Table 1.
Effect of solvent on Impurity E (1) content in the oxidation of pantoprazole sulfide (4) to pantoprazole sulfoxide (5).a
| Entry | Solvent | HPLC conversion (%) |
|||||
|---|---|---|---|---|---|---|---|
| Sulfoxide (5) | Imp A (7) | Sulfide/Imp B (4) | Imp C (3) | Imp D + F (8,9) | Imp E (1) | ||
| 1 | Acetone | 27.48 | 0.05 | 70.76 | nd | nd | nd |
| 2 | EtOAc | 93.26 | 0.10 | 0.09 | nd | nd | nd |
| 3 | DCM | 93.49 | 0.01 | 0.04 | nd | 0.04 | 0.06 |
| 4 | ACN | 99.18 | 0.02 | 0.11 | nd | nd | 0.14 |
| 5 | Water | 97.27 | 0.24 | 0.13 | nd | 0.05 | 0.94 |
nd: not detected.
a
Reaction condition: 5-(difluoromethoxy)-1H-benzimidazole-2-thiol (3), 10 mmol; NaOH, 25 mmol; NaOCl, 10.5 mmol, assay 9.0%; solvent, 10 mL at 0–5 °C for 3–4 h.