Solid acid catalysts based on the direct incorporation of the vanadium Keggin heteropolyacid (PMo11V) structure during the synthesis of silica by the sol-gel technique, in acidic media using tetraethyl orthosilicate (PMo11VSiO(2)1, PMo11VSiO(2)2, PMo11VSiO(2)3, and PMo11VSiO(2)4), were prepared and characterized by P-31-NMR, FT-IR, XRD, and textural properties (S-BET). The acidic characteristics of the catalysts were determined by potentiometric titration with n-butylamine. A series of highly substituted hexahydropyrimidines were synthesized using these new materials, encapsulated in a silica framework, as catalyst in solvent-free conditions. This methodology requires short reaction time (1.5 h), a temperature of 80 A degrees C in solvent free-conditions to obtain good to excellent yields of trifluoromethyl-hexahydropyrimidine derivatives. The Keggin catalyst embedded in the silica matrix is insoluble in polar media, which allows easy removal of the reaction products without affecting their catalytic activity.