The present invention concerns the compounds of formula the N-oxides, the pharmaceutically acceptable addition salts and the stereochemically isomeric forms thereof, wherein each R1 is independently hydrogen, halogen, C1-6alkyl, nitro, hydroxy or C1-4alkyloxy; Alk is C1-6alkanediyl; n is 1 or 2; p is 0, 1 or 2; D is an optionally substituted mono-, bi- or tricyclic nitrogen containing heterocycle having central &agr;2-adrenoceptor antagonist activity. It further relates to their preparation, compositions comprising them and their use as a medicine.