A solution of 1-{[(2-chloro-5,6-dimethyl-3-nitropyridin-4-yl)amino]methyl}cyclohexanol (prepared as described in Part A, 27.1 mmol), dibenzylamine (15.6 mL, 81.3 mmol), and triethylamine (5.67 mL, 40.7 mmol) in toluene (100 mL) was heated at reflux for 7 d. The volatiles were removed under reduced pressure and the residue was partitioned between chloroform (300 mL) and water (100 mL). The aqueous layer was extracted with chloroform (2×75 mL). The combined organic layers were washed with brine (50 mL), dried over MgSO4, filtered, and concentrated to give a semi-solid. The semi-solid was triturated with 1:2 ethyl acetate/hexanes and filtered. The filtrate was concentrated to an orange oil that was purified on a Biotage (gradient elution, 0-30% ethyl acetate/hexanes) to yield an oil contained both product and dibenzylamine. The oil was dissolved in ethyl acetate (100 mL) and 1 M HCl in diethyl ether (50 mL) and methanol (100 mL) were added. The solution was stirred for 10 minutes and the solvent was removed in vacuo. The residue was triturated with 1:2 ethyl acetate/hexanes and filtered. The filtrate was concentrated, and the resulting oil was dissolved in chloroform (300 mL), washed with saturated aqueous sodium bicarbonate (50 mL), dried over MgSO4, filtered, and concentrated. The material was dissolved in ethyl acetate (400 mL) and washed with 10% aqueous citric acid (2×100 mL), saturated aqueous sodium bicarbonate (50 mL) and brine (50 mL), dried over MgSO4, filtered, and concentrated in vacuo to yield 1-({[2-(dibenzylamino)-5,6-dimethyl-3-nitropyridin-4-yl]amino}methyl)cyclohexanol (10.14 g, 79% yield over two steps).
