Pentamethylcyclopentadienyl rhodium(III)–chiral disulfonate hybrid catalysis for enantioselective C–H bond functionalization

Though Cp*Rh(iii) complexes are prominent and versatile catalysts for C–H bond functionalization reactions, catalytic stereocontrol is difficult due to the lack of vacant coordination sites. Here, we report a hybrid strategy for inducing chirality without using previously reported chiral Cpx ligands. A preformed hybrid catalyst, [Cp*RhLN][6,6′-Br-(S)-BINSate], catalysed C–H activation and subsequent conjugate addition of 2-phenylpyridine derivatives to enones in good yield and enantioselectivity (enantiomeric ratio up to 95:5). In addition to 2-phenylpyridines, the conjugate addition of 6-arylpurines proceeded with an enantiomeric ratio of up to 91:9 using [Cp*RhLN][(R)-SPISate]. The results demonstrate that a chiral organic anion can efficiently control the enantioselectivity of Cp*Rh(iii)-catalysed C–H bond functionalization without a chiral Cpx ligand. Though pentamethylcyclopentadienyl rhodium(iii) complexes have been successfully employed for C–H functionalizations, stereocontrol can be difficult due to the lack of vacant coordination sites on the metal centre. Here, Yoshino, Matsunaga and co-workers show that chiral anions can be used alongside the achiral rhodium complex to catalyse C–H activation and subsequent asymmetric conjugate addition.