Table 3.
Annulations with Methyl Carbamate: Dihydrooxazines
 | ||||
|---|---|---|---|---|
| entry | aldehyde | yielda | drb | product 3 |
| 1 | Benzaldehyde | 63% | >20:1 | 3a |
| 2 | 2-Bromobenzaldehyde | 81% | >20:1 | 3b |
| 3 | 2, 3-Dimethoxybenzaldehyde | 54% | >20:1 | 3c |
| 4 | 2-Nitrobenzaldehyde | 58% | >20:1 | 3d |
| 5 | 4-Chlorobenzaldehyde | 59% | >20:1 | 3e |
| 6 | Valeraldehyde | 61% | >20:1 | 3f |
| 7 | Hydrocinnamaldehyde | 38% | >20:1 | 3g |
| 8 | Isobutyraldehyde | 47% | >20:1 | 3h |
| 9 | Cyclohexanecarboxaldehyde | 48% | >20:1 | 3i |
a
Isolated yields after purification over silica gel.
b
Diastereomeric ratios determined by 1H NMR analysis on crude material.