(1,2,4)triazolo[4,3-A]quinoxaline derivatives as inhibitors of phosphodiesterases

A compound of formula (I):

• or a pharmaceutically acceptable salt thereof;
• wherein:
• R1 is
• -phenyl, 2-pyridyl, 3-pyridyl or 4-pyridyl,
• in each case substituted with a substituent different from H in an ortho position of the linkage to the backbone structure;
• R2 is hydrogen, C1-4 alkyl, optionally substituted with up to 2 halo atoms;
• R3, R4 and R6 are independently selected from the group consisting of
• hydrogen,
• halogen,
• C1-4 alkyl, optionally substituted with up to 5 halo atoms or —OC1-2 (halo)alkyl,
• C3-8 cycloalkyl, optionally substituted with halo, —C1-2 (halo)alkyl or —OC1-2 (halo)alkyl,
• —CN,
• —OH,
• —OC1-4 alkyl, optionally substituted with up to 5 halo atoms or —OC1-2 (halo)alkyl,
• C3-8 cycloalkyl optionally substituted with halo, —C1-2 (halo)alkyl, or —OC1-2 (halo)alkyl,
• —O(CH2)n—R10, wherein n can be 1 or 2;
• R5 is selected from the group consisting of
• halogen,
• C1-4 alkyl, optionally substituted with up to 5 halo atoms or —OC1-2 (halo)alkyl,
• C3-8 cycloalkyl, optionally substituted with halo, —C1-2 (halo)alkyl or —OC1-2 (halo)alkyl,
• —CN,
• —OH,
• —OC1-4 alkyl, optionally substituted with up to 5 halo atoms or —OC1-2 (halo)alkyl,
• C3-8 cycloalkyl optionally substituted with halo, —C1-2 (halo)alkyl, or —OC1-2 (halo)alkyl,
• —O(CH2)n—R10, wherein n can be 1 or 2;
• R10 is a cyclic group which can be unsubstituted or substituted preferably up to 4 times by halogen, C1-4 alkyl, optionally substituted with up to 5, preferably up to 3 halogen atoms, or OC1-4 alkyl, optionally substituted with up to 5, preferably up to 3 halogen atoms,
• wherein the compound of formula (I) is not
• 1-(2-hydroxyphenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline,
• 1-(2-chlorophenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline,
• 1-(2-nitrophenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline,
• 1-(2-methoxyphenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline,
• 1-(5-amino-2-chlorophenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline,
• 1-(5-amino-2-methoxyphenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline,
• 1-(5-amino-2-methylphenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline, or
• 1-(2-hydroxy-3-methoxyphenyl)-4-methyl-(1,2,4)triazolo[4,3-a]quinoxaline.