Entry | Solvent | C/S | Temp. | Yield (%)d | Ee (%)e |
1a | MeOH | 0.5% | r.t. | Trace | ND |
2 a | CH2Cl2 | 0.5% | r.t. | Trace | ND |
3 a | THF | 0.5% | r.t. | Trace | ND |
4 a | EtOAc | 0.5% | r.t. | 27 | 45 |
5 a | t-BuOMe | 0.5% | r.t. | 42 | 60 |
6 a | DMF | 0.5% | r.t. | 74 | 79 |
7 | DMF | 0.5% | -20˚C | 66 | 84 |
8 | DMF | 0.5% | -40˚C | Trace | ND |
9b | DMF | 0.25% | -20˚C | 38 | 75 |
10c | DMF | 1% | -20˚C | 72 | 83 |