Step 4 Synthesis of 5-fluoro-4-methylbenzene-1,2-diamine: 4-fluoro-5-methyl-2-nitroaniline (3.12 g, 0.018 mol), sodium dithionite (Na2S2O4, 9.58 g, 0.055 mol), water (45 mL), and ethanol (90 mL) were added to a 250 mL round bottom flask. The reaction mixture was heated to reflux and kept for 1 hour. Upon completion of the reaction, the solvent was removed by rotary evaporator. The residue was suspended in a mixture of triethylamine (15 mL) and ethyl acetate (300 mL) and subsequently filtered. The filtrate was concentrated under reduced pressure to give 2.1 g (82% yield) of the target product 5-fluoro-4-methylbenzene-1,2-diamine as a light red solid.
