u201c heterocyclic group u201d means rings containing one or more heteroatoms selected from nitrogen sulphur and oxygen the heterocycle may be aromatic or non aromatic i e may be saturated partially or fully unsaturated examples of 5 membered groups include isoxazole oxadiazole pyrazole oxazole triazole tetrazole and thiadiazole when the heteroatom n replaces a carbon atom in a c 1 12 alkyl group the n atom will where appropriate be substituted by one or two substituents selected from hydrogen and c 1 6 alkyl as used herein the term u201c aliphatic heterocyclic group u201d as defined for r 1 means a cyclic group of 4 to 7 carbon atoms wherein one or more of the carbon atoms is are replaced by heteroatoms independently selected from nitrogen oxygen or sulfur this group may be unsubstituted or substituted with one to four substituents preferably one or two substituents as defined hereinabove examples of aliphatic heterocyclic groups include piperidinyl tetrahydrofuranyl and tetrahydropyranyl as used herein the term u201c aliphatic amine u201d means an amine group comprising straight or branched chains of carbon atoms saturated or unsaturated as used herein the term u201c alicyclic amine u201d means an amine group comprising at least one closed ring of carbon atoms e g cycloalkyl groups as used herein the term u201c aromatic amine u201d means an amine group comprising at least one benzene ring preferably r 2 represents halogen or hydrogen more preferably hydrogen preferably r 3 represents an acetylene group or a 5 membered heterocyclic group optionally substituted by a c 1 4 alkyl preferably the heterocyclic group is selected from an isoxazole oxadiazole pyrazole oxazole triazole tetrazole or thiadiazole more preferably an isoxazole a 1.