Triphenylphosphine → (+)-(3R,4R)-4-(4-Fluoro-phenyl)-piperidine-1,3-dicarboxylic acid 1-tert-butyl ester 3-methyl ester

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Reaction Steps

To a solution of triphenylphosphine (3.82 g, 14.6 mmol) in 70 ml tetrahydrofuran was added diethyl azodicarboxylate (2.53 g, 14.6 mmol) at 0° C. After 30′ methanol (4.55 ml, 112.0 mmol) and a solution of (+)-(3R,4R)-4-(4-fluoro-phenyl)-piperidine-1,3-dicarboxylic acid 1-tert-butyl ester (3.62 g, 11.2 mmol, 93.6% ee) in 30 ml tetrahydrofuran were added subsequently at 0-5° C. The reaction mixture was stirred for 20 h at room temperature. Quenching with water was followed by extraction with tert-butyl methyl ether (3×100 ml). The combined organic layers were dried over sodium sulfate, concentrated under reduced pressure and purified by flash chromatography (n-heptane/ethyl acetate) to give the title compound (3.55 g, 94%) as a colorless oil.

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