Piperazine derivatives

A compound of the formula ##STR5## or a pharmaceutically acceptable acid addition salt thereof, wherein A is a C.sub.1 -C.sub.2 alkylene chain, optionally substituted by one or more C.sub.1 -C.sub.6 alkyl groups, Z is a bicyclic nitrogen containing heteroaromatic radical selected from the group consisting of indolyl, isoindolyl, quinolinyl, isoquinolinyl, indazolyl and benzotriazolyl, which may be optionally substituted bv one or two substitutents selected from C.sub.1 -C.sub.6 alkyl, halogen, trifluoromethyl, nitro, cyano, oxo, hydroxy, C.sub.1 -C.sub.6 alkoxy, hydroxy -C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy-C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkanoyloxy-C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 acyl, C.sub.1 -C.sub.6 acyl-C.sub.1 -C.sub.6 alkyl, carboxamido, C.sub.1 -C.sub.6 alkoxycarbonyl, amino, mono- or di-C.sub.1 -C.sub.6 alkylamino;

• R represents H or one or two same or different C.sub.1 -C.sub.6 alkyl groups;
• R.sup.1 is an aryl radical or aryl-C.sub.1 -C.sub.6 alkyl where aryl is phenyl or naphthyl, optionally substituted by 1 or 2 groups selected from C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, C.sub.1 -C.sub.6 alkylthio, cyano, amino, mono- or di-C.sub.1 -C.sub.6 alkylamino;
• R.sup.2 and R.sup.3 together with the nitrogen atom to which they are both attached represent a saturated heterocyclic ring having 4 to 8 members, one of which can be an additional heteroatom selected from oxygen, sulfur, or nitrogen wherein said ring may be optionally substituted by C.sub.1 -C.sub.6 alkyl, phenyl or phenyl-C.sub.1 -C.sub.6 alkyl.