Magical Chiral Spiro Ligands

Transition metal catalyzed asymmetric reaction is a hot issue and a frontier of the research in current organic chemistry.The design and synthesis of new type of efficient chiral ligands and chiral catalysts, esspecially those with novel skeleton is the focus of research in asymmetric catalysis.Since 1990's, chiral ligands based on spiro skeletons have received increasing attention and gradually developed into a new type of chiral ligands with distinctive characteristics.The skeletons of the chiral spiro ligands developed from spiro[4.4]nonane with three chiral stereocenters to spirobiindane and spiro[4.4]nonadienewith only one axial chirality, as well as other types of spiro skeletons.Nowadays, the library of chiral spiro ligands contains a wide range of chiral spiro ligands with different skeletons, including chiral spiro monophosphorus ligands, diphosphine ligands, phosphine-nitrogen ligands, dinitrogen ligands, and etc.Many of these chiral spiro ligands and related catalysts not only have shown high catalytic activity and high enantioselectivity for various asymmetric reactions such as asymmetric hydrogenations, asymmetric carbon-carbon bond forming reactions, and asymmetric carbon-heteroatom bond forming reactions, but also have made the enantiocontrol of many catalytic asymmetric reactions, which are difficult in obtaining high enantioselectivities, more easily and possible.The chiral spiro skeleton has become a 'privileged structure', and chiral spiro ligands and catalysts have been used in the syntheses of different type of chiral compounds including chiral natural products and chiral drugs.The emergence of chiral spiro ligands increased the dynamism of research on finding new chiral ligands and catalysts, and promoted asymmetric synthesis chemistry.Henceforth, the focus of study in chiral spiro ligands will continue to be the development of new chiral spiro ligands and catalysts with high activity and high enantioselectivity.At the same time, the applications of chiral spiro ligands in the new catalytic asymmetric reactions, and in the asymmetric synthesis of bioactive chiral compounds, chiral natural products and chiral drugs will become a new focus of research.