摘要:
The invention covers a process for preparing olopatadine free base and/or its hydrochloride salt by performing a Wittig reaction, wherein said Wittig reaction comprises the use of at least one of hexyllithium, sodium hydride and combinations thereof. The process of invention achieves olapatadine free base and/or its hydrochloride salt having less than approximately 0.5% by area percentage HPLC of olapatadine trans isomer and a reduced level of bromide impurities.