Table 3.
Entry | Donor | Acceptor | Product | Conditions | Yield[a] | Ratio[b] (α/β) |
---|---|---|---|---|---|---|
1 | 2 |
9 |
1031 |
TMSOTf rt | 79% | 8.2 |
2 | 2 | 9 | 10 | HClO4-SiO2 rt | 81% | 19 |
3 | 2 |
11 |
1232 |
TMSOTf 0°C | 96% | 6.1 |
4 | 2 | 11 | 12 | HClO4-SiO2 0°C | 94% | 8.1 |
5 | 2 |
13 |
14 |
TMSOTf 0°C | 84% | 13 |
6 | 2 | 13 | 14 | HClO4-SiO2 0°C | 86% | 32 |
7 |
15 |
11 |
1633 |
TMSOTf 0°C | 93% | 3.0 |
8 | 15 | 11 | 16 | HClO4-SiO2 0°C | 90% | 3.0 |
9 | 15 | 11 | 16 | HClO4-SiO2 rt | 85% | 4.0 |
10 | 15 | 13 |
1734 |
TMSOTf 0°C | 84% | 4.0 |
11 | 15 | 13 | 17 | HClO4-SiO2 0°C | 88% | 9.3 |
12 |
18 |
11 |
1935 |
TMSOTf 0°C | 85% | 3.0 |
13 | 18 | 11 | 19 | HClO4-SiO2 0°C | 88% | 10 |
Combined yield of both anomers after purification
Determined by 1H NMR spectroscopy