Abstract: The invention relates to novel pyrimido [5,4-b][1,4]oxazine derivatives of the formula (I), and the acid addition salts thereof, pharmaceutical compositions containing them and a process for their preparation. In the formula (I) ##STR1## wherein R.sup.1 stands for a C.sub.1-4 alkyl group;R.sup.2 stands for hydrogen or halogen or an azido group or an --NR.sup.5 R.sup.6 group, whereinR.sup.5 represents hydrogen or a benzyl group, or a C.sub.1-4 alkyl group unsubstituted or substituted by a hydroxyl group,R.sup.6 stands for hydrogen, an amino group, a C.sub.3-6 cycloalkyl group, a straight or branched-chain C.sub.1-4 alkyl group optionally substituted by a hydroxyl, mercapto, aminocarbonyl, furyl, 2-benzo[1,4]dioxanyl, di(C.sub.1-4 alkyl)amino group or by a phenyl or phenoxy group optionally mono- or polysubstituted by halogen or C.sub.1-4 alkoxy group (s) or by a 6-membered, saturated nitrogen-containing heterocycle optionally containing an additional nitrogen or oxygen atom and optionally substituted by a C.

Abstract: The invention relates to a novel process for the preparation of 6-(substituted amino)-3-pyridazinylhydrazines having the general formula I ##STR1## and their pharmaceutically acceptable acid addition salts, wherein R.sup.1 stands for hydrogen atom or an alkyl group containing from 1 to 4 carbon atoms;R.sup.2 and R.sup.3 may be the same or different and stand for alkyl groups containing from 1 to 6 carbon atoms, alkenyl groups containing from 2 to 6 carbon atoms, hydroxyalkyl groups containing from 2 to 4 carbon atoms, cycloalkyl groups containing from 3 to 8 carbon atoms, phenyl or benzyl groups or phenyl, benzyl or phenylethyl groups containing one or two halogen atoms, nitro, methoxy or hydroxyl groups, and one of R.sup.2 and R.sup.3 may stand also for a hydrogen atom, or R.sup.2 and R.sup.3 together with the neighboring nitrogen atom may build up also a morpholino, pyrrolidino, piperidino, heptamethyleneimino or N-methylpiperazino group.

Abstract: Pyridazinylhydrazones capable of lowering blood pressure have the formula ##STR1## wherein R.sup.1 is hydrogen, chlorine, alkyl having from 1 to 4 carbon atoms, methoxy, hydroxyl, carbamoyl or cyano;R.sup.2 is chloro; andK is a group having the formula ##STR2## wherein one of R.sup.3, R.sup.4, R.sup.5 or R.sup.6 is carboxyl or alkoxycarbonyl.

Abstract: Pyridazinylhydrazones capable of lowering blood pressure having the formula ##STR1## wherein R.sup.1 is hydrogen, chlorine, alkyl having from 1 to 4 carbon atoms, methoxy, hydroxyl, carbamoyl or cyano;R.sup.2 is morpholino; andK is a group having the formula ##STR2## wherein one of R.sup.3, R.sup.4, R.sup.5 or R.sup.6 is carboxyl or alkoxycarbonyl.