Merging C-H and C-C Activation in Pd(II)-Catalyzed Enantioselective Synthesis of Axially Chiral Biaryls

The merging of C-H and C-C bond cleavage into one single chemical process remains a daunting challenge, especially in an asymmetric manner. Herein, a Pd(II)-catalyzed enantioselective tandem C-H/C-C activation for the synthesis of axially chiral biaryls is described. Two types of simple cyclopropanes, such as vinylcyclopropanes and cyclopropanols, were used as efficient and readily available coupling partners. This catalytic system features good functional group compatibility, excellent enantiocontrol (up to >99% ee) and the first use of palladium catalyst in this process. The synthetic utility of this protocol was demonstrated by gram-scale synthesis and further synthetic transformations to access various axially chiral biaryls with high enantiopurity. Two distinct but closely related C-C cleavage pathways of cyclopropanes were achieved in the enantioselective C-H/ C-C activation process, which represents a novel platform to further utilize the ring-opening attribute of cyclopropanes in asymmetric catalysis. Preliminary mechanistic studies provide insights into the role of cyclopropanols, which may pave the way for the development of novel catalytic transformations.