Conditions optimization of the enantioselective reaction.
| |||||
|---|---|---|---|---|---|
| Entrya | CPA | Solvent | Temp [oC] | Yield [%]b | ee [%]c |
| 1 | B1 | CH2Cl2 | rt | Trace | — |
| 2 | B2 | CH2Cl2 | rt | Trace | — |
| 3 | C1 | CH2Cl2 | rt | 64 | 65 |
| 4 | C2 | CH2Cl2 | rt | 20 | 46 |
| 5 | C3 | CH2Cl2 | rt | 44 | 53 |
| 6 | C4 | CH2Cl2 | rt | Trace | — |
| 7 | C5 | CH2Cl2 | rt | 18 | 7 |
| 8d | C1/B1 | CH2Cl2 | rt | 40 | 61 |
| 9e | C2/B2 | CH2Cl2 | rt | 34 | 90 |
| 10f | C1/B2 | CH2Cl2 | rt | 44 | 90 |
| 11f | C1/B2 | MeCN | rt | Trace | — |
| 12f | C1/B2 | EtOAc | rt | Trace | — |
| 13f | C1/B2 | THF | rt | Trace | — |
| 14g | C1/B2 | CH2Cl2 | rt | 44 | 90 |
| 15h | C1/B2 | CH2Cl2 | rt | 32 | 88 |
| 16g | C1/B2 | CH2Cl2 | 0 | Trace | — |
| 17g,i | C1/B2 | CH2Cl2 | rt to 0 | 56 | 93 |
a
Unless noted, under Ar atmosphere, a mixture of 1a (0.05 mmol), 2a (0.10 mmol) and CPA (10 mol%) in the solvent (2.0 mL) was stirred at room temperature (rt) for 24 h.
b
Determined by 1H NMR with CH2Br2 as internal standard.
c
Determined by chiral-HPLC analysis.
d
C1 (10 mol%), B1 (10 mol%).
e
C2 (10 mol%), B2 (10 mol%).
f
C1 (10 mol%), B2 (10 mol%).
g
C1 (8 mol%), B2 (8 mol%).
h
C1 (5 mol%), B2 (5 mol%).
i
The mixture was stirred at rt under Ar atmosphere for 5 min (2a was totally dissolved), then it was cooled to 0 °C for 6 days.