KCNQ2-5 channel activator

A compound represented by the general formula (I) or a pharmaceutically acceptable salt thereof:

• wherein R1 is (1) a hydrogen atom or (2) a C1-4 alkyl group;
• R2 is (1) a hydrogen atom or (2) a C1-4 alkyl group which may be substituted with a halogen;
• R3, R4, R5, and R6 are each independently (1) a hydrogen atom, (2) a halogen, or (3) a C1-4 alkyl group which may be substituted with a halogen;
• R7 and R8 are each independently (1) a halogen, (2) a C1-4 alkyl group which may be substituted with a halogen, or (3) a C1-4 alkoxy group which may be substituted with a halogen;
• Y is (1) a bond, (2) —NH—, or (3) —O—;
• Z is (1) a bond, (2) —NR12—, or (3) —O—;
• R12 is (1) a hydrogen atom, (2) a C1-4 alkyl group which may be substituted with a halogen, or (3) a C2-5 acyl group which may be substituted with a halogen;
• R10 and R11 are each independently (1) a hydrogen atom or (2) a C1-4 alkyl group which may be substituted with a halogen or a hydroxy group;
• n is an integer of 1 to 4, and when n is 2 to 4, a plurality of R10's or a plurality of R11's may be the same as or different from one another;
• R9 is (1) a ring A, (2) a C1-4 alkyl group, (3) a C2-4 alkenyl group, (4) a C2-4 alkynyl group, (5) —C1-4 alkylene group-ring A, (6) —C2-4 alkenylene group-ring A, (7) —C2-4 alkynylene group-ring A, (8) -ring B-ring C, (9) -ring B—C1-4 alkylene group-ring C, (10) -ring B—C2-4 alkenylene group-ring C, (11) -ring B—C2-4 alkynylene group-ring C, or (12) -ring B—O-ring C, where the alkyl group, the alkenyl group, the alkynyl group, the alkylene group, the alkenylene group, or the alkynylene group each may be substituted with a halogen or a hydroxy group;
• the ring A is (1) a C3-8 cycloalkane, (2) a 3- to 8-membered heterocycloalkane, (3) a C3-12 monocyclic or bicyclic unsaturated carbocyclic ring or the carbocyclic ring which may be partially saturated, or (4) a 3- to 12-membered monocyclic or bicyclic unsaturated heterocycle containing one to four heteroatoms selected from an oxygen atom, a nitrogen atom, and a sulfur atom or the heterocycle which may be partially saturated;
• the ring B and the ring C are each independently (1) a C3-8 monocyclic cycloalkane, (2) a 3- to 8-membered monocyclic heterocycloalkane, (3) a C3-7 monocyclic unsaturated carbocyclic ring or the carbocyclic ring which may be partially saturated, or (4) a 3- to 7-membered monocyclic unsaturated heterocycle containing one to three heteroatoms selected from an oxygen atom, a nitrogen atom, and a sulfur atom or the heterocycle which may be partially saturated;
• where the ring A, the ring B, and the ring C may be each independently substituted with one to five R13's, and when a plurality of R13's is present, the R13's may be the same as or different from one another;
• R13 is (1) a halogen, (2) a hydroxy group, (3) a cyano group, (4) a C1-6 alkyl group which may be substituted with a halogen or a hydroxy group, (5) a C1-6 alkoxy group which may be substituted with a halogen or a hydroxy group, or (6) an amino group which may be substituted with a C1-4 alkyl group or a C2-5 acyl group.