反应详情

Another alternative is an enantioselective cyclopropanation using for example a bis-oxazoline chiral ligand/copper complex and diazoacetate (Evans et al. J. Am. Chem. Soc. 1991, 113, 726) to prepare optically active ethyl 2-(trans)-(4-bromophenyl)cyclopropanecarboxylate from 4-bromostyrene. Selective hydrolysis of the mixture of cis and trans isomer with LiOH (1 eq based on the trans ester) gave 2-(trans)-(4-bromophenyl)cyclopropanecarboxylic acid and ethyl 2-(cis)-(4-bromophenyl)cyclopropanecarboxylate which can be used in EXAMPLE 8.

1. customhydrolysis of the mixture of cis and trans