Methanol Methylphenidate hydrochloride

Enrichment of the enantiomeric purity of (2R,2 R -(+)-Z/zreo-methylphenidate hydrochloride (1) was lirst reported by Patrick et af by crystallization from a mixture of methanol and ether. We (Novartis) also recently reported that the enantiomeric purity of (2/J,2 / )-(+)-ZZzreo-methylphenidate hydrochloride salt (1) was enhanced from 80% ee to >98% ee by recrystallization from a mixture of methanol and Z-butyl methyl ether (1 1.7 v/v). ] An enrichment of the enantiomeric purity of 1 from this solvent mixture was then reported by Faulconbridge et al. Thus, any approach which yields enriched (2R,2 R)-(+)-threo-methylphenidate hydrochloride (1) would afford enantiomerically pure 1 after recrystallization from this solvent mixture, but at the cost of loss in yield. 

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