Disclosed are compounds of formula (I) or a pharmaceutically acceptable salt thereof, pharmaceutical compositions containing them, and to a process for the preparation of the compounds: R1 is independently selected from hydrogen atom, amine group, monocyclic or bicyclic aliphatic, aromatic, heteroaliphatic or heteroaromatic ring. R2 is independently selected from monocyclic or bicylic aliphatic, heteroaliphatic, aromatic or heteroaromatic ring, C1-C6 alkyl, alkenyl or alkynyl chain. n is 1 or 2; preferably n is 1. m is 0, 1 or 2; preferably m is 0. R3 and R4 can be, independently, —H, —F, C1-C4 alkyl, —OH, —OC1-C4 alkyl; preferably they are both —H. X is O or S. R5 is —H or —CH3 optionally substituted by one or more fluorine atoms; preferably R5 is hydrogen. The compounds can be used in the treatment of conditions or diseases mediated by P2X7 receptor.