Because of the tremendous effort of a great number of researchers, the catalytic asymmetric dialkylzinc addition to aldehydes has become a mature method. Ligands of diverse structures have been obtained, and high enantioselectivity for all different types of aldehydes have been achieved. Among the representative excellent catalysts are compounds 1, 8, 120, 325, 352, and 360 discussed above. However, compared to the well-developed dialkylzinc addition, the catalytic asymmetric reactions of aryl-, vinyl-, and alkynylzinc reagents with aldehydes are still very much under developed. Although catalysts such as (S)-402 and 210 prepared by Pu and Bolm have shown good enantioselectivity for the reaction of diphenylzinc with certain aromatic and aliphatic aldehydes, the generality of these catalysts for other [formula: see text] arylzinc reagents have not been studied. The vinylzinc additions using ligands 1 and 412 reported by Oppolzer and Wipf were highly enantioselective for certain aromatic aldehydes but not as good for aliphatic aldehydes. Carreira discovered highly enantioselective alkynylzinc additions to aldehydes promoted by the chiral amino alcohol 415, but this process was not catalytic yet. Ishizaki achieved good enantioselectivity for the catalytic alkynylzinc addition to certain aldehydes by using compounds 160, but the enantioselectivity for simple linear aliphatic aldehydes was low. Another much less explored area is the organozinc addition to ketones. Yus and Fu showed very promising results by using ligands 381 and 406 for both dialkylzinc and diphenylzinc additions to ketones, but the scope of these reactions were still very limited. Therefore, more work is needed for the aryl-, vinyl-, and alkynylzinc additions and for the organozinc addition to ketones, although many good catalysts have been obtained for the dialkylzinc addition to aldehydes. Development of these reactions will allow the catalytic asymmetric synthesis of a great variety of functional chiral alcohols that are either the structural units or synthons of many important organic molecules as well as molecules of biological functions. Macromolecular chiral catalysts have become a very attractive research subject in recent years because these materials offer the advantages of simplified product isolation, easy recovery of the generally quite expensive chiral catalysts, and potential use for continuous production. Three types of macromolecules including flexible achiral polymers anchored with chiral catalysts, rigid and sterically regular main chain chiral polymers, and chiral dendrimers have been used for the asymmetric organozinc addition to aldehydes. Among these materials, the binaphthyl-based polymers such as (R)-451 developed by Pu have shown very high and general enantioselectivity. Study of the binaphthyl polymers in the asymmetric organozinc addition has demonstrated that it is possible to systematically modify the structure and function of the rigid and sterically regular polymer for the development of highly enantioselective polymer catalysts. The catalytic properties of highly enantioselective monomer catalysts can also be preserved in the rigid and sterically regular polymer provided the catalytically active species of the monomer catalyst is not its aggregate. The TADDOL-based polymers and dendrimers prepared by Seebach showed very high and stable enantioselectivity for the diethylzinc addition to benzaldehyde even after many cycles. These studies on macromolecular chiral catalysts demonstrate that these materials are potentially very useful for practical applications.

Catalytic Asymmetric Organozinc Additions to Carbonyl Compounds

Recoverable Catalysts for Asymmetric Organic Synthesis

1 Review 1.1 Overview 1.2 Solid-phase organic synthesis (SPOS) 1.3 Beyond conventional solid-phase organic synthesis 1.4 The review 1.5 Some definitions 1.6 Solid-supported reagents and scavengers 1.7 Multi-step use of solid-supported reagents and scavenging reagents 1.8 Conclusions and future perspective 2 Introduction to the tables 2.1 Organisation of tables (reagent and catalyst section) 2.2 Representative data entry (reagent and catalyst section) 2.3 Organisation of tables (scavenging agents section) 2.4 Representative data entry (scavenging agents section) 3 Tables of reagents and catalysts 4 Tables of scavengers 5 Other relevant reviews 5.1 Insoluble polymers 5.1.1 Structure and physical properties (insoluble polymers) 5.1.2 General (insoluble polymers) 5.1.3 Reactions (insoluble polymers) 5.1.4 Miscellaneous (insoluble polymers) 5.2 Soluble polymers 5.2.1 General (soluble polymers) 5.2.2 Reactions (soluble polymers) 5.3 Inorganic solids 5.3.1 Structure and physical properties (inorganic solids) 5.3.2 General (inorganic solids) 5.3.3 Reactions (inorganic solids) 5.3.4 Miscellaneous (inorganic solids) 5.4 Miscellaneous supports 5.4.1 Structure and physical properties (miscellaneous supports) 5.4.2 General (miscellaneous supports) 5.4.3 Reactions (miscellaneous supports) 5.4.4 Miscellaneous (miscellaneous supports) 5.5 Purification strategies 5.5.1 Various supports (purification strategies) 5.5.2 Insoluble polymers (purification strategies) 6 Acknowledgements 7 Abbreviations 8 References 1 Review

Multi-step organic synthesis using solid-supported reagents and scavengers: a new paradigm in chemical library generation

Dendrimers as support for recoverable catalysts and reagents.

Dendrimers are well-defined hyperbranched macromolecules with characteristic globular structures for the larger systems These novel polymers have inspired many chemists to develop new materials and several applications have been explored, catalysis being one of them The recent impressive strides in synthetic procedures increased the accessibility of functionalized dendrimers, resulting in a rapid development of dendrimer chemistry The position of the catalytic site(s) as well as the spatial separation of the catalysts appears to be of crucial importance Dendrimers that are functionalized with transition metals in the core potentially can mimic the properties of enzymes, their efficient natural counterparts, whereas the surface-functionalized systems have been proposed to fill the gap between homogeneous and heterogeneous catalysis This might yield superior catalysts with novel properties, that is, special reactivity or stability Both the core and periphery strategies lead to catalysts that are sufficiently larger than most substrates and products, thus separation by modern membrane separation techniques can be applied These novel homogeneous catalysts can be used in continuous membrane reactors, which will have major advantages particularly for reactions that benefit from low substrate concentrations or suffer from side reactions of the product Here we review the recent progress and breakthroughs made with these promising novel transition metal functionalized dendrimers that are used as catalysts, and we will discuss the architectural concepts that have been applied

Transition Metal Catalysis Using Functionalized Dendrimers.

Synthesis of chiral dendrimers with a hydrocarbon backbone and application to the catalytic enantioselective addition of dialkylzincs to aldehydes

Chiral dendrimers bearing three or six chiral β-amino alcohols on the hyperbranched hydrocarbon chain-ends act as efficient chiral ligands for the enantioselective addition of diethylzinc to N -diphenylphosphinylimines to afford enantiomerically enriched N -diphenylphosphinylamines with up to 94% e.e.

Highly enantioselective addition of diethylzinc to N-diphenylphosphinylimines using dendritic chiral ligands with hydrocarbon backbones

Highly Enantioselective Addition of Diethylzinc to N-Diphenylphosphinylimines Using Dendritic Chiral Ligands with Hydrocarbon Backbones.

Chiral dendrimers with three or six β-amino alcohols on hyperbranched hydrocarbon chain-ends were synthesized. These macromolecules can act as chiral catalysts for the enantioselective addition of dialkylzincs to aldehydes. The corresponding secondary alcohols are obtained in high enantiomeric excess (up to 86% e.e.).

Koji Ohtake

Papers

Synthesis of chiral dendrimers with a hydrocarbon backbone and application to the catalytic enantioselective addition of dialkylzincs to aldehydes

Highly enantioselective addition of diethylzinc to N-diphenylphosphinylimines using dendritic chiral ligands with hydrocarbon backbones

Highly Enantioselective Addition of Diethylzinc to N-Diphenylphosphinylimines Using Dendritic Chiral Ligands with Hydrocarbon Backbones.

Synthesis of Chiral Dendrimers with a Hydrocarbon Backbone and Application to the Catalytic Enantioselective Addition of Dialkylzincs to Aldehydes.