Ethyl diazoacetate → (+)-Ethyl 2-(4-bromo-2-fluorophenyl)cyclopropanecarboxylate

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Reaction Steps

To a suspension of copper(I) trifluoromethanesulfonate benzene complex (0.01 eq) in chloroform (100 mL) at rt, was added (R,R)-2,2′-isopropylidene-bis(4-tert-butyl-2-oxazoline) (0.01 eq). The mixture was stirred at for 1 h then cannulated through glass wool in a solution of styrene from step 5 (1.2 eq) in chloroform (0.1M) at 4° C. To this solution was added a solution of ethyl diazoacetate (0.8 eq) in of chloroform (1M) dropwise over 3 h. The final mixture was stirred overnight at 4° C. The mixture was concentrated. Flash chromatography (Hexane, EtOAc; 95:5) afforded the desired compound. (84:16, trans:cis isomers, methodology described in Evans et al. J. Am. Chem. Soc. 1991, 113, 726)

Provenance & Evidence