Alkylations anisole, over Nafion

The surface phenolates tue also suggested to be the intermediates for ortho-alkylation of phenol with methanol over ZnO —Fe20s and Ca3(P04)2 from infrared spectroscopic studies. Kapsi and Olah studied the methylation of phenol and the rearrangement of anisole and methyl anisole over Nafion-H , and concluded that o-methylation forming anisole is followed by intermolecular 0 C methyl transfer leading to the formation of cresols. ... 

Nafion-H is also very efficiently catalyzes the rearrangement of anisole, methy-lanisoles, and phenetole to ring-alkylated phenols and products of transalkylation when vapors of the alkyl aryl ethers are passed over it at temperatures higher than 160°C. At these reaction temperatures, some of the starting alkyl phenyl ethers... 

The sulfonic acid resins such as Dowex-50 and Amberlyst-15 have been used to promote the alkylation of the more active aromatic rings but attempts to increase their acidity generally resulted in the degradation of the solid. 2 The more strongly acidic perfluorinated resin sulfonic acid, Nafion-H,2>3 has, however, been used to promote the alkylation of benzene and other aromatic compounds. Nafion-H catalyzed the vapor phase reaction between toluene and methanol. When nm at 185°C a 12% yield of the isomeric xylenes was obtained with the ortho isomer the major product. 0 Methylation of phenol at 205°C over this catalyst gave, at 63% conversion. 37% anisole and 10% of a mixture of the ortho and para cresols in a 2 1 ratio. Reaction of anisole with methanol under these conditions resulted in a 14% selectivity to the methyl anisoles at 40% conversion, with the ortho and para isomers formed in nearly equal amounts. ... 

A number of works have been reported on the alkylation of phenol with methanol over metal oxides as catalyst. Generally, alkylation over acidic oxides such as silica-alumina, phosphoric acid and Nafion-H give mainly anisole and a mixture of three isomers of cresol. On the other hand, basic metal oxides sudi as MgO and Mg-containing mixed oxides favor alkylation at ortho positions. This reaction is industrially important since the reaction product, 2,6-xylenol, is a monomer for good heat-resisting resin. 

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