Development of diverse adjustable axially chiral biphenyl ligands and catalysts

Development of highly efficient and practical chiral ligands and catalysts is an eternal theme in asymmetric synthesis. Here, we report the design, synthesis, and evaluation of a new kind of adjustable axially chiral biphenyl ligands and catalysts, in which six model reactions including asymmetric additions of diethylzinc or alkynes to aldehydes in the presence of axially chiral [1,1'-biphenyl]-2,2'-diol ligands, palladium-catalyzed asymmetric cycloadditions in the presence of phosphoramidite ligands, and chiral phosphoric acid-catalyzed asymmetric synthesis of 1,1'-spirobiindane-7,7'-diol derivative and [4 + 3] cyclization were attempted. The results showed that variation of 2,2'-substituent groups could provide different types of ligands and catalysts, and adjustment of substituent groups at the 3,3', 5,5', 6,6'-positions could make ligands and catalysts more efficient in the asymmetric catalytic synthesis. Therefore, our present research should provide a new and useful strategy for development of diverse axially chiral ligands and catalysts.