Sulfates Friedel-Crafts acylations

Thioacetals eliminate to vinylsulfides in the presence of CuOTf (Scheme 46).192 Cu1 and Cu11 triflates are mild Lewis acids for Friedel-Crafts acylation and alkylation reactions. CuOTf effectively catalyzes the reaction of anisole with selenoesters.193,194 Copper(II) sulfate promotes epoxide ring opening reactions in the presence of pyridine,195 with retention of configuration being observed. Cu(OTf)2 is a catalyst for the ring opening of aziridine by aniline.196... 

By in situ MAS NMR spectroscopy, the Koch reaction was also observed upon co-adsorption of butyl alcohols (tert-butyl, isobutyl, and -butyl) and carbon monoxide or of olefins (Ao-butylene and 1-octene), carbon monoxide, and water on HZSM-5 (Ksi/ Ai — 49) under mild conditions (87,88). Under the same conditions, but in the absence of water (89), it was shown that ethylene, isobutylene, and 1-octene undergo the Friedel-Crafts acylation (90) to form unsaturated ketones and stable cyclic five-membered ring carboxonium ions instead of carboxylic acids. Carbonylation of benzene by the direct reaction of benzene and carbon monoxide on solid catalysts was reported by Clingenpeel et al. (91,92). By C MAS NMR spectroscopy, the formation of benzoic acid (178 ppm) and benzaldehyde (206 ppm) was observed on zeolite HY (91), AlC -doped HY (91), and sulfated zirconia (SZA) (92). 

From the preceding experimental data and comments, it is clear that both Lewis and Bronsted acid sites exist on sulfated oxide catalysts, but the detailed role of fhe two types of acidity in various reactions, including Friedel-Crafts acylation, is still controversial. 

Yadav, G. D. and Pujari, A. A. 1999. Friedel-Crafts acylation using sulfated zirconia as a catalyst. Acylation of benzene with 4-chlorobenzoyl chloride over sulfated zirconia as catalyst. Green Chem. 1 69-74. 

Hosseini-Sarvari M, Safary E (2011) Nano-sulfated titania (TiO) as a new solid acid catalyst for Friedel-Crafts acylation and Beckman rearrangement in solvent-free conditions. J Sulfur Chem 32(5) 463 73... 

Salehi, R, Khodaei, M.M., Zolfigol, M.A., Zeinoldini, S. Catalytic Friedel-Crafts acylation of aUtoxybenzenes by ferric hydrogen sulfate. Synth. Commun. 2003, 33(8), 1367-1373. 

Ethers and esters have not been widely applied in syntheses by the Friedel-Crafts reaction, chiefly because they offer no particular advantage over the alcohols. In fact, with esters of organic acids and aluminum chloride as catalyst, a disadvantage is the simultaneous acylation, which may occur. However, the synthesis of toluene in 60% yield from benzene, methyl sulfate, and aluminum chloride represents the most successful procedure for the monomethylation of benzene (see p. 22). 

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