General procedure for the synthesis of 6-fluoro-1,2,3,4-tetrahydro-2-methylquinoline from 6-fluoro-1,2,3,4-tetrahydro-2-methylquinoline: 6-fluoro-1,2,3,4-tetrahydro-2-methylquinoline (0.50 mmol), FeCl2 (1.9 mg, 1.5 × 10-2 mmol), DMSO (31.2 mg, 0.4 mmol) and p-xylene (1 mL). The reaction mixture was stirred using a balloon at 110 °C and oxygen atmosphere and the progress of the reaction was monitored by TLC. Upon completion of the reaction, the mixture was cooled to room temperature and purified by fast chromatography (eluent: hexane-ethyl acetate, 10:1) to afford the target product 6-fluoro-2-methylquinoline in 70% yield. 6-fluoro-2-methylquinoline was a colorless oil.1H NMR (400 MHz, CDCl3): δ = 8.93 (m, 1H), 8.10 (m, 1H) , 7.64 (d, J=4.0 Hz, 1H), 7.54 (m, 1H), 7.43-7.35 (m, 2H), 2.82 (s, 3H).13C NMR (100 MHz, CDCl3): δ=149.2, 147.3, 137.1, 136.3, 129.6, 128.3, 126.3, 125.9. 120.8, 18.2. HRMS: m/z calculated value of [C10H9FN+H]+: 144.0813; measured value: 144.0813.
