KCNQ potassium channel agonist, and preparation method therefor and use thereof

A method for treating a neurological disease selected from the group consisting of epilepsy, convulsion, neuropathic pain, acute ischemic stroke, and Alzheimer's disease, comprising:

• administering to a subject in need thereof an effective amount of a compound represented by formula I or a pharmaceutical acceptable salt thereof,
• wherein,
• X is selected from a group consisting of oxygen and sulfur;
• n is 1, 2 or 3;
• R1 is H or halogen;
• R2 and R3 are each independently selected from a group consisting of H, D and C1-C3 alkyl;
• or R2 and R3 together with the carbon atom to which they attached form C3-C6 saturated ring;
• R4 and R5 are each independently selected from a group consisting of H;
• halogen;
• C1-C6 alkyl;
• C3-C6 cycloalkyl;
• cyano;
• alkoxyl;
• C1-C6 alkyl substituted by hydroxy, amino, C1-C4 alkoxy, C1-C4 alkylcarbonyl, or halogen;
• C1-C4 alkoxy substituted by halogen;
• C1-C6 alkylcarbonyl;
• C1-C6 alkoxycarbonyl;
• C1-C6 alkylaminocarbonyl;
• C2-C6 alkenyl;
• and C2-C6 alkynyl;
• provided that R4 and R5 are not simultaneously hydrogen;
• R6 is selected from a group consisting of C1-C6 alkoxy;
• C1-C6 alkylamino;
• C1-C6 alkyl;
• C3-C6 cycloalkyl;
• C2-C6 alkenyl;
• C2-C6 alkynyl;
• C6-C10 aryl;
• C1-C6 alkyl substituted by halogen, cyano, hydroxy, C1-C6 alkoxyl, di(C1-C4 alkyl) amino, C1-C6 alkylcarbonyl, C1-C6 alkylcarbonylamino, or C1-C6 alkoxycarbonyl;
• C3-C6 cycloalkyl substituted by halogen;
• C2-C6 alkenyl substituted by halogen;
• C2-C6 alkynyl substituted by halogen;
• tetrahydrofuranyl;
• and
• wherein, R7 and R8 are each independently selected from a group consisting of C1-C4 alkyl.