摘要:
An investigation into the acidification step of the zafirlukast nitroacid process was conducted by varying a range of parameters, including acid molarity, addition time, final pH, and temperature. A significant and unexpected improvement in product quality was achieved by using dilute rather than concentrated acid, independent of the final pH, and without a reduction in yield. The change to the dilute-acid process could be accommodated within the constraints of the existing registered process.