Alkylation–acylation of p-xylene with γ-butyrolactone or vinylacetic acid catalyzed by heteropolyacid supported on silica

Friedel–Crafts-type reaction of p-xylene with γ-butyrolactone or vinylacetic acid over H4SiW12O40 supported on SiO2 have been investigated with different loadings of H4SiW12O40. The catalytic performance of H4SiW12O40/SiO2 have been compared with those of typical solid acid catalysts such as zeolites, ion-exchanged resins, and binary oxides. H4SiW12O40 supported on SiO2 was superior in activity and selectivity to 5,8-dimethyl-α-tetralone compared to other catalysts for the reaction between p-xylene and γ-butyrolactone. SiO2-supported H4SiW12O40 also was efficient for the formation of 3,4,7-tetramethyl-α-indanone from p-xylene and vinylacetic acid. The formation of 5,8-dimethyl-α-tetralone is extremely sensitive to the load of H4SiW12O40 on SiO2, reaching a maximum at approximately 30 wt%, due to the change in the acid amount of the outermost surface as determined by benzonitrile-temperature programmed desorption. By analogy with reaction between 1,3,5-trimethylbenzene and γ-butyrolactone, the reaction pathway involves initial alkylation of p-xylene with γ-butyrolactone, followed by intramolecular acylation to 5,8-dimethyl-α-tetralone, which was supported by quantum calculations of γ-butyrolactone and protonated γ-butyrolactone.

Friedel–Crafts-type reaction of p-xylene with γ-butyrolactone or vinylacetic acid over solid acids were investigated. H4SiW12O40 supported on SiO2 was found to be the most active and selective catalyst for these reactions. Figure optionsDownload as PowerPoint slide