Triethylamine → Tert-butyl 2-oxo-1-oxa-3,8-diazaspiro[4.5]decane-8-carboxylate

Participants

Reaction Conditions

Reaction Steps

Triethylamine (5.59 mL, 39.78 mmol) and diphenylphosphoryl azide (10.86 mL, 5.1 mmol) were added in succession under a nitrogen atmosphere to a solution of A2 (7.9 g) in dry toluene (205 mL). The reaction mixture was heated to 80 to 90° C., evolution of gas being observed which ceased after 90 min. Stirring was continued for a further 2 h at 115° C. After cooling, the reaction mixture was diluted with EtOAc and repeatedly washed with water. The combined aqueous phases were extracted with EtOAc and the combined organic phases were washed with sat. aq. NaCl solution, dried over Na2SO4 and the solvent was removed under a vacuum. The residue was washed repeatedly with ether. 5.72 g (60.6% of theoretical over three stages starting from 1-(tert-butyloxycarbonyl)-4-piperidone) of the desired product 2-oxo-1-oxa-3,8-diazaspiro[4.5]decane-8-carboxylic acid tert-butyl ester (A3) remained as a white solid.

Provenance & Evidence