Ethyl pentanoate hydrogenation

ID) Obtaining Ethyl [3-l6-Methoxy-2-Naphthyl)J2,2-Dimethyl Pentanoate by Hydrogenation of the Previous Ethylene Ester 3.5 g of the previous ethylene ester, purified by chromatography, are hydrogenated in the presence of 3.6 g of platinum in 30 cc of ether. The quantity of hydrogen fixed corresponds to the theoretical quantity calculated. After filtering, the ether is evaporated, 3.45 g of ester are thus obtained in the form of an oil which quickly solidifies. Purification is effected by chromatography. 

Typical procedure. tert-Butyl 2-isocyano-4-methyl pentanoate 1554 [1182] N-Formyl-leucine tert-butyl ester 1553 (5.00 g, 23.2 mmol) and triethylamine (7.13 g, 69.7 mmol) were dissolved in dichloromethane (36 mL) and the solution was cooled to 0 °C. At this temperature, a solution of triphosgene (2.30 g, 7.74 mmol) in dichloromethane (25 mL) was added dropwise. The mixture was stirred for 2 h at room temperature, water (5 mL) was then poured into it, and the phases were separated. The organic layer was washed with 5% aq. sodium hydrogen carbonate solution, dried over sodium sulfate, and concentrated in vacuo. The residue was chromatographed on silica gel eluting with ethyl acetate to furnish tert-butyl 2-isocyano-4-methyl pentanoate 1554 (4.29 g, 94%) as a colorless oil. 

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