Asymmetric cross-coupling of racemic α-bromo esters with aryl Grignard reagents catalyzed by cyclopropane-based bisoxazolines cobalt complexes

Abstract Four new cyclopropane-based bisoxazolines were synthesized and applied to cobalt-catalyzed cross-coupling reactions between racemic α-bromo esters and aryl Grignard reagents. The reaction afforded a series of chiral α-arylalkanoic esters with high yields and good enantioselectivities (up to 93% yield, 92:8 er). This research focuses on the cross-coupling between racemic α-bromopropanoate and p -isobutylphenyl Grignard reagent’s which provides ibuprofen ester efficiently. Furthermore, ibuprofen ester 7e was transformed into ( S )-ibuprofen (99:1 er) via hydrolysis and recrystallization.