This invention concerns the compounds of formula (I), the N-oxide forms, the pharmaceutically acceptable addition salts and the stereochemically isomeric forms thereof, wherein n is zero, 1, 2, 3, 4, 5 or 6; X is CH2 or O; R1 and R2 each independently are hydrogen, C1-6alkyl, C1-6alkylcarbonyl, halomethylcarbonyl or C1-6alkyl substituted with hydroxy, C1-6alkyloxy, carboxyl, C1-6alkylcarbonyloxy, C1-6alkyloxycarbonyl or aryl; or R1 and R2 taken together with the nitrogen atom to which they are attached may form a morpholinyl ring or an optionally substituted heterocycle; R3 and R4 are both halogen; or R3 is halogen and R4 is hydrogen; or R3 is hydrogen and R4 is halogen; and aryl is phenyl or phenyl substituted with 1, 2 or 3 substituents selected from halo, hydroxy, C1-6alkyl and halomethyl. The compounds of formula (I) may be used as therapeutic agents.