C([Li])CCC.[Br-].C1([C:13]([PH3+])([C:20]2[CH:25]=[CH:24]C=[CH:22][CH:21]=2)C2C=CC=CC=2)C=CC=CC=1.[C:27]([O:31][C:32]([N:34]1CCC(C=O)C1)=[O:33])([CH3:30])([CH3:29])[CH3:28].[Cl-].[NH4+]>CCCCCC.O1CCCC1.C(OCC)(=O)C>[C:27]([O:31][C:32]([N:34]1[CH2:24][CH2:25][CH:20]([CH:21]=[CH2:22])[CH2:13]1)=[O:33])([CH3:30])([CH3:29])[CH3:28]n-Butyllithium in hexane (44 cm3 of a 1.6 N solution) was added drop-wise to a suspension of 25.5 g (71 mmol) of triphenylmethylphosphonium bromide in 300 cm3 of tetrahydrofuran, which was under argon and cooled to 0° C. The reaction mixture was stirred at 0° C. for 0.5 h and then admixed with a solution of 7.1 g (35.6 mmol) of racemic 3-formylpyrrolidine-1-carboxylic acid tert-butyl ester in 100 cm3 of tetrahydrofuran. After 2.5 hours of reaction at a temperature in the region of 22° C., the mixture was poured into 600 cm3 of saturated aqueous ammonium chloride solution. Following addition of ethyl acetate the organic phase was taken off by decanting, washed twice with water and with saturated sodium chloride solution and then dried over magnesium sulfate and concentrated to dryness under reduced pressure (2.7 kPa). The resulting oil was purified by chromatography on silica gel [eluent: cyclohexane/ethyl acetate (95/5 then 9/1 by volume)]. Concentration of the fractions under reduced pressure (2.7 kPa) gave 6.3 g of racemic 3-vinylpyrrolidine-1-carboxylic acid tert-butyl ester in the form of a colorless oil. Mass spectrum (ES): m/z 198 (MH+), m/z=142.
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