Carbon tetrabromide → (S)-N-Boc-2-ethynylpyrrolidine

Participants

Reaction Steps

A solution of (2S)-N-(tert-butoxycarbonyl)-2-formylpyrrolidine (4.0 g, 20 mmole), carbon tetrabromide (6.67 g, 20.1 mmole) and triphenylphosphine (5.26 g, 20.1 mmole) in methylene chloride (100 mL) was stirred at ambient temperature under a nitrogen atmosphere for 24 hours. The mixture was concentrated, then purified by chromatography, using (1:1) ethyl acetate: hexane as eluant to provide the desired product as an oil. The product was dissolved in dry tetrahydrofuran (50 mL) and cooled to −78° C. A solution of n-butyllithium (50.25 mL, 20.1 mmole, 2.5 M solution in hexanes) was added and the mixture was stirred at −78° C. for 1 h. The material was quenched with water (20 mL) and extracted with ethyl acetate (3×50 mL). The combined extracts were dried (K2CO3), concentrated and purified by chromatography, using (1:1) ethyl acetate:hexane as eluant to provide (3.10 g, 91%) of a colorless oil.

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