Asymmetric [3+n]-Cycloaddition Reactions of Donor-Acceptor Cyclopropanes

[3+n]-Cycloaddition reactions that employ donor-acceptor cyclopropanes using either chiral catalysts and racemic cyclopropanes or achiral catalysts and chiral, non-racemic, cyclopropanes have become useful transformations for the construction of carbocyclic and heterocyclic compounds, with both processes offering mechanistic and structural advantages in ring formation. Although the vast majority of asymmetric cycloaddition reactions of donor-acceptor cyclopropanes have been performed with racemic cyclopropane compounds catalyzed by Lewis acids with chiral ligands, optically active cyclopropane compounds can serve the same role using Lewis acids without chiral ligands. This review covers the use of chiral catalysts with racemic donor-acceptor cyclopropanes and the use of chiral non-racemic donor-acceptor cyclopropanes with achiral Lewis acid catalysts.