New derivatives of cyanoaryl (or cyanoheteroaryl)-carbonyl-piperazinyl-pyrimidines (I), where R.sub.1 represents an OR.sub.3 radical, where R.sub.3 represents a radical derived from a saturated hydrocarbon, with a linear or branched chain of 1 to 4 carbon atoms, and R.sub.2 represents a phenyl radical substituted at least by one cyan radical (--C.ident.N), or a radical of a heteroaromatic ring of 5 or 6 members substituted at least by one cyan radical (--C.ident.N); and their physiologically acceptable salts, are useful for application in human and/or veterinary therapeutics as sedatives, anticonvulsants, hypnotics and general anaesthetics ##STR00001##
