Hydrochloric Acid → 2,9-Diazaspiro(5.5)undecan-1-one hydrochloride

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Reaction Steps

To the stirred solution of tert-butyl 1-oxo-2,9-diazaspiro[5.5]undecane-9-carboxylate (3.0 g, 11.19 mmol) in DCM (60 mL) was added 4N HCl in dioxane (20 mL) and the mixture was stirred at rt for 18 h. The solvent was removed under reduced pressure and triturated with diethyl ether (2×5 mL) to yield the title compound as a solid (2.2 g, 96%). Note: The product is moisture sensitive. [1H-NMR (DMSO-d6, 300 MHz): δ 9.25-8.68 (m, 2H), 7.43 (s, 1H), 7.20-6.25 (m, 2H), 3.61-2.90 (m, 5H), 2.12-1.95 (m, 2H), 1.76-1.49 (m, 5H); LCMS RtA=0.326, [M+H]+=169.0].

Provenance & Evidence