463 mg |
With pyridinium p-toluenesulfonate; In acetonitrile; at 80℃; for 24h;Inert atmosphere; Sealed tube; |
To a 40-mL sealed I-Chem vial under nitrogen was added racemic 2-butyl boronic acid (+/-)-la (6 mmol), BIDA (4 mmol), pyridinium /?-toluenesulfonate (0.4 mmol) followed by acetonitrile (27 mL, 0.15 M for 5). The reaction was allowed to stir at 80 C for 24 hours. After cooling down, the mixture was passed through a pad of Florisil before concentration. The light brown solid mixture was then dissolved in Et20 to make a heterogeneous mixture and filtered; the filtrate was washed with copious amount of Et20. The white solid was recrystallized with acetone:Et20 twice to give 5a [463 mg, 97:3 d.r. (1H NMR) 31%]. TLC: (hexanes:EtOAc = 1 : 1, KMn04) Rf = 0.41, (S) isomer 5a; Rf = 0.16, (R) isomer 5b 1H NMR (500 MHz, DMSO) delta 8.19 (m, 4H), 8.14 (m, 1H), 5.36 (d, J = 11, 1H), 5.30 (d, J = 11, 1H), 5.03-4.90 (m, 4H), 4.77 (d, J = 17, 1H), 4.35 (q, J = 6, lH), 4.17 (s, 3H), 2.89 (m, 1H), 2.83 (m, 1H), 2.83 (m, 1H), 2.26 (m, 1H), 1.90 (m, 1H), 1.69 (t, J = , 3H), 1.66-1.58 (m, 3H). 13C NMR (125 MHz, DMSO-d6) delta 169.8, 168.3, 137.9, 128.3, 127.8, 127.6, 79.8, 72.1, 70.9, 59.3, 56.4, 39.5, 29.4, 26.2, 24.9, 21.0, 14.2, 12.6. HRMS (ESI+) Calculated for C2oH29BN05: 374.2139 Found: 374.2119 |