Ammonium formate → Tert-butyl 2-phenyl-1-oxa-4,9-diazaspiro[5.5]undecane-9-carboxylate

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Reaction Conditions

Reaction Steps

To tert-butyl 10-benzyl-8-phenyl-7-oxa-3,10-diazaspiro[5.5]undecane-3-carboxylate (1.58 g, 3.74 mmol) and Pd(OH)2 (280 mg, 0.40 mmol) in ethanol (16 mL) was added ammonium formate (1.10 g, 17.39 mmol) and the reaction mixture was heated to 60° C. for 40 min. The reaction mixture was cooled, filtered, concentrated to 10% of original volume, diluted with ethyl acetate and washed with sat. aq. NaHCO3 (pH 10)/brine. The aqueous was extracted further with ethyl acetate and the combined organics were dried over Na2SO4, filtered and concentrated in vacuo to give tert-butyl 8-phenyl-7-oxa-3,10-diazaspiro[5.5]undecane-3-carboxylate (1.15 g, 93%) as a white solid. ESI-MS m/z calc. 332.2. Found 333.3 (M+1)+; Retention time: 1.13 minutes (3 min run). 1H NMR (400 MHz, CDCl3) δ 7.40-7.23 (m, 5H), 4.69 (dd, J=10.7, 2.7 Hz, 1H), 3.76 (br. s, 2H), 3.31 (t, J=10.7 Hz, 1H), 3.17-3.02 (m, 2H), 2.75 (dd, J=35.5, 12.4 Hz, 2H), 2.63 (dd, J=12.3, 10.8 Hz, 1H), 2.49 (d, J=12.5 Hz, 1H), 1.69-1.57 (m, J=12.6 Hz, 1H), 1.57-1.39 (m, 11H).

Provenance & Evidence