A compound of the formula (I) in which R 1 is phenyl or thienyl, said phenyl and thienyl are optionally substituted 1 to 3 times by substituents independently selected from the group consisting of hydroxyl, halogen, C 1-7 alkyl, C 1 alkoxy -7, C1-7 haloalkyl, C1-7 haloalkoxy, (C1-7 alkoxy) -C 1-7 alkyl, -OC (O) -C 1-7 alkyl, -OCH2C (O) -C 1-7 alkoxy and phenyl； R2 is a monocyclic heteroaryl of 5 or 7 links having 1 to 3 heteroatoms independently selected from N and O, said heteroaryl is optionally substituted 1 to 3 times by substituents chosen independently from the group consisting of, halogen, hydroxyl, nitro, C 1-7 alkyl, C 1-7 alkenyl, C 1-7 alkoxy, C 1-7 alkoxy (O) -, C 1-7 hydroxyalkyl, C 1-7 haloalkyl, (C 1-7 alkoxy) -C 1-7 alkyl, (C1-7 alkyl) -C (O) -, cycloalkyl, heterocyclyl, aryl, heteroaryl and amino optionally substituted by heteroaryl, in which two R2 substituents, together with said heteroaryl to which they are attached, can form a bicyclic ring 9 or 10 links； R 3 and R 3 'are independently hydrogen, C 1-7 alkyl, C 1-7 hydroxyalkyl, C 1-7 cyanoalkyl, C 1-7 haloalkyl, (C 1-7 alkoxy) -C 1-7 alkyl, cycloalkyl, cyanocycloalkyl, heterocyclyl or aryl, said C1-7 alkyl is optionally substituted by C1-7 haloalkoxy, cycloalkyl, aryl or heteroaryl, said heteroaryl is optionally substituted 1 to 3 times by substituents independently selected from the group consisting of halogen, nitro, cyano, C1-7 alkyl, C1-7 haloalkyl, C1-7 alkoxy and cycloalkyl and said heterocyclyl is optionally substituted by C1-7 alkyl, or R3 and R3 ', together with the nitrogen atom to which they are attached, form a heterocyclyl, 2,5-dihydro- 1H-pyrrole, 2-methyl-2,4,5,7-tetrahydropyrrolo [3,4-c] pyrazol or 2-oxa-7-aza-spiro [3.3] heptane, said heterocyclyl is optionally substituted 1 to 3 times by halogen, hydroxyl, oxo, C1-7 alkyl or heteroaryl； R 8 is hydrogen, C 1-7 alkyl, C 1-7 alkoxy or (C 1-7 alkoxy) -C 1-7 alkyl； or its pharmaceutically acceptable salts.Un compuesto de la fórmula
