Acetic Anhydride → Tert-butyl 9-acetyl-3,9-diazaspiro[5.5]undecane-3-carboxylate

Participants

Reaction Steps

To a solution of 3,9-diaza-spiro[5.5]undecane-3-carboxylic acid tert-butyl ester (400 mg, 1.57 mmol) in DCM (16 mL) was added acetic anhydride (177 μL, 1.88 mmol) and triethylamine (656 μL, 4.71 mmol) and the mixture was stirred (rt, 16 h). The reaction mixture was diluted with DCM (16 mL), washed with water (3×10 mL) and brine (1×10 mL). The organic layer was dried, filtered and concentrated in vacuo to provide the 9-acetyl-3,9-diaza-spiro[5.5]undecane-3-carboxylic acid tert-butyl ester (466 mg, 100%). This intermediate was dissolved in DCM (4 mL), treated with HCl (4 M in dioxane, 4 mL) and stirred (rt, 16 h). The dispersion was concentrated in vacuo to provide the title compound as a white powder (365 mg, 100%). MS (ESI): mass calcd. for C11H20N2O, 196.16; m/z found, 197.1 [M+H]+. 1H NMR (400 MHz, MeOD): 3.63-3.51 (m, 4H), 3.23-3.17 (m, 4H), 2.13 (s, 3H), 1.82-1.73 (m, 4H), 1.67-1.53 (m, 4H).

Provenance & Evidence