Fnedel-Crafts alkylation

One drawback to Fnedel-Crafts alkylation is that rearrangements can occur espe cially when primary alkyl halides are used For example Friedel-Crafts alkylation of benzene with isobutyl chloride (a primary alkyl halide) yields only tert butylbenzene... 

An important difference between Fnedel-Crafts alkylations and acylations is that acyl cations do not rearrange The acyl group of the acyl chloride or acid anhydride is transferred to the benzene ring unchanged The reason for this is that an acyl cation is so strongly stabilized by resonance that it is more stable than any ion that could con ceivably arise from it by a hydride or alkyl group shift... 

Fnedel-Crafts alkylation Alcohols in combination with acids serve as sources of carbocations Attack of a carbocation on the electron rich ring of a phe nol brings about its alkylation... 

Unsaturated fluorocarbons are much more reactive toward nucleophiles than then hydrocarbon counterparts owing to fluorme s ability to both stabihze carban ions and mductively increase the electrophihcity of multiple bonds and aromatic nngs Nucleophihc attack dominates the chemistry of unsaturated fluorocarbons, and the role of fluonde ion in fluorocarbon chemistry is analogous to that of the proton in hydrocarbon chemistry [129] Like the related electrophilic reactions for hydrocarbons, there are fluonde-promoted isomenzations and dimenzations (equation 9), oligomenzations (equation 10), additions (equation 11), and amomc Fnedel-Crafts alkylations (equation 12) that all proceed via carbamomc intermediates [729 7 7]... 

Many fluormated aromatic compounds are alkylated with alkyl halides under Fnedel-Crafts conditions For example, the intramolecular alkylation of 3-fluoro-AHchloroace-tyl)amline with aluminum chloride gives 6-fluorooxindole [5] (equation 5) Similarly, 3 -chloro-4-fluoropropiophenone affords 5-fluoroindanone [6] (equation 6)... 

Alkyl fluorides are more reactive than other alkyl halides under Fnedel-Crafts conditions, whereas tnfluoromethyl groups are less reactive than other trihalomethyl groups Thus, a bromoindane is prepared from 1-bromo-l-fluoro-2,2,3,3-letramethylcyclopropane and benzene [S] (equation 8) whereas 3-tnfluo romethylphenyldiphenylchloromethane is obtained from 3-trifluoromethyl-benzotrichlonde and benzene [9] (equation 9)... 

Tetralone 31 could also be synthesized much more efficiently by employing a chemoselective ketone reduction of 32 to give the lactone 33. A double Fnedel-Crafts alkylation/acylation sequence employing a variety of Lewis or protic acids and benzene gave the tetralone 31 directly. Triflic acid and HF produced the highest yields of tetralone, presumably through the intermediacy of the diaryl acid 34 (Scheme 6).29,33... 

ZINCKE - SUHL Cyclohexadtenone synthesis Synthesis ot cyclohexadienones from phenols by Fnedel Crafts alkylation... 

Maximum temperatura at publicatiort consult factory for use at higher temperaturep Not recommended in anhydrous condition as in Fnedel-Crafts and alkylation type reactions Not recommended in processes where mercury amalgam is formed... 

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