Compounds of formula (I): wherein: R1 and R2, which may be the same or different, each represent a hydrogen or halogen atom or an alkyl, alkoxy, alkylthio, acyl, alkoxycarbonyl, carboxy, hydroxy, hydroxyalkyl, cyano, nitro, amino, substituted or unsubstituted aminocarbonyl, aminosulphonyl, alkylsulphonylaminoalkyl, N-hydroxy-carboximidamide or benzyloxy group, R3 represents a hydrogen atom or an alkyl, cycloalkyl or cycloalkylalkyl group, R4 represents a hydrogen atom or a substituted or unsubstituted alkyl group Medicinal products containing the same which are useful in treating or preventing conditions treatable by an AMPA receptor modulator and/or an NMDA receptor antagonist.