Practical enantioselective synthesis of axially chiral biaryl diphosphonates and dicarboxylates by cationic rhodium(I)/Segphos-catalyzed double [2+2+2] cycloaddition

A cationic rhodium(I)/Segphos complex catalyzes a [2 + 2 + 2] cycloaddition of internal 1,6-diynes with a phosphonate- or ester-substituted 1,3-butadlyne leading to C-2-symmetric axially chiral biaryl diphosphonates or dicarboxylates, respectively, in high yields with outstanding ee's. The use of a phosphonate- or ester-substituted 1,3-butadiyne as a cycloaddition partner and Segphos as a ligand is crucial for the success of this transformation.