反应详情

TFA (20 ml) was added to an ice cold stirred solution of the t-butyl ester 211e (4.15 g, 10.34 mmol) in dry CH2Cl2 (20 ml). The mixture was kept cold for 1.5 h then left for 2.5 h at rt, concentrated. TFA was removed by repeated concentrations of CH2Cl2\ether and ether solutions of the residue. Finally trituration of the residue with ether afforded 212e 3.05 g (85%) of a white glassy solid: mp 118-126° C.; [α]D24 −70.5° (c 0.1, CH2Cl2). IR (KBr) 3361, 2943, 1737, 1659, 1537, 1426, 1220, 1174; 1H NMR (CDCl3) δ 7.80 (2H, m), 7.54-7.33 (4H, m), 8.83 (brs), 5.44 (1H, m), 5.26-5.13 (1H, m), 4.66 (1H, m), 3.59-3.41 (1H, m), 2.97, 2.76 (2H, 2m), 2.36 (2H, m), 1.98 (2H, m), 1.75 (2H, m). MS (ES−, m/z) 344 (M−1, 100%).

1. waitthen left for 2.5 h at rt
2. concentrationconcentrated
3. customTFA was removed