Friedel–Crafts Acylation Reactions

The electrophile is an acylium ion

Mechanism for Friedel-Crafts acylation

Must be carried out with more than one equivalent of AlCl3

Friedel-Crafts Alkylation of Benzene

Mechanism for Friedel-Crafts alkylation

The carbocation will rearrange to a more stable species

However, a 100% of the 2-methyl-2-phenylbutane product can be obtained if a bulky alkyl halide is used

It is not possible to obtain a good yield of an alkylbenzene containing a straight-chain group via Friedel–Crafts alkylation due to carbocation rearrangement

Acylium ions, however, do not rearrange

Methodologies Used for the Reduction Step

Using Coupling Reactions to Alkylate Benzene

The Gilman reagent

The Stille reaction

The Suzuki reaction

One needs to consider an alternative if there is another functional group present in the compound

Chemical Modification of Substituents of Benzene

Reactions of alkyl substituents

The resulting halide product can undergo a nucleophilicsubstitution reaction

Remember that halo-substituted alkyl groups can alsoundergo E2 and E1 reactions (Section 9.8)

Substitutions with double and triple bonds can undergocatalytic hydrogenation (Section 4.11 and 6.9)

Oxidation of an alkyl group bonded to a benzene ring…

Provided that a hydrogen is bonded to the benzylic carbon,

The same reagent that oxidizes alkyl substituents willoxidize benzylic alcohols

However, aldehydes or ketones can be generated if amilder oxidizing agent is used

Reducing a Nitro Substituent

It is possible to selectively reduce just one of the two nitrogroups