Process for the preparation of methylphenidate and pharmaceutical salts thereof

The present invention is directed to an improved process for the preparation of methylphenidate, stereoisomer, mixture of stereoisomers and pharmaceutically acceptable salts thereof, more particularly, the sulfate and hydrochloride salts of methylphenidate, di-threo-methylphenidate and dexmethylphenidate. Methods of removing or reducing the amount of impurities from the above described process are also disclosed. 本发明涉及种用于制备哌甲酯、立体异构体、立体异构体的混合物及其药学上可接受的盐，更具体地为哌甲酯、di-苏型-哌甲酯和dex-哌甲酯的硫酸盐和盐酸盐的改进方法。本发明还公开了通过上述方法移除或减少杂质的量的方法。