Table 1.
Results of Survey of Optically Active Enol Ethers
| Dienophile | Time (h) | Major Adduct (% Conversion)a | Total Conv (%) | Ratio of Diastereomersb |
Endo : Exo | Endo Facial Selectivity | ||
|---|---|---|---|---|---|---|---|---|
| endo | exo | |||||||
| 2a | 60 | 2b (52)c | 97 | 54: 40 | : | 3: 3 | 16 : 1 | 1.4 : 1 |
| 3a | 60 | 3b (72) | 94 | 77: 19 | : | 4: – | 19 : 1 | 4 : 1 |
| 4a | 60 | 4b (49) | 63 | 78: 18 | : | 4: – | 24 : 1 | 4 : 1 |
| 5a | 60 | 5b (63) | 80 | 79: 14 | : | 7: – | 13 : 1 | 6 : 1 |
| 6a | 72 | 6b (48) | 64 | 75: 14 | : | 11: – | 8 : 1 | 5 : 1 |
| 7a | 60 | 7b (71) | 91 | 78: 18 | : | 4: – | 24 : 1 | 4 : 1 |
| 8a | 60 | 8b (53) | 69 | 77: 15 | : | 8: – | 12 : 1 | 5 : 1 |
| 9a | 60 | 9b (71) | 88 | 81: 19 | : | –: – | >25 : 1 | 4 : 1 |
| 10a | 60 | 10b (85) | 98 | 86: 10 | : | 4: – | 24 : 1 | 9 : 1 |
| 11a | 48 | 11b (12)c | 31 | 37: 18 | : | 29: 16 | 1 : 1 | 2 : 1 |
| 12a | 60 | 12b (41) | 55 | 75: 25 | : | –: – | >25 : 1 | 3 : 1 |
| 13a | 60 | 13b (55) | 86 | 62: 19 | : | 13: 6 | 4 : 1 | 3 : 1 |
| 14a | 60 | 14b (12) | 18 | 69: 31 | : | –: – | >25 : 1 | 2 : 1 |
| 15a | 60 | 15b (27) | 45 | 83: 9 | : | 8: – | 12 : 1 | 11 : 1 |
| 16a | 60 | 16b (32) | 38 | 85: 9 | : | 6: – | 16 : 1 | 9 : 1 |
| 17a | 60 | 17b (54)d | 68 | 80: 14 | : | 6: – | 16 : 1 | 6 : 1 |
| 18a | 60 | 18b (59)d | 65 | 91: 5 | : | 4: – | 24 : 1 | 18 : 1 |
| 19a | 48 | 19b (96)d | ≥98 | 96: 2 | : | 2: – | 49 : 1 | 48 : 1 |
| ethyl vinyl ether | 46 | (82)e | – | >25 : 1 | – | |||
Reactions performed at RT, 0.3 M with respect to diene in toluene.
a
Based on integration of major product C2-H versus minor diastereomer C2-H’s and diene C2-H. Some hydrolysis of diene ocassionally observed (< 5%)
b
Ratios based on 1H NMR integration of C2-H of products unless otherwise noted. Endo and exo compounds assigned based on 1H NMR splitting patterns. Some peaks could not be located due to overlap, small size or low conversion.
c
Integration based on C5-H.
d
Anhydrous CHCl3 as solvent, 1 M with respect to diene.
e
Yield from reference 1c.