The product from the previous step, [3-(2-methyl-[1,3]dioxolan-2-yl)propyl](3-nitro-quinolin-4-yl)amine (29.5 g, 93.0 mmol), was stirred with sodium dithionite (67.0 g, approximately 85% pure), potassium carbonate (51.4 g, 372 mmol), and ethyl viologen dibromide (0.37 g, 1 mmol) in a mixture of dichloromethane and water (375 mL each) for 15 hours. The layers were then separated, and the organic phase was washed successively with a saturated aqueous sodium bicarbonate solution and water (250 mL each), dried over potassium carbonate, filtered, and concentrated under reduced pressure to provide N4-[3-(2-methyl-[1,3]dioxolan-2-yl)-propyl]quinoline-3,4-diamine (26.0 g) as a dark solid that was used directly in the next step without further purification.
