Highly Rigid Diphosphane Ligands with a Large Dihedral Angle Based on a Chiral Spirobifluorene Backbone

摘要

Asymmetric catalysis is undoubtedly a powerful, economically feasible tool for the synthesis of optically active organic compounds both in the laboratory and on a production scale. The design and synthesis of chiral phosphane ligands have played a significant role in the development of efficient, transition-metal-catalyzed asymmetric reactions.[1] In the last decades, a large number of chiral diphosphane ligands, such as diop,[2] binap,[3] josiphos,[4] duphos,[5] pennphos,[6] bisp,[7] p-phos,[8] and tangphos,[9] have been prepared and used in asymmetric catalysis with excellent enantioselectivities. Since there are no universal ligands and catalysts for asymmetric transformations, and most asymmetric reactions are substrate dependent, the search for chiral ligands that are more efficient in terms of high enantioselectivity and high turnover number (TON) remains one of the most important goals in asymmetric catalysis.