Ethyl diazoacetate → Ethyl 2-chloro-2-fluorocyclopropanecarboxylate

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Cyclohexane (76.6 g), 2,2′-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline] (75.8 mg, 0.26 mmol), and copper (I) trifluoromethanesulfonate benzene complex (58.3 mg, 0.23 mmol) were added in an autoclave, and then 1-chloro-1-fluoroethylene (78.9 g, 0.98 mol) was charged under elevated pressure. After the mixed solution was cooled to 10° C., the a mixed solution containing 95% of ethyl diazoacetate (12.0 g, 100 mmol) and cyclohexane (50 g) was charged into the autoclave under elevated pressure over five hours. Cyclohexane (20 ml) was further charged under elevated pressure and stirring was continued at the same temperature for 1 hour, and then the internal pressure was released to give a solution of ethyl 2-chloro-2-fluorocyclopropanecarboxylate in cyclohexane (170.0 g). The content of the ethyl 2-chloro-2-fluorocyclopropanecarboxylate was 6.45% (yield based on ethyl diazoacetate: 65.6%), and the ratio of cis-isomer/trans-isomer was 64.6/35.4. The optical purity of the cis-isomer was 99% e.e. (1S,2R), and the optical purity of the trans-isomer was 92% e.e. (1S,2S).

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