The present invention is concerned with compounds of formula ##STR1## the pharmaceutically acceptable acid addition salts thereof, and the stereochemically isomeric forms thereof, wherein R.sup.1 is hydrogen or C.sub.1-6 alkyl; R.sup.2 is hydrogen or C.sub.1-6 alkyl; R.sup.3 is hydrogen or C.sub.1-6 -alkyl; R.sup.4 is hydrogen, halo, C.sub.1-6 alkyl, hydroxy, C.sub.1-6 alkyloxy, aryloxy or arylmethoxy; R.sup.5 and R.sup.6 designate R.sup.5a and R.sup.6a wherein R.sup.5a and R.sup.6a taken together form a bivalent radical; or R.sup.5 and R.sup.6 can designate R.sup.5b and R.sup.6b wherein R.sup.5b is hydrogen and R.sup.6b is a heterocycle or an optionally substituted alkenyl or alkynyl group; or R.sup.5 and R.sup.6 designate R.sup.5c and R.sup.6c, wherein R.sup.5c and R.sup.6c are hydrogen, halo, C.sub.1-6 alkyl, C.sub.3-6 alkenyl, C.sub.3-6 alkynyl, hydroxy, C.sub.1-6 alkyloxy, cyano, aminoC.sub.1-6 alkyl, carboxyl, C.sub.1-6 alkyloxycarbonyl, nitro, amino, aminocarbonyl, C.sub.1-6 alkylcarbonylamino, or mono-di(C.sub.1-6 alkyl)amino; Q is a heterocyclic ring containing at least one nitrogen atom or a radical of formula ##STR2## pharmaceutical compositions, preparations and use as a medicine are also described.