金属催化的不对称氢化反应研究进展与展望

手性过渡金属络合物催化的不对称氢化反应是合成光学活性化合物的重要方法.本文从手性配体及手性催化剂、不对称催化新反应、新方法和新策略三个方面简要评述新世纪以来过渡金属催化的不对称氢化反应研究领域的新进展.从新世纪初至今,手性单磷配体得到了复兴,出现了如MonoPhos、SiPhos、DpenPhos等高效单齿亚磷酰胺酯配体;磷原子手性(P-手性)配体也得到了快速发展,如BenzP*、ZhanPhos、TriFer等已成为新的高效手性双膦配体;螺环骨架手性配体成为新世纪手性配体设计合成的亮点,除了SiPhos、SIPHOX、SpinPHOX等高效手性螺环配体外,手性螺环吡啶胺基磷配体SpiroPAP的铱催化剂成为目前最高效的分子催化剂.不对称催化氢化新反应研究也取得了突破,如非保护烯胺、杂芳环化合物及N-H亚胺的氢化等反应都实现了高对映选择性.自组装手性催化剂、树枝状手性催化剂、铁磁性纳米负载的可回收手性催化剂,以及"混合"配体手性催化剂等新方法和新策略也在不对称催化氢化反应中得到了应用.然而,手性过渡金属络合物催化的不对称氢化研究仍然充满挑战,也期待新的突破.

New Progress and Prospects of Transition Metal-Catalyzed Asymmetric Hydrogenation

Chiral transition metal complexes-catalyzed asymmetric hydrogenation is one of the most efficient methods for the synthesis of optically active compounds,and has been intensively investigated in the past decades.This review presents a brief overview on the progress in the transition metal-catalyzed asymmetric hydrogenation since the beginning of this new century from three aspects:(1) chiral ligands and catalysts;(2) new catalytic asymmetric hydrogenations;(3) new methods and new strategies in asymmetric hydrogenations.Chiral monodentate phosphorus ligands have been a renaissance from the beginning of new century,and many efficient chiral monophosphoramidites such as MonoPhos,SiPhos,DpenPhos have been developed.The chiral phosphine ligands with a chirality on the phosphorus atom(P-chirality),such as BenzP*,ZhanPhos,and TriFer,have also been explored.Chiral ligands with a spiro skeleton have been a highlight of design and synthesis of chiral ligands.The chiral spiro ligands such as SDP,SiPhos,SIPHOX,and SpinPHOX are very efficient in asymmetric hydrogenations.The iridium complexes of chiral spiro pyridine-aminophosphine ligands SpiroPAP is the most efficient molecular catalysts up to now with a turnover number(ratio of converted substrate to catalyst) over 4500000 in the hydrogenation of acetophenone.A number of breakthroughs have been made in the researches on new catalytic asymmetric hydrogenations.Highly enantioslective hydrogenations of unprotected enamines,heteroaromatic compounds,and N-H imines have been developed.New methods and strategies including self-assembled,dendrimerized,and ferromagnetic nanomaterials-loaded chiral catalysts with recyclability and reusability,the catalysts with "mixed" chiral ligands have also been successfully applied in the catalytic asymmetric hydrogenations.However,the chiral transition metal complexes catalyzed asymmetric hydrogenation still has many challenges and is looking forward to new breakthroughs in the future.In addition to the continuous developments of new chiral ligands and catalysts with high efficiency,high enantioselectivity,and high chemoselectivity,new strategies such as co-operative or relay catalysis are becoming focuses of the asymmetric hydrogenations studies.