29419-95-2Relevant articles and documents
The asymmetric synthesis of (S,S)-methylphenidate hydrochloride via ring-opening of an enantiopure aziridinium intermediate with phenylmagnesium bromide
Davies, Stephen G.,Fletcher, Ai M.,Peters, Matthew E.,Roberts, Paul M.,Thomson, James E.
, (2019)
The key step in our synthetic strategy towards (S,S)-methylphenidate hydrochloride employs the ring-opening of an in situ formed aziridinium intermediate. Treatment of an α-hydroxy-β-amino ester with methanesulfonic anhydride promoted aziridinium formation and the subsequent addition of phenylmagnesium bromide resulted in stereospecific and regioselective ring-opening to give the corresponding α-phenyl-β-amino ester with overall retention of configuration. Subsequent functional group manipulation followed by N-deprotection and cyclisation generated the piperidine ring within the target compound, and transesterification gave (S,S)-methylphenidate hydrochloride, in only 8 steps from 1,5-pentanediol, in 15% overall yield. These results demonstrate the synthetic utility of enantiopure aziridinium intermediates as substrates for the generation of stereodefined C–C bonds, and crucially this methodology provides access to α-substituted-β-amino ester substrates that are not accessible via enolate alkylation chemistry. The strategy reported herein is potentially applicable to all possible stereoisomers of methylphenidate as well as differentially substituted analogues.
IMPROVEMENTS IN OR RELATING TO ORGANIC MATERIAL
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Paragraph 0056; 0057, (2018/04/13)
The invention provides a method for the preparation of an intermediate for use in synthesizing a lower alkyl phenidate compound of formula (I), wherein each R1 independently represents an optionally substituted aryl, heteroaryl, alkyl, cycloalkyl, alkoxy, aryloxy, acyl, carboxyl, hydroxyl, halogen, amino, nitro, sulfo or sulfhydryl group, R2 represents a hydrogen atom or a lower alkyl group, n represents an integer from 1 to 5 and m represents an integer from 1 to 3 or a pharmaceutically acceptable salt thereof; which method comprises the steps of: (a) flowing a tosylhydrazone compound of formula (IV), wherein R1, n and m are as defined above in relation to the methylphenidate of formula (I), an organic base and an organic solvent into a fluidic network; and (b) reacting the tosylhydrazone compound of formula (IV) and the base in the fluidic network under thermal and/or photochemical conditions to form a transient diazoamide compound of formula (V), wherein R1, n and m are as defined above in relation to the methylphenidate of formula (I).
PROCESS FOR THE PREPARATION OF METHYLPHENIDATE AND PHARMACEUTICAL SALTS THEREOF
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Page/Page column 0345-0347, (2015/05/26)
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 dex-methylphenidate. Methods of removing or reducing the amount of impurities from the above described process are also disclosed.