Novel process for preparing pramipexole and its optical isomeric mixture by reduction with sodium triacetoxyborohydride
申请人:Xia Guangxin
公开号:US20060148866A1
公开(公告)日:2006-07-06
A novel process is provided for producing pramipexole base or its optical isomeric mixture as defined hereinabove i.e. (R,S)-2-amino-6-propyl-4,5,6,7-tetrahydrobenzothiazole avoiding the use of borane tetrahydrofuran complex and using a more convenient reducing agent like sodium triacetoxyborohydride instead. The provided process comprises reacting the starting material (S)-2,6-diamino-4,5,6,7-tetrahydrobenzothiazole or its optical isomeric mixture as defined hereinabove i.e. (R,S)-2,6-diamino-4,5,6,7-tetrahydrobenzothiazole with propionaldehyde in an organic solvent to obtain the respective enamine, which is subsequently reduced in situ, optionally without isolation, to obtain pramipexole or its optical isomeric mixture as defined hereinabove i.e. (R,S)-2-amino-6-propyl-4,5,6,7-tetrahydrobenzothiazole, and the acid addition salts thereof. The present invention also provides a process for purifying pramipexole dihydrochloride or the dihydrochloride salt of its optical isomeric mixture as defined hereinabove i.e. (R,S)-2-amino-6-propyl-4,5,6,7-tetrahydrobenzothiazole dihydrochloride by re-crystallization from a suitable solvent.
本发明提供了一种生产普拉米贝克索尔碱或其光学异构体混合物的新工艺,即避免使用四氢呋喃硼烷复合物,而使用更方便的还原剂如三乙酰氧基硼氢化钠。所提供的工艺包括将起始物质(S)-2,6-二氨基-4,5,6,7-四氢苯并噻唑或其光学异构体混合物如上所述,即(R,S)-2,6-二氨基-4,5,6,7-四氢苯并噻唑与丙醛在有机溶剂中反应,得到相应的烯胺,然后原位还原,可选地不进行分离,得到普拉米贝克索尔或其光学异构体混合物如上所述,即(R,S)-2-氨基-6-丙基-4,5,6,7-四氢苯并噻唑及其酸盐。本发明还提供了一种从适当溶剂中重新结晶纯化普拉米贝克索尔二盐酸盐或其光学异构体混合物如上所述,即(R,S)-2-氨基-6-丙基-4,5,6,7-四氢苯并噻唑二盐酸盐的工艺。