Ethyl diazoacetate → Ethyl chrysanthemate

Beteiligte Stoffe

Reaktionsschritte

18.05 mg (0.05 mmol) of copper trifluoromethanesulfonate, 19.9 mg (0.055 mmol) of bis[2-[4(R)-phenyl-5,5-dimethyl-2-oxazoline]]methane and 5 ml of n-butyl chloride were charged in a 50 ml Schienk's tube wherein the atmosphere is substituted with nitrogen, followed by stirring at room temperature for 10 minutes. After 30.0 g (275 mmol) of 2,5-dimethyl-2,4-hexadiene was further added, 5.70 g (50 mmol) of ethyl diazoacetate was added dropwise at 50° C. over 2 hours. After the completion of the dropwise addition of ethyl diazoacetate, the mixture was further stirred at 50° C. for 1 hour. The amount of chrysanthemic acid ethyl ester formed was determined by gas chromatography. As a result, it was 8.43 g and the yield was 86.0% based on ethyl diazoacetate and, furthermore, the trans/cis ratio was 72/28. After 2,5-dimethyl-2,4-hexadiene (boiling point: 51° C./30 mmHg) was distilled off from the reaction mixture, 1 g of the concentrated solution was taken out. Then, 10 ml of an aqueous 1N sodium hydroxide solution and 5 ml of ethanol were added and alkali hydrolysis was performed by stirring at 100° C. for 1 hour. The resulting chrysanthemic acid was reacted with I-menthol and the formed diastereomer ester was analyzed by gas chromatography. As a result, the optical purity of the (+)-trans isomer was 60% e.e., whereas, the optical purity of the (+)-cis isomer was 27% e.e.

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