A method of preparing a compound of Formula 7, the method comprising: reacting a compound of Formula 2 to obtain a compound of Formula 3, reacting the compound of Formula 3 with oxalyl halide to obtain a compound of Formula 4, reacting the compound of Formula 4 with a compound of Formula 5 to obtain a compound of Formula 6, and deoxygenating the compound of Formula 6 to obtain a compound of Formula 7, wherein the reaction between the compound of Formula 4 and the compound of Formula 5 is performed at -20°C to -10°C: Wherein n is 1 or 2, X, Y and Hal are each independently halogen, and wherein Ra, Rb, Rc, and Rd are each independently hydrogen, halogen, hydroxy, mercapto, cyano, nitro, amino, carboxy, oxo, C1-7alkyl, C1-7alkylthio, C2-7alkenyl, C2-7alkynyl, C1-7alkoxy, C1-7alkoxy-C1-7alkyl, C2-7alkenyl-C1-7alkyloxy, C2-7alkynyl-C1-7alkyloxy, C3-10cycloalkyl, C3-7cycloalkylthio, C5-10cycloalkenyl, C3-10cycloalkyloxy, C3-10cycloalkyloxy-C1-7alkoxy, phenyl-C1-7alkyl, C1-7alkylthio-phenyl, phenyl-C1-7alkoxy, mono- or di-C1-7alkylamino, mono- or di-C1-7alkylamino-C1-7alkyl, C1-7alkanoyl, C1-7alkanoylamino, C1-7alkylcarbonyl, C1-7alkoxycarbonyl, carbamoyl, mono- or di-C1-7alkylcarbamoyl, C1-7alkylsulfonylamino, phenylsulfonylamino, C1-7alkylsulfinyl, C6-14arylsulfanyl, C6-14arylsulfonyl, C6-14aryl, 5-13 membered heteroaryl, 5-10 membered heterocycloalkyl, 5-10 membered heterocycloalkyl-C1-7alkyl, or 5-10 membered heterocycloalkyl-C 1-7alkoxy; Ring C is C3-10cycloalkyl, C5-10cycloalkenyl, C6-14aryl, 5-13 membered heteroaryl, or 5-10 membered heterocycloalkyl; the alkyl, the alkenyl, the alkynyl and the alkoxy, each independently, are unsubstituted or have one or more substituents selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C1-7alkyl, and C2-7alkynyl; the cycloalkyl, the cycloalkenyl, the aryl, the heteroaryl and the heterocycloalkyl, each independently, are unsubstituted or have one or more substituents selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C1-4alkyl, and C1-4alkoxy; and the heteroaryl and the heterocycloalkyl, each independently, contain one or more heteroatoms selected from the group consisting of N, S and O. reacting a compound of Formula 2 to obtain a compound of Formula 3, reacting the compound of Formula 3 with oxalyl halide to obtain a compound of Formula 4, reacting the compound of Formula 4 with a compound of Formula 5 to obtain a compound of Formula 6, and deoxygenating the compound of Formula 6 to obtain a compound of Formula 7, wherein the reaction between the compound of Formula 4 and the compound of Formula 5 is performed at -20°C to -10°C: Wherein n is 1 or 2, X, Y and Hal are each independently halogen, and wherein Ra, Rb, Rc, and Rd are each independently hydrogen, halogen, hydroxy, mercapto, cyano, nitro, amino, carboxy, oxo, C1-7alkyl, C1-7alkylthio, C2-7alkenyl, C2-7alkynyl, C1-7alkoxy, C1-7alkoxy-C1-7alkyl, C2-7alkenyl-C1-7alkyloxy, C2-7alkynyl-C1-7alkyloxy, C3-10cycloalkyl, C3-7cycloalkylthio, C5-10cycloalkenyl, C3-10cycloalkyloxy, C3-10cycloalkyloxy-C1-7alkoxy, phenyl-C1-7alkyl, C1-7alkylthio-phenyl, phenyl-C1-7alkoxy, mono- or di-C1-7alkylamino, mono- or di-C1-7alkylamino-C1-7alkyl, C1-7alkanoyl, C1-7alkanoylamino, C1-7alkylcarbonyl, C1-7alkoxycarbonyl, carbamoyl, mono- or di-C1-7alkylcarbamoyl, C1-7alkylsulfonylamino, phenylsulfonylamino, C1-7alkylsulfinyl, C6-14arylsulfanyl, C6-14arylsulfonyl, C6-14aryl, 5-13 membered heteroaryl, 5-10 membered heterocycloalkyl, 5-10 membered heterocycloalkyl-C1-7alkyl, or 5-10 membered heterocycloalkyl-C 1-7alkoxy; Ring C is C3-10cycloalkyl, C5-10cycloalkenyl, C6-14aryl, 5-13 membered heteroaryl, or 5-10 membered heterocycloalkyl; the alkyl, the alkenyl, the alkynyl and the alkoxy, each independently, are unsubstituted or have one or more substituents selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C1-7alkyl, and C2-7alkynyl; the cycloalkyl, the cycloalkenyl, the aryl, the heteroaryl and the heterocycloalkyl, each independently, are unsubstituted or have one or more substituents selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C1-4alkyl, and C1-4alkoxy; and the heteroaryl and the heterocycloalkyl, each independently, contain one or more heteroatoms selected from the group consisting of N, S and O.