Development of Chiral Spiro Ligands for Metal-Catalyzed Asymmetric Reactions

This account focuses our works on the development of chiral spiro ligands bearing N-heterocycles as metal-coordinating units and their applications in the metal-catalyzed asymmetric reactions. The spiro bis(isoxazoline) ligands (SPRIXs), spiro bis(isoxazole) ligands, and spiro (isoxazole-isoxazoline) ligands were readily synthesized through intramolecular double nitrile oxide cycloaddition of the corresponding dioximes as a key step. An unprecedented activation of olefins was displayed by the Pd-11 complexes of these chiral spiro ligands in the enantioselective oxidative cyclizations, for example; the asymmetric tandem cyclization of dialkenyl alcohol via oxy-palladation produced a bicyclic ether in excellent enantioselectivity and enantioselective version of the aminocarbonylation proceeded for the first time. Other hitherto known chiral ligands we examined failed to promote these reactions.