Atropoisomeric
(hetero)biaryls are scaffolds with increasing importance
in the pharmaceutical and agrochemical industries. Although it is
the most obvious disconnection to construct such compounds, the direct
enantioselective C–H arylation through the concomitant induction
of the chiral information remains extremely challenging and uncommon.
Herein, the unprecedented earth-abundant 3d-metal-catalyzed atroposelective
direct arylation is reported, furnishing rare atropoisomeric C2-arylated
indoles. Kinetic studies and DFT computation revealed an uncommon
mechanism for this asymmetric transformation, with the oxidative addition
being the rate- and enantio-determining step. Excellent stereoselectivities
were reached (up to 96% ee), while using an unusual N-heterocyclic carbene ligand bearing an essential remote
substituent. Attractive dispersion interactions along with positive
C–H---π interactions exerted by the ligand were identified
as key factors to guarantee the excellent enantioselection.
Ligand-free manganese-catalyzed homocoupling of arenes or aryl halides can be carried out under aerobic conditions via the in situ formation of the corresponding aryllithiums. A wide range of biaryls and derivatives has been obtained and a mechanism involving monomeric manganese-oxo complexes has been proposed on the basis of DFT calculations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.