Friedel-Crafts Reaction(redirected from Darzens synthesis of unsaturated ketones)
Friedel-Crafts reaction[frē¦del ′krafs rē‚ak·shən]
a method of alkylating and acylating aromatic compounds in the presence of acidic catalysts, such as AlCl3, BF3, ZnCl2, FeCl3, mineral acids, oxides, and cation-exchange resins. The alkylating agents used are alkyl ha-lides, olefins, alcohols, and esters. The acylating agents include carboxylic acids and their acid halides and their anhydrides.
The Friedel-Crafts reaction is a typical electrophilic substitution reaction in the aromatic nucleus; the role of the catalyst amounts to the generation of an attacking particle—an alkyl or acyl cation.
Examples are given below of the interaction of benzene with the ethyl chloride and the acid chloride of acetic acid:
Friedel-Crafts alkylation is used in industry to produce high-octane fuels, antioxidants, surfactants, perfumes, ethylbenzene (starting material in styrene manufacture), and other important products, such as cumene and thymol. Friedel-Crafts acylation is a basic method of synthesizing aromatic and aliphatic-aromatic ketones, many of which are intermediate products in the manufacture of pharmaceuticals and various dyes, such as Michler’s ketone.
The Friedel-Crafts reaction was discovered by C. Friedel and J. Crafts in 1877–78.