Pyridazino›4',5':3,4!pyrrolo-›2,1-a!-isoquinolines and the use thereof for preparing pharmaceutical preparations

A compound of formula (I) ##STR91## wherein X is O, S or NHO;

• R.sub.1 has one of the following meanings:
• a) C.sub.3-7 -cycloalkyl;
• b) a straight-chained or branched alkyl group having 1 to 10 or an alkenyl or alkynyl group having 2 to 10 carbon atoms, which alkyl, alkenyl or alkynl group may be substituted by hydroxy, C.sub.1-4 -alkoxy, halogen, NH.sub.2, NH-alkyl having 1 to 2 carbon atoms, N,N-di(C.sub.1-2)alkylamino, NH-acyl having 2 to 4 carbon atoms, 1 or 2 C.sub.3-7 -cycloalkyl groups, phenoxy, 1 or 2 phenyl groups (wherein the phenyl ring or rings or phenoxy may in turn be mono- or disubstituted by halogen, CF.sub.3, C.sub.1-4 -alkyl, C.sub.1-2 -alkoxy, NH-alkyl having 1 to 2 carbon atoms, N,N-dialkyl having 1 to 2 carbon atoms, NH.sub.2, N-acyl having 2 to 3 carbon atoms, --OCH.sub.2 O--, (C.sub.1 or C.sub.2) alkylsulphonylamino, phenoxy or benzyloxy), furyl or thienyl;
• R.sub.3, R.sub.4 and R.sub.5, which may be identical or different, are hydrogen or a C.sub.1-4 -alkyl group;
• R.sub.7 and R.sub.8, which may be identical or different, are hydroxy;
• C.sub.1-4 -alkoxy;
• or C.sub.1-4 -alkylthio;
• R.sub.6 and R.sub.9, which may be identical or different, are hydrogen;
• hydroxy;
• C.sub.1-4 -alkoxy;
• C.sub.1-4 -alkylthio;
• or 2 adjacent substituents of the substituents R.sub.6, R.sub.7, R.sub.8 and R.sub.9 together form the group --O--(CH.sub.2).sub.1 or 2 --O-- and the other 2 substituents are as hereinbefore defined,
• or a pharmaceutically acceptable salt thereof,
• with the exception of compounds of formula I as hereinbefore defined wherein XR.sub.1 is the group SR.sub.1 wherein R.sub.1 is C.sub.1-5 alkyl or benzyl.