Ag + > Ni 2+ > Fe 3+ . Pristine acidic zeolites were not only found to be the most active, but also to be the most selective toward ortho - and para -acylation products. H-ZSM-5 zeolites yielded the highest intrinsic activity, with TOF values of 0.09 h −1 . The catalyst activity proved to be essentially attributed to the density and accessibility of Brønsted acid sites, playing a key role in the activation of the reactants. Brønsted sites are proposed to be the most likely catalytic species for performing this Friedel–Crafts acylation. [ABSTRACT FROM AUTHOR]

Zeolite catalyzed Friedel-Crafts acetylation of 2-methoxynaphthalene to produce 2-methoxy-6-acetylnaphthalene with high selectivity and conversion has been a challenging task, because the obtained compound is a key intermediate for an anti-inflammatory agent, Naproxen. However, no satisfactory results have been obtained with zeolite catalysts, and harmful solvents have been used to gain a high selectivity together with a high conversion. Here, we report the synthesis of 2-methoxy-6-acetylnaphthalene from 2-methoxynaphthalene with a high selectivity and a high conversion under an unprecedented simple reaction system; acetic anhydride as an acetylating agent, acetic acid as a solvent, and proton-type zeolite catalysts with low acidity. Among the examined zeolites, a proton-type H-MOR (SiO 2 /Al 2 O 3 = 200) with a low acid content shows a conversion of 82% and an 86% selectivity for 2-methoxy-6-acetylnaphthalene. Further, detailed control experiments using H-MOR catalyst in acetic acid solvent were carried out to propose a plausible reaction mechanism. [ABSTRACT FROM AUTHOR]