Boron trifluoride etherate → (2S,5R/S)-5-Allyl-1-(tert-butoxycarbonyl)pyrrolidine-2-carboxylic acid tert-butyl ester

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Reaction Steps

A solution of 12.6 g of the α-methoxycarbamate 45 (40.0 mmol) and 16.0 ml of allyltrimethylsilane (100 mmol, 2.5 eq.) in 100 ml of anhydrous CH2Cl2 was cooled to −78° C. and added dropwise with 10.1 ml of BF3.OEt2 (80.0 mmol, 2 eq.). After completed addition, stirring was continued for 30 min, and completion of the reaction was checked by means of TLC (EE/CH 1:9). Thereafter, 10 ml of a saturated NaHCO3 solution was added, and the batch was allowed to come to RT. After transferring into a separating funnel together with 200 ml of MTBE, the phases were separated and the aqueous phase was extracted with 2×100 ml of MTBE. The combined organic phases were washed with 100 ml of half-conc. NaCl solution, dried over MgSO4 and concentrated. The residue was purified using silica gel column chromatography (EE/CH 1:9), thereby obtaining 9.62 g of allyl substitution product 46 (30.9 mmol, 77%) as a colorless oil (mixture of epimers, cis/trans 75:25).

Provenance & Evidence