[H-].[Na+].C(OP([CH2:11][C:12]([O:14][CH2:15][CH3:16])=[O:13])(OCC)=O)C.O=[C:18]1[CH2:22][CH2:21][N:20]([C:23]([O:25][C:26]([CH3:29])([CH3:28])[CH3:27])=[O:24])[CH2:19]1>O1CCCC1>[C:26]([O:25][C:23]([N:20]1[CH2:21][CH2:22][C:18](=[CH:11][C:12]([O:14][CH2:15][CH3:16])=[O:13])[CH2:19]1)=[O:24])([CH3:29])([CH3:27])[CH3:28]A flask was charged with NaH (50 g, 1.25 mol, 60% in mineral oil) and tetrahydrofuran (2,500 ml) and cooled to 0° C. A solution of ethyl 2-(diethoxyphosphoryl)acetate (260 g, 1.16 mol) in tetrahydrofuran F (200 ml) was added dropwise. The resulting solution was allowed stir for 1 h at 0° C. Then a solution of tert-butyl 3-oxopyrrolidine-1-carboxylate (215 g, 1.16 mol) in tetrahydrofuran (300 ml) was added dropwise. The resulting solution was allowed to stir for 0.5 hours at 0° C. The reaction mixture was quenched by the addition of 1,000 ml of saturated aqueous ammonium chloride. The resulting mixture was extracted with ethyl acetate (3×2,000 ml) and the combined organic layers were dried over sodium sulfate, filtered and concentrated. The residue was purified by column chromatography on silica gel (ethyl acetate/petroleum ether gradient) to afford tert-butyl-3-(2-ethoxy-2-oxoethylidene)pyrrolidine-1-carboxylate as colorless oil.
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