Table 1.
Reaction conditions for the asymmetric reduction of enamides.
 | ||||||
|---|---|---|---|---|---|---|
| entry | catalyst (mol%) | solvent | temp (¼ C) | time (h) | yield (%)a | ee (%) |
| 1 | A1 (10) | toluene | rt | 17 | 95 | 0 |
| 2 | A2 (5) | toluene | 50 | 36 | <15b | nd |
| 3 | A3 (5) | toluene | 50 | 36 | <10b | nd |
| 4 | A4 (5) | toluene | 50 | 15 | 92 | 91 |
| 5 | A4 (5) | Et20 | 50 | 22 | <13b | nd |
| 6 | A4 (5) | THF | 50 | 22 | < 5b | nd |
| 7 | A4 (5) | EtOAc | 50 | 48 | < 15b | nd |
| 8 | A4 (5) | MeOH | 50 | 48 | < 5b | nd |
| 9 | A4 (2) | toluene | 50 | 41 | 85 | 91 |
| 10 | A4 (1) | toluene | 50 | 117 | 39 | 90 |
| 11 | A4 (1)+ AcOH(10) | toluene | 50 | 15 | 97 | 91 |
| 12 | AcOH(10) | toluene | 50 | 17 | 0b | nd |
a
Isolated yields
b
Yield determined by 1H NMR.
ce values determined by Chiral-HPLC (see Supporting Information).