Table 1.
| ||||
---|---|---|---|---|
entry | catalyst | conditions | yield (%)b | d.r.c |
1 | A | CH2CI2, 23 °C, 24 h | 35 | >20:1 |
2 | B | CH2CI2, 23 °C, 24 h | 29 | >20:1 |
3 | C | CH2CI2, 23 °C, 24 h | 39 | >20:1 |
4 | C | THF, 50 °C, 24 h | 15 | >20:1 |
5 | C | 10:1 THF/tBuOH, 50 °C, 24h | 23 | >20:1 |
6 | C | CH2CI2, 23 °C, 3 h | 45 | >20:1 |
7 | C | 10:1 THF/tBuOH, 50 °C, 3h | 59 | >20:1 |
8 | C | CH2CI2, 40 °C, 2 h | 79 | >20:1 |
9d | C | CH2CI2, 40 °C, 2 h | 46 | >20:1 |
2 equiv. 1a and 1 equiv. 2a.
Isolated yield after purification.
As determined by 1H NMR spectroscopy.
10 mol % C, 10 mol % DBU.