Compounds of formula (I) in which R1 represents (C1-C4) alkyl, R2 represents (C1-C6) alkyl, (C2-C4) alkenyl, (C2-C4) alkynyl or (C3-C7) cycloalkyl, which may be (C1-C6) alkyl substituted with 1 to 3 substituents independently selected from the group of fluorine, chlorine, trifluoromethyl, trifluoromethoxy, alkoxy (C1-C4), cycloalkyl (C3-C7), cycloalkoxy (C3-C7), alkylsulfanyl ( C1-C4) or alkylsulfonyl (C1-C4), and may be alkenyl (C2-C4) and alkynyl (C2-C4) substituted with 1 or 2 substituents independently selected from each other from the group of fluorine, trifluoromethyl, (C1-C4) alkyl ), trifluoromethoxy and (C1-C4) alkoxy, and cycloalkyl (C3-C7) may be substituted with 1 or 2 substituents independently selected from the group of fluorine, chlorine, trifluoromethyl, (C1-C4) alkyl, trifluoromethoxy and alkoxy ( C1-C4), or R1 and R2 together with the nitrogen atom to which they are attached, form a 4- to 7-membered heterocycle, which it may contain an additional heteroatom of the N, O and S series, the 4- to 7-membered heterocycle may be substituted with 1 or 2 substituents independently selected from the group of fluorine, chlorine, oxo, trifluoromethyl, (C1-C4) alkyl , trifluoromethoxy and (C1-C4) alkoxy, R3 represents hydrogen or a group of formulaCompuestos de fórmula (I) en la que R1 representa alquilo (C1-C4), R2 representa alquilo (C1-C6), alquenilo (C2-C4), alquinilo (C2-C4) o cicloalquilo (C3-C7), pudiendo estar alquilo (C1-C6) sustituido con 1 a 3 sustituyentes seleccionados independientemente entre sí del grupo de flúor, cloro, trifluorometilo, trifluorometoxilo, alcoxilo (C1-C4), cicloalquilo (C3-C7), cicloalcoxilo (C3-C7), alquilsulfanilo (C1-C4) o alquilsulfonilo (C1-C4), y pudiendo estar alquenilo (C2-C4) y alquinilo (C2-C4) sustituidos con 1 o 2 sustituyentes seleccionados independientemente entre sí del grupo de flúor, trifluorometilo, alquilo (C1-C4), trifluorometoxilo y alcoxilo (C1-C4), y pudiendo estar cicloalquilo (C3-C7) sustituido con 1 o 2
