Table 1.
Tandem deprotection–Henry reaction.[a]
| Entry | Catalyst | Substrate | Conversion [%] | Yield GC/isolated [%] | |
|---|---|---|---|---|---|
| 2 | 3 | ||||
| 1 | SAB[b] | 1 | ≈98 | tr | 97/92 |
| 2 | SB | 1 | – | – | –/– |
| 3 | SABTable [c] | 1 | ≈99 | 95/– | 5/– |
| 4 | SB[e] | 2 | >99 | – | >99/91 |
| 5 | S | 1 | tr | tr | tr |
| 6 | SAB[d] | 1 | 95 | tr | 94/90 |
[a]
Reaction conditions: benzaldehyde dimethyl acetal (1 mmol), CH3NO2 (10 mL), 50 °C, 12 h.
[b]
Phosphotungstic acid (HPW)/aminopropyl (AP) ratio around 0.5:1 (molar).
[c]
HPW/AP ratio around 1:1 (molar).
[d]
Fourth recycle of the catalyst of entry 1.
[e]
For Henry reaction alone starting from entry 2. tr: trace.