Table 1.
| |||||
---|---|---|---|---|---|
Entry | Cu(OTf)2 (amount) | Ligand (amount) | Temp, time | Yield (%)[b] | ee (%)[c] |
1 | 30 | L1 (40 | 120 °C | 84 | -- |
mol % | mol%) | 24 h | |||
2 | 20 | L2 (25 | 120 °C | 78 | 67 |
mol % | mol %) | 24 h | |||
3[d] | 20 | L2 (25 | 120 °C | 81 | 91 |
mol % | mol %) | 24 h | |||
4[d] | 15 | L2 (19 | 110 °C | 76 | 95 |
mol % | mol %) | 12 h | |||
5[d,e] | 10 | L2 (13 | 110 °C | 72 | 66 |
mol % | mol %) | 12 h |
Conditions: Cu(OTf)2 was combined with L1 or L2 under argon and heated in dry PhCF3 (0.8 mL) for 2 h in a sealed tube. Substrate 1b (50.0 mg, 0.158 mmol), K2CO3 (0.158 mmol), MnO2 (0.473 mmol) and PhCF3 (0.8 mL) were added and the mixture was heated and stirred.
Isolated yield following flash chromatography on silica gel.
Enantiomeric excess determined by chiral HPLC analysis.
Activated flame-dried molecular sieves (20 mg/mL) were used.
Reaction did not go to completion.