Trifluoroacetic acid → 1-Oxa-9-azaspiro[5.5]undec-2-en-4-one

Participants

Reaction Steps

To a solution of tert-butyl 8-oxo-11-oxa-3-azaspiro[5.5]undec-9-ene-3-carboxylate (200 mg, 0.748 mmol) in CH2Cl2 (2.4 mL) was added TFA (0.6 mL, 7.8 mmol). The mixture was stirred at room temperature for 15 min. Solvent was removed. The crude material was evaporated again from toluene (2×) and dried under high vacuum overnight to provide 11-oxa-3-azaspiro[5.5]undec-9-en-8-one (300 mg). 1H NMR (400 MHz, CDCl3) δ 7.34 (d, J=6.1 Hz, 1H), 5.57 (d, J=6.1 Hz, 1H), 3.45 (d, J=11.7 Hz, 2H), 3.34 (dd, J=24.1, 12.7 Hz, 2H), 2.67 (s, 2H), 2.38 (d, J=14.6 Hz, 2H), 1.98 (td, J=14.8, 4.8 Hz, 2H). ESI-MS m/z calc. 167.09, found 168.2 (M+1)+; Retention time: 0.17 minutes (3 minute run).

Provenance & Evidence