Formula (I) compounds: wherein R1 is alkyl substituted by fluorine(s); R2 is hydroxy, alkoxy, alkoxy substituted by phenyl, NR3R4, in which R3, R4 is (i) hydrogen, (ii) alkyl, (iii) phenyl, (iv) phenyl substituted by alkoxy or carboxyl, (v) heterocyclic ring containing nitrogen atom, (vi) alkyl substituted by phenyl, phenyl subsituted by alkoxy or carboxyl, heterocyclic ring containing nitrogen atom, (vii) the nitrogen bonded to R3 and R4, taken together is a saturated heterocyclic ring or amino acid residue; and non-toxic salts and acid addition salts thereof. Also, Formula (X) compounds: wherein n is 0 or 1, R11 is hydrogen and chlorine, R5 is R7—CH2— or R8, or R5 and R11, taken together is alkylidene; R6 is hydroxy, alkoxy, alkoxy substituted by phenyl, NR9R10, in which R9, R10 is (i) hydrogen, (ii) alkyl, (iii) phenyl, (iv) phenyl substituted by alkoxy or carboxyl, (v) heterocyclic ring containing nitrogen atom, (vi) alkyl substituted by phenyl, phenyl-substituted by alkoxy or carboxyl, heterocyclic ring containing nitrogen atom, (vii) the nitrogen bonded to R9 and R10, taken together is a saturated heterocyclic ring or amino acid residue, R7 is (i) F—(CH2)m— or F3C—CH2—, (ii) alkyl subsstituted by chlorine, (iii) alkyl substituted by alkoxy, cycloalkyl, phenyl, phenoxy; R8 is alkyl, alkenyl, alkoxy, alkylthio, cycloalkyl, phenyl, phenoxy. Non-toxic and acid addition salts thereof are useful to prevent and/or treat neurodegenerative disease (e.g., Alzheimer's) and neuronal dysfunction by stroke or traumatic injury (e.g., Multiple sclerosis).