Table 20.
Results from the enantioselective HDA reaction between Brassard's diene and benzaldehyde (0.5 mmol) catalyzed by TADDOL derivatives A - D (Figure 20).
| entry | catalyst | solvent (mL)a | temp (°C) | time (h) | yield (%) | ee (%) |
|---|---|---|---|---|---|---|
| 1 | A | none | rt | 12 | 30 | 7 |
| 2 | B | none | rt | 12 | 40 | 50 |
| 3 | B | none | −30 | 24 | 70 | 71 |
| 4b | B | none | −30 | 24 | 50 | 72 |
| 5b | C | none | −30 | 24 | 40 | 0 |
| 6b | D | none | −30 | 24 | 37 | 74 |
| 7 | B | toluene (0.05) | −30 | 24 | 70 | 75 |
| 8 | B | toluene (0.1) | −30 | 24 | 68 | 76 |
| 9 | B | toluene (0.2) | −60 | 48 | 67 | 83 |
| 10 | B | toluene (0.4) | −60 | 48 | 50 | 86 |
| 11 | B | toluene (0.2) | −78 | 48 | 26 | 89 |
a
All the reactions were carried out with 2.5 mmol of benzaldehyde and 0.5 mmoll of diene.
b
10 mol% catalyst was used.