Boron trifluoride etherate → 4-tert-Butyl 3-methyl (3S)-morpholine-3,4-dicarboxylate

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Reaction Steps

A solution of example 1109C (522 mg, 2.0 mmol) in 4 mL of methylene chloride was cooled in an ice/acetone bath and triethylsilane (1.6 mL, 10.0 mmol) was added. The solution was then treated with a solution of boron trifluoride etherate (0.27 mL, 2.2 mmol) in 1 mL of methylene chloride. After stirring 30 minutes, the bath was removed and stirring continued for 30 minutes and the mixture was quenched by the addition of 2M aqueous sodium carbonate. The mixture was diluted with water and methylene choride and the layers separated. The aqueous layer was extracted with 2 portions of methylene chloride and the combined organic layers were dried, filtered and concentrated. The residue was purified by column chromatography on silica gel (40 g, 20% ethyl acetate/hexanes) to provide 200 mg (41%) of the title compound. MS (DCI, NH3): 246 (MH+); 263 (M+NH4)+.

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