ABSTRACT
This chapter focuses on the utilization of chiral dirhodium(II) paddlewheel complexes in the enantioselective synthesis of chiral three-membered carbocycles. It discusses both inter- and intramolecular asymmetric cyclopropanation and cyclopropenation reactions. Electrophilicity of the metal-carbenoid intermediate is an important feature to control the reactivity; low electrophilicity can lead to less reactivity, while too much electrophilicity can cause side reaction. Altering the electronic profile of ligands mainly affects the reactivity of the dirhodium(II) catalyst as electronically different bridging ligands coordinated to the Rh–Rh axes donate distinct degrees of charge to the metal changing the overall electronic profile of the complex. Heteroaryldiazoacetates carrying both electron-rich and electron-deficient heterocycles, including thiophene, furan, pyridine, indole, oxazole, isoxazole, and benzoxazole, were suitable for this transformation. In a different context, the electron-rich character of dirhodium(II) carboxamidate catalysts make them catalytically less active compared to dirhodium(II) carboxylates.
