Kinetic resolution of planar chiral metallocenes using Rh-catalysed enantioselective C–H arylation

Planar chiral metallocenes have found application in the fields of asymmetric catalysis, medicinal chemistry and materials science. Asymmetric C–H functionalisation provides an efficient synthetic route to substituted chiral metallocenes. However, these methods are often limited by the metallocene substitution patterns they can access. Here, we report a Rh-catalysed asymmetric C–H arylation of 1,2-disubstituted and 1,3-disubstituted pyridyl ferrocenes. Pre-installation of substituents at either the 2- or 3-position of the pyridyl ferrocenes enables this kinetic resolution process to provide access to enantio-enriched 1,2-disubstituted and 1,3-disubstituted metallocenes, and their corresponding C–H arylated products, in excellent enantioselectivity, with selectivity factor values up to 618. This process is able to tolerate a broad range of pre-installed functional groups, such as alkyl, alkenyl, aryl, silyl, thio and fluoro, as well as substitution on the 1′-cyclopentadienyl ring. The utility of the process has been shown through synthesis and examination of chiral ferrocene ligands.