Diisopropylamine → Ethyl 2-oxo-3-phenylcyclopentanecarboxylate

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To a solution of diisopropylamine (6.62 mL, 46.8 mmol) in THF (200 mL) at −78° C. was added a 1.6 M solution of n-butyllithium in hexanes (29.3 mL, 46.8 mmol). The solution was stirred for 30 min at −78° C. and treated with a solution of 2-phenylcyclopentanone (5 g, 31.2 mmol) in 50 mL of dry THF. After stirring for 30 min at −78° C., ethyl carbonocyanidate (3.36 mL, 34.3 mmol) was added to the reaction mixture. The resulting solution was warmed to 25° C. with stirring over 3 h. The reaction mixture was quenched with 10 mL of water, washed with brine, dried over anhydrous sodium sulfate, concentrated in vacuo. The residue was purified by column chromatography on silica gel to afford ethyl 2-oxo-3-phenylcyclopentanecarboxylate (5.3 g, 22.82 mmol, 73% yield) as a colorless oil. LC-MS (M+K)+=273.2. 1H NMR (500 MHz, chloroform-d) δ ppm 7.32-7.39 (2H, m), 7.25-7.31 (1H, m), 7.19-7.25 (2H, m), 4.18-4.32 (2H, m), 3.29-3.55 (2H, m), 1.87-2.62 (4H, m), 1.28-1.39 (3H, m).

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