A compound of formula I ** Formula ** or a pharmaceutically acceptable salt thereof, wherein: R1 and R2 are each independently selected from hydrogen and C1-C6 alkyl； Y is selected from -O-C1-C6 alkyl, -O-C3-C8 cycloalkyl, -O-C1-C3 alkyl-C3-C8 cycloalkyl, -O (CH2) to -aryl, - O (CH2) b -heteroaryl , -C (O) C1-C6 alkyl, -C (O) -C3-C8 cycloalkyl, -C (O) -C1-C3-alkyl-C3-C8 cycloalkyl, -C (O) aryl, and -C (O ) heteroaryl, when the cycloalkyl, aryl and heteroaryl ring systems are each optionally substituted by one or more substituents selected from List X； A is N； List X is represented by hydroxy, halo, cyano, nitro, C1-C6 alkyl, C3-C8 cycloalkyl, C1-C3 alkyl-C3-C8 cycloalkyl, -O-C1-C6 alkyl, -O-C3-C8 cycloalkyl, -O-C1-C3 alkyl-C3-C8 cycloalkyl, when each of the alkyl groups is optionally substituted by one or more halogen, hydroxy, or cyano； Ar 'is a group ** Formula ** where E is N or CRe； Ra is selected from H, halo, C1-C6 alkyl, C1-C6 haloalkyl, O-C1-C6 alkyl and -O-C1-C6 haloalkyl； Rb is selected from H, -NR40R41, halo, C1-C6 alkyl, C1-C6 haloalkyl, -O-C1-C6 alkyl and -OH； Rc is S (O) 2R45, wherein R45 is -NHR43 or heterocyclyl； Rd is selected from H, C1-C6 alkyl and -O-C1-C6 alkyl； Re is selected from H, C1-C3 alkyl, C1-C3 haloalkyl and halo； R40, R42 and R44 are each independently selected from H and C1-C6 alkyl.Un compuesto de fórmula I**Fórmula** o una sal de este farmacéuticamente aceptable, en donde: R1 y R2 cada uno se selecciona independientemente de hidrógeno y alquilo C1-C6； Y se selecciona de -O-alquilo C1-C6, -O-cicloalquilo C3-C8, -O-alquilo C1-C3- cicloalquilo C3-C8,-O(CH2)a -arilo, - O(CH2)b -heteroarilo, -C(O)alquilo C1-C6, -C(O)- cicloalquilo C3-C8, -C(O)-alquilo C1-C3- cicloalquilo C3-C8, -C(O)arilo, y -C(O) heteroarilo, cuando los sistemas del anillo cicloalquilo, arilo y heteroarilo cada uno se sustituye opcionalmente por uno o más sustituyentes seleccionados de la Lista X； A es N； La Lista X se representa por hidroxi, halo, ciano, nitro, alquilo
