Table 1.
Discovery and optimization
| |||
|---|---|---|---|
| Entry | Solvent (M) | Acid (eq) | Yield (%)a |
| 1 | CH2Cl2 (0.1) | HCOOH (1.0) | 35 |
| 2 | CH2Cl2 (0.1) | CH3COOH (1.0) | 75 |
| 3 | CH2Cl2 (0.1) | CH3COOH (0.2) | 31 |
| 4 | CH2Cl2 (0.1) | CH3COOH (1.2) | 82 (78b) |
| 5 | CH2Cl2 (0.1) | CH3COOH (2.0) | 78 |
| 6 | CH2Cl2 (0.2) | CH3COOH (1.2) | 80 |
| 7 | CH2Cl2 (0.05) | CH3COOH (1.2) | 20 |
| 8 | DCE (0.1) | CH3COOH (1.2) | 76 |
| 9 | toluene (0.1) | CH3COOH (1.2) | 78 |
| 10 | CH2Cl2 (0.1) | diphenyl phosphate (1.2) | <10 |
| 11 | CH2Cl2 (0.1) | camphorsulphonic acid (1.2) | trace |
| 12 | CH2Cl2 (0.1) | 4-nitrophenol (1.2) | N.O. |
| 13 | CH2Cl2 (0.1) | ZnCl2 (1.2) | N.O. |
Reactions were performed on 0.3 mmol of amide
N.O. not observed
aNMR yields with 1-bromo-2-methoxylnaphthlene as internal standard
bIsolated yield. DCE: 1,2-dichloroethane