Acetaldehyde → Tert-butyl 8-ethyl-10-phenyl-11-oxa-3,8-diazaspiro[5.5]undecane-3-carboxylate

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Reaction Steps

To a solution of tert-butyl 8-phenyl-7-oxa-3,10-diazaspiro[5.5]undecane-3-carboxylate (735 mg, 2.21 mmol) in methanol (10 mL) was added acetaldehyde (107 mg, 136 μL, 2.43 mmol), then sodium cyanoborohydride (195 mg, 1.5 mL, 3.10 mmol) and the reaction mixture was stirred for 2 hours. The reaction mixture was concentrated in vacuo, diluted with DCM (50 mL), washed with 1:1 aq. sat. NaHCO3/25% NaOH (10 mL), and the aqueous layer was extracted with DCM (2×25 mL). The combined organics were dried (MgSO4), concentrated in vacuo and purified by silica gel column chromatography using (0-75% EtOAc/DCM) as eluent to give tert-butyl 8-ethyl-10-phenyl-11-oxa-3,8-diazaspiro[5.5]undecane-3-carboxylate (540 mg, 68%) as a viscous yellow oil. ESI-MS m/z calc. 360.5. Found 361.7 (M+1)+; Retention time: 1.15 minutes (3 min run).

Provenance & Evidence