PYRIDAZINONE DERIVATIVES PHARMACEUTICAL COMPOSITIONS CONTAINING THEM AND PROCESS FOR PRODUCING THEM

PCT No. PCT/JP94/01015 Sec. 371 Date Mar. 22, 1996 Sec. 102(e) Date Mar. 22, 1996 PCT Filed Jun. 24, 1994 PCT Pub. No. WO95/01343 PCT Pub. Date Jan. 12, 1995A 3(2H)-pyridazinone derivative of the formula (I) its salt, a process for its production and a pharmaceutical composition containing it. (I) wherein each of R1, R2 and R3 which are independent of one another, is a hydrogen atom or a C1-4 alkyl group, X is a chlorine atom or a bromine atom, Y1 is a hydrogen atom, a halogen atom, a nitro group, an amino group or a C1-4 alkoxy group, Y2 is a hydrogen atom, a halogen atom, a hydroxyl group, a C1-4 alkyl group or a C1-4 alkoxy group, A is a C1-5 alkylene chain which may be substituted by a hydroxyl group, B is a carbonyl group or a methylene chain which may be substituted by a C1-4 alkyl group, and each of R4 and R5 which are independent of each other, is a C1-4 alkyl group, or R4 is a hydrogen atom and R5 is -Z-Ar (wherein Z is a C1-5 alkylene chain, and Ar is an aromatic 6-membered ring which may contain a nitrogen atom), or R4 and R5 together form a C2-6 cyclic alkylene group, or R4 and R5 form together with the adjacent nitrogen atom a 4-substituted piperazine ring of the formula: wherein R6 is a C1-4 alkyl group.