Highly selective catalytic Friedel-Crafts acylation and sulfonylation of activated aromatic compounds using indium metal

The Friedel-Crafts acylation of activated benzenes with various aromatic and aliphatic acid chlorides was studied in the presence of indium metal. The reaction was accomplished in high isolated yields under solvent or solvent-less conditions. The method is also applicable for preparing diaryl sulfones from aromatic compounds and aryl sulfonyl chlorides.     

Electrochemical synthesis and study of coordination compounds part 1: tin(II) catechol complexes

The electrochemical synthesis of tin(II) complexes of catechols, Sn(O₂Ar) (1a–9a), have carried out using tin metal as a sacrificial anode in acetonitrile, in the presence of catechol derivatives. The cyclic voltammetric characteristics of the synthesized complexes Sn(O₂Ar) (1a–9a) have been studied at glassy carbon electrode in dichloromethane. Anodic oxidation of Sn(O₂Ar) produces a single wave which shows irreversibility. Also, the electronic effects of ligands on the redox potential of complexes 1a–9a have been investigated. The synthesis of Sn(O₂Ar) species in high yields and purity has been successfully performed in an undivided cell using constant current conditions.     

Silica gel supported AlCl3 catalyzed Friedel-Crafts acylation of aromatic compounds

<正>Silica gel supported aluminium trichloride(SiO_2-AlCl_3) has been shown to be a mild,efficient,and chemoseiective heterogeneous Lewis acid catalyst for the acylation of aromatic compounds with acid chlorides.The catalyst can be reused up to five times after simple washing with ether and is stable(as a bench top catalyst).     

Tf2O as a rapid and efficient promoter for the dehydrative Friedel-Crafts acylation of aromatic compounds with carboxylic acids

The Friedel-Crafts acylation of aromatic compounds with carboxylic acids was investigated in the presence of Tf₂O. The reaction was carried out efficiently and very rapidly under mild reaction conditions without the need of any catalyst.     

MoO2Cl2 as a novel catalyst for Friedel-Crafts acylation and sulfonylation

The use of MoO₂Cl₂ as a novel catalyst for Friedel-Crafts acylation and sulfonylation is described. A series of aromatic ketones and sulfones were prepared in moderate to good yields using acyl chloride or sulfonyl chloride in the presence of MoO₂Cl₂ (20 mol %), under solvent-free conditions.     

Formation of upper rim acylated calix[4]arenes using a sacrificial zinc anode

A straightforward electrosynthetic method is described, which allows upper rim acylation of non-p-halogenated calix[4]arenes. For example, a solution of tetrapropoxycalix[4]arene 4 was electrolysed in the presence of ZnBr₂ in an undivided cell fitted with a sacrificial zinc anode using pure acetonitrile as solvent, yielding an organozinc species, which was then treated with acetyl chloride in the presence of a palladium catalyst to afford 5,11-diacetyl-25,26,27,28-tetrapropoxycalix[4]arene 5 in ca. 35% yield after workup.     

Regioselectivity of Friedel-Crafts acylation of aromatic compounds with several cyclic anhydrides

The Friedel-Crafts acylations of various aromatic compounds with cyclic anhydrides such as 2-(p-substituted phenyl)butanedioic, 3-phenylpentanedioic and homophathlic anhydrides were carried out under various conditions in order to obtain informations about the regioselectivity of the ring opening of the cyclic anhydrides and about the possible reaction pathways in the acylations.     

The Friedel-Crafts acylation of aromatic compounds with carboxylic acids by the combined use of perfluoroalkanoic anhydride and bismuth or scandium triflate

Aromatic ketones were synthesized by solventless Friedel-Crafts acylation of anisole, mesitylene, xylenes, and toluene with acetic acid and benzoic acid in the presence of trifluoroacetic anhydride by use of bismuth or scandium triflate at 30 °C. Toluene, benzene, and even deactivated substrate such as chlorobenzene were benzoylated by the combined use of heptafluorobutyric anhydride and bismuth triflate at 75-100 °C. The catalyst could be easily recovered and reused repeatedly for the reaction.     

Friedel-Crafts acylation of ferrocene with alkynoic acids

Ferrocene reacts with alkynoic acids (conjugated or nonconjugated terminal), trifluoroacetic anhydride and triflic acid (or boron trifluoride etherate) to afford the corresponding ferrocenyl ynones in good yields. Only in the case of propynoic- and 3-butynoic acid complex, untreatable reaction mixtures were obtained. However, propynoilferrocene was obtained by desilylation of (trimethylsilyl)propynoilferrocene with KF/18-crown-6. Reaction with nonconjugated terminal alkynoic acids, carried out in the presence of a large excess of triflic acid (4 equiv.) results in formation of complex mixtures of products (in the reaction with 4-pentynoic acid enol triflate of ferrocenyl 1,4-diketone and 2-ferrocenyl-5-methylfuran were isolated). Ferrocenyl ynones obtained in this work can be used for synthesis of more complex ferrocenyl systems by “click” chemistry.     

Aluminum dodecatungstophosphate (AlPW12O40) as a non-hygroscopic Lewis acid catalyst for the efficient Friedel-Crafts acylation of aromatic compounds under solvent-less conditions

Stable and non-hygroscopic aluminum dodecatungstophosphate (AlPW₁₂O₄₀), which is prepared easily from cheap and commercially available compounds was found to be an effective catalyst for Friedel-Crafts acylation reactions using carboxylic acids, acetic anhydride and benzoyl chloride in the absence of solvent under mild reaction conditions.     

Sand: A natural and potential catalyst in renowned Friedel Craft's acylation of aromatic compounds

The aim of this work is to develop a cheap and green chemical process and this paper describes the catalytic commotion of locally collected sand in Friedel–Craft's Acylation of aromatic compounds like benzene, anisole, aniline, naphthalene and phenol etc. The sand consists of silica and alumina as analyzed by means of EDAX and acts as a green Lewis acid. The catalyst was also characterized by using BET, SEM, and XRD techniques.     

Site directed nuclear bromination of aromatic compounds by an electrochemical method

Direct bromination of a wide range of aromatic compounds possessing electron-donating groups, such as methoxy, hydroxy or amino groups, have been carried out by two-phase electrolysis. This electrochemical method results in high yields (70-98%) of monobromo compounds and usually with high regioselectivity (>95%) for the para position.     

Studies on the reactions of fluoroalkanesulfonyl azide with aromatic compounds

The thermal decomposition reactions of fluoroalkanesulfonyl azides R_fSO₂N₃ (1) in the presence of various substituted benzene X_nC₆H_6−n [X: CH₃ (n=1, 2, 4, 6), OCH₃ (n=1, 2), C₆H₅CH₂ (n=1), F, Cl, Br] were studied in detail. The N-aryl fluoroalkanesulfonyl amides [R_fSO₂NHC₆H_5−nX_n] were produced as the major products. The ortho/para ratio resembled that of an electrophilic aromatic substituted reaction. An ionic π- or σ-complex was postulated as the intermediate for these reactions.     

A simple and regioselective α-bromination of alkyl aromatic compounds by two-phase electrolysis

Electrochemical bromination of toluene and substituted toluenes by two-phase electrolysis yields the corresponding α-brominated products. The reaction has been carried out in a single compartment cell with platinum electrodes at 0 °C in chloroform using an aqueous sodium bromide solution (60%) containing a catalytic amount of HBr. Two-phase electrolysis results in high yields (60-95%) of monobromo compounds with very high regioselectivity (>95%).     

Advances in liquid-phase Friedel-Crafts acylation of aromatics catalyzed by heterogeneous solids

In the last few decades, significant improvements toward the development of environmentally benign processes have been achieved in the liquid-phase Friedel-Crafts acylation reactions. Many efforts have been devoted to the research on solid catalysts adequate to substitute homogeneous protonic acids or Lewis acids as traditionally employed catalysts in the acid-catalyzed Friedel-Crafts acylation processes. This short article describes the recent developments on catalysis by gallium (Ga), indium (In) and thallium (Tl) based novel heterogeneous solids for the liquid-phase Friedel-Crafts acylation of aromatics by acyl halide. The above heterogeneous catalysts are efficient for Friedel-Crafts acylation reaction and exhibited superior activity than the traditionally employed strongly acidic solid catalysts. Unlike conventional acidic catalyst, the acylation activity of Ga, In and Tl based solids, additionally having redox functions, does not depend solely on their acidic properties, even present. These solids in their non-acidic or basic form also show high acylation activity. Based on the catalytic results over these novel solids a plausible reaction mechanism for the acylation is proposed.Dedicated to Professor Seitaro Namba on the occasion of his 64th birthday.     

Niobium pentachloride-silver perchlorate as an efficient catalyst in the Friedel-Crafts acylation and Sakurai-Hosomi reaction of acetals

Friedel-Crafts acylation catalyzed by niobium pentachloride with silver salt is described. Aromatic compounds with Ac₂O or Bz₂O were smoothly converted into the corresponding ketones in good to excellent yields. This system was also applied to the Sakurai-Hosomi reaction using acetals. The reaction proceeded quite rapidly to give the desired products in excellent yields.     

Radical promoted cyclizations of aromatic carbonyl compounds to benzopyrans using titanocene(III) chloride

Aromatic carbonyl compounds undergo smooth intramolecular radical cyclization with alkenes or alkynes using titanocene(III) chloride to furnish the corresponding benzopyrans. The radical initiator, Cp₂TiCl, was prepared in situ from commercially available titanocene dichloride (Cp₂TiCl₂) and zinc dust in THF under argon.     

Chemoselective acylation of some oxidofunctionalised organolithium compounds

Once oxidofunctionalised organolithium compounds 1 (easily prepared by reductive ring opening of isochroman and phthalan by DTBB-catalysed lithiation) were transmetallated with ZnBr₂/CuCN·2LiCl and reacted successively with a carboxylic acid anhydride and an acyl chloride in THF at 0°C, the corresponding differently acylated compounds 4 were obtained after hydrolysis with water. The anhydride performed the O-acylation exclusively and the acyl chloride carried out the C-acylation.     

Solvent-free Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of trifluoroacetic anhydride and aluminum dodecatungstophosphate

The stable and non-hygroscopic aluminum dodecatungstophosphate (AlPW₁₂O₄₀), was found to be an effective catalyst (3 mol%) for the solvent-free Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of trifluoroacetic anhydride under mild reaction conditions.     

Regioselective iodination of aromatic compounds with potassium iodide in the presence of benzyltriphenylphosphonium perchlorate

A simple and efficient method for the selective iodination of various aromatic compounds by using potassium iodide in the presence of benzyltnphenylphosphonium perchlorate,is reported.This method provides several advantages such as good selectivity between ortho and para positions of aromatic compounds and high yields of the products.