Palladium(0) Catalyzed Enantioselective C(sp2)–H Arylation Reactions: From Axial, Helical to Planar Chirality

Palladium(0)-catalyzed enantioselective C–H functionalization has been developed to be one of the most straightforward and efficient strategies to access small chiral molecules. However, many challenges and problems in this field still need to be addressed. In this thesis, the Pd0-catalyzed C(sp2)–H arylation enabled the construction
of chiral axis with extremely high enantioselectivities and reactivities. In addition, the method can also access to molecules displaying planar chirality.
In the first part, the use of a Pd(0) complex equipped with H8-BINAPO as chiral ligand enables the direct functionalization of a broad range of 1,2,3-triazoles and pyrazoles in excellent yields and enantioselectivities of up to 97.5:2.5 er. The method also allows for an atroposelective double C–H arylation for the construction of two stereogenic axes with >99.5:0.5 er. This work provided a straightforward method for the construction of
chiral biaryl compounds.
In the second part, a general enantioselective process for the construction of lower, nonfused low-order carbo[n]helicenes (n = 4-6) was developed. Computational
mechanistic studies indicate that both the C–H activation and reductive elimination steps contribute to the overall enantioselectivity. Moreover, a systematic study of the
circularly polarized luminescence (CPL) properties of the synthesized carbo[n]helicenes showed that carbo[4]helicenes are able to display comparable CPL responses to the higher carbo[6]helicenes.
In the last part, the method was extended to the C(sp2)–H arylation of paracyclophanes. A very good enantioselectivity of 16:84 er was obtained during the early exploration of
the C(sp2)–H arylation of [2.2]paracyclophane by using chiral bifunctional ligand developed by the Baudoin group. In addition, an applicable plan was proposed for the
following study.