Table 7.
Entry | P | R | R' | R” | Conditions | Yield (%) | 25 : 26 | Ref. |
---|---|---|---|---|---|---|---|---|
1 | H | Ph | i-Pr | Me | 2.0 M, LPDE, -15 °C | 90 | 88 : 12 | 63 |
2 | H | Ph | t-Bu | Me | 2.0M,LPDE, -15 °C | 95 | 91 : 09 | 63 |
3 | H | Ph | c-Hexyl | Me | 2.0 M, LPDE, -15 °C | 94 | 90 : 10 | 63 |
4 | Me | Ph | Ph | Et | Yb(OTf)3/MgSO4 | 95 | 78 : 22 | 67 a |
5 | Me | Ph | 4-MeOC6H4 | Et | Yb(OTf)3/MgSO4 | 91 | 78 : 22 | 67 a |
6 | Me | i-Bu | Ph | Et | Yb(OTf)3/MgSO4 | 82 | 74 : 26 | 67 a |
7 | Me | i-Bu | 4-MeOC6H4 | Et | Yb(OTf)3/MgSO4 | 81 | 74 : 26 | 67 a |
The configuration of chiral auxiliary was (S) and the principal product was the diastereoisomer (S,S)-25.