A compound of formula structure I: ** Formula ** in which: a is 0 or 1； b is 0 or 1； c is 0, 1, 2, 3 or 4； d is 1 or 2； e is 0, 1, 2, 3 or 4； f is 0, 1, 2, 3 or 4； A is a 6 to 15-membered monocyclic, condensed, bridged or spiro saturated heterocyclic ring containing two N and zero atoms or an O atom, substituted with an oxo group； each R1 is independently C1-6 alkyl, C1-6 haloalkyl, halogen or cyano； each R2 is independently hydroxy, halogen, cyano, C1-6 alkyl, C1-6 haloalkyl, C1-6 alkoxy, C1-6 haloalkoxy or NRaRb； each of R3 and R4 is independently hydrogen, halogen, C1-6 alkyl or C1-6 haloalkyl； each R5 is independently cyano, halogen, hydroxy, C1-6 alkyl, C1-6 alkoxy, C2-10 alkenyl, C1-6 haloalkyl, C1-6 haloalkoxy, C1-6 alkylcarbonyl, C1-6 alkoxycarbonyl or a ring which is: C3-10 cycloalkyl, C6-10 aryl, C6-10 aryloxy, oxetanyl, azetidinyl, a saturated or partially saturated 5 or 6 membered heterocyclic ring containing 1, 2 or 3 atoms independently selected from N, O and S, a ring 5-membered heteroaromatic containing 1, 2, 3 or 4 heteroatoms independently selected from N, O and S, not more than one heteroatom of which is O or S, a 6-membered heteroaromatic ring containing 1, 2 or 3 atoms of N or an unsaturated, partially saturated or saturated 7-10 membered heterocyclic ring containing 1, 2, 3 or 4 heteroatoms independently selected from N, O and S； any of whose rings is optionally substituted with one, two or three groups independently selected from R6； each R6 is independently hydroxy, oxo, cyano, halogen, nitro, C1-6 alkyl, C1-6 alkoxy, C2-10 alkenyl, C1-6 haloalkyl, C1-6 haloalkoxy, -O (C>； = O) C1- alkyl 6, - (C>； = O) C1-6alkyl, NRaRb, CONRaRb, NRaCORb, S (O) rNRaRb, S (O) rRc, NRaS (O) rRc or a ring which is: C3-10 cycloalkyl, C6 aryl -10, C6-10 aryl-C 1-6 alkyl, C6-10 arylcarbonyl, C6-10 aryloxycarbonyl, C6-10 arylC 1-6 alkoxycarbonyl, a 5-membered heteroaromatic ring containing 1, 2, 3 or 4 heteroatoms selected independently between N, O and S, no mor
