Use of solid catalysts in Friedel-Crafts acylation reactions.

A large number of inorganic oxides, mixed oxides, including alumina, silica, titania, zirconia, zeolites, carbon, clays and ion exchange resins have been employed as both supports and solid acid catalysts. Clay structure collapses at high temperatures and has to be stablilized. The thermal stability and pore size issues were addressed by pillaring of clays. Natural clays are acid treated or ion-exchanged to be used as solid acids, and the acidity and pore structure are dependent on the treatment methodology. Another important class of catalysts is the heteropoly acids (HPA), which are employed as homogeneous or heterogeneous catalysts, having both acid and redox properties. The focus of the current paper is to address the work done in our laboratory on the synergism between clays and heteropoly acids for the development of green processes. A comparison is also provided for the activity of these catalysts with other solid acids. Several alkylation, acylation, isomerization, condensation, dehydration, esterification, nitration and oxidation reactions which are useful in a wide spectrum of industries such as bulk, intermediates, dyes, plasticizer, pharmaceuticals, perfumes, flavours and other fine chemicals were investigated to improve the selectivity of the desired products.

Synergism of clay and heteropoly acids as nano-catalysts for the development of green processes with potential industrial applications

Friedel-Crafts acylation of aromatic compounds such as anisole, 2-methoxynaphthalene, veratrole, isobutylbenzene and aromatic heterocycle compounds such as pyrrole, furan, thiophene, benzothiophene with different acid anhydrides is carried out in the batch mode with different forms of beta zeolite. The micronized beta zeolite shows manifold activity over normal zeolite in acylation reactions of aromatics.

Friedel–Crafts acylation of aromatics and heteroaromatics by beta zeolite

The use of zeolitic catalysts in organic syntheses is reviewed with emphasis on recent developments in the areas of acid and redox catalysis and on their relationship with environmental issues. Examples of acid‐catalyzed reactions are chosen from the acylation, alkylation, hydroxyalkylation of aromatic and heterocyclic compounds and from rearrangement reactions. The epoxidation of olefins, the hydroxylation of arenes and the oxidation of O‐, S‐ and N‐functionalities with hydrogen peroxide on Ti‐zeolites illustrate catalyzed oxidations.

Zeolites for fine chemicals production

Update 1 of: Use of Solid Catalysts in Friedel Crafts Acylation Reactions Giovanni Sartori* and Raimondo Maggi Clean Synthetic Methodologies Group and National Interuniversity Consortium “Chemistry for Environment” (INCA), Unit PR2, Dipartimento di Chimica Organica e Industriale, Universit a degli Studi di Parma, Parco Area delle Scienze 17A, I-43100 Parma, Italy This is a Chemical Reviews Perennial Review. The root paper of this title was published in Chem. Rev. 2006, 106 (3), 1077 1104, DOI: 10.1021/cr040695c; Published (Web) February 14, 2006. Updates to the text appear in red type.

Update 1 of: Use of Solid Catalysts in Friedel−Crafts Acylation Reactions

Friedel–Crafts acylation of aromatic ethers with acid anhydrides in the presence of mesoporous material, cation-exchanged K10 montmorillonite (M n + – mont., where M n + =Fe 3+ , Zn 2+ , Cu 2+ , Al 3+ and Co 2+ ) was investigated. Fe 3+ - and Zn 2+ -exchanged montmorillonites displayed higher activities ascribed to the synergistic effect of Bronsted and Lewis acidities. Selective acylation is a significant achievement with the formation of 1-acyl-2-methoxynaphthalene, 4-acyl anisole and 4-acyl veratrole from respective aromatic ethers.

Acylation of aromatic ethers with acid anhydrides in the presence of cation-exchanged clays

The present invention relates to a process for the production of nitroarenes with high para-selectivity from monosubstituted aromatic hydrocarbons using aluminosilicates as catalysts, which comprises nitration of monosubstituted aromatic hydrocarbons using aluminosilicates of different ratios wherein Si/Al ranges between 5 to 1000 and the said aluminosilicates being manifested in the form of variety of zeolites and K10 montmorillonite as catalysts using nitric acid in the molar ratio of nitric acid to monosubstituted aromatic hydrocarbons ranging between 0.25 to 2.5 at a temperature in the range of 30-160° C. for a period ranging between 0.25 to 3.0 h and followed by continuous removal of water formed from the reaction mixture with a Dean-Stark apparatus and recovery of the product mixture by concentration of the reaction mixture after separation of the catalyst by filtration.

Kompella Vishweshwar Ram Prasad

Papers

Acylation of aromatic ethers with acid anhydrides in the presence of cation-exchanged clays

Process for the production of nitroarenes with high para-selectivity from monosubstituted aromatic hydrocarbons using alumino-silicates as catalysts