Synthesis
Diphenylphosphoryl azide (488 mg, 1.77 mmol) and triethylamine (180 mg, 1.77 mmol) were added to a solution of the acid (500 mg, 1.77 mmol) in tert-butanol (12 mL). The reaction mixture was stirred at reflux for 18 h and then quenched with water. The volatiles were removed under reduced pressure. The residue was dissolved in 4:1 TFA/DCM (5 mL) and stirred at rt for 1 h. The volatiles were removed under reduced pressure. The residue was dissolved in DCM and washed with 1N aq. NaOH. The combined organic extracts were dried (Na2SO4), filtered and concentrated. The crude residue was purified by SiO2 chromatography eluting with an EtOAc/hexane gradient to afford 3,6-dibromopyrazin-2-amine 120 mg (27%) of bromoanisol as a colorless oil. MS m/z (ES): 253 (M+H)+.
