CO[CH:3]1[N:7]([C:8]([O:10][CH3:11])=[O:9])[C@H:6]([C:12]([O:14][CH3:15])=[O:13])[CH2:5][CH2:4]1.C[Si]([C:20]#[C:21][CH3:22])(C)C.[Sn](Cl)(Cl)(Cl)Cl.[Cl-].[Al+3].[Cl-].[Cl-]>C(Cl)Cl>[C:20]([C@@H:3]1[N:7]([C:8]([O:10][CH3:11])=[O:9])[C@H:6]([C:12]([O:14][CH3:15])=[O:13])[CH2:5][CH2:4]1)#[C:21][CH3:22]
To a cold −45° C. solution of dimethyl (2S)-5-methoxypyrrolidine-1,2-dicarboxylate (10 g, 46.08 mmol, Example 1B) and trimethylsilylpropyne (14.24 mL, 92.16 mmol, 2.0 equiv) in methylene chloride (180 mL) was added a solution of tin (IV) chloride (1 M in methylene chloride, 60.0 mL, 60.0 mmol, 1.3 equiv) dropwise via an addition funnel over 30 minutes. To the dark yellow solution was added solid aluminum chloride (8.58 g, 64.52 mmol, 1.4 equiv) in one portion. The resulting mixture was allowed to warm to room temperature and stirred at room temperature for 48 hours. The reaction mixture was carefully quenched by saturated aqueous NH4OH (100 mL) with ice cooling. A white precipitate formed and was removed by filtration. The crude product was obtained after concentration. The residue was chromatographed on a Biotage flash 40 M eluting with 70% hexane/30% ethyl acetate to afford the titled compound. MS (DCI/NH3) m/e 226 (M+H)+.
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