Friedel-Crafts acylation, alkylation and related reactions

Friedel-Crafts acylation, alkylation and related reactions 

The Friedel-Crafts acylation of ferrocene, which was mentioned above, has been studied in considerable detail. Substitution can be effected under very mild conditions, for instance with acetic anhydride containing phosphoric add as catalyst, to give mono-acetylferrocene. With aluminium chloride as catalyst, good yields of either mono- or l,l -diacetylferrocene can be obtained according to the proportions of reagents taken. 

Ferrocene also undergoes the Vilsmeier reaction to yield ferrocene-carboxaldehyde, which is a useful starting material for the synthesis of other ferrocene derivatives, for example by condensation with compounds containing active CH2 groups such as malonic acid  

With formaldehyde and secondary amines, (Mannich condensation) ferrocene yields mpno-dialkylaminomethyl derivatives,. 8.2. The ability of ferrocene to react under Vilsmeier or Mannich conditions is further evidence of its high susceptibility to electrophilic substitution, as these reactions are observed in the benzene series only for reactive compounds such as phenol. 

Direct Friedel-Crafts alkylation of ferrocene gives only low yields of mono- and poly-alkylated ferrocenes. Better yields are obtained using aluminium chloride and olefins under pressure  

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Friedel-Crafts Acylation, Alkylation, and Related Reactions. While a stoichiometric amount of AICI3 is needed in Friedel-Crafts acylations, a small amount of Sc(OTf)3 smoothly catalyzes the same reaction. In the acetylation of thioanisole and o- or m-dimethoxybenzene, a single acetylated product is formed in an excellent yield. In the benzoylation of anisole, both benzoic anhydride and benzoyl chloride are effective, while benzoic anhydride gives a slightly higher yield. Addition of lithium perchlorate (LiC104) as a cocatalyst improves the yield dramatically (eq 13). ... 

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