Synthesis
GENERAL METHOD: 2a (2 mmol) was dissolved in acetic acid (10 mL) and powdered iron (12 mmol) was added with stirring. The reaction mixture was heated to reflux for 2 hours, during which time the progress of the reaction was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the mixture was cooled to room temperature and concentrated under reduced pressure to remove acetic acid. Ethyl acetate (EtOAc, 20 mL) was added, stirred for 2 min and filtered to remove iron impurities. The insoluble iron residue was washed with ethyl acetate (20 mL). The filtrate and washings were combined and dried with anhydrous magnesium sulfate (MgSO4). The solvent was removed by concentration under reduced pressure and the resulting crude product was purified by column chromatography to give the pure product 3a.
References
[1] Tetrahedron, 2011, vol. 67, # 6, p. 1187 - 1192
[2] European Journal of Medicinal Chemistry, 2017, vol. 132, p. 90 - 107
