Ethanol → 2,8-Diazaspiro[4.5]decane-1,3-dione

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Reaction Steps

To 8-benzyl-2,8-diaza-spiro[4.5]decane-1,3-dione (28.3 g, 0.11 mol) and Pd(OH)2 (8.5 g) in 2 l of flask, EtOH (438 ml) and acetic acid (5.5 ml) are added at ambient temperature. The reaction mixture is stirred under H2 at room temperature for 15 h. The catalysts are removed by filtration and EtOH is evaporated down to give 2,8-diaza-spiro[4.5]decane-1,3-dione in quantitative yield. To a suspension of 2,8-diaza-spiro[4.5]decane-1,3-dione (4.2 g, 25.2 mmol) in dichloromethane (60 ml), 1N NaOH (26 ml, 26 mmol) and di-t-butyldicarbonate (6.1 g, 27.7 mmol) in dichloromethane (20 ml) are added at ambient temperature. The reaction mixture is stirred for 15 h. 10% Citric acid is added to the reaction mixture and the pH of the mixture is adjusted to 5. The combined extracts are washed with brine, dried over magnesium sulfate and concentrated under vacuum to give solid product, which filtrated with diethyl ether.

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