P-phenylenediamine derivative as potassium channel regulator and preparation method and medical application thereof

The compound represented by formula A or a pharmaceutically acceptable salt thereof:

• wherein:
• when ring B is
• ring A is a saturated or unsaturated heterocyclic containing 1 to 2 heteroatoms selected from N, S and O;
• when ring B is
• ring A is a benzene ring or the saturated or unsaturated heterocyclic containing 1 to 2 heteroatoms selected from N, S and O;
• wherein, R6 and R7 are independently hydrogen, halogen, C1-6 alkyl, C1-6 alkoxy, halogenated C1-6 alkyl, C1-6 alkylamino, halogenated C1-6 alkoxy, C3-6 cycloalkyl;
• R1 is a substituent on ring A;
• R2 is a substituent on ring B;
• R3 and R4 are substituents on six-membered ring;
• R1, R2, R3 and R4 are each independently hydrogen, halogen, nitro, cyano, C1-6 alkyl, C1-6 alkoxy, halogenated C1-6 alkyl, halogenated C1-6 alkoxy, C3-6 cycloalkyl, C1-6 alkylamino;
• Y is N or CH;
• Z is O or (CH2)n, n is an integer from 1 to 6;
• R5 is C1-6 alkyl, C3-6 cycloalkyl, C3-6 cycloalkenyl, C2-6 alkenyl or C2-6 alkynyl, wherein the C1-6 alkyl, C3-6 cycloalkyl, C3-6 cycloalkenyl, C2-6 alkenyl or C2-6 alkynyl are optionally substituted with one or more substituents selected from halogen, nitro, cyano, amine or hydroxyl;
• the saturated or unsaturated heterocyclic containing 1 to 2 heteroatoms selected from N, S and O is selected from the group consisting of pyridine, pyrazine, pyridazine, pyrimidine, thiophene, furan pyrrole, thiazole and oxazole.