Silica-supported H4SiW12O40 catalyzed efficiently alkylation/acylation of 1,3,5-trimethylbenzene or p-xylene with gamma-butyrolactone to 4-(2,4,6-trimethylphenyl) butyric acid or to dimethyl-alpha-tetralone (5,8-dimethyl-3,4-dihydro-2H-naphtalen-1-one), while other typical solid acids such as zeolites and SiO2-Al2O3 were much less active.