The catalytic conversion of mixtures of ethers with aliphatic and aromatic nitriles in supercritical conditions on zeolites (HY, HCaREEY), individual oxides (Al2O3, SiO2, MoO3, WO3, TiO2), and oxide systems (Al2O3-SiO2, H-8[Si(Mo2O7)(5)], Al-2(WO4)(3)) has been studied. It has been found that acid catalysts, such as zeolites, mixed oxides, and TiO2 (anatase), are active at 350A degrees C in the direct synthesis of N-acylpyrrolidines from tetrahydrofuran and nitriles (CH3CN, n-C4H9CN, C6H5CN): the product yield reaches 40% and the selectivity is 65-94%. The activity and selectivity of TiO2 samples increase with an increase in the specific surface area (from 37 to 139 m(2)/g) or with a decrease in the particle size of anatase (from 43 to 13 nm according to XRD data). The character of interaction of the components of the reaction mixture with the TiO2 surface has been studied by the TG-DTA technique. After oxidative regeneration, TiO2 exhibits the initial catalytic properties, suggesting the possibility of its repeated use in the direct synthesis of acylpyrrolidines. Replacing THF by other compounds (diethyl ether, 1,4-dioxane, tetrahydropyran) drastically reduces the yield of respective alkylamides.