Aromatic benzoylation

Laboratoire des Materiaux Catalytiques et Catalyse en Chimie Organique, UMR 5618 CNRS-ENSCM-UM1, Institut C. Gerhardt FR 1878, 8 rue de VEcole Normale, 34296 Montpellier Cedex 05, France 

The Friedel-Crafts acylation of aromatics is the main route for the formation of aromatic ketones, intermediates widely used for the production of pharmaceuticals, fragrances, flavours insecticides and other products. 

Our pioneering work in 1986[1] has shown that acid zeolites are efficient catalysts in the Friedel-Crafts acylation of toluene and xylene with carboxylic acids and constitutes a breakthrough in environmentally friendly fine chemistry replacing the conventional AICI3 method by a heterogeneous catalysts. Since this initial study, a tremendous amount of work has been performed in this area[2] and particularly, in recent years, the acetylation reaction, which is a field of research with large potential for the production of fine chemicals, has been intensively investigated. 

In literature in this field, a large number of zeolite catalysts (FAU, MOR, ZSM-5, BEA, etc.) have been described as active catalysts in the acylation of aromatics.[2] One of the solid acid catalysts that gives very high activities and selectivities is the 

Catalysts for Fine Chemical Synthesis, Vol. 4, Microporous and Mesoporous Solid Catalysts Edited by E. Derouane 2006 John Wiley Sons, Ltd 

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This second case is particularly interesting since the addition of an EPD solvent is connected with a shift from the olefinic nonafulvenoxide anion in (2b) to the aromatic benzoyl [9] annulene anion in (3b). Without association of the lithium cation with the enolate oxygen atom, the negative charge is preferably delocalized in the [9] annulene ring. Therefore, the aromatic character of this ionophore depends on its ion-pair character [288]. 

A closely related example, the equilibrium between tight and solvent-separated ion pairs of lithium lO-phenylnonafulvene-10-oxide, has already been given in Section 2.6 (formulas (2b) and (3b)). Depending on the solvent-influenced association with the lithium cation, the anion exists either as the aromatic benzoyl [9]annulene anion or as the olefinic nonafulvene oxide anion [208],... 

Alkyl aromatics Benzoyl compounds Aromatic hydrocarbons... 

Lauroyl peroxide (61°C) is used for somewhat higher reactivity. Its aliphatic structure also gives lighter color in polymers than can be obtained with the aromatic benzoyl peroxide. 

Water-Soluble Photolnitlators. Water-soluble photoinitiators are needed for systems snch as printing inks and emulsion processes, where the reaction system is an aqneons solution rather than simply a monomer. Since free radical photoinitiators are based on the aromatic benzoyl chromophore, the molecules are generally nonpolar and therefore incompatible with water. Research has fo-cnsed on developing photoinitiators with hydrophilic substituents that increase water solnbility (3,25). Both unimolecular and bimolecular systems have been suc-cessfnlly demonstrated. An example of a imimolecular photoinitiator is sodium 4-benzoylbenzenemethane sulfonate (13). 

Gray s group also prepared the propanoate of (2-hydroxypropyl)cellulose (PPC or C3PC) from the esterification reaction of HPC (Mw = 100,000 g/mol) and propionyl chloride or propionic anhydride in acetone (Tseng et al. 1982). The appearance and behavior of the polymer is similar to APC, however this ester displayed iridescent colors at room temperature. In the same year (Bhadani and Gray 1982), the synthesis of the benzoic acid ester of HPC (BzPC) from the reaction of the aromatic benzoyl chloride with HPC in pyridine was described. The polymer showed a thermotropic liquid crystalline phase below 160 °C. Benzoic acid ester of HPC was fractionated from acetone solution by precipitation with methanol-water and polymers with different molecular weights were obtained (Bhadani et al. 1983). 

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