Friedel Crafts catalysts for

Koch Chemical Company is the only U.S. suppHer of all PMBs (except hexamethylbenzene). Its process has the flexibility of producing isodurene, prehnitene, and pentamethylbenzene, should a market develop. Koch s primary process (20) is based on isomerization, alkylation, and disproportionation conducted in the presence of a Friedel-Crafts catalyst. For the synthesis of mesitylene and hemimellitene, pseudocumene is isomerized. If durene, isodurene, or prehnitene and pentamethylbenzene are desired, pseudocumene is alkylated with methyl chloride (see Alkylation Friedel-CRAFTSreactions). 

The Friedel-Crafts reaction is a very important method for introducing alkyl substituents on an aromatic ring. It involves generation of a carbocation or related electrophilic species. The most common method of generating these electrophiles involves reaction between an alkyl halide and a Lewis acid. The usual Friedel-Crafts catalyst for preparative work is AICI3, but other Lewis acids such as SbFj, TiC, SnCl4, and BF3 can also promote reaction. Alternative routes to alkylating ecies include protonation of alcohols and alkenes. 

Homogeneous catalysis by lin compounds is also of great indusirial importance. The use of SnCU as a Friedel-Crafts catalyst for homogeneous acylation, alkylation and cyclizaiion reactions has been known for many decades. The most commonly used industrial homogeneous tin catalysis, however, are the Sn(ll) salts of organic acids (e.g. acetate, oxalate, oleale, stearate and ocToate) for the curing of silicone elasloniers and, more importantly, for the production of polyurethane foams. World consumption of tin catalysts for the.se Iasi applications alone is over 1000 tonnes pa. 

Inflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Friedel-Crafts catalysts for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides in the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the Inflates in comparison with the correspond 1 ng fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

ReCl5 has been found to act as a Friedel-Crafts catalyst for the alkylation of benzene with ethylene. Ethylbenzene, x-butylbenzene and hexaethylbenzene were formed.612 When propylene was used in place of ethylene, cumene and di-, tri- and tetra-isopropylbenzenes were obtained.613 Ethylbenzene and anisole were also alkylated with ethylene. A carbonium ion mechanism was proposed, in some cases with dimerization of ethylene preceding alkylation. 

These catalytic reactions provide a unique pathway for addition of aromatic C-H bonds across C=C bonds. In contrast with Friedel-Crafts catalysts for olefin hydroarylation, the Ru-catalyzed hydrophenylation reactions of a-olefins selectively produce linear alkyl arenes rather than branched products. Although the selectivity is mild, the formation of anti-Markovnikov products is a unique feature of the Ru(II) and Ir(III) catalysts discussed herein. Typically, the preferred route for incorporation of long-chain linear alkyl groups into aromatic substrates is Friedel-Crafts acylation then Clemmensen reduction, and the catalysts described herein provide a more direct route to linear alkyl arenes. 

The preparation and properties of SDVB copolymers have been described in the preceding section. SDVB copolymers can be converted to anion-exchange resins through chloromethylation with monochlorodimethyl ether using a FriedehCrafts catalyst followed by treatment with different aminesAnderson studied in detail the influence of various Friedel-Crafts catalysts for the diloromethylation of SDVB copolymers. A chlorosulfonic acid — methylal mixture has also been used for the chloromethylation of SDVB copolymers... 

Particularly high-yield preparations of both alkyl- and aryldichlorophosphines are obtained through the use of aluminum chloride. The aluminum chloride mediated reaction of phosphorus trichloride with haloalkanes generates an intermediate that can be reduced to the corresponding alkyldichlorophosphine (equation 4). For the preparation of aryldichlorophosphines, aluminum chloride serves a Friedel-Crafts catalyst for electrophilic aromatic substitution by phosphorus on the aromatic ring (equation 5). These synthetic approaches to dihalophosphines have been reviewed. ... 

Fujiwara and coworkers" have discovered that anhydrous lanthanoid trichloride salts are reusable Friedel-Crafts catalysts for the benzylation of benzene. All of the lanthanoid trichlorides offer fairly good yields of benzylated product (equation 15). The yields do not drop if the recovered catalyst is used for a second time, or in some cases even a third time, for the benzylation of benzene. 

TiCU, as a Lewis acid, is used as a catalyst in Friedel-Crafts reactions. AICI3, SnCU, and BFj OEt2 are more commonly used Friedel-Crafts catalysts for reactions with arenes. Use of TiCU as catalyst in the preparation of aromatic aldehydes is shown in eq 40. ... 

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