Chloro-N,N-dimethylformiminium chloride → (2R,3R)-2,3-dimethyl-hexanoyl chloride

Participants

Reaction Steps

To a solution containing 1.0 g (6.9 mmol) of (2R,3R)-2,3-dimethyl-hexanoic acid in 10 mL of dichloromethane was added 1.1 g of chloromethylene dimethyl-ammonium chloride (8.3 mmol). The resulting solution was stirred under nitrogen for 1.5 hours. The solvent was subsequently evaporated to give (2R,3R)-2,3-dimethyl-hexanoyl chloride. To a solution containing 2.5 g (14.6 mmol) of potassium monoethyl malonate in 50 mL of acetonitrile was added 1.7 g (17.3 mmol) of magnesium chloride and 1.2 g (11.4 mmol) of triethylamine. The resulting mixture was stirred at room temperature for 2.5 hours. The reaction was cooled to 0° C. and a solution of the (2R,3R)-2,3-dimethyl-hexanoyl chloride in acetonitrile (20 mL) was slowly added followed by the addition of triethylamine (0.4 g, 0.4 mmol). The reaction was heated to 40° C. and stirred at that temperature for 6 hours. The reaction mixture was cooled to 25° C., quenched with a saturated solution of ammonium chloride and extracted into ethyl acetate. The solution was washed with brine, dried over MgSO4 and concentrated. The resulting residue was filtered through a silica plug, eluting with 60/40 solution of hexane/ethyl acetate to afford 1.3 g (87.8% yield) of the titled compound as an oil.

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