A mixture of 3-bromo-4-nitropyridine N-oxide (2.2g,10 mmol), trichlorooxobis (triphenylphosphine) rhenium(V) [Re(0)(Ph3P)2Cl3, Aldrich, 50 mg, 0.08mmol), and triphenyphosphine (2.7 g, 10.3 mmol) in dichloromethane (100 mL) was flushed with argon and stirred at rt for 1 h, then, at 40 °C for 2 h. The reaction mixture was cooled to rt and concentrated under vacuum. The residue was triturated with hexanes (300 mL), and the precipitated (triphenylphosphine oxide) was removed by filtration. The organic layer was concentrated and purified by column (silica gel, EtOAc/hexanes 1/7) to give 3-Bromo-4-nitropyridine as yellow solid (1.8 g, 86%)[1].
