Table 50.
Comparison of the enantioselective aldol reaction catalyzed by (S)-proline under solvent-free conditions using ball milling (method A) and stirring (method B).
 | ||||||
|---|---|---|---|---|---|---|
| entry | product | method | time (h) |
yield (%) |
anti / syn | ee of anti (%) |
| 1 |  |
A | 7 | 97 | 93:7 | 97 |
| 2 | B | 36 | 89 | 91:9 | 97 | |
| 3 |  |
A | 7 | 94 | 88:12 | >99 |
| 4 | B | 16 | 89 | 82:18 | 98 | |
| 5 |  |
A | 5.5 | 99 | 89:11 | 94 |
| 6 | B | 96 | 98 | 87:13 | 94 | |
| 7 |  |
A | 36 | 65 | 66:34 | 63 |
| 8 | B | 96 | 64 | 71:29 | 67 | |
| 9 |  |
A | 20 | 87 | 74:26 | 75 |
| 10 | B | 72 | 85 | 78:22 | 67 | |
| 11 |  |
A | 5 | 93 | 50:50 | 90 |
| 12 | B | 36 | 93 | 46:54 | 75 | |
| 13 |  |
A | 5 | 53 | 57:43 | 95 |
| 14 | B | 24 | 90 | 52:48 | 87 | |
| 15 |  |
A | 19 | 73 | — | 56 |
| 16 | B | 36 | 69 | — | 54 | |