876617-06-0

To a mixture of cuprous iodide (I) (9.4 g) and ether (180 ml) was added about 1 M methyl lithium/ether solution (100 ml) dropwise over a period of 30 min at an internal temperature ranging from 0 to 5°C. Stirring was continued for 15 min after completion of the dropwise addition. Subsequently, a solution of tert-butyl (2S)-2-({[(4-methylphenyl)sulfonyl]oxy}methyl)pyrrolidine-1-carboxylate (7.0 g) in dichloromethane (30 ml) was added to the reaction mixture, keeping the internal temperature at no more than 5°C, and added dropwise over 20 min. After completion of the dropwise addition, the reaction mixture was stirred at room temperature for 2.5 hours. After completion of the reaction, saturated aqueous ammonium chloride solution was added dropwise to the reaction mixture and extracted with ethyl acetate. The organic layer was dried with anhydrous sodium sulfate, filtered to remove insoluble matter and the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: cyclohexane-ethyl acetate) to give tert-butyl (2R)-2-ethylpyrrolidine-1-carboxylate as an oil (3.52 g).

[1] Journal of the American Chemical Society, 1989, vol. 111, # 20, p. 7921 - 7925
[2] Patent: KR2015/120516, 2015, A. Location in patent: Paragraph 0412; 0413
[3] Patent: EP3153511, 2017, A1. Location in patent: Paragraph 0166