Table 2.
Addition of the anion of 11 to (+)-20 at −78 °C in THF.
| entry | (+)-20 R = | (+)-20, PG = | Conditions, base, timea | sulfinamide (−)-21 % isolated yieldb (% de)c |
|---|---|---|---|---|
| 1 | 20a (p-Tolyl) | Bn | LiHMDS, 30 min | 27 (40) |
| 2 | 20a (p-Tolyl) | Bn | KHMDS, 30 min | 50 (64) |
| 3 | 20a (p-Tolyl) | Bn | NaHMDS, 2 min | 68 (80) |
| 4 | 20b (p-Tolyl) | PMB | NaHMDS, 2 min | 81 (82) |
| 5 | 20c (t-Bu) | Bn | NaHMDS, 2 min | No reaction |
a
Time for anion formation, before adding 20.
b
Isolated yield of major diastereoisomer.
c
Determined by 1H NMR on the crude reaction mixture.