Pyridone compound as c-met inhibitor

A compound represented by formula (I) or a pharmaceutically acceptable salt,

• R1 is selected from H or F;
• R2 is selected from H or CH3;
• while R2 is not H, the configuration of the carbon atom bonded to R2 is R or S;
• A is selected from the group consisting of phenyl, pyridyl, pyrazolyl, isoxazolyl, isothiazolyl and thiazolyl, each of which is optionally substituted by 1, 2 or 3 R3;
• R3 is selected from CN, halogen, C(═O)NH2, or is selected from the group consisting of C1-6 alkyl, C1-6 heteroalkyl, and C3-6 cycloalkyl, each of which is optionally substituted by 1, 2 or 3 R0;
• R0 is selected from F, Cl, Br, I, OH, CN, NH2, C(═O)NH2, or is selected from the group consisting of C1-3 alkyl and C1-3 heteroalkyl, each of which is optionally substituted by 1, 2 or 3 R′;
• R′ is selected from F, Cl, Br, I, CN, OH, NH2, CH3, CH3CH2, CF3, CHF2 or CH2F;
• the “hetero” in the C1-3 heteroalkyl or C1-6 heteroalkyl is selected from the group consisting of —O—, —C(═O)NR′—, —C(═O)NH—, —NR′—, and —NH—;
• in any of the above cases, the number of the heteroatom or the heteroatomic group is independently selected from 1, 2 or 3.