A compound of formula I: where: R 1 is H, -C 1-8 alkyl, -CH(CH 3)OC -O-cyclohexyl, -(CH 2) 2 -morpholinyl, or -CH 2 -5-methyl-[1,3]dioxol-2-one; R 2 is -CH 2 -O-R 20, where R 20 is -C 1-6 alkyl, -CH 2 NR 27 CHR 28 -, -C 2-3 alkylene-OH, or -C 2-3 alkylene-NR 29 R 30; R 27 is H, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 6 fluoro atoms, - (CH 2) 2 OH, or -(CH 2) 2 OC 1-6 alkyl; R 28 is H, -C 1-6 alkyl, -C 1-2 alkylene-OH, or -C 1-2 alkylene-OC 1-6 alkyl; and R 29 and R 30 are independently H, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 6 fluoro atoms, -(CH 2) 2 OH, or -(CH 2) 2 OC 1-6 alkyl; or R 29 and R 30 are taken together to form -CH 2 -CH 2 -CH 2 -; R 3, R 4 and R 5 are independently H or halo; R 6 is a heterocycle selected from the group consisting of 3H-oxazol-2-one, [1,2,4]oxadiazol-5-one, [1,2,3,5]oxatriazole, dihydro-[1,2,4]triazol-3-one, [1,2,4]triazolo[1,5-α]pyridine, triazole, pyrazole, imidazole, oxazole, isoxazole, isothiazole, pyridine, oxadiazole, and pyrimidine; the heterocycle is attached at a carbon atom; and each nitrogen atom in the heterocycle is unsubstituted or substituted with an R 60 group selected from the group consisting of -OH, -(CH 2) 2 OH, -C 0-2 alkylene-O-C 1-6 alkyl, -C 1-6 alkyl, -CHF 2, -CF 3, and phenyl; and each carbon atom in the heterocycle is unsubstituted or substituted with an R 61 group independently selected from the group consisting of halo, -OH, -C 1-6 alkyl, -C 0-2 alkylene-O-C 1-6 alkyl, -C CH 3, -C NH(CH 3), -C N(CH 3) 2, -C 3-6 cycloalkyl, -CF 3, -CH 2 SO 2 CH 3, -NH 2, -CH 2 NH 2, -CH 2 N(CH 3) 2, pyrazine, and phenyl substituted with methyl or halo; or a pharmaceutically acceptable salt thereof. R 1 is H, -C 1-8 alkyl, -CH(CH 3)OC -O-cyclohexyl, -(CH 2) 2 -morpholinyl, or -CH 2 -5-methyl-[1,3]dioxol-2-one; R 2 is -CH 2 -O-R 20, where R 20 is -C 1-6 alkyl, -CH 2 NR 27 CHR 28 -, -C 2-3 alkylene-OH, or -C 2-3 alkylene-NR 29 R 30; R 27 is H, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 6 fluoro atoms, - (CH 2) 2 OH, or -(CH 2) 2 OC 1-6 alkyl; R 28 is H, -C 1-6 alkyl, -C 1-2 alkylene-OH, or -C 1-2 alkylene-OC 1-6 alkyl; and R 29 and R 30 are independently H, -C 1-6 alkyl, -C 1-6 alkyl substituted with 1 to 6 fluoro atoms, -(CH 2) 2 OH, or -(CH 2) 2 OC 1-6 alkyl; or R 29 and R 30 are taken together to form -CH 2 -CH 2 -CH 2 -; R 3, R 4 and R 5 are independently H or halo; R 6 is a heterocycle selected from the group consisting of 3H-oxazol-2-one, [1,2,4]oxadiazol-5-one, [1,2,3,5]oxatriazole, dihydro-[1,2,4]triazol-3-one, [1,2,4]triazolo[1,5-α]pyridine, triazole, pyrazole, imidazole, oxazole, isoxazole, isothiazole, pyridine, oxadiazole, and pyrimidine; the heterocycle is attached at a carbon atom; and each nitrogen atom in the heterocycle is unsubstituted or substituted with an R 60 group selected from the group consisting of -OH, -(CH 2) 2 OH, -C 0-2 alkylene-O-C 1-6 alkyl, -C 1-6 alkyl, -CHF 2, -CF 3, and phenyl; and each carbon atom in the heterocycle is unsubstituted or substituted with an R 61 group independently selected from the group consisting of halo, -OH, -C 1-6 alkyl, -C 0-2 alkylene-O-C 1-6 alkyl, -C CH 3, -C NH(CH 3), -C N(CH 3) 2, -C 3-6 cycloalkyl, -CF 3, -CH 2 SO 2 CH 3, -NH 2, -CH 2 NH 2, -CH 2 N(CH 3) 2, pyrazine, and phenyl substituted with methyl or halo;