1,1'-Carbonyldiimidazole → (1-(5-Oxo-4,5-dihydro-[1,2,4]oxadiazol-3-yl)-spiro[2.5]oct-1-ylmethyl]-carbamic acid tert-butyl ester

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Reaction Steps

To a solution of [1-(N-hydroxycarbamimidoyl)-spiro[2.5]oct-1-ylmethyl]-carbamic acid tert-butyl ester (5.8 g, 19.5 mmol) in THF (250 mL) was added CDI (4.74 g, 29.3 mmol). After 3 hours at reflux another portion of CDI (1 g) was added. The solution was heated to reflux for an additional 4 hours and then the solvent was removed under reduced pressure. The residue was partitioned between ether (200 mL) and 1N NaOH (75 mL). The organic layer was extracted with 1N NaOH (2×75 mL). The combined aqueous layers were washed with ether (100 mL). The aqueous layer was acidified to pH=3 by the addition of potassium hydrogen sulfate with ice bath cooling while layered over methylene chloride (100 mL). The layers were separated and the aqueous layer was extracted with methylene chloride (2×200 mL). The combined organic layers were washed with water (75 mL), dried over sodium sulfate, filtered and evaporated under reduced pressure to give an off white foam. The residue was chromatographed on a wet-packed silica gel column (6.5×28 cm) eluting with 3-4% methanol in methylene chloride. The appropriate fractions were combined and evaporated to give 4.4 g (70%) of [1-(5-oxo-4,5-dihydro-[1,2,4]oxadiazol-3-yl)-spiro[2.5]oct-1-ylmethyl]-carbamic acid tert-butyl ester as a white foam: 1H NMR (300 MHz, CDCl3) δ0.78 (d, J=5.3 Hz, 1H), 1.44 (s, 9H), 1.3-1.7 (m, 11H), 3.24 (dd, J=5.0, 13.9 Hz, 1H), 3.84 (dd, J=5.0, 13.9 Hz, 1H), 4.97 (s, 1H); MS (APCI) m/z 324 [M+H]+.

Provenance & Evidence