Compounds of the formula: ##STR1## in which each R.sup.1 is hydrogen, C.sub.1-4 alkyl, C.sub.1-4 alkoxy, halogen or nitro, and n is 0, 1, 2 or 3, R.sup.2 is hydrogen, C.sub.1-4 alkyl or C.sub.2-4 alkenyl, R.sup.3 and R.sup.4 are each hydrogen, C.sub.1-4 alkyl, optionally substituted phenyl or C.sub.6-9 cycloalkyl optionally substituted by 1 to 4 C.sub.1-4 alkyl groups, R.sup.5 is optionally substituted phenyl, tetrahydronaphthyl, phthalimido, saccharinyl, glutaramido, C.sub.6-10 cycloalkyl optionally substituted with 1 to 4 C.sub.1-4 alkyl groups or a phenyl group, or C.sub.4-9 heterosubstituted cycloalkyl optionally substituted with 1 to 4 alkyl groups, x is 1, 2 or 3, y is 0 or 1 and z is 0, 1, 2 or 3; and salts thereof.The compounds are indicated for use in the treatment of disorders of the central nervous system.