Modular phospholane ligands in asymmetric catalysis

This Account outlines the preparation and application of a class of phosphine ligands based upon the trans-2,5-disubstituted phospholane moiety. The modular nature of these ligands has allowed facile variation of both phospholane substituent and backbone structure, thus providing access to a series of ligands. Bidentate bis(phospholane) ligands have been found to be very useful in asymmetric catalytic hydrogenation reactions. In particular, we highlight the versatility of highly efficient bis(phospholane)rhodium catalysts that allow enantioselective hydrogenation to produce a diverse range of compounds containing C-N, C-O, and C-C stereogenic centers.     

Applications of planar-chiral heterocycles as ligands in asymmetric catalysis

A new family of ligands for asymmetric transition metal-catalyzed reactions has been designed and synthesized. Thus, planar-chiral heterocycles furnish high enantioselectivity in a variety of processes, including isomerizations of allylic alcohols, O-H insertions, and 1,3-dipolar cycloadditions.     

不对称催化中的手性配体和底物之间的相互作用

讨论了手性配体和底物之间的相互作用及其在对映选择催化中的应用。     

Recent advances in homogeneous and heterogeneous asymmetric catalysis with nitrogen–containing ligands

Nitrogen–containing chiral ligands are being used more and more in asymmetric catalysis. This article is an overview of results published in 1993--1996 in this field and tries to open new perspectives for this type of ligand, more particularly with the purpose of heterogenization of the catalytic systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

P-Phos: a family of versatile and effective atropisomeric dipyridylphosphine ligands in asymmetric catalysis

This Account outlines our efforts in the design and synthesis of a family of highly effective atropisomeric dipyridylphosphine ligands (P-Phos and its variants) and in the development of their widespread applications in transition-metal-catalyzed asymmetric reactions including hydrogenation, hydrosilylation, and C-C bond formation. Desirable attributes, such as air stability, broad substrate scope, fast rates of reaction, excellent enantioselectivities, low catalyst loading, and mild conditions, make the catalyst systems highly attractive and thus may provide excellent opportunities for practical applications.     

New carbon- and sulfur-based ligands in catalysis

Homogeneous catalysis is a field of research that has gained central importance in both organic and inorganic chemistry and the use of well-defined ligand systems in the synthesis of transition metal complexes has had an enormous impact on the development of such catalysts. Neutral, two-electron donor ligands based on phosphorous and nitrogen have been tremendously successful as ancillary entities for late-transition metal (LTM) catalysts, whereas ligands based on anionic nitrogen, oxygen and the cyclopentadienyl motif (Cp(-)) have propelled early-transition metal (ETM) catalysis forward. We believe that expanding the ligand families capable of acting as successful entities in metal-mediated reactivity and catalysis is crucial for future discoveries in this field. Research in our group therefore tries to identify new non-chiral and chiral ligands for late-transition metal chemistry that are based on neutral, two-electron carbon and sulfur donor atoms. In particular, we have until now focused on the development of modular, monodentate N-heterocyclic carbene ligands (NHCs) that can serve as a basis for the development of chiral ligand frameworks for the application to asymmetric catalytic transformations. In the second major research project developed over the last six years, we have started an investigation on the use of chelating sulfoxide-based ligands in asymmetric late transition-metal based catalysis.     

Kinetic aspects of nonlinear effects in asymmetric catalysis

Probing catalyst systems for a nonlinear relationship between product enantioselectivity and catalyst enantiopurity is now commonly being used as a mechanistic tool. We show that in some cases striking consequences for reaction rate can ensue for reactions carried out using non-enantiopure catalysts. We also demonstrate how consideration of the kinetic behavior may serve to enhance the use of nonlinear effects as a diagnostic tool for identifying active catalytic species and for providing mechanistic insight. Kinetic information may also help in the development of efficient synthetic strategies using non-enantiopure systems.     

Asymmetric catalysis with chiral ferrocene ligands

Chiral ferrocene ligands have been widely used in asymmetric catalysis. The advantages of using ferrocene as a scaffold for chiral ligands are described, particularly those regarding planar chirality, rigid bulkiness, and ease of derivatization. The role of planar chirality in 1,2- and 1,1'-disubstituted ferrocene systems is discussed. By using a bulky ferrocene fragment, novel ferrocene ligands were designed, and high enantioselectivity and regioselectivity were achieved in the allylic substitution reaction of monosubstituted allyl substrates. Using the tunable electronic properties of a diphosphine-oxazoline ferrocenyl ligand, the regioselectivity of the intermolecular asymmetric Heck reaction was also examined.     

乙醛酸酯-烯不对称催化反应的研究进展

催化乙醛酸酯-烯反应(glyoxylate-ene reaction)合成具有光学活性的α-羟基酯需要运用手性催化剂。本文主要介绍了该类手性催化剂的研究进展。     

Self-supported chiral catalysts for heterogeneous asymmetric catalysis

A conceptually new strategy for chiral catalyst immobilization, self-supported catalysts, in heterogeneous asymmetric catalysis is highlighted in the present article. Various homochiral metal-organic polymers with diverse structures have been designed and readily prepared through coordination assembly of modular polytypic/polyfunctional ligands and metal ions without using any supports. These polymers have been successfully employed as chiral catalysts in a variety of heterogeneous asymmetric ractions, including hydrogenation, epoxidation, sulfoxidation, carbonyl-ene reactions, diethylzinc addition, and Michael addition. The self-supported heterogeneous chiral catalysts showed activity and enanioselectivity comparable or even superior to those obtained with their corresponding homogeneous counterparts, and could be readily recovered and reused several times without significant loss of activity or enantioslectivity.