Compound 6
2,4-Dimethylpentan-3-yl 2-diazoacetate
From: Generation and exploitation of acyclic azomethine imines in chiral Brønsted acid catalysis
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InChIKey FFFNUZMPGPIMKW-UHFFFAOYSA-N
Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
To an ice cold solution of 2,4-dimethylpentan-3-ol (5.0 mmol, 581 mg) and 4-(N,N-dimethylamino)pyridine (0.25 mmol, 31 mg) in anhydrous THF (5.0 mL) was added diketene (10 mmol, 841 mg) slowly and the mixture was stirred for 2 h at room temperature. The resulting mixture was concentrated under vacuum. The residue was then purified by column chromatography on silica gel (eluting with pentane/Et2O = 10:1) to give 2,4-dimethyl-3-pentyl 3-oxobutanoate as a colorless oil (941 mg, 94%).
To a solution of 2,4-dimethyl-3-pentyl 3-oxobutanoate (4.7 mmol, 941 mg), tosyl azide (4.7 mmol, 927 mg) and tetra-n-butylammonium bromide (0.24 mmol, 75.6 mg) in pentane (5.0 mL), 3 N aqueous sodium hydroxide (3.1 mL) was added with vigorous stirring at room temperature. After stirring for 24 h, the resulting mixture was extracted with Et2O. The combined organic layers were washed with brine, dried over sodium sulfate and concentrated under vacuum. The residue was then purified by column chromatography on silica gel (eluting with hexane/Et2O = 20:1) to give 6 as a yellow oil (667 mg, 77%). The spectral data of the product is reported in the literature (Müller, P. & Polleux, P. Enantioselective formation of bicyclic lactones by rhodium-catalyzed intramolecular CH-insertion reactions. Helv. Chim. Acta 77, 645-654 (1994))
