A compound of the formula I ** Formula ** wherein R1 is hydrogen； halogen； cyano； nitro； hydroxy； Not me； -C (O) H； -C (O) OH； -C (O) NH2； C1-6 alkyl； C1-6 halogenoalkyl； C1-6 hydroxyalkyl； C1-4-C1-6 alkoxy； C1-6 aminoalkyl； C2-6 alkenyl； C2-6 halogenoalkenyl； C2-6 alkynyl； C2-6 halogenoalkynyl； C1-6 alkoxy； C1-6 halogenoalkoxy； C1-4 alkoxy-C1-6 alkoxy； C1-6 alkylamino； di (C1-6 alkyl) amino； or C3-7 cycloalkyl, where a carbon atom can be replaced by an oxygen atom, where the C3-7 cycloalkyl can be attached directly to the pyridine ring or through a C1-2 alkylene or an oxygen, and in where C3-7 cycloalkyl can be substituted once or more than once by halogen, C1-4 alkyl or C1-4 alkoxy； R2 is hydrogen or fluoro； R3 is hydrogen； halogen； cyano； nitro； hydroxy； Not me； -C (O) H； -C (O) OH； -C (O) NH2； or -X1-R6； X1 is selected from the link； carbonyl； oxygen； sulfur； -SW)-； -S (O) 2-； amino, which can be substituted by C1-4 alkyl； -NH-C (O) -； - C (O) -NH-； -NH-S (O) 2-； and -S (O) 2-NH-； R6 is C1-6 alkyl； C1-6 halogenoalkyl； C1-6 cyanoalkyl； C1-6 carboxyalkyl； C1-6 hydroxyalkyl； C1-4-C1-6 alkoxy； C1-4 C1-4 alkoxy C1-6 alkoxy； C1-4 alkylcarbonyl-C1-6 alkyl； C1-4 alkoxycarbonyl-C1-6 alkyl； C1-4 alkylcarbonyloxy-C1-6 alkyl； C1-6 aminoalkyl； C1-4 alkylamino-C1-6 alkyl； di (C1-4 alkyl) amino-C1-6 alkyl； aminocarbonyl-C1-6 alkyl； C1-4 alkylaminocarbonyl-C1-6 alkyl； di (C1-4 alkyl) aminocarbonyl-C1-6 alkyl； C1-4 alkylcarbonylamino-C1-6 alkyl； C 1-4 alkylaminosulfonyl-C 1-6 alkyl； di (C1-4 alkyl) aminosulfonyl-C1-6 alkyl； C2-6 alkenyl； C2-6 halogenoalkenyl； C2-6 alkynyl； C2-6 halogenoalkynyl； or R6 is a three to seven membered monocyclic ring system that may be aromatic, saturated or unsaturated unsaturated and may contain 1 to 4 heteroatoms selected from nitrogen, oxygen and sulfur, where the ring system may contain no more of 2 oxygen atoms and not more than 2 sulfur atoms, where the ring system can be attached directly to the group X1 or through a C1-2 alkylene, where the r
