A compound of formula wherein R 1 is halogen, cycloalkylalkoxy, halophenylalkyl, oxetanyloxy, haloalkoxy, halophenylalkoxy or alkyloxetanylalkoxy; R 2 is halogen, cycloalkyl, haloazetidinyl, halopyrrolidinyl, cycloalkenyl, halocycloakyl or halooxetanyl; one of R 3 and R 4 is hydrogen or alkyl and the other one is -(CR 5 R 6)-(CR 7 R 8) n -R 9; or R 3 and R 4 together with the nitrogen atom to which they are attached form 2-oxo-5-aza-spiro[3.4]octyl, haloazetidinyl or halopyrrolidinyl; R 5 and R 6 are independently selected from hydrogen, alkyl, cycloalkylalkyl, haloalkyl, cycloalkyl, alkylsulfonylalkyl, phenylalkoxyalkyl, hydroxyalkyl, haloazetidinylalkyl, haloazetidinylcarbonyl, 2-oxa-6-azaspiro[3,3]heptanylcarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, aminocarbonyl, azetidinylcarbonyl, oxetanylalkyl and alkyloxetanyl; or R 5 and R 6 together with the carbon atom to which they are attached form cycloalkyl, oxetanyl, oxanyl or dioxothietanyl; R 7 and R 8 are independently selected from hydrogen, alkyl and cycloalkyl; or R 7 and R 8 together with the carbon atom to which they are attached form cycloalkyl; R 9 is alkyl, alkoxycarbonyl, hydroxyl, hydroxyalkyl, aminocarbonyl, cyano, pyridinyl, alkylaminocarbonyl, thiazol-2-yl, oxazol-2-yl, 5-alkyl-[1,2,4]oxadiazol-3-yl, alkyltetrazolyl, alkylthiazol-2-yl, 1H-tetrazolyl, 5-amino-[1,2,4]-oxadiazol-3-yl, 5-alkyl-[1,3,4]-oxadiazol-2-yl, azetidinylcarbonyl, haloazetidinylcarbonyl, 6-oxa-1-azaspiro[3.3]heptanyl, 5-phenyl-[1,3,4]-oxadiazol-2-yl or haloalkylaminocarbonyl; and nis 0 or 1; provided that when R 3 and R 4 are both alkyl at the same time, then R 1 and R 2 are not both halogen at the same time; or a pharmaceutically acceptable salt or ester therof. R 1 is halogen, cycloalkylalkoxy, halophenylalkyl, oxetanyloxy, haloalkoxy, halophenylalkoxy or alkyloxetanylalkoxy; R 2 is halogen, cycloalkyl, haloazetidinyl, halopyrrolidinyl, cycloalkenyl, halocycloakyl or halooxetanyl; one of R 3 and R 4 is hydrogen or alkyl and the other one is -(CR 5 R 6)-(CR 7 R 8) n -R 9; or R 3 and R 4 together with the nitrogen atom to which they are attached form 2-oxo-5-aza-spiro[3.4]octyl, haloazetidinyl or halopyrrolidinyl; R 5 and R 6 are independently selected from hydrogen, alkyl, cycloalkylalkyl, haloalkyl, cycloalkyl, alkylsulfonylalkyl, phenylalkoxyalkyl, hydroxyalkyl, haloazetidinylalkyl, haloazetidinylcarbonyl, 2-oxa-6-azaspiro[3,3]heptanylcarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, aminocarbonyl, azetidinylcarbonyl, oxetanylalkyl and alkyloxetanyl; or R 5 and R 6 together with the carbon atom to which they are attached form cycloalkyl, oxetanyl, oxanyl or dioxothietanyl; R 7 and R 8 are independently selected from hydrogen, alkyl and cycloalkyl; or R 7 and R 8 together with the carbon atom to which they are attached form cycloalkyl; R 9 is alkyl, alkoxycarbonyl, hydroxyl, hydroxyalkyl, aminocarbonyl, cyano, pyridinyl, alkylaminocarbonyl, thiazol-2-yl, oxazol-2-yl, 5-alkyl-[1,2,4]oxadiazol-3-yl, alkyltetrazolyl, alkylthiazol-2-yl, 1H-tetrazolyl, 5-amino-[1,2,4]-oxadiazol-3-yl, 5-alkyl-[1,3,4]-oxadiazol-2-yl, azetidinylcarbonyl, haloazetidinylcarbonyl, 6-oxa-1-azaspiro[3.3]heptanyl, 5-phenyl-[1,3,4]-oxadiazol-2-yl or haloalkylaminocarbonyl; and nis 0 or 1; provided that when R 3 and R 4 are both alkyl at the same time, then R 1 and R 2 are not both halogen at the same time; or a pharmaceutically acceptable salt or ester therof.