Reaction Steps
To a stirred solution of tert-Butyl 4-(3-(3-(2,6-Dimethylstyryl)phenyl)propanoyl)piperazine-1-carboxylate (12) (0.450 g, 1.00 mmol) in methylene chloride (6 mL) was added trifluoroacetic acid (3 mL) at room temperature. After 1 h, the reaction mixture was basified by slow addition of saturated aqueous sodium bicarbonate (30 mL) followed by 10% aqueous potassium carbonate to pH 10. The resulting mixture was extracted with hexanes (3×50 mL) and the combined extracts were dried (Na2SO4), filtered and concentrated. The resulting residue was purified by Preparative HPLC (Method 1) to give (E)-3-(3-(2,6-dimethylstyryl)phenyl)-1-(piperazin-1-yl)propan-1-one (13) (0.147 g, 42%) as a colorless oil. Rf 0.58 (silica gel, 50:40:10 ethyl acetate/hexanes/7N ammonia in methanol); 1H NMR (500 MHz, CD3OD) δ 7.41 (s, 1H), 7.37 (d, J=7.7 Hz, 1H), 7.28 (t, J=7.5 Hz, 1H), 7.18 (d, J=16.7 Hz, 1H), 7.15 (d, J=7.5 Hz, 1H), 7.03 (s, 3H), 6.57 (d, J=16.7 Hz, 1H), 3.53 (t, J=5.1 Hz, 2H), 3.41 (t, J=5.1 Hz, 2H), 2.95 (t, J=7.4 Hz, 2H), 2.71 (m, 4H), 2.59 (t, J=5.1 Hz, 2H), 2.34 (s, 6H); 13C NMR (75 MHz, CD3OD) δ 173.5, 142.8, 139.3, 138.3, 137.3, 135.4, 130.1, 129.1, 129.0, 128.3, 127.9, 127.7, 125.5, 47.9, 46.7, 46.4, 43.6, 35.5, 32.9, 21.3; ESI MS m/z 349 [M+H]+; HPLC (Method 5) >99% (AUC), tR=10.63 min. HRMS Calcd for C23H28N2O [M+H]: 349228. Found: 349.2275.
