Friedel-Crafts reaction alkylating agents

Apart from the alkyl halide-Lewis acid combination, two other sources of carbo-cations are often used in Friedel-Crafts reactions. Alcohols can serve as carbocation precursors in strong acids such as sulfuric or phosphoric acid. Alkylation can also be effected by alcohols in combination with BF3 or A1C13.37 Alkenes can serve as alkylating agents when a protic acid, especially H2S04, H3P04, and HF, or a Lewis acid, such as BF3 and A1C13, is used as a catalyst.38... 

Oxetanes have also been used as alkylating agents in the Friedel-Crafts reaction for example, 2-isopropyloxetane was reacted with benzene in superacidic trifluoromethanesulfonic acid (TFSA) to give a mixture of alkylated aromatic products (Equation 9) <2003CAL1>. The main product of the reaction was the tetralin derivative 46 which could be isolated in up to 75% yield. Other notable side products are shown, resulting from monoalkylation or other skeletal rearrangements. 

Stannic chloride is also used widely as a catalyst in Friedel-Crafts acylation, alkylation and cyclization reactions, esterifications, halogenations, and curing and other polymerization reactions. Minor uses are as a stabilizer for colors in soap (19), as a mordant in the dyeing of silks, in the manufacture of blueprint and other sensitized paper, and as an antistatic agent for synthetic fibers (see Dyes, application AND EVALUATION Antistatic agents). 

Friedel and Crafts (who later became the president of MIT) discovered this reaction in 1879, but seven years before, Baeyer and his colleagues carried out very similar reactions using aldehydes as the alkylating agent and strong acids as catalysts. These reactions, like the Friedel-Crafts reaction, proceed through carbocation intermediates. Consider the synthesis of DDT (l,l,l-trichloro-2,2-di(p-chlorophenyl)ethane)) ... 

Some of the earliest-known examples of Friedel-Crafts reactions were alkylations of arenes using alkyl halides. Since then, however, a wide variety of alkylating agents has been used (Table 1) they include alkenes, alkynes, alcohols and various other reagents. 

Friedel-Crafts reaction Activation by Sm(OTf)3 an electrophilic halogenating agent attacks alkenes and thereby gravitating the alkylation of arenes. 

Friedel-Crafts reactions are commonly performed both at the laboratory and industrial scale by using acid catalysts and acyl chlorides or alcohols as acylating or alkylating agents. The advantages of SCFs for these types of reactions are clear. There is less need for reactive acid catalysts such as AICI3, which are difficult to separate from the reaction mixture and are, on the whole, environmentally unfriendly [45]. Instead, solid acid catalysts can be used efficiently [46, 47]. 

Nitroalkanes as alkylating agents in Friedel-Crafts reactions. An interesting reaction was recently reported by Casini and co-workers (64). They found that Friedel-Crafts reaction of benzylic or tertiary nitro compounds with benzene gave normal alkylation products (8) and (9) respectively. 2-Nitropropane gave cumene (10) subject to further transformations. 

Because of the involvement of carbonium ions and related intermediates, Friedel-Crafts reactions are often accompanied by rearrangements in the alkylating agent. For example, isopropyl groups are often introduced when /t-propyl compounds are used as reactants.Under a variety of reaction conditions, alkylation... 

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