Triethylamine → tert-butyl (2S,4E)-4-methoxyimino-2-(2-oxo-3H-1,3,4-oxadiazol-5-yl)pyrrolidine-1-carboxylate

Participants

Reaction Steps

To a stirring solution of tert-butyl (2S,4EZ)-2-(hydrazinocarbonyl)-4-(methoxyimino)-1-pyrrolidinecarboxylate (Intermediate 9, 1.84 mmoles; 500 mg) and triethylamine (2.76 mmoles; 27 mg) in THF (25 mL) at 0° C. was added 1,1′-carbonyldiimidazole (2.76 mmoles, 448 mg). The stirring was continued for 5 hours. Another portion of triethylamine and 1,1′-carbonyldiimidazole were added and stirring was continued at room temperature overnight. The solvent was evaporated and the residue was dissolved in EtOAc and washed with NH4Clsat., and 10% NaHCO3, and brine. The organic layer was dried over Na2SO4 and evaporated to dryness to give the desired N-protected intermediate, tert-butyl (2S,4E)-4-(methoxyimino)-2-(5-oxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)-1-pyrrolidinecarboxylate, as a white foam (460 mg, 84%).

Provenance & Evidence