Compounds, exhibiting central nervous system activity, of the formula ##STR1## wherein R.sub.1 is phenyl which is unsubstituted or substituted by at least one member selected from the group consisting of halogen, CF.sub.3, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy and COOH, orR.sub.1 is ##STR2## or R.sub.1 is a heterocycle selected from the group consisting of ##STR3## R.sub.2 R.sub.3 R.sub.4 and R.sub.5, which may be identical or different, are H or CH.sub.3 ;R.sub.6 and R.sub.7, which may be identical or different, are C.sub.1 -C.sub.6 alkyl, which may be straight-chained or branched, orR.sub.7 can be H when R.sub.6 is a branched-chain alkyl, orR.sub.6 and R.sub.7 can form, with the nitrogen to which they are bonded, a heterocycle selected from the group consisting of ##STR4## R.sub.8 R.sub.9 R.sub.10 and R.sub.11, which may be identical or different, are H, halogen, CF.sub.3, hydroxy or C.sub.1 -C.sub.4 alkoxy, or two contiguous members of R.sub.8 R.sub.9, R.sub.10 and R.sub.11 may together form a chain --O--(CH.sub.2).sub.n --O--, where n=1 or 2, or a chain --O--CH.sub.2 --O--CH.sub.2 --;and pharmaceutically acceptable addition salts thereof are disclosed, along with a method of producing the same, and pharmaceutical compositions comprising the same.