Pyridazine derivatives as ligands for gaba receptors

A compound of formula I, or an N-oxide thereof or a pharmaceutically acceptable salt thereof:

• wherein:
• Z represents an optionally substituted five-membered heteroaromatic ring selected from furan, thiophene, pyrrole, oxazole, thiazole, isoxazole, isothiazole, imidazole, pyrazole, oxadiazole, thiadiazole, triazole and tetrazole;
• or
• Z represents an optionally substituted six-membered heteroaromatic ring selected from pyridine, pyrazine, pyrimidine and pyridazine;
• or
• Z represents an optionally substituted fused bicyclic heteroaromatic moiety selected from benzofuran, benzothiophene, indole, indazole, benzimidazole and pyrazolo(1,5-a)pyridine;
• R1 represents hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifluoromethyl, nitro, —ORa, —SRa, —SORa, —SO2Ra, —SO2NRaRb, —NRaRb, —NRaCORb, —NRaCO2Rb, —CORa, —CO2Ra, —CONRaRb or —CRa═NORb;
• and
• Ra and Rb independently represent hydrogen, hydrocarbon or a heterocyclic group.

A compound which is selected from:

• 3-phenyl-5-(pyridin-4-yl)pyridazine;
• 3-(6-phenylpyridazin-4-yl)thiophene-2-carboxylic acid methyl ester;
• 3-phenyl-5-(pyridin-3-yl)pyridazine;
• 5-(6-phenylpyridazin-4-yl)thiophene-2-sulfonic acid amide;
• 3-(6-phenylpyridazin-4-yl)pyrazolo[1,5-α]pyridine;
• 2-[2-(6-phenylpyridazin-4-yl)pyrimidin-4-yl]benzonitrile;
• 2-[6-(6-phenylpyridazin-4-yl)pyridin-2-yl]benzonitrile;
• 5-fluoro-2-[6-(6-phenylpyridazin-4-yl)pyridin-2-yl]benzonitrile;
• 4-fluoro-2-[6-(6-phenylpyridazin-4-yl)pyridin-2-yl]benzonitrile;
• 5-[2-(3-fluorophenyl)pyridin-4-yl]-3-phenylpyridazine;
• 3-phenyl-5-[2-(pyridin-4-yl)pyrimidin-4-yl]pyridazine;
• 3-phenyl-5-(2-trifluoromethylpyrimidin-4-yl)pyridazine;
• and pharmaceutically acceptable salts thereof.