Imidazolophthalazine derivatives as ligands for gabaa receptors

A compound of formula I, or a pharmaceutically acceptable salt thereof:

• 5
• wherein:
• L is O, S or NRn where Rn is H, C1-6alkyl or C3-6cycloalkyl;
• X is a 5-membered heteroaromatic ring containing 1, 2, 3 or 4 heteroatoms independently chosen from oxygen, nitrogen and sulphur, at most one of the heteroatoms being oxygen or sulphur, or a 6-membered heteroaromatic ring containing 1, 2 or 3 nitrogen atoms, the 5- or 6-membered heteroaromatic ring being optionally fused to a benzene or pyridine ring and the heteroaromatic ring being optionally substituted by Rx and/or Ry and/or Rz, where Rx is halogen, R3, OR3, OCOR3, NR4R5, NR4COR5, OH, tri(C1-6alkyl)silylC1-6alkoxyC1-4alkyl, CN or R6, Ry is halogen, R3, OR3, OCOR3, NR4R5, NR4COR5, NR4R5(C1-6)alkyl or CN and Rz is R3, OR3 or OCOR3, providing that when X is a pyridine derivative, the pyridine ring is optionally in the form of the N-oxide, and providing that when X is a tetrazole derivative it is protected by a C1-4alkyl group;
• or X is phenyl optionally substituted by one, two or three groups independently selected from halogen, cyano, C1-6alkyl, C2-6alkenyl, C2-6alkynyl and C3-6cycloalkyl;
• Y is optionally branched C1-4alkylene optionally substituted by an oxo group or Y is a group (CH2)jO wherein the oxygen atom is nearest the group X and j is 2, 3 or 4;
• Z represents a phenyl ring, a 5-membered heteroaromatic ring containing 1, 2 or 3 heteroatoms independently selected from oxygen, nitrogen and sulphur, at most one of the heteroatoms being oxygen or sulphur, or a 6-membered heteroaromatic ring containing 1, 2 or 3 nitrogen atoms, each of which rings may be optionally substituted with one or more substituents selected from halogen, R3, OR3COR3R4R5, NR4R5(C1-6)alkyl, NR4R5CO, NR4R5CO(C1-6)alkyl, CN, cyano(C1-6)alkyl or R6;
• R3 represents C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-6cycloalkyl, C3-6Cycloalkyl(C1-6)alkyl, cyano(C1-6)alkyl, hydroxyC1-6alkyl and R3 is optionally mono, di- or tri-fluorinated;
• R4 and R5 are each independently hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-6cycloalkyl or CF3 or R4 and R5, together with a nitrogen atom to which they are commonly attached, form a 4-7 membered heteroaliphatic ring containing the said nitrogen atom and optionally one other heteroatom selected from O, N and S;
• and
• R6 is C6-10aryl, C6-10aryl (C1-6)alkyl heteroaryl or heteroaryl(C1-6)alkyl, where heteroaryl is a five-membered aromatic ring containing one, two, three or four nitrogen atoms or one oxygen atom or sulphur atom and optionally one or two nitrogen atoms or a six-membered aromatic ring containing one, two or three nitrogen atoms, and R6 is optionally substituted by one, two or three substituents independently chosen from halogen atoms and C1-4alkyl, C2-4alkenyl, C2-4alkynyl, C1-4alkoxy, C2-4alkenyloxy and C2-4alkynyloxy groups each of which groups is unsubstituted or substituted by one, two or three halogen atoms.