A compound selected from those of formula (I): wherein: n represents integer from 0 to 6, R1 represents a group selected from hydrogen, hydroxy, cyano, alkoxy, alkoxycarbonyl, carboxy, optionally substituted aminocarbonyl, and NR4R5 wherein R4, and R5 are as defined in the description, R2 represents a group selected from hydrogen, alkyl, hydroxymethyl,  and -U-V-W wherein T, U, V, and W are as defined in the description, and R3 represents a group selected from hydrogen, linear or branched (C1-C6)alkyl, aryl, and, heteroaryl, its isomers, and also addition salts thereof with a pharmaceutically-acceptable acid or base, and medicinal products containing the same are useful in the treatment of CNS disorders.