Showing papers on "Nucleophile published in 1998"
TL;DR: The first example of the catalytic asymmetric oxidation of tert-butyl disulfide is described and thiosulfinate ester 2 is obtained with 91% enantiomeric excess in yields of ≥92% on scales as large as 1 mol.
Abstract: The first example of the catalytic asymmetric oxidation of tert-butyl disulfide (1) is described. The product, tert-butyl tert-butanethiosulfinate (2) is obtained with 91% enantiomeric excess in yields of ≥92% on scales as large as 1 mol. The application of H2O2 as stoichiometric oxidant in the presence of 0.25 mol % of VO(acac)2 and 0.26 mol % of a chiral Schiff base ligand, 6a, is both convenient and cost-effective. Thiosulfinate ester 2 is chemically and optically stable and serves as an excellent precursor to chiral tert-butanesulfinyl compounds by the stereospecific nucleophilic displacement of tert-butyl thiolate. Addition of LiNH2 in liquid ammonia and THF provides tert-butanesulfinamide (3; 91% yield). A single recrystallization provides enantiomerically pure 3 in 71−75% overall yield from disulfide 1. Enantiomerically pure thiosulfinate ester 2 also reacts readily and stereospecifically with Grignard reagents, organolithiums, lithium amides, and lithium imine salts to provide enantiomerically pur...
316 citations
TL;DR: Comparing the behavior of the ionic reaction in the gas phase with that in solution is compared and the relation of structure and reactivity, and the effects of small numbers of solvent molecules on the reaction are reviewed.
Abstract: Nucleophilic displacement reactions (the SN2 reaction) of ions in the gas phase are a prototypical reaction system that allows a study of dynamics, mechanisms, and structure-energy relations. This article reviews aspects of the kinetics (especially the applicability of statistical reaction rate theory), the relation of structure and reactivity, and the effects of small numbers of solvent molecules on the reaction and compares the behavior of the ionic reaction in the gas phase with that in solution.
264 citations
TL;DR: In this article, a chiral PCP-type ligand with PdCl2(PhCN)2 and [Pt2(μ-Cl)2(η3-CH2C(CH3)CH2)2] was obtained for the first time and their X-ray crystal structures were determined.
192 citations
TL;DR: In this article, a metal insertion into the strong sp2−sp3 aryl−O bond was shown to occur directly, with no intermediacy of C−H activation or insertion into adjacent weaker ArO−CH3 bond.
Abstract: Reaction of [RhCl(C8H14)2]2 (C8H14 = cyclooctene) with 2 equiv of the aryl methyl ether phosphine 1 in C6D6 results in an unprecedented metal insertion into the strong sp2−sp3 aryl−O bond. This remarkable reaction proceeds even at room temperature and occurs directly, with no intermediacy of C−H activation or insertion into the adjacent weaker ArO−CH3 bond. Two new phenoxy complexes (8 and 9), which are analogous to the product of insertion into the ArO−CH3 bond (had it taken place) were prepared and shown not to be intermediates in the Ar−OCH3 bond cleavage process. Thus, aryl−O bond activation by the nucleophilic Rh(I) is kinetically preferred over activation of the alkyl−O bond. The phenoxy Rh(I)−η1-N2 complex (8) is in equilibrium with the crystallographically characterized Rh(I)−μ-N2−Rh(I) dimer (12). Reaction of [RhCl(C8H14)2]2 with 2 equiv of the aryl methyl ether phosphine 2, PPh3, and excess HSiR3 (R = OCH2CH3, CH2CH3) results also in selective metal insertion into the aryl−O bond and formation o...
161 citations
TL;DR: The development of enantioselective Lewis acid catalyzed carbonyl addition reactions of π-nucleophiles such as enolsilanes and allylstannanes is a topic of current interest.
Abstract: The development of enantioselective Lewis acid catalyzed carbonyl addition reactions of π-nucleophiles such as enolsilanes and allylstannanes is a topic of current interest.1 The extension of this general process to include simple olefinic nucleophiles via the carbonyl-ene reaction2 has important practical implications. In this context, Mikami and Nakai have reported a catalytic enantioselective ene reaction with glyoxylate esters;3 however, due to the limiting reactivity of the catalyst-glyoxylate complex,4 only nucleophilic 1,1-disubstituted olefins may be employed. We have recently reported that bidentate bis(oxazolinyl) (box) Cu(II) complexes 1-3 are effective enantioselective catalysts in Diels-Alder5 and aldol reactions6 with substrates that can participate in catalyst chelation. In this study, we demonstrate that
157 citations
TL;DR: A calix[4]arene derivative 2-[Cu(II)]2 with two cis-diaqua Cu(II) centers at the distal positions of the upper rim was synthesized and investigated as a model for dinuclear metalloenzymes that catalyze chemical transformations of phosphate esters as discussed by the authors.
Abstract: A calix[4]arene derivative 2-[Cu(II)]2 functionalized with two cis-diaqua Cu(II) centers at the distal positions of the upper rim was synthesized and investigated as a model for dinuclear metalloenzymes that catalyze chemical transformations of phosphate esters. The flexible dinuclear calix[4]arene efficiently catalyzes the transesterification of the RNA model 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) and the hydrolysis of the DNA model ethyl-p-nitrophenyl phosphate (EPNP) with turnover conversion, thereby exhibiting rate enhancement factors of 1.0 × 104 and 2.7 × 104, respectively. The mononuclear reference complex, 3-Cu(II), lacking the macrocyclic backbone, has a much lower activity, showing that the high catalytic activity of the dinuclear calix[4]arene complex is due to synergetic action of the two Cu(II) centers. Saturation kinetics and pH variation studies point to the formation of a Michaelis-Menten complex in which the phosphate group is doubly Lewis acid activated by coordination to the two Cu(II) centers. In this complex, a Cu(II) bound hydroxide ion, which is present already at pH 6.5, can act as a base in the intramolecular transesterification of HPNP or as a nucleophile in the hydrolysis of EPNP. The remarkably low pKa of the Cu(II) bound water molecules in the hydrophobic calix[4]arene 2-[Cu(II)]2 mimics the low pKa of metal bound water molecules in hydrophobic enzyme active sites, which makes the enzyme (model) active under slightly acidic to neutral conditions. The high catalytic efficiency of this enzyme model is attributed to a dynamic binding of the substrate and (pre)transition state, possible by rapid low energy conformational changes of the flexible calix[4]arene backbone.
150 citations
TL;DR: Glycosyl donors based on the 2,6-di-O-acyl-3,4-Oisopropylidene-d-galactopyranosyl-(leaving group) structure have been shown experimentally to have a high propensity for giving acyl transfer to the alcohol nucleophile as major side products in the glycosylation reaction.
Abstract: Glycosyl donors based on the 2,6-di-O-acyl-3,4-O-isopropylidene-d-galactopyranosyl-(leaving group) structure have been shown experimentally to have a high propensity for giving acyl transfer to the alcohol nucleophile as major side products in the glycosylation reaction The corresponding cations of these relatively rigid glycosyl donors were investigated by density functional methods The precursor cations resulting from neighboring group assistance from the 2-O-acyl group were found to be the most stable The nucleophile methanol most favorably approaches the LUMO of such cations on the former carbonyl carbon The resulting stable intermediate has a long C−O bond of 279 A It is suggested that such intermediates can lead to both acyl transfer and β-glycoside after passing through at least one further transition state
149 citations
TL;DR: The third in a series that summarises organic reactions performed on solid supports is presented in a graphical abstract format and examples are given of the following reactions: amide formation, aromatic substitution (nucleophilic/electrophilic), cleavage, condensation, cycloaddition, deprotection/protection, Grignard and related reactions.
146 citations
TL;DR: Carbenoid, electrophilic and carbanionic, nucleophilic character is shown by compounds 1, which bear a lithium atom and an electronegative element X as leaving group at the vinyl carbon center.
Abstract: Carbenoid, electrophilic and carbanionic, nucleophilic character is shown by compounds 1, which bear a lithium atom and an electronegative element X as leaving group at the vinyl carbon center. Now that structural investigations have contributed significantly to their understanding, these ambiphilic, thermally unstable compounds are increasingly being used as reagents for synthetic purposes.
127 citations
TL;DR: In this paper, the clay has been found to be an efficient catalyst in transesterifying long chain alcohols, unsaturated alcohols and phenols to give their corresponding β-keto esters in high yields.
Abstract: Transesterification and transthiolesterification of β-keto esters with variety of alcohols and thiols and selective protection of carbonyl functions with various protecting groups catalyzed by natural kaolinitic clay are described. The clay has been found to be an efficient catalyst in transesterifying long chain alcohols, unsaturated alcohols, and phenols to give their corresponding β-keto esters in high yields. For the first time, transthiolesterification of β-keto esters with a variety of thiols has been achieved under catalytic conditions. Clay also catalyzes selective transesterification of β-keto esters by primary alcohols in the presence of secondary and tertiary alcohols giving corresponding β-keto esters. A systematic study involving the reactivity of different nucleophiles (alcohols, amines, and thiols) toward β-keto esters is also described. Sterically hindered carbonyl groups as well as α,β-unsaturated carbonyl groups underwent protection without the deconjugation of the double bond. Chemosele...
122 citations
TL;DR: Docking experiments with the four possible ortho transition states of the reaction explain the specific exo effect and suggest that the (3R,4R)-exo stereoisomer is the preferred product.
Abstract: A highly specific Diels-Alder protein catalyst was made by manipulating the antibody repertoire of the immune system. The catalytic antibody 13G5 catalyzes a disfavored exo Diels-Alder transformation in a reaction for which there is no natural enzyme counterpart and that yields a single regioisomer in high enantiomeric excess. The crystal structure of the antibody Fab in complex with a ferrocenyl inhibitor containing the essential haptenic core that elicited 13G5 was determined at 1.95 angstrom resolution. Three key antibody residues appear to be responsible for the observed catalysis and product control. Tyrosine-L36 acts as a Lewis acid activating the dienophile for nucleophilic attack, and asparagine-L91 and aspartic acid-H50 form hydrogen bonds to the carboxylate side chain that substitutes for the carbamate diene substrate. This hydrogen-bonding scheme leads to rate acceleration and also pronounced stereoselectivity. Docking experiments with the four possible ortho transition states of the reaction explain the specific exo effect and suggest that the (3R,4R)-exo stereoisomer is the preferred product.
TL;DR: In this article, a mechanism for the olefination reaction involving PdII/PdIV was proposed, in which a key step is reversible nucleophilic attack on the Pd II-coordinated olefin to give an electron-rich σ-alkyl- or, with carbonate, a chelated σdialkyl-complex, which then oxidatively adds the organic halide e.g. ArX.
Abstract: A mechanism for the olefination reaction is proposed, involving PdII/PdIV, in which a key step is reversible nucleophilic attack on the PdII-coordinated olefin to give an electron-rich σ-alkyl- or, with carbonate, a chelated σ-dialkyl-complex, which then oxidatively adds the organic halide e.g. ArX. Loss of nucleophile, migration of Ar from PdIV to coordinated olefin, β-hydrogen elimination and loss of HX then gives the product of olefination and regenerates the PdII catalyst.
TL;DR: In this article, the authors proposed a new reagent CF3H/Base/DMF for trifluoromethyl aryl alcohols, ketones or sulfides.
TL;DR: In this paper, the complete mechanistic sequence of the atropo-diastereoselective ring opening reaction of configuratively unstable lactone-bridged biaryls with the chiral 2R,5R-1-lithio-2,5-dimethylpyrrolidine was calculated using the semi-empirical PM3 method.
Abstract: The complete mechanistic sequence of the atropo-diastereoselective ring opening reaction of configuratively unstable lactone-bridged biaryls with the chiral 2R,5R-1-lithio-2,5-dimethylpyrrolidine was calculated using the semiempirical PM3 method. It was shown that the stereochemically deciding key step of the reaction sequence is the first attack of the chiral nucleophile to the carbon atom of the lactone moiety. The diastereoselectivity of this synthetically useful and mechanistically challenging biaryl synthesis was found to originate from a dynamic kinetic resolution of the axially chiral, but configuratively unstable lactone substrates. For a further understanding of the complex stereochemical process, the geometries resulting from IRC-calculations have been visualized and are presented as an Quicktime-movie.
TL;DR: In this paper, an aza-Payne rearrangement of N-activated 2-aziridinemethanols, synthesized in an optically active form, with potassium tert-butoxide (ButOK), potassium hydride (KH), or sodium hydrides (NaH) at near 0 °C in common aprotic solvents such as tetrahydrofuran (THF), toluene, or a mixed solvent of THF-HMPA followed by quenching at low temperature gives the corresponding epoxy sulfon
Abstract: An aza-Payne rearrangement of N-activated 2-aziridinemethanols, synthesized in an optically active form, with potassium tert-butoxide (ButOK), potassium hydride (KH), or sodium hydride (NaH) at near 0 °C in common aprotic solvents such as tetrahydrofuran (THF), toluene, or a mixed solvent of THF–HMPA followed by quenching at low temperature gives the corresponding epoxy sulfonamides in high yields. The anionic reaction intermediates, generated by treatment of 2-aziridinemethanols with a base, react readily in a one-pot manner with a variety of nucleophiles such as organocopper reagents, thiols, and trimethylsilyl cyanide to yield the optically active corresponding functionalized 1,2-amino alcohols in good yields. Upon exposure of 2,3-epoxy amines to an equimolar mixture of ButOK and BuLi (super base) in a mixed solvent of THF and n-hexane at –78 °C, the equilibrium lies exclusively toward the hydroxyaziridine forming direction.
TL;DR: The mechanism of hydrolysis of the metallo-β-lactamase involves a dianionic tetrahedral intermediate stabilised by zinc(II) and the rate enhancement may be greater than 109 if the mechanism occurs by an inhibitor assisted reaction involving intramolecular general acid catalysis.
TL;DR: These findings crystallographically demonstrate that the enzyme reaction proceeds through the formation of an ester intermediate with the enzyme’s nucleophile Asp-10, and may play an important role in stabilizing the alkyl group of the substrate moiety through hydrophobic interactions and in determining the stereospecificity of the enzyme.
ARCO1
TL;DR: The beta-glycosidase from the hyperthermophilic Archaeon Sulfolobus solfataricus hydrolyzes beta- Glycosides following a retaining mechanism based upon the action of two amino acids, which acts as the nucleophile of the reaction.
Abstract: The β-glycosidase from the hyperthermophilic Archaeon Sulfolobus solfataricus hydrolyzes β-glycosides following a retaining mechanism based upon the action of two amino acids: Glu387, which acts as the nucleophile of the reaction, and Glu206, which acts as the general acid/base catalyst. The activities of inactive mutants of the catalytic nucleophile Glu387Ala/Gly were restored by externally added nucleophiles. Sodium azide and sodium formate were used as external nucleophiles and the products of their reaction were characterized. Glu387Ala/Gly mutants were reactivated with 2,4-DNP-β-Glc substrate and the Glu387Gly mutant showed recovered activity, with the same nucleophiles, also on 2-NP-β-Glc. The reaction catalyzed by the Glu387Gly mutant proceeded differently depending on the type of externally added nucleophile. Sodium azide restored the catalytic activity of the mutant by attacking the α-side of the anomeric carbon of the substrates, thereby yielding an inverting glycosidase. Sodium formate promote...
TL;DR: A hyperbranched polyfluorinated benzyl ether polymer was prepared from the A2B monomer 3,5-bis[(pentafluorobenzyl)oxy]benzyl alcohol.
Abstract: A hyperbranched polyfluorinated benzyl ether polymer was prepared from the A2B monomer 3,5-bis[(pentafluorobenzyl)oxy]benzyl alcohol The polymerization was based upon deprotonation of the benzylic alcohol (B), followed by nucleophilic substitution of the p-fluorines of the two pentafluorophenyl (A) groups to form tetrafluorophenyl benzyl ether linkages Optimized reaction conditions for the polymerization involved the addition of sodium metal (<01 mm particle size, 30 wt % suspension in toluene) to a solution of monomer (03 M) in THF heated at reflux The molecular weight and molecular-weight distribution of the resulting polymer were affected by the surface area of the sodium particles, the concentration of the monomer, and the polymerization temperature An average of one pentafluorophenyl chain end per repeat unit plus one pentafluorophenyl end group was present within the hyperbranched polymer, which allowed for chemical modification by nucleophilic displacement reactions upon the p-fluorines, to a
TL;DR: In this article, the second-order rate laws of benzhydryl cations with 19 silyl enol cations, four silyyl ketene acetals, and two alkyyl enol ethers have been determined photometrically in dichloromethane solution.
Abstract: The kinetics of the reactions of benzhydryl cations with 19 silyl enol ethers, four silyl ketene acetals, and two alkyl enol ethers have been determined photometrically in dichloromethane solution. All reactions reported in this investigation follow second-order rate laws, and the rates are independent of the nature of the complex counterion (BF4-, F3CSO3-, or ZnCl3-) in accord with rate-determining C−C bond formation. The nucleophilic reactivities span over a range of 108 from the vinyl ethers 1a,x as the least reactive compounds (comparable to allylsilanes) to the highly nucleophilic silyl ketene acetal 1u (comparable to enamines). Linear free enthalpy relationships are used to compare the reactivities of these compounds with those of other aliphatic and aromatic π-nucleophiles.
TL;DR: In this article, the group electronegativity of the ferrocenyl group is found to be 1.87 (Gordy scale) as inferred from a linear β-diketone pKa1-group electricity relationship.
Abstract: 1-Ferrocenyl-4,4,4-trifluorobutane-1,3-dione (ferrocenoyltrifluoroacetone, Hfctfa, pKa1 = 6.53 ± 0.03), 4,4,4-trichloro-1-ferrocenylbutane-1,3-dione (trichloroferrocenoylacetone, Hfctca, pKa1 = 7.15 ± 0.02), 1-ferrocenylbutane-1,3-dione (ferrocenoylacetone, Hfca, pKa1 = 10.01 ± 0.02), 1-ferrocenyl-3-phenylpropane-1,3-dione (benzoylferrocenoylmethane, Hbfcm, pKa1 = 10.41 ± 0.02) and 1,3-diferrocenylpropane-1,3-dione (diferrocenoylmethane, Hdfcm, pKa1 = 13.1 ± 0.1) were prepared by Claisen condensation of acetylferrocene with an appropriate ester under the influence of sodium amide, sodium ethoxide or lithium diisopropylamide. The group electronegativity of the ferrocenyl group is 1.87 (Gordy scale) as inferred from a linear β-diketone pKa1–group electronegativity relationship as well as from a linear methyl ester IR carbonyl stretching frequency–group electronegativity relationship. Complexes [Rh(β-diketone)(cod)] were obtained in yields approaching 80% by treating the β-diketones with [Rh2Cl2(cod)2], while the copper(II) chelates form just as readily. Treatment of all [Rh(β-diketone)(cod)] complexes with 1,10-phenanthroline (phen) and some of its derivatives resulted in substitution of the β-diketone ligand to form [Rh(cod)(phen)]+. The uncomplexed β-diketones are increasingly stable towards the OH– nucleophile in the order Hdfcm (apparent most unstable) < Hfctfa < Hbfcm < Hfctca < Hfca (most stable). Asymmetric enolisation in the direction furthest from the ferrocenyl group was observed for all β-diketones. This finding is considered to be the result of resonance driving forces rather than inductive electronic effects of substituents on the pseudo-aromatic β-diketone core.
TL;DR: E138A yields the beta-glycosyl azide product arising from nucleophilic attack of azide on the glycosyl-enzyme intermediate of retaining glycosidases, thus proving that Glu138 is the general acid-base residue.
Abstract: The role of the key catalytic residues Glu134 and Glu138 in the retaining 1,3-1,4-beta-glucanase from Bacillus licheniformis is probed by a chemical rescue methodology based on enzyme activation of inactive mutants by the action of added nucleophiles. While Glu134 was proposed as the catalytic nucleophile on the basis of affinity labeling experiments, no functional proof supported the assignment of Glu138 as the general acid-base catalyst. Alanine replacements are prepared by site-directed mutagenesis to produce the inactive E138A and E134A mutants. Addition of azide reactivates the mutants in a concentration-dependent manner using an activated 2, 4-dinitrophenyl glycoside substrate. The chemical rescue operates by a different mechanism depending on the mutant as deduced from 1H NMR monitoring and kinetic analysis of enzyme reactivation. E138A yields the beta-glycosyl azide product arising from nucleophilic attack of azide on the glycosyl-enzyme intermediate, thus proving that Glu138 is the general acid-base residue. Azide activates the deglycosylation step (increasing kcat), but it also has a large effect on a previous step (as seen by the large decrease in KM, the increase in kcat/KM, and the pH dependence of activation), probably increasing the rate of glycosylation through Bronsted acid catalysis by enzyme-bound HN3. By contrast, azide reactivates the E134A mutant through a single inverting displacement to give the alpha-glycosyl azide product, consistent with Glu134 being the catalytic nucleophile. Formate as an exogenous nucleophile has no effect on the E138A mutant, whereas it is a better activator of E134A than azide. Although the reaction yields the normal hydrolysis product, a transient compound was detected by 1H NMR, tentatively assigned to the alpha-glycosyl formate adduct. This is the first case where a nonmodified sugar gives a long-lived covalent intermediate that mimics the proposed glycosyl-enzyme intermediate of retaining glycosidases.
TL;DR: In this article, the imido hydride complex Cp*2Ta(NCMe3)H (Cp* = (η5-C5Me5)) with [Ph3C][B(C6F5)4] in tetrahydrofuran solution yields the cationic imido complex [Cp * 2Ta(NHCMe3)(THF)][B 6F5] (1).
TL;DR: In this article, the role of the Lewis acid in the Friedel-Craft's reaction was investigated theoretically by performing high-level ab initio calculations on two model systems C6H6−BCl3 and C6 H6−AlCl3.
Abstract: Electrophilic aromatic substitution reactions, which are highly exemplified by the widely used Friedel-Craft's reaction, have been extensively studied using theoretical and experimental techniques. A number of elegant mechanisms have been proposed for the Friedel-Craft's reaction till date. In all the proposed mechanisms, the role of the Lewis acid has been limited to the generation of the electrophile, which subsequently attacks the aromatic system to form either a π or a σ complex. A recent experimental report on the reaction of CO with benzene in zeolite catalysts intrigued us because the presence or absence of AlCl3 was found to govern the reaction product. These clearly indicated that AlCl3 has an additional role in the reaction. We probed this role theoretically by performing high-level ab initio calculations on two model systems C6H6−BCl3 and C6H6−AlCl3. Our results clearly indicate that one of the benzene carbon tends to become highly nucleophilic, thereby facilitating an attack by an incipient el...
TL;DR: In this paper, the application of the rhodium(COD) complexes as catalysts in an asymmetric hydrosilylation reaction has been examined, resulting in enantiomeric excesses of up to 44%.
Abstract: Deprotonation of chiral triazolium salts 1 and reaction of the resulting nucleophilic carbenes with [(COD)RhCl]2 or [(NBD)RhCl]2 afforded square-planar complexes 2–6 in yields of 65–95%. The complexes contain an axis of chirality and a diastereomeric excess of up to 97% was achieved. The relative and absolute configurations of these complexes were determined by NMR spectroscopic investigations and X-ray structure analysis. The application of the rhodium(COD) complexes as catalysts in an asymmetric hydrosilylation reaction has been examined, resulting in enantiomeric excesses of up to 44%. Similar results were achieved for aromatic and aliphatic ketones and a nonlinear temperature effect (principle of isoinversion) was observed.
TL;DR: In this article, two title reactions were investigated by means of ab initio molecular orbital calculations, and their enhanced reactivities were attributed to the stability of the silyl cation and a hypervalent intermediate.
Abstract: The two title reactions were investigated by means of ab initio molecular orbital calculations. Under neutral conditions, the hydrolysis of methylmethoxydihydroxysilane was examined, and the water-trimer cluster was found to be a reactant for ready bond interchange. The condensation of methyltrihydroxysilane was caused by the participation of the water dimer. Two of the observed reactions involved a front-side nucleophilic attack to the silicon center or a similar mechanism. Acid- and base-promoted hydrolyses were also examined, and their enhanced reactivities were ascribed to the stability of the silyl cation and a hypervalent intermediate, respectively.
TL;DR: In this article, three ruthenium complexes that bear π-bound nitrogen heterocycles have been synthesized, and it is established that these complexes serve as effective nucleophilic catalysts for a range of processes, including the acylation of alcohols with diketene and the ring opening of azlactones.
Abstract: Three ruthenium complexes that bear π-bound nitrogen heterocycles have been synthesized. It is established that these complexes serve as effective nucleophilic catalysts for a range of processes, including the acylation of alcohols with diketene, the ring opening of azlactones, and the addition of alcohols to ketenes; their activity is comparable to or somewhat greater than the corresponding iron catalysts. The relative efficiency of the ruthenium complexes as asymmetric catalysts is also evaluated: in the kinetic resolution of secondary alcohols, ruthenium is markedly less effective than iron, but in the deracemization/ring opening of azlactones, ruthenium is slightly more enantioselective. This study documents for the first time the impact of the metal on the reactivity and on the enantioselectivity of nucleophilic catalysts based on π-bound nitrogen heterocycles.
TL;DR: In this paper, the 1,3-diphenylallyl Pd(II) complexes were shown to exist in solution as a mixture of (syn/syn) exo and endo diastereomeric complexes.