Table 1.
entry | conditions | T (°C) | time | product | % yield (ee) |
---|---|---|---|---|---|
1 | HCO2H, H3PO4 | 115 | 12 h | 26+28 | 18 + 38 |
2 | HCO2H, 31c | 110 | 96 h | 26+28 | 43 + 14 |
3 | BBr3, CH2Cl2 | −78 to 0 | 30 min | 27 | 45 |
4 | BF3·Et2O, CH2Cl2 | −78 to rt | 2h | 27 | 0 |
5 | TMSI, toluene | 70 | 4h | 30 | 54 |
6 | 32, BBr3, CH2Cl2 | 0 | 20 min | 27 | 20 (< 20) |