Cesium carbonate → tert-Butyl 2-(but-3-yn-1-yl)-2,9-diazaspiro[5.5]undecane-9-carboxylate

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Reaction Steps

Cesium carbonate (46.66 g, 143.21 mmol) is added to a suspension of tert-butyl 4,9-diazaspiro[5.5]undecane-9-carboxylate hydrochloride (16.66 g, 57.28 mmoles) in acetonitrile (167 mL). The mixture is stirred for 10 minutes at ambient temperature then 4-bromobutyne (6.45 mL, 68.74 mmol) is added. The reaction is heated to reflux and stirred for 18 hours. The mixture is cooled and concentrated under reduced pressure. The residue is partitioned between water (200 mL) and ethyl acetate (150 mL). The phases are separated and the aqueous layer is extracted with ethyl acetate (100 mL). The combined organic layers are washed with water (200 mL), then brine (150 mL), dried over MgSO4, filtered, and concentrated under reduced pressure to give the title compound (17.2 g, 98% yield). 1H NMR (300.11 MHz, CDCl3): δ 3.43-3.31 (m, 4H), 2.53-2.48 (m, 2H), 2.37-2.29 (m, 4H), 2.20 (s, 2H), 1.94 (t, J=2.6 Hz, 1H), 1.44 (s, 17H).

Provenance & Evidence