Diphenyl phosphoryl azide (196 μL, 0.9 mmol) was added to a stirred solution of Eltrombopag (365 mg, 0.83 mmol) and Et3N (140 μL, 1.0 mmol) in CH2Cl2 (10 mL) at 0° C. under an atmosphere of nitrogen. The mixture was stirred at 0° C. for 2 min, then allowed to warm to room temperature and stirred for 2 hr. Further aliquots of diphenyl phosphoryl azide (196 μL, 0.9 mmol) and Et3N (140 μL, 1.0 mmol) were added and the mixture was stirred at room temperature overnight. H2O (15 mL) and CH2Cl2 (10 mL) were added and the aqueous and organic layers were partitioned. The aqueous layer was extracted with CH2Cl2 (1×20 mL), and the combined organic layers were dried over Na2SO4, filtered and the solvent removed under vacuum to leave a crude solid.
