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Ligand,chiral

SCHEME 8.20 Chiral catalyzed asymmetric nuclet hilic aromatic substitution. [Pg.211]

In Chapter 1, we have seen a few examples of the use of homogeneous catalysis for the manufacture of chiral molecules. Here we discuss some of the general characteristics of ligands that are used in such reactions. A simple definition of a chiral molecule is that the mirror image of such a molecule is not superimposable on the original. [Pg.40]

A more rigorous symmetry-based definition is that a chiral molecule does not have an improper axis of rotation (S ). There are several ligands [Pg.40]

Depending on the number of asymmetric centers, chiral molecules have two or more optical isomers. Chiral ligands are no different from the general categories of ligands that we have already encountered. They, however, have one or more chiral or asymmetric centers and can be broadly divided into two types. [Pg.41]

Structure 2.49 is a complex with a chiral Schiff base ligand and is probably the first example of an asymmetric homogeneous catalyst used in catalytic cyclopropanation reaction (see Section 7.5). The ligand in structure 2.50 is similar to SALEN but has two chiral centers. It has been used effectively as a chiral catalyst in some epoxidation reactions. [Pg.41]

Structures 2.51 and 2.52 show ligands used in enantioselective epoxidation of allylic alcohols and asymmetric alkene dihydroxylation (ADH) reactions, respectively (see Section 8.5). [Pg.41]

Ligand Ligand Product % ee % Yield Ligand Ligand Product % ee % Yield [Pg.128]

This reflects significant changes in cuprate solvation and aggregation [215]. [Pg.129]

High levels of asymmetric induction can be achieved intramolecularly if the substrate functionality and the heteroatom ligand are contained in the same molecule. Chiral amido(a]kyl)cuprates derived from allylic carbamates [(RCH= CHCH20C(0)NR )CuR undergo intramolecular allylic rearrangements with excellent enantioselectivities (R = Me, n-Bu, Ph 82-95% ee) [216]. Similarly, chiral alkoxy(alkyl)cuprates (R OCuRLi) derived from enoates prepared from the unsaturated acids and trans-l,2-cyclohexanediol undergo intramolecular conjugate additions with excellent diasteroselectivities (90% ds) [217]. [Pg.129]

Non-coordinating solvents such as toluene or mixed toluene/chloroalkane solvent systems afford the highest ee values. [Pg.131]

The first example of a chiral carbanionic residual ligand has recently been reported [238]. Chiral mixed cuprates generated from alkyllithium reagents and cyclic a-sulfonimidoyl carbanions transfer alkyl ligands [such as n-Bu, Me, (CH2)30CH(Me)0Etj to cyclic enones with excellent enantioselectivities (77-99% ee). [Pg.133]

12 I J Hete OotO -ncfAp Otei onrf a-Hete DatomolkyhiAp Otes O O VC iy thesls [Pg.128]

Non-coordinating solvents sucli as toluene or mixed toluene/cliloroalkane solvent systems afford tlie higliest tt values. [Pg.131]

Attention has increasingly focused on neutral ligands diat can complex to cuprate reagetits dirougli soft beteroatoms sudi as sulfur and phosphorous fSclieme 3.50) [218-219]. Leyetidecker s bydroxyproline-derived tridentate ligand IS repre- [Pg.131]

Hie first example of a diital catbanionic residual ligand has recently been reported [238]. Chiral mixed cuprates generated from alkyilitliium reagents [Pg.133]


Chiral ligands for homogeneous hydrogenation of olefins and ketones... [Pg.36]

Asymmetric cyclization using chiral ligands has been studied. After early attempts[142-144], satisfactory optical yields have been obtained. The hexahy-dropyrrolo[2,3-6]indole 176 has been constructed by the intramolecular Heck reaction and hydroaryiation[145]. The asymmetric cyclization of the enamide 174 using (S j-BINAP affords predominantly (98 2) the ( )-enoxysilane stereoisomer of the oxindole product, hydrolysis of which provides the ( l-oxindole aldehyde 175 in 84% yield and 95% ec. and total synthesis of (-)-physostig-mine (176) has been achieved[146]. [Pg.154]

Simple esters cannot be allylated with allyl acetates, but the Schiff base 109 derived from o -amino acid esters such as glycine or alanine is allylated with allyl acetate. In this way. the o-allyl-a-amino acid 110 can be prepared after hydrolysis[34]. The Q-allyl-o-aminophosphonate 112 is prepared by allylation of the Schiff base 111 of diethyl aminomethylphosphonates. [35,36]. Asymmetric synthesis in this reaction using the (+ )-A, jV-dicyclohex-ylsulfamoylisobornyl alcohol ester of glycine and DIOP as a chiral ligand achieved 99% ec[72]. [Pg.306]

Asymmetric hydrogenolysis of allylic esters with formic acid with satisfactory ee was observed[387], Geranyl methyl carbonate (594) was reduced to 570 with formic acid using l,8-bis(dimethylamino)naphthalene as a base and MOP-Phen as the best chiral ligand, achieving 85% ee. [Pg.371]

Asymmetric dimerization with cyclopentanone-2-carboxylate using BPPM as a chiral ligand gave the telomer in 41% eefSS]. [Pg.433]

Most chiral chromatographic separations are accompHshed using chromatographic stationary phases that incorporate a chiral selector. The chiral separation mechanisms are generally thought to involve the formation of transient diastereomeric complexes between the enantiomers and the stationary phase chiral ligand. Differences in the stabiHties of these complexes account for the differences in the retention observed for the two enantiomers. Often, the use of a... [Pg.61]

Astemi2ole (10) has further been modified into a series of 4-phenylcyclohexylamine compounds, resulting in the synthesis of cabastine, for example. Cabastine is a highly active compound and its geometric isomers are also active, demonstrating the stereoselectivity of histamine receptors toward chiral ligands. The > S, 4 R-levo antipode of cabastine was the most active, and therefore this isomer, levocabastine (13), has been chosen for further development. Because of high potency, levocabastine has been developed for topical appHcation such as eye drops and nasal spray. [Pg.139]

Catalytic asymmetric hydrogenation was one of the first enantioselective synthetic methods used industrially (82). 2,2 -Bis(diarylphosphino)-l,l -binaphthyl (BINAP) is a chiral ligand which possesses a Cg plane of symmetry (Fig. 9). Steric interactions prevent interconversion of the (R)- and (3)-BINAP. Coordination of BINAP with a transition metal such as mthenium or rhodium produces a chiral hydrogenation catalyst capable of inducing a high degree of enantiofacial selectivity (83). Naproxen (41) is produced in 97% ee by... [Pg.248]

Efficient enantioselective asymmetric hydrogenation of prochiral ketones and olefins has been accompHshed under mild reaction conditions at low (0.01— 0.001 mol %) catalyst concentrations using rhodium catalysts containing chiral ligands (140,141). Practical synthesis of several optically active natural... [Pg.180]

The advantages of titanium complexes over other metallic complexes is high selectivity, which can be readily adjusted by proper selection of ligands. Moreover, they are relative iaert to redox processes. The most common synthesis of chiral titanium complexes iavolves displacement of chloride or alkoxide groups on titanium with a chiral ligand, L ... [Pg.151]

The strategy of the catalyst development was to use a rhodium complex similar to those of the Wilkinson hydrogenation but containing bulky chiral ligands in an attempt to direct the stereochemistry of the catalytic reaction to favor the desired L isomer of the product (17). Active and stereoselective catalysts have been found and used in commercial practice, although there is now a more economical route to L-dopa than through hydrogenation of the prochiral precursor. [Pg.165]

In recent years the solid-phase hydrosilylation reaction was successfully employed for synthesis of hydrolytically stable surface chemical compounds with Si-C bonds. Of special interest is application of this method for attachment of functional olefins, in particular of acrolein and some chiral ligands. Such matrices can be used for subsequent immobilization of a wide range of amine-containing organic reagents and in chiral chromatography. [Pg.248]

The hydride-donor class of reductants has not yet been successfully paired with enantioselective catalysts. However, a number of chiral reagents that are used in stoichiometric quantity can effect enantioselective reduction of acetophenone and other prochiral ketones. One class of reagents consists of derivatives of LiAlH4 in which some of die hydrides have been replaced by chiral ligands. Section C of Scheme 2.13 shows some examples where chiral diols or amino alcohols have been introduced. Another type of reagent represented in Scheme 2.13 is chiral trialkylborohydrides. Chiral boranes are quite readily available (see Section 4.9 in Part B) and easily converted to borohydrides. [Pg.110]

The Sharpless-Katsuki asymmetric epoxidation reaction (most commonly referred by the discovering scientists as the AE reaction) is an efficient and highly selective method for the preparation of a wide variety of chiral epoxy alcohols. The AE reaction is comprised of four key components the substrate allylic alcohol, the titanium isopropoxide precatalyst, the chiral ligand diethyl tartrate, and the terminal oxidant tert-butyl hydroperoxide. The reaction protocol is straightforward and does not require any special handling techniques. The only requirement is that the reacting olefin contains an allylic alcohol. [Pg.50]

The AE reaction has been applied to a large number of diverse allylic alcohols. Illustration of the synthetic utility of substrates with a primary alcohol is presented by substitution pattern on the olefin and will follow the format used in previous reviews by Sharpless but with more current examples. Epoxidation of substrates bearing a chiral secondary alcohol is presented in the context of a kinetic resolution or a match versus mismatch with the chiral ligand. Epoxidation of substrates bearing a tertiary alcohol is not presented, as this class of substrate reacts extremely slowly. [Pg.54]

Asymmetric catalysis using chiral ligands, including cyclic phosphine or pyra-zole fragments covalent-bonded with ferrocene system 98PAC1477. [Pg.211]

To overcome these problems with the first generation Brmsted acid-assisted chiral Lewis acid 7, Yamamoto and coworkers developed in 1996 a second-generation catalyst 8 containing the 3,5-bis-(trifluoromethyl)phenylboronic acid moiety [10b,d] (Scheme 1.15, 1.16, Table 1.4, 1.5). The catalyst was prepared from a chiral triol containing a chiral binaphthol moiety and 3,5-bis-(trifluoromethyl)phenylboronic acid, with removal of water. This is a practical Diels-Alder catalyst, effective in catalyzing the reaction not only of a-substituted a,/ -unsaturated aldehydes, but also of a-unsubstituted a,/ -unsaturated aldehydes. In each reaction, the adducts were formed in high yields and with excellent enantioselectivity. It also promotes the reaction with less reactive dienophiles such as crotonaldehyde. Less reactive dienes such as isoprene and cyclohexadiene can, moreover, also be successfully employed in reactions with bromoacrolein, methacrolein, and acrolein dienophiles. The chiral ligand was readily recovered (>90%). [Pg.13]

A chiral titanium complex with 3-cinnamoyl-l,3-oxazolidin-2-one was isolated by Jagensen et al. from a mixture of TiCl 2(0-i-Pr)2 with (2R,31 )-2,3-0-isopropyli-dene-l,l,4,4-tetraphenyl-l,2,3,4-butanetetrol, which is an isopropylidene acetal analog of Narasaka s TADDOL [48]. The structure of this complex was determined by X-ray structure analysis. It has the isopropylidene diol and the cinnamoyloxazolidi-none in the equatorial plane, with the two chloride ligands in apical (trans) position as depicted in the structure A, It seems from this structure that a pseudo-axial phenyl group of the chiral ligand seems to block one face of the coordinated cinnamoyloxazolidinone. On the other hand, after an NMR study of the complex in solution, Di Mare et al, and Seebach et al, reported that the above trans di-chloro complex A is a major component in the solution but went on to propose another minor complex B, with the two chlorides cis to each other, as the most reactive intermediate in this chiral titanium-catalyzed reaction [41b, 49], It has not yet been clearly confirmed whether or not the trans and/or the cis complex are real reactive intermediates (Scheme 1.60). [Pg.39]

A remarkable change in reaction course is notable when changing the metal from aluminum to titanium for cydoaddition reactions using BINOL as the chiral ligand. When the chiral aluminum(III) catalyst is applied the cydoaddition product is the major product, whereas for the chiral titanium(IV) catalyst, the ene product is the major product. The reason for this significant change in reaction course is not fully understood. Maybe the glyoxylate coordinates to the former Le-... [Pg.166]


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Addition reactions chiral ligands

Allylic chiral ligands

Amino acids as chiral ligands

Applications of Chiral Phosphorous Ligands in Rhodium-Catalyzed Asymmetric Hydrogenation

As Chiral Auxiliaries and Ligands

Asymmetric ligands allylic derivatives, substitution reactions, chiral

Asymmetric transfer hydrogenation chiral amino alcohol ligand

Atropisomerically chiral ligand, BINAP

Axial chiral compounds ligands

Based Chiral Ligands in C-F Bond Forming Reactions

Bidentate ligand, chiral

Butenyl ligands chirality

C2 Symmetric chiral diphosphite ligands

Catalytic Reactions with Chiral Ligands

Central chirality bidentate ligands

Central chirality monodentate ligands

Chiral Auxiliaries and Ligands in Asymmetric Synthesis

Chiral Bisphosphane Ligands through Modifications of DuPhos and BPE

Chiral Ferrocene-based Bisphosphane Ligands

Chiral Ligands for Special Substrates

Chiral Monophosphorus Ligands

Chiral N, P Ligands

Chiral Phosphorus Ligands

Chiral Phosphorus Ligands for Stereoselective Hydroformylation

Chiral Schiff-base salen ligands

Chiral Separation by Ligand Exchange

Chiral amidinate ligands

Chiral amidophosphine ligands

Chiral aminophosphine chelate ligands

Chiral aminophosphine ligands

Chiral aminophosphine-phosphinite ligands

Chiral asymmetric ligands

Chiral atropisomeric biaryl bisphosphine ligands

Chiral bidentate phosphorus ligands

Chiral bidentate phosphorus ligands BINAP

Chiral binaphtholate ligands

Chiral binaphthyl ligand

Chiral biphosphine ligands

Chiral bisoxazoline ligand

Chiral bisphosphane ligands

Chiral bridging ligands

Chiral catalysts ligands

Chiral chelating ligands

Chiral complexes, drugs, ligands

Chiral compounds monodentate ligands

Chiral diaminophenolate ligands

Chiral diaza ligand

Chiral diene ligand

Chiral ferrocene based phosphine phosphoramidite ligands

Chiral ferrocene diphosphine ligand

Chiral ferrocenyldiphosphine ligand

Chiral formamide ligand

Chiral hydrophobic ligands

Chiral ligand acceleration

Chiral ligand asymmetrical synthesis

Chiral ligand elements

Chiral ligand exchange chromatograph

Chiral ligand exchange chromatography CLEC)

Chiral ligand phosphorus-based

Chiral ligand, -sparteine

Chiral ligand, chemical shifts

Chiral ligand-exchange

Chiral ligand-exchange CLEC)

Chiral ligand-exchange chromatography

Chiral ligand-exchange separations

Chiral ligand-exchange-type

Chiral ligand-exchangers

Chiral ligands 1.2] -Wittig rearrangement

Chiral ligands BINAP

Chiral ligands BINOL

Chiral ligands Fujiwara-Moritani reaction

Chiral ligands Lewis acid catalysts

Chiral ligands Subject

Chiral ligands TADDOL

Chiral ligands TADDOL catalysis with

Chiral ligands TADDOL-derived

Chiral ligands addition with

Chiral ligands alkyl halide carbonylation

Chiral ligands alkynylation

Chiral ligands allylic derivatives, substitution reactions

Chiral ligands asymmetric Heck reaction

Chiral ligands asymmetric amplification

Chiral ligands asymmetric hydrogenation

Chiral ligands bidentate phosphine

Chiral ligands carbene

Chiral ligands chlorohydrin synthesis

Chiral ligands design

Chiral ligands dioxaborolane

Chiral ligands disulfonamide

Chiral ligands enantioselectivity

Chiral ligands ferrocenes

Chiral ligands for asymmetric hydrosilylation

Chiral ligands future developments

Chiral ligands multidentate

Chiral ligands nitrogen-containing

Chiral ligands phosphoramidite

Chiral ligands salans

Chiral ligands sulfinyl groups

Chiral ligands sulfur-palladium complexes

Chiral ligands terpenes

Chiral ligands, Betti reaction

Chiral ligands, Sharpless asymmetric

Chiral ligands, Sharpless asymmetric hydroxylation reactions

Chiral ligands, bifunctional

Chiral ligands, introduced into polymers

Chiral ligands, preparation

Chiral ligands, uses

Chiral macrocyclic ligand

Chiral metal complexes ligand transformation

Chiral monodentate phosphite ligands

Chiral monodentate phosphoramidite ligands

Chiral monodentate phosphorus ligands

Chiral monophosphoramidite ligand

Chiral nonracemic ligands

Chiral norbomadiene ligand

Chiral oxazoline ligands

Chiral phases ligand exchange

Chiral phosphane ligands

Chiral phosphinamine ligands

Chiral phosphine ligand

Chiral phosphine-phosphite ligands containing a stereocenter in the backbone

Chiral phosphorous ligands

Chiral poly-NHC ligands

Chiral salen ligands

Chiral salicylaldimine ligands

Chiral spiro ligands

Chiral tertiary amine ligand

Chiral thioether ligands

Chiral tosylated diamine ligands

Chiral water soluble ligands

Chirality transfer bipyridine ligands

Chirality transfer ligands

Chirality transfer phosphite ligands

Chirality transfer via resolved bridging ligands

Chirality-Directed Self-Assembly An Enabling Strategy for Ligand Scaffold Optimization

Cinchona Alkaloids as Chiral Ligands in Asymmetric Oxidations

Cinchona chiral ligands

Coordinated ligands, chirality polymerization

Coordinated ligands, chirality polymerization mechanisms

Covalent chiral ligand/catalyst

DIOP ligands, chiral palladium complexes

Davankov ligand exchange chiral

Diamine ligands, chiral

Dinitrogen ligands, chiral

Diphosphine ligand, chiral

Duphos chiral ligand

Effect of chiral ligand

Enantioselective Synthesis or Resolution of Chiral Ligands

Enantioselective addition chiral ligands

Ferrocene derivatives chiral ligands

Ferrocene-based chiral ligands

Ferrocenyloxazolines, chiral ligands

General Features of Chiral Ligands and Complexes

Hayashi-Miyaura reaction chiral ligands

Helical chiral phosphorus ligand

Helically chiral ligands

Hexadentate chiral ligand

High-Throughput Screening of Chiral Ligands and Activators

High-throughput screening chiral ligands

Hydrogenation, catalytic, alkene chiral ligands

INFLUENCE OF CHIRAL LIGANDS

Lewis acids chiral acid-ligand system

Ligand chiral sulfoxide

Ligand chiral tertiary phosphine

Ligand containing chiral phosphine

Ligand exchange chiral selectors

Ligand structures chirality

Ligand, Chiral bipyridine

Ligand-exchange chiral stationary phases

Ligand-exchange chromatography chiral separations

Ligands chiral Schiff base

Ligands chiral amino alcohol-based

Ligands chiral binaphthyl ligand

Ligands chiral bisphospholane

Ligands chiral chelate

Ligands chiral geometry

Ligands chiral phosphines, influence

Ligands chirality

Ligands chirality

Ligands external chiral

Ligands planar chiral

Ligands, chiral reaction

Ligands, chiral, immobilization

Ligands, chirally selective

Lithium aluminum hydride chiral ligands

Macrocyclic ligands chirality

Metal Complexes of Chiral Ligands

Metallomesogens Where the Metal and Ligands Generate Helical Chirality

Monodentate chiral ligands

Monodentate chiral ligands phosphites

Monodentate chiral ligands phosphonites

Monodentate chiral ligands phosphoramidites

New Chiral Ligands Based on Substituted Heterometallocenes

New chiral benzothiazine ligand for catalysis and molecular recognition

Nickel catalysts chiral oxazoline ligands

Nontransferable ligands chiral

Organolithium reagents chiral ligands

Organolithium reagents, external chiral ligands

Other Water-soluble Chiral Ligands

Oxazoline-based chiral ligands

P-chiral Bisphosphane Ligands

Paracyclophanes as Chiral Ligands

Phosphaferrocene ligands, planar chirality

Phosphinooxazolines ligands , chiral

Planar Chiral Ferrocene ligands

Planar chiral compounds bidentate ligands

Poly-NHCs ligands chiral

Polydentate ligands chirality

Protic chiral ligands

Pyrrolidine 2- -: chiral ligand

Pyrrolidine, chiral copper ligand

Reaction of Other Organometals Using External Chiral Ligands

Reaction of homoorganocoppers using external chiral ligands

Reaction of organozinc using external chiral ligands

Reactivity chiral aminophosphine ligands

Rhodium catalyzed asymmetric chiral 1,4 diphosphine ligands

Rhodium different chiral ligands

Ruthenium complexes chiral chelating ligands

Ruthenium compounds with chiral ligand

Segphos chiral ligand

Stereoinduction from chiral ligands on the enolate metal

Sulfoxide complexes of chiral ligands

Tethered chiral ligands

Tetradentate chiral ligand

Titanium complexe chiral ligand

Tridentate chiral ligands

Tridentate chiral ligands, enantioselective

Zinc catalysts supported by chiral diaminophenolate ligands

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