Acetonitrile → Ethyl 2-[4-(3-chlorophenyl)-2-oxo-1-pyrrolidinyl]butanoate

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In a 2 l three necked flask fitted with reflux condenser, magnetic stirrer and dropping funnel under inert atmosphere, 54.4 g (278 mmoles, 1 eq) of 4-(3-chlorophenyl)-2-pyrrolidinone 379 are dissolved in 1.4 l acetonitrile. 64 ml (100.7 g, 556 mmoles, 2 eq) of methyl 2-bromobutanoate are added and the temperature raised to 50° C. 22.24 g (556 mmoles, 2 eq) of sodium hydride are added by portions, the temperature raising to 65° C. The mixture is stirred one more hour at 50° C. The mixture is concentrated to dryness, the residue suspended in ethyl acetate, washed with water, the aqueous phase reextracted with ethyl acetate. The combined organic phases are dried over magnesium sulfate, filtered and concentrated to dryness. The residue is purified by PrepLC (1 kg SiO2, pet. ether/EtOAc, 70:30) to give 56.7 g of pure 380, 69%. 1H NMR (250 MHz, (CD3)2SO): 0.80-1.00 (m, 3H), 1.60-1.90 (2H, m), 2.35-2.55 (m, 1H: partially overlapped with solvent), 2.60-2.90 (m, 1H: partially overlapped with solvent), 3.70 (s, 3H), 3.50-3.80 (m, 3H), 4.50 (m, 1H), 7.20-7.50 (m, 4H).

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