Dexmethylphenidate: An Efficient Process for the Racemization of Unwanted (2<i>S</i>,2′<i>S</i> or <i>l</i>-<i>threo</i>)-α-Phenyl-α-(2-piperidyl)acetamide
作者:Anil B. Chavan、Sachin S. Gundecha、Pramod N. Kadam、Golak C. Maikap、Mukund K. Gurjar
DOI:10.1021/op100197g
日期:2010.11.19
(2R,2'R)-d-threo-alpha-Phenyl-alpha-(2-piperidyl)acetamide (3), an advanced intermediate for dexmethylphenidate hydrochloride synthesis, is prepared by the resolution of dl-threo-alpha-phenyl-alpha-(2-piperidyl)acetamide (2) with dibenzoyl-d-tartaric acid in isopropanol with To yield and 99% ee. Although this process is efficient, there is a need to recycle the unwanted l-threo-amide and uncrystallized d-threo- amide from the mother liquor. The purpose of this study is 2-fold, first being the pollution issue to discard large amounts of unwanted isomer and the second to reduce the cost of (1). This aspect of recovery of unwanted isomer 4 formed the basic objective of this study. We have developed a new, simple, and cost-effective process for the racemization in which 4 was treated with potassium carbonate and At-chlorosuccinimide in DMF followed by treatment with DBU to afford the olefinic intermediate (5). Subsequent hydrogenation of the double bond provided dl-erythro-alpha-phenyl-alpha-(2-piperidyl)acetamide (6); the latter intermediate has already been converted into 1.
(2R,2'R)-d-threo-α-苯基-α-(2-哌啶基)乙酰胺(3)是右旋甲基苯丙胺盐酸盐合成的高级中间体,通过使用二苯酰基-d-酒石酸在异丙醇中对dl-threo-α-苯基-α-(2-哌啶基)乙酰胺(2)进行拆分以获得99%的收率和对映体纯度(ee)。尽管该工艺高效,但仍需从母液中回收不需要的l-threo酰胺和未结晶的d-threo酰胺。本研究的目标是双重的:首先是处理大量弃置的不需要的异构体所带来的污染问题,其次是降低(1)的生产成本。回收不需要的异构体4形成了本研究的基本目标。我们开发了一种新的、简单且经济有效的消旋化工艺,其中4用碳酸钾和At-氯代琥珀酰亚胺在DMF中处理,随后用DBU处理以得到烯烃中间体(5)。随后对双键进行加氢提供dl-赤型-α-苯基-α-(2-哌啶基)乙酰胺(6);后者的中间体已经转化为1。