Table 1 Optimization for cobalt-catalyzed asymmetric hydrogenation of (E)-2,3-diphenylacrylic acid.
From: Cobalt-catalyzed highly enantioselective hydrogenation of α,β-unsaturated carboxylic acids
| |||||
|---|---|---|---|---|---|
Entry | x (mol%) | Additive | Solvent | Conv. (%)a | ee (%)b |
1 | 5 | — | MeOH | 70 | 94 |
2 | 5 | — | iPrOH | >98 | 93 |
3c | 5 | — | TFE | >98 | 84 |
4 | 5 | — | DME | 7 | 43 |
5 | 5 | — | Toluene | 15 | 86 |
6 | 5 | — | THF | NR | — |
7 | 5 | — | 1,4-Dioxane | NR | — |
8 | 1 | — | iPrOH | 61 | 93 |
9 | 1 | Cs2CO3 | iPrOH | 7 | 88 |
10 | 1 | KOtBu | iPrOH | 55 | 93 |
11 | 1 | Mn | iPrOH | >98 | 96 |
12 | 1 | Zn | iPrOH | >98 | 97 |
13d | 1 | Zn | iPrOH | >98 | 97 |
14e | 0.1 | Zn | iPrOH | >98 | 97 |
15e | 0.05 | Zn | iPrOH | 93 | 97 |
