A concise and stereoselective synthesis of (+/−)-erythro-methylphenidate

A concise and stereoselective synthesis of racemic erythro-methylphenidate (1) is described. The coupling reaction between piperidine-2-thione (3) and 2-bromo-2-phenylmethylacetate (4) afforded the β-enaminocarbonyl compound 2 in 60% yield by a modified Eschenmoser sulfide contraction reaction. In most cases the bicyclic thiazolidinone 5 was produced. Diastereoselective reduction of 2 in the presence of borohydrydes furnished the (+/−)-erythro-methylphenidate in good yields with dr >95%.