Benzene Fnedel Crafts alkylation

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... 

Tetralone 31 could also be synthesized much more efficiently by employing a chemoselective ketone reduction of 32 to give the lactone 33. A double Fnedel-Crafts alkylation/acylation sequence employing a variety of Lewis or protic acids and benzene gave the tetralone 31 directly. Triflic acid and HF produced the highest yields of tetralone, presumably through the intermediacy of the diaryl acid 34 (Scheme 6).29,33... 

Alkyl fluorides are more reactive than other alkyl halides under Fnedel-Crafts conditions, whereas tnfluoromethyl groups are less reactive than other trihalomethyl groups Thus, a bromoindane is prepared from 1-bromo-l-fluoro-2,2,3,3-letramethylcyclopropane and benzene [S] (equation 8) whereas 3-tnfluo romethylphenyldiphenylchloromethane is obtained from 3-trifluoromethyl-benzotrichlonde and benzene [9] (equation 9)... 

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See also in sourсe #XX -- [ , , , ]

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