Table 1 Optimization of the reaction conditions
| ||
|---|---|---|
Entry | Variation from the “Initial Conditions” | Isolated yield (%), dr & ee |
1 | none | 31%, 7:1 dr, 96% ee |
2 | (S, R)-L2 instead of (S, R)-L1 | 19%, 5:1 dr, 63% ee |
3 | (S, R)-L3 instead of (S, R)-L1 | 44%, 4:1 dr, 96% ee |
4 | (S, R)-L4 instead of (S, R)-L1 | 63%, 7:1 dr, 32% ee |
5 | (S, R)-L5 instead of (S, R)-L1 | 16%, 6:1 dr, 83% ee |
6 | (S, R)-L6 instead of (S, R)-L1 | 42%, 6:1 dr, 2% ee |
7 | (S)-L7 instead of (S, R)-L1 | 70%, 10:1 dr, 22% ee |
8 | (S, R)-L8 instead of (S, R)-L1 | 31%, 5:1 dr, 3% ee |
9 | (S)-L9 instead of (S, R)-L1 | 26%, 7:1 dr, 0% ee |
10 | (S)-L10 instead of (S, R)-L1 | 80%, 9:1 dr, 4% ee |
11 | 10 mol% PC1 | 47%, 7:1 dr, 95% ee |
12 | 10 mol% PC1, THF + DCE (0.6/1.4 mL, 0.1 M) “Optimized Conditions” | 79%, 10:1 dr, 98% ee |
13 | Entry 12 with DCM instead of DCE | 73%, 10:1 dr, 91% ee |
14 | Entry 12 with MeCN instead of DCE | 51%, 7:1 dr, 96% ee |
15 | Entry 12 with 1.5 equiv. of LiBF4 as additive | 67%, 10:1 dr, 73% ee |
16 | Entry 12 with 1 equiv. of NH4H2PO4 as additive | 56%, 10:1 dr, 98% ee |
17 | Entry 12, 12 h instead of 17 h | 71%, 10:1 dr, 99% ee |
18 | Entry 12, 24 h instead of 17 h | 74%, 10:1 dr, 98% ee |
19 | Entry 12 with (S)-L11 instead of (S, R)-L1 | 58%, 7:1 dr, 87% ee |
20 | Entry 12 with (S)-L12 instead of (S, R)-L1 | 65%, 4:1 dr, 50% ee |
21 | Entry 12 with PC2 instead of PC1 | trace |
22 | Entry 12 with PC3 instead of PC1 | 37%, 9:1 dr, 89% ee |
23 | Entry 12 with PC4 instead of PC1 | N.D. |
24 | Entry 12 with PC5 instead of PC1 | N.D. |
25 | Entry 12 with (R, S)-L1 instead of (S, R)-L1 | 79%, 11:1 dr, −97% ee |
26 | Entry 12, no (S, R)-L1 | 80%, 11:1 dr, 0% ee |
27 | Entry 12, no PC1 or no light at 40 oC | 0/0 |
28 | Entry 12, no CrCl2 and (S, R)-L1 | 7% |
29 | Entry 12 with CrCl3 instead of CrCl2 | 58%, 8:1 dr, 89% ee |
