(S)-2-(3,5-dimethylphenyl)pyrrolidine((S)-1), a key intermediate in the synthesis of aticaprant, was effectively prepared via a recycle process of resolution/racemization. The desired (S)-1 was obtained by resolution of its racemate with D-tartaric acid and some alkaline conditions were screened to racemize the undesired (R)-1 in the resolution mother liquor, and the best (in DMSO with KOH) was identified. Finally, the desired freebase (S)-1 was obtained in a yield of 63.6% with excellent enantioselectivity (98.7% ee) after three times of recycle process.

中文翻译：

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通过拆分循环过程高效制备 (S)-2-(3,5-二甲基苯基) 吡咯烷

( S )-2-(3,5-二甲基苯基)吡咯烷(( S )- 1 )是合成阿替卡普兰的关键中间体，通过拆分/外消旋的循环过程有效制备。用D-酒石酸拆分其外消旋体得到所需的( S )- 1 ，筛选碱性条件使拆分母液中不需要的( R )- 1外消旋，最好的(在DMSO和KOH中)确定。最终，经过3次循环过程，以63.6%的收率和优异的对映选择性（98.7% ee）获得了所需的游离碱（S）- 1 。