Precursor compounds to substituted 1,2,4-triazolo[3,4,-a]phathalazine GABA alpha 5 ligands

A compound of formula III:

• wherein:
• R1 is hydrogen, halogen, CF3, OCF3, CN or a group C1-4alkyl, C2-4alkenyl, C2-4alkynyl, C1-4alkoxy, C2-4alkenyloxy or C2-4alkynyloxy, each of which groups is unsubstituted or substituted with one or two halogen atoms or with a pyridyl or phenyl ring each of which rings may be unsubstituted or independently substituted by one or two halogen atoms or nitro, cyano, amino, methyl or CF3 groups;
• R2 is hydrogen, halogen, CF3, OCF3, CN or a group C1-4alkyl, C2-4alkenyl, C2-4alkynyl, C1-4alkoxy, C2-4alkenyloxy or C2-4alkynyloxy, each of which groups is unsubstituted or substituted with one or two halogen atoms;
• Z is 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 and providing that when two of the heteroatoms are nitrogen then an oxygen or sulphur atom is also present and that when one of the atoms is oxygen or sulphur then at least one nitrogen atom is present, or a 6-membered heteroaromatic ring containing 2 or 3 nitrogen atoms, Z being optionally substituted by Rv and/or Rw, where Rv is halogen, R6, NR7R8, NR7COR8, CN, furyl, thienyl, phenyl, benzyl, pyridyl or a 5-membered heteroaromatic ring containing at least one nitrogen atom and optionally 1, 2 or 3 other heterotoms independently selected from oxygen, nitrogen and sulphur, at most one of the other heteroatoms being oxygen or sulphur and Rw is R6 or CN;
• R6 is C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-6cycloalkyl, hydroxyC1-6alkyl, C1-6alkoxy, C2-6alkenyloxy, C2-6alkynyloxy, C1-6alkoxyC1-6alkyl, CH2F or CF3;
• R7 and R8 are each independently hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-6cycloalkyl or CF3;
• or R7 and R8, together with the nitrogen atom to which they are attached, form a 4-7 membered heteroaliphatic ring containing the nitrogen atom as the sole heteroatom;
• and
• G is a leaving group.