Lawesson's reagent → tert-Butyl (S)-5-thioxo-2-pyrrolidinecarboxylate

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Reaction Steps

To a solution of (S)-pyrrolidin-2-one-5-carboxylic acid t-butyl ester (2.04 g, 11.01 mmol) in benzene was added Lawesson's Reagent (2.22 g, 5.50 mmol). The reaction mixture was heated at reflux overnight, concentrated under vacuum, and purified by column chromatography on silica gel (5% MeOH/CHCl3) to provide (S)-pyrrolidin-2-thione-5-carboxylic acid t-butyl ester (1.75 g, 79%) as a tan solid. 1H NMR (CDCl3) δ 1.49 (s, 9H), 2.30 (m, 1H), 2.53 (m, 1H), 2.85-3.04 (m, 2H), 4.42 (t, 1H, J=7.7 Hz), 7.88 (bs, 1H). MS calcd for C9H15NO2S+H 202, found 202.

Provenance & Evidence