Under an argonatmosphere, to a solution of 2-Oxo-cyclopentanecarboxylic acid ethyl ester (1.56 g, 10 mmol) in dry ether (20 mL) wasadded 60% NaH (0.48 g,12 mmol) at 0oC, the mixture was stirred for 30 min, N-fluoro sultam(-)-31 (3.5 g,15 mmol) was added in several portions. The reaction mixture was stirred for another 1 h at room temperature,then quenched by saturated NH4Cl solution, and extracted withEA. The combined organic layer was driedover Na2SO4, concentrated under reduced pressure. Theresidue was purified by column chromatography on silica gel to give the desiredproduct (1.09 g, 63%, 70% ee).
【Differding, E; Lang, R, W. Tetrahedron. Lett. 1988, 29, 6087.】
【Davis, F, A; Han, W. Tetrahedron. Lett. 1992, 33, 1153】