A compound of formula 2: or a pharmaceutically acceptable salt thereof, wherein m is selected from 0, 1, and 2; n is selected from 0, 1, and 2; each R 1 is independently selected from the group consisting of cyano, halo, hydroxy, amino, C 1-4 alkyl, C 1-4 alkoxy, trifluoromethyl, and trifluoromethoxy; each R 4 is independently selected from the group consisting of cyano, halo, hydroxy, amino, C 1-4 alkyl, C 1-4 alkoxy, trifluoromethyl, fluoromethoxy, difluoromethoxy, and trifluoromethoxy; and R 5 is selected from the group consisting of hydrogen, trifluoromethyl, and C 1-4 alkyl, provided: (a) if R 5 is hydrogen, methyl, n-propyl, i-propyl, or i-butyl, then m and n are not both 0; (b) if R 5 is hydrogen, m is 0, and n is 1, then R 4 is not chloro, methoxy, 3-trifluoromethyl, 4-trifluoromethyl, 4-methyl, 4-fluoro, 2-difluoromethoxy, 3-difluoromethoxy, 2-trifluoromethoxy, 4-trifluoromethoxy, or 2-(i-butoxy); (c) if R 5 is methyl, m is 0, and n is 1, then R 4 is not chloro, 2-fluoro, 4-fluoro, 2-bromo, 4-ethyl, 2-methyl, 4-(i-propyl), 4-(i-butyl), or 3-trifluoromethyl; (d) if R 5 is ethyl, m is 0, and n is 1, then R 4 is not 3-chloro, 4-chloro, 4-bromo, 4-methyl, 4-methoxy, or 2-difluoromethoxy; (e) if R 5 is n-propyl, m is 0, and n is 1, then R 4 is not 3-trifluoromethyl; (f) if R 5 is i-propyl, m is 0, and n is 1, then R 4 is not 4-fluoro or 4-methoxy; (g) if R 5 is i-butyl, m is 0, and n is 1, then R 4 is not 3-trifluoromethyl; (h) if R 5 is hydrogen, m is 0, and n is 2, then R 4 is not 2,6-difluoro, 2,4-dichloro, 3,5-dimethoxy, 3,4-dimethoxy, 4-methoxy-3-difluoromethoxy, 4-fluoro-2-trifluoromethyl, or 5-bromo-2-difluormethoxy; and (i) if R 5 is methyl, m is 0, and n is 2, then R 4 is not 3,4-dimethyl, 3,4-dichloro, 2,4-dichloro, 3-fluoro-4-methoxy, 3-bromo-4-methoxy, 3-methoxy-4-isopropyloxy, or 3-methoxy-4-isobutyloxy. m is selected from 0, 1, and 2; n is selected from 0, 1, and 2; each R 1 is independently selected from the group consisting of cyano, halo, hydroxy, amino, C 1-4 alkyl, C 1-4 alkoxy, trifluoromethyl, and trifluoromethoxy; each R 4 is independently selected from the group consisting of cyano, halo, hydroxy, amino, C 1-4 alkyl, C 1-4 alkoxy, trifluoromethyl, fluoromethoxy, difluoromethoxy, and trifluoromethoxy; and R 5 is selected from the group consisting of hydrogen, trifluoromethyl, and C 1-4 alkyl, provided: (a) if R 5 is hydrogen, methyl, n-propyl, i-propyl, or i-butyl, then m and n are not both 0; (b) if R 5 is hydrogen, m is 0, and n is 1, then R 4 is not chloro, methoxy, 3-trifluoromethyl, 4-trifluoromethyl, 4-methyl, 4-fluoro, 2-difluoromethoxy, 3-difluoromethoxy, 2-trifluoromethoxy, 4-trifluoromethoxy, or 2-(i-butoxy); (c) if R 5 is methyl, m is 0, and n is 1, then R 4 is not chloro, 2-fluoro, 4-fluoro, 2-bromo, 4-ethyl, 2-methyl, 4-(i-propyl), 4-(i-butyl), or 3-trifluoromethyl; (d) if R 5 is ethyl, m is 0, and n is 1, then R 4 is not 3-chloro, 4-chloro, 4-bromo, 4-methyl, 4-methoxy, or 2-difluoromethoxy; (e) if R 5 is n-propyl, m is 0, and n is 1, then R 4 is not 3-trifluoromethyl; (f) if R 5 is i-propyl, m is 0, and n is 1, then R 4 is not 4-fluoro or 4-methoxy; (g) if R 5 is i-butyl, m is 0, and n is 1, then R 4 is not 3-trifluoromethyl; (h) if R 5 is hydrogen, m is 0, and n is 2, then R 4 is not 2,6-difluoro, 2,4-dichloro, 3,5-dimethoxy, 3,4-dimethoxy, 4-methoxy-3-difluoromethoxy, 4-fluoro-2-trifluoromethyl, or 5-bromo-2-difluormethoxy; and (i) if R 5 is methyl, m is 0, and n is 2, then R 4 is not 3,4-dimethyl, 3,4-dichloro, 2,4-dichloro, 3-fluoro-4-methoxy, 3-bromo-4-methoxy, 3-methoxy-4-isopropyloxy, or 3-methoxy-4-isobutyloxy. (a) if R 5 is hydrogen, methyl, n-propyl, i-propyl, or i-butyl, then m and n are not both 0; (b) if R 5 is hydrogen, m is 0, and n is 1, then R 4 is not chloro, methoxy, 3-trifluoromethyl, 4-trifluoromethyl, 4-methyl, 4-fluoro, 2-difluoromethoxy, 3-difluoromethoxy, 2-trifluoromethoxy, 4-trifluoromethoxy, or 2-(i-butoxy); (c) if R 5 is methyl, m is 0, and n is 1, then R 4 is not chloro, 2-fluoro, 4-fluoro, 2-bromo, 4-ethyl, 2-methyl, 4-(i-propyl), 4-(i-butyl), or 3-trifluoromethyl; (d) if R 5 is ethyl, m is 0, and n is 1, then R 4 is not 3-chloro, 4-chloro, 4-bromo, 4-methyl, 4-methoxy, or 2-difluoromethoxy; (e) if R 5 is n-propyl, m is 0, and n is 1, then R 4 is not 3-trifluoromethyl; (f) if R 5 is i-propyl, m is 0, and n is 1, then R 4 is not 4-fluoro or 4-methoxy; (g) if R 5 is i-butyl, m is 0, and n is 1, then R 4 is not 3-trifluoromethyl; (h) if R 5 is hydrogen, m is 0, and n is 2, then R 4 is not 2,6-difluoro, 2,4-dichloro, 3,5-dimethoxy, 3,4-dimethoxy, 4-methoxy-3-difluoromethoxy, 4-fluoro-2-trifluoromethyl, or 5-bromo-2-difluormethoxy; and (i) if R 5 is methyl, m is 0, and n is 2, then R 4 is not 3,4-dimethyl, 3,4-dichloro, 2,4-dichloro, 3-fluoro-4-methoxy, 3-bromo-4-methoxy, 3-methoxy-4-isopropyloxy, or 3-methoxy-4-isobutyloxy.