Compound of formula (I): ** Formula ** in which X1 is selected from the group consisting of nitro, cyano, trifluoromethyl and -C (>； = O) OT4； Z and X2 are each independently selected from the group consisting of F, Cl, Br and I； X3 is isopropyl or ethyl； X4 is either absent or is selected from -NR4- and -N (R4) (CH2) -； R4 is selected from H and -C 1-6 alkyl； Y1 is selected from the group consisting of H, -C1-6 alkyl and a saturated or unsaturated aromatic carbocycle or heterocycle of 4 to 7 members, with the proviso that the point of attachment in said heterocycle is carbon if X4 is - NR4- or -N (R4) (CH2) -, wherein said -C1-6 alkyl is optionally substituted with one or more substituents independently selected from F, - OT1, -N (T2) (T3), -C ( >； = O) N (T2) (T3), -C (>； = O) OT1, -ST1, -S (>； = O) 2T1, -S (>； = O) 2N (T2) (T3) and a heterocycle saturated from 5 to 6 members, and wherein said 4 to 7 member carbocycle or heterocycle is optionally substituted with one or more substituents independently selected from F, - OT1, -N (T2) (T3), -C (>； = O) N (T2) (T3), -C (>； = O) OT1, -ST1, -S (>； = O) 2T1, -S (>； = O) 2N (T2) (T3), oxo and -alkyl C1-3, wherein said C1-3alkyl is optionally substituted with one or more substituents independently selected from -OT7, -N (T2) (T3) and a 6-membered saturated heterocycle； T1, T2 and T3 are each independently selected from H and -C 1-6 alkyl optionally substituted with one or more substituents independently selected from F, -N (T5) (T6), -OT7, -ST7, cyano, -C ( >； = O) OT7, -C (>； = O) N (T5) (T6), -OC (>； = O) N (T5) (T6), -S (>； = O) 2T7, -S (>； = O) 2OT8 and - S (>； = O) 2N (T5) (T6)； T4 is -C 1-6 alkyl optionally substituted with one or more substituents independently selected from F, -N (T5) (T6), -OT7, -ST7, cyano, -C (>； = O) OT7, -C (>； = O) N (T5) (T6), - OC (>； = O) N (T5) (T6), -S (>； = O) 2T8, -S (>； = O) 2OT7 and -S (>； = O) 2N (T5) (T6)； T5, T6 and T7 are each independen
