All-Carbon Quaternary Stereogenic Centers via Cu-Catalyzed Conjugate Additions

Significance

The synthesis of all-carbon quaternary stereocenters with high enantioselectivity is an important transformation in organic chemistry (see review below). The conjugate addition of alkyl zinc reagents (Et, n-Bu, i-Pr) to tetrasubstituted cyclic enones (cyclohexenone and cyclopentenone) gave optically active cyclohexanones (82-95% ee). A large screening yielded 1 as the best ligand for this reaction. The use of air-stable CuCN as well as of commercially available unpurified toluene are attractive features for this reaction.