反应详情

An enantioselective cyclopropanation analogous to a literature procedure (Evans et al. J. Am. Chem. Soc. 1991, 113, 726) using commercial 2,2′-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline] in conjunction with copper(I) triflate and ethyldiazoacetate was used to prepare optically active ethyl (1R,2R)-2-(4-bromophenyl)cyclopropanecarboxylate from 4-bromostyrene. The absolute configuration was assigned by analogy based on the sense of the optical rotation. Selective hydrolysis of the trans isomer with LiOH (1 equivalent based on the trans ester) from the mixture of cis and trans esters (that was obtained by the cyclopropanation procedure) gave the title compound.

1. customwas obtained by the cyclopropanation procedure)