Hydrochloric Acid → 3-[(S)-1-(4-Bromo-phenyl)-ethyl]-1-oxa-3-aza-spiro[5.5]undecane-2,9-dione

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Reaction Steps

Triphosgene (2.51 g) is added to a solution of 9-{2-[(S)-1-(4-bromo-phenyl)-ethylamino]-ethyl}-3,3-dimethyl-1,5-dioxa-spiro[5.5]undecan-9-ol (4.00 g) and ethyl-diisopropyl-amine (1.7 mL) in dichloromethane (40 mL) chilled in an ice bath. The cooling bath is removed and the solution is stirred at room temperature overnight. Water is added and the organic phase is separated. The organic phase is dried (Na2SO4) and concentrated to give an oil that is dissolved in acetone (20 mL). 1 M Hydrochloric acid (19 mL) is added and the solution is stirred at room temperature for 3 h. The acetone is then evaporated, and the residue is diluted with saturated aqueous K2CO3 solution and extracted with ethyl acetate. The combined extracts are washed with water and brine, dried (MgSO4), and concentrated. The residue is chromatographed on silica gel (cyclohexane/ethyl acetate 1:1→0:1) to give the title compound. Yield: 1.89 g (52% of theory); LC (method 8): tR=1.27 min; Mass spectrum (ESI+): m/z=366/368 (Br) [M+H]+.

Provenance & Evidence