The Friedel–Crafts acylation is the reaction of an arene with acyl chlorides or anhydrides using a strong Lewis acid catalyst. This reaction proceeds via electrophilic aromatic substitution to form monoacylated products.1,2
Figure 1.Friedel–Crafts acylation reaction shown as molecular structures
The Friedel–Crafts Acylation reaction involves formation of a complex between the Lewis acid and the chlorine atom of the acid chloride. An acylium ion is formed by the cleavage of C-Cl bond of the complex. The acylium ion has a positive charge on the carbon and is resonance stabilized. This acylium ion acts as an electrophile and reacts with the arene to yield the monoacylated product (aryl ketone).1
Figure 2.Friedel-Crafts acylation mechanism with an AlCl3 catalyst shown as molecular structures
The Friedel–Crafts acylation reaction is named after Charles Friedel and James Mason Crafts who developed the reaction in 1877 to attach substituents to an aromatic ring.3
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The Friedel–Crafts acylation reaction is useful for the synthesis of:
Figure 3.One pot solvent-free synthesis of diarylacetic acid derivatives by Friedel–Crafts hydroxyalkylation reaction of glyoxylic acid