Fnedel

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... 

The key here is to recognize that an ethyl substituent can be introduced by Fnedel-Crafts acylation followed by a Clemmensen or Wolff-Kishner reduction step later in the syn thesis If the chlorine is introduced prior to reduction it will be directed meta to the acetyl group giving the correct substitution pattern... 

Fnedel-Crafts acylation of the individual isomers of xylene with acetyl chlonde and alu minum chloride yields a single product different for each xylene isomer in high yield in each case Write the structures of the products of acetylation of o m and p xylene... 

What combination of acyl chlonde or acid anhydnde and arene would you choose to pre pare each of the following compounds by Fnedel-Crafts acylation" ... 

Each of the compounds indicated undergoes an intramolecular Fnedel-Crafts acylation reac tion to yield a cyclic ketone Wnte the structure of the expected product in each case... 

Partial rate factors may be used to estimate product distributions in disubstituted benzene derivatives The reactivity of a particular position in o bromotoluene for example is given by the product of the partial rate factors for the corresponding position in toluene and bromobenzene On the basis of the partial rate factor data given here for Fnedel-Crafts acylation predict the major product of the reaction of o bromotoluene with acetyl chlonde and aluminum chloride... 

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... 

Fnedel-Crafts acylation In the presence of alumi num chloride acyl chlorides and carboxylic acid an hydrides acylate the aromatic ring of phenols... 

Acylation (Section 12 7 and Chapter 20) Reaction in which an acyl group becomes attached to some structural unit in a molecule Examples include the Fnedel-Crafts acylation and the conversion of amines to amides Acyl chloride (Sections 4 1 and 20 1) Compound of the type... 

DARZENS - NENITZESCU Acylation Zn-Cu catalyzed Fnedel-Crafts type acylation of oleTms with acyl chlorides... 

ZINCKE - SUHL Cyclohexadienone synthesis Synthesis of cyclohexadienones from phenols by Fnedel Crafts alkylafion... 

Other well-known reactions are those offluorinated olefins with fluoride ion and negatively substituted aromatic compounds leading to the formation of per-fiuoroalkylated aromatic compounds The reaction may be considered an amonic version of a Fnedel Crafts process and can result in introduction of one or several perfluoroalkyl substituents [/ /] Aromatic substrates include substituted and unsuhstiluled perfiuorobenzenes [J3l, 212, 213, 214], fiuorinated heterocycles [131, 203, 215, 216, 217, 218, 219, 220, 221, 222, 223],perchlorinated heterocycles [224] (equation 44), and other activated aromatic compounds [225] (equation 45) The fluonnated olefins can be linear or cyclic [208] (equation 46)... 

Many Jluonnaled aromatic compounds are alkylated with alkyl halides under Fnedel-Crafis conditions For example, the intramolecular alkylation of 3-fluoro-At-(chloroaee-tyl)amhne with alununum chlonde gives 6-fluorooxmdole [5] (equation 5) Similarly, 3 -chloro-4-fluoropropiophenone affords 5-fluoromdanone [6] (equation 6)... 

The strong para-directing influence of fluorine in Fnedel-Crafts acylation is illustrated by the reaction of fluorotoluenes with acetyl chloride Treatment of 2-fluorotoluene, 3-fluorotoluene, and 2-fluoro-3-methyltoluene with acetyl chloride and aluminum chloride gives, respectively, 91, 82, and 80% substitution para to fluorine [27]... 

The regioseleciivicy of Fnedel-Crafts-lypc acylations on heteroaromatic compounds has been studied intensively [57 58, 59] In the case of pyrroles, the orientation of the entering acyl group strongly depends on the bulkiness of the group at the nitrogen atom (equation 29)... 

Triflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Fnedel-Crafis catalysis for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides m the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the triflates in comparison with the correspond mg fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

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]... 

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