Reaction Steps
Compound 41 was prepared following the general procedure described by Wähälä and Hase, Heterocycles 1989, 28, (1), 183-186, herein incorporated by reference. To a 10 mL round bottom flask was added 2′-chloroisoflavone (152 mg, 0.592 mmol) and ammonium formate (149 mg, 2.37 mmol). The flask was purged with N2, followed by addition of methanol (8 mL) and 10% Pd/C (151 mg). The reaction was allowed to stir at room temperature and monitored by reverse phase HPLC. Upon consumption of starting material, the reaction mixture was passed through a pad of silica gel using EtOAc as the eluent. The solvent was concentrated in vacuo to afford crude 41. Purified by flash column chromatography (SiO2, 10% EtOAc/Hex) to afford 41 (21 mg, 14%) as an off-white solid. Analytical data for isoflavanone 41: 1H NMR (500 MHz, CDCl3) δ 7.98 (d, J=9.5 Hz, 1H), 7.53 (app t, J=9 Hz, 1H), 7.39-7.28 (m, 4H), 7.09-7.03 (m, 2H), 4.71-4.66 (m, 2H), 4.04-4.01 (app t, J=6.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 192.4, 161.8, 136.3, 133.2, 129.1, 128.9, 128.1, 128.0, 121.9, 121.3, 118.1, 71.7, 52.6; GCMS: Mass calculated for C15H11ClO2, [M]+, 259. Found 225. 4′-fluoroisoflavanone (46). Prepared according to the general procedure using 4′-fluoroisoflavone (77 mg, 0.319 mmol), ammonium formate (81 mg, 1.28 mmol), methanol (6.4 mL) and 10% Pd/C (81 mg). Purified by flash column chromatography (SiO2, 10% EtOAc/Hex) to afford 46 (18 mg, 23%) as an off-white solid. Analytical data for isoflavanone 46: 1H NMR (500 MHz, CDCl3) δ 7.97 (d, J=9.5 Hz, 1H), 7.53 (app t, J=9 Hz, 1H), 7.29-7.26 (m, 2H), 7.09-7.03 (m, 3H), 4.70-4.62 (m, 2H), 4.02-3.99 (m, 1H); 13C NMR (125 MHz, CDCl3) δ 205.8, 192.2, 191.9, 161.8, 136.4, 130.9, 130.5, 128.0, 122.0, 121.1, 118.1, 116.2, 116.0, 71.6, 51.8; LCMS: Mass calculated for C15H11FO2, [M+H]+, 243. Found 243.
