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

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Reaction Conditions

Reaction Steps

A mixture of tert-butyl 4,9-diazaspiro[5.5]undecane-9-carboxylate hydrochloride (170.00 g, 584.53 mmoles), cesium carbonate (476.13 g, 1.46 moles), and 4-bromobutyne (93.28 g, 701.43 mmoles) in acetonitrile (1.70 L) is heated to 60° C. and stirred at this temperature overnight. Further 4-bromobutyne (46.64 g, 350.72 mmoles) is added and the mixture is stirred at 60° C. overnight. The mixture is cooled and filtered. The filtrate is concentrated under reduced pressure and the residue dissolved in ethyl acetate (500 mL), washed with water (1 L), and saturated aqueous sodium chloride (1 L), then dried over MgSO4, and filtered. The filtrate is concentrated under reduced pressure and the residue is purified by silica column chromatography eluting with 20 to 70% ethyl acetate in dichloromethane to provide the title compound (129 g, 72% yield). Mass spectrum (m/z): 307.25 (M+1).

Provenance & Evidence