Montmorillonites Friedel-Crafts alkylations

Zinc chloride exchanged clay catalysts have been reported to be highly active for the Friedel-Crafts alkylation and acylation reactions these are commercially sold by Contract Catalysts under the name Envirocats. These are montmorillonite catalysts modified by ZnCU and FeCli. Some of the reported examples of Friedel-Crafts reactions are given below there are claims that some of the processes are commercially practised. 

Clays or acid-treated clays are also effective supports for Lewis acids such as ZnCl2 or FeCl3 [23]. Montmorillonite-supported zinc chloride, known as Clayzic, has been extensively studied as a catalyst for e.g. Friedel-Crafts alkylations [24, 25] (see Fig. 2.2). 

Tateiwa, J. I., H. Horiuchi, K. Hashimoto, and T. Kamauchi. 1994a. Cation-exchanged montmorillonite-catalyzed facile Friedel-Crafts alkylation of hydroxy and methoxy aromatics with 4-hydroxybutan-2-one to produce raspberry ketone and some pharmaceutically active compounds. J. Org. Chem. 59 5901-5904. 

Clark, J. H., Kybett, A. P., Macquarrie, D. J., Barlow, S. J., Landon, P. Montmorillonite supported transition metal salts as Friedel-Crafts alkylation catalysts. J. Chem. Soc., Chem. Commun. 1989, 1353-1354. 

Impregnation of metal chlorides on to natural kaolinites and its modified forms results in efficient Friedel-Crafts alkylation catalysts. A synergistic interaction between the halide and the surface of support as well as mesopore surface of the support is possible. The present study shows that kaolinite and its metakaolinised acid activated forms are efficient support material with comparable performance to the existing commercial montmorillonite K 10. 

Laszlo and co-workers have reported that K10 montmorillonites ion-exchanged with various transition metal cations are effident catalysts for Friedel-Crafts alkylation of aromatics with a wide range of alkylating agents such as alcohols, alkenes and alkyl halides.25... 

Okado et al. reported on the use of natural vermiculite as a highly active and selective catalyst for the Friedel-Crafts alkylation reaction between benzene and 4-methylbenzyl chloride.30 The important feature of vermiculite for this reaction appears to be its unusually high structural iron content. Indeed, a vermiculite containing a much smaller amount of iron exhibited a lower activity than H+ montmorillonite. 

Polverejan et al. (117) reported on another catalytic application of mesos-tructured clay catalysts. Saponite-derived PCH has been used for the condensed-phase Friedel-Crafts alkylation of bulky 2,4-di-ferf-butylphenol (DBP) with cin-namyl alcohol to produce a large flavan, namely, 6,8-di-tert-butyl-2,3-dihy-dro[4H]benzopyran. Because the molecular dimensions of DBP are very large (1.35 X 0.79 X 0.49 nm), conventional zeolites and pillared clays are not suitable to catalyze this reaction, while the mesopores of saponite PCH are large enough to allow access to the interlayer acid sites. The catalytic results obtained on saponite-PCH are compared to those on H -saponite, zeolite HY, and acid-treated montmorillonite K-10 (Table 9). The reaction is visualized in figure 24. 

Acidic clay catalysts can also be used in alkylation with alcohols 98 The main advantages of these catalysts are the reduced amount necessary to carry out alkylation compared with conventional Friedel-Crafts halides, possible regeneration, and good yields. Natural montmorillonite (K10 clay) doped with transition metal cations was shown to be an effective catalyst 200... 

Friedel-Crafts reactions are practically unexplored in sonochemistry. One example of acylation is reported, with a modest yield increase.Alkylation is represented by the benzylation of benzene (Eq. 64), in the presence of zinc chloride on montmorillonite or bentonite. ... 

Friedel-Crafts Acylation and Alkylation. The Friedel-Crafts acylation of aromatic substrates with various acyclic carboxylic acids in the presence of cation-exchanged (H" ", Al " ", Ni +, Zr, Ce " ", Cu " ", La +) montmorillonites has been reported. Curiously, the use of iron-doped montmorillonite was not included in the report however, some catalysis is expected. Under these conditions, the yield of the desired ketones was found to be dependent on acid chain length and the nature of the interlayer cation. 

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