Friedel-Crafts alkylation reactions chloromethylation

The mechanism of the chloromethylation reaction is related to that of Friedel-Crafts alkylation and acylation and probably involves an incipient chloro-methyl cation, CH2C1 ... 

This reaction, which is comparable to a Friedel-Crafts Alkylation, is useful for the preparation of chloromethylated arenes (for example, the Merrifield resin based on polystyrene) from the parent arene with formaldehyde, HC1, and ZnCl2. 

Although 3-pyridinol is not sufficiently reactive to undergo chloromethylation or Friedel Crafts alkylation or arylation it is readily aminomethylated. The ease of reaction appears to be in the order of 2- > > 4-positions in... 

An additional difficulty in the Blanc reaction is the tendency for activated aromatic rings to undergo polychloromethylation under the typically harsh reaction conditions. For example, in the chloromethylation of benzene, the product benzylchloride (4) is often accompanied by small amounts of / -xylylene dichloride 10, as well as a small amoxmt of diphenylmethane, the product resulting from Friedel-Crafts alkylation of benzene with benzylchloride (4). With more activated ring systems, such as phenols, the reaction is increasingly difficult to control, resulting often in the formation of polymeric materials. ... 

Use in C-C Bond-Forming Reactions. Since MOMCl is an excellent electrophile it readily reacts with enolates and other carbanions and thus serves as an easily handled one-carbon synthon. Friedel-Crafts alkylation with MOMCl and a Lewis acid such as Tin(IV) Chloride, Titanium(IV) Chloride, Zinc Chloride,and Aluminum Chloride or Acetic AcU is a common method for introduction of a chloromethyl group onto an aromatic nucleus (eqs 9 and 10). The reaction is quite general and tolerates a broad range of functionality. 

Although the aluminum chloride or tin(IV) chloride-promoted reactions of alkenylsilanes with acid halides or highly reactive alkyl halides such as chloromethyl alkyl ethers or the corresponding sulfides afford the Friedel-Crafts type products, it is noted that these reactions are not always stereospecific (eq (16)) [13]. The similar reactions of alkynylsilanes with electrophiles have been studied (eq (17)) [14]. 

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