5-heteroarylamino-6-oxy-substituted 3(2H)-pyridazinones

A 3(2H)-pyridazinone of the formula:

• ##STR50## wherein R.sup.1 is a hydrogen atom, a straight chain or branched C.sub.1 -C.sub.4 alkyl group, a C.sub.3 -C.sub.4 alkenyl group or (CH.sub.2).sub.n CO.sub.2 R.sup.5 where n is an integer from 1 to 4, R.sup.5 is a hydrogen atom or a straight chain or branched C.sub.1 -C.sub.4 alkyl group;
• R.sup.1 is A.sup.1 -Y.sup.1 where A.sup.1 is a straight chain or branched C.sub.1 -C.sub.12 alkylene group, Y.sup.1 is CO.sub.2 R.sup.5, a cyano group, OR.sup.6 where R.sup.6 is a hydrogen atom, a straight chain or branched C.sub.1 -C.sub.4 alkyl group or a phenyl group, a thienyl or pyridyl group, ##STR51## where R.sup.7 and R.sup.8 are independently a hydrogen atom, a straight chain or branched C.sub.1 -C.sub.4 alkyl group, a C.sub.3 -C.sub.8 cycloalkyl group, a phenyl group, a thiazolyl or thiadiazolyl group, or R.sup.7 and R.sup.8 together form a C.sub.2 -C.sub.8 alkylene group which is unsubstituted or substituted with a straight chain or branched C.sub.1 -C.sub.3 alkyl group or a phenyl group, or form a morpholine ring with a nitrogen atom, ##STR52## where R.sup.5 is as defined above and R.sup.9 is a straight chain or branched C.sub.1 -C.sub.4 alkyl group or a phenyl group which is unsubstituted or substituted with a straight chain or branched C.sub.1 -C.sub.4 alkyl group or a halogen atom, ##STR53## where R.sup.10 and R.sup.11 are independently a hydrogen atom, a halogen atom, a straight chain or branched C.sub.1 -C.sub.4 alkyl group, a C.sub.1 -C.sub.4 acylamino group, OR.sup.5, NHSO.sub.2 R.sup.9 or S(O).sub.m --R.sup.12 where m is an integer from 0 to 2 and R.sup.12 is a straight chain or branched C.sub.1 -C.sub.4 alkyl group, provided that R.sup.10 and R.sup.11 are not hydrogen atoms at the same time, ##STR54## where R.sup.13 is a hydrogen atom and R.sup.14 is a phenyl group, or R.sup.13 and R.sup.14 together form a C.sub.2 -C.sub.8 alkylene group which is unsubstituted or substituted with a straight chain C.sub.1 -C.sub.3 alkyl group, ##STR55## where R.sup.15 is a hydrogen atom or a straight chain or branched C.sub.1 -C.sub.4 alkyl group, R.sup.16 is a straight chain or branched C.sub.1 -C.sub.4 alkyl group, or R.sup.15 and R.sup.16 together form a C.sub.2 -C.sub.8 alkylene group which is unsubstituted or substituted with a straight chain C.sub.1 -C.sub.3 alkyl group, ##STR56## where R.sup.17 and R.sup.18 are independently a straight chain or branched C.sub.1 -C.sub.4 alkyl group, or R.sup.17 and R.sup.18 together form a C.sub.2 -C.sub.8 alkylene group which is unsubstituted or substituted with a straight chain C.sub.1 -C.sub.3 alkyl group, ##STR57## where l is 1 or 2, k is an integer from 0 to 3, and R.sup.19 is a hydrogen atom or a halogen atom, or ##STR58## or R.sup.2 is A.sup.2 -Y.sup.2 where A.sup.2 is a C.sub.2 -C.sub.10 alkylene group which is unsubstituted or substituted with a straight chain C.sub.1 -C.sub.3 alkyl group, except where a carbon chain connecting an oxygen atom with Y.sup.2 has one carbon, and Y.sup.2 is a phenyl group;
• R.sup.3 and R.sup.4 are independently a hydrogen atom or a straight chain or branched C.sub.1 -C.sub.3 alkyl group;
• X is a chlorine atom, a bromine atom, a hydrogen atom or a cyano group;
• and
• Ar is ##STR59## where j is 0 or 1 and R.sup.20 is a hydrogen atom, a halogen atom or OR.sup.12 where R.sup.12 is as defined above, ##STR60## where Z.sup.1 is an oxygen atom or sulfur atom;
• and a pharmaceutically acceptable salt thereof.