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Compared with chiral β3-amino phosphorus compounds, which can be easily derived from natural optically pure α-amino acids, obtaining chiral β2-amino phosphorus derivatives remains a challenge. These derivatives, which cannot be derived from chiral natural amino acids, possess unique biological activities or potential catalytic activities. Herein, highly enantioselective hydrogenation for the preparation of chiral β2-amino phosphorus derivatives from E-β-enamido phosphorus compounds is reported by using a green and low-cost earth-abundant metal nickel catalyst (13 examples of 99% ee). In particular, this catalytic system provides the same enantiomer product from the E- and Z-alkene substrates, and the E/Z-substrate mixtures provide good results (up to 96% ee). The products can be diversely derivatized, and the derivatives exhibit good catalytic activities as novel chiral β2-aminophosphine ligands. Density functional theory calculations reveal that the weak attractive interactions between the nickel catalyst and the substrate are crucial for achieving perfect enantioselectivities. In addition, the different coordination modes between the E- or Z-substrates and the catalyst may result in the formation of the same enantiomer product.

Chiral hydroxylamines are vital substances in bioscience and versatile subunits in the preparation of a variety of functional molecules. However, asymmetric and non-asymmetric synthetic approaches to these compounds are far from satisfactory. Although atom-economic metal-catalysed asymmetric hydrogenations have been studied for over 50 years, the asymmetric hydrogenation of oximes to the corresponding chiral hydroxylamines remains challenging because of the labile N–O bond and inert C=N bond. Here we report an environmentally friendly, earth-abundant, transition-metal nickel-catalysed asymmetric hydrogenation of oximes, affording the corresponding chiral hydroxylamines with up to 99% yield, 99% e.e. and with a substrate/catalyst ratio of 1,000. Computational results indicate that the weak interactions between the catalyst and substrate play crucial roles not only in the transition states, but also during the approach of the substrate to the catalyst, by selectively reducing the reaction barriers and thus improving the reaction efficiency and securing the generation of chirality.

A novel intermolecular tandem oxidative aromatic coupling between arylidene fluorenes and unfunctionalized aromatics mediated by a DDQ/TFA oxidation system has been developed for the construction of 9,10-diarylphenanthrenes (DAPs). The formation of a benzylic carbocation species possessing a quaternary sp3-carbon center on the fluorene moiety by an intermolecular oxidative Friedel–Crafts reaction of two different arenes successfully triggered the subsequent ring expansion to afford DAPs.

Significant solvent effects on enantioselection exist in the reaction of Cu-catalyzed asymmetric conjugate addition of alkylzinc reagents to a,ß-unsaturated carbonyl compounds. Results of our DFT study suggest that solvent effects on enantioselection can be caused by structural changes in the stereodetermining Transition States (TS). We have seen how unconventional hydrogen bonding of the nucleophilic solvent results in a change of the computed optical yield comparable to that caused by well-known coordination of the solvent to the electrophilic metal center. Significant solvent effects on enantioselection exist in the reaction of Cu-catalyzed asymmetric conjugate addition of alkylzinc reagents to a,ß-unsaturated carbonyl compounds. Results of our DFT study suggest that solvent effects on enantioselection can be caused by structural changes in the stereodetermining Transition States (TS). We have seen how unconventional hydrogen bonding of the nucleophilic solvent results in a change of the computed optical yield comparable to that caused by well-known coordination of the solvent to the electrophilic metal center.

Recent observation of the acetal species in the course of autoamplifying Soai reaction was analysed by the formal kinetic analysis of the experimental data and DFT computations. Kinetic analysis demonstrated convincingly that the observed species cannot be a precursor of the reaction product. Hence, it is an off-loop species that is not important for the process of the chirality amplification. DFT search for a kinetically stable acetal species resulted in the location of a Zn3cluster stabilized with three Zn–O–Zn bridges.

DFT (density functional theory) computations of the chemical fixation of copper ions on the naturally functionalized surface of nanodiamond crystallites bound by (111) planes revealed exothermic formation of chelate Cu complexes with two appropriately located carboxylic groups on the (111) surface. The irreversible strict fixation of copper ions is achieved via removing acetic acid in low-pressure conditions yields the corresponding chelate complexes not bearing any other ligands except for the surface carboxylic groups. Optimization of positional isomers of the chelating complexes showed that complexation is more likely to take place near the edges (linear ribs) of the nanoparticle. Nearby functional groups like –F, –Cl, or –OH substituents on the surface strongly affect the structures and stabilities of the resulting chelate complexes. Some of the copper atoms may be incorporated into unusual Cu(III) complexes with Cu–C covalent bonds.

Transformation of C–F to C–O bond mediated by bifunctional ruthenium and iridium complexes is described. This reaction proceeds through water O–H bond cleavage via metal–ligand cooperation in the newly developed 16e bifunctional ruthenium and iridium complexes bearing chiral (S,S)-C6F5SO2-dpen ligand. The 16e Ru amido complex, [Ru{(S,S)-Pfbsdpen}(η6-hmb)] (1a), readily reacted with water at room temperature producing oxometallacyclic compound, (R)-[Ru{κ3(N,N′,O)-(S,S)-OC6F4SO2dpen}(η6-hmb)] (3aR), as a result of bifunctional water activation followed by ortho-oxometallation via SNAr. Complex 3aRcan be prepared either from 1aor, more conveniently from its 18e chlorido precursor, complex (R)-[RuCl{(S,S)-Pfbsdpen}(η6-hmb)]. On the contrary, the 16e Ir amido complex, [Cp*Ir{(S,S)-Pfbsdpen}] (2), is kinetically stable toward water at room temperature. Oxometallacyclic compound (R)-[Cp*Ir{κ3(N,N′,O)-(S,S)-OC6F4SO2dpen}] (4R) was prepared in high yield by the reaction of [Cp*IrCl2]2with 2 equiv of (S,S)-Pfbsdpen in the presence of KOH under reflux in THF. In either case 3Ror 4Ris obtained as a single diastereomer, the structure of which has been determined by single-crystal X-ray diffraction studies in solid state and NMR-analysis in solution. Reaction mechanism was studied by NMR spectroscopy combined with continuum solvent reaction-field density functional theory (DFT) analysis. Experimental studies showed that diastereoselective oxocyclometallation 1a→ 3aRproceeds at temperatures >0 °C in a stepwise manner through the detectable intermediate, hydroxo complex (R)-[Ru(OH){(S,S)-Pfbsdpen}(η6-hmb)] (6aR), which exists in equilibrium with less-populated diastereomer (S)-[Ru(OH){(S,S)-Pfbsdpen}(η6-hmb)] (6aS) in 10:1 ratio at −80 °C in CD2Cl2. Computational analysis essentially explains the diastereoselectivity in this reaction via a significant difference in the stabilities of the corresponding transition states: although diastereomers 6aRand 6aSare in equilibrium via complex 1a, only 6aRis transformed into 3aRvia rate-determining Meisenheimer-type transition state.

The mechanism of two enantioselective reactions, direct amination of a-cyanoacetates 3with azodicarboxylates 4and C–C bond formation reaction of a-cyanoacetates with acetylenic esters 6, catalyzed by chiral bifunctional Ir and Ru complexes, Cp*Ir[(S,S)-N-sulfonated dpen] 1and Ru[(S,S)-N-sulfonated dpen](?6-arene) 2(DPEN: 1,2-diphenylethylenediamine) was studied by NMR spectroscopic analysis combined with DFT analysis. Notably, these two reactions using the same chiral amide catalysts 1, 2and pronucleophile, a-cyanoacetates 3gave quantitatively the conjugate adducts bearing quaternary chiral carbon centers in excellent enantiomeric excess albeit with the opposite absolute configuration depending on the acceptor molecules 4and 6. NMR investigation of the reactions between Ir complexes 1a–1cwith a-cyanoacetates 3showed that a stereoselective deprotonation reaction takes place to give an equilibrium mixture of N-bound amine complexes 8and 9, the former with intramolecular hydrogen bonding and the latter without it, respectively. Computational study revealed the full details of the mechanism of the asymmetric C–N and C–C bond forming reactions catalyzed by the chiral Ir catalyst 1b. In the C–N bond forming reaction, the dimethyl azodicarboxylate 4aundergoes productive bifunctional activation by a non-hydrogen-bonded N-bound complex 9b(re)resulting in the formation of the R-product through the energetically favorable transition state. On the other hand, the linear geometry of the acetylenic ester molecule 6allows its bifunctional activation with both types of the N-bound complexes: 8band 9bwith and without the intramolecular hydrogen bond respectively. The hydrogen-bond stabilized transition state for the C–C bond formation leading to the S-enantiomer is significantly lower in energy than the corresponding non-hydrogen-bonded transition state leading to the R-enantiomer. Thus, chiral induction of these two reactions is determined by the structures of the acceptor molecules.

Metal‐based catalysts: The title reaction provided the chiral adducts in high yields, excellent enantiomeric excess, and high Z/Eselectivity. A combined NMR/DFT study revealed a key intermediate for the stereoselective reaction and a possible reaction mechanism (see the optimized transition‐state structure).

Metallbasierte Katalysatoren: Die Titelreaktion lieferte die chiralen Addukte in hohen Ausbeuten, mit ausgezeichnetem Enantiomerenüberschuss und mit hoher Z/E‐Selektivität. Mit einer kombinierten NMR/DFT‐Studie konnten ein Schlüsselintermediat der stereoselektiven Reaktion und ein möglicher Reaktionsmechanismus identifiziert werden (die optimierte Übergangszustandsstruktur ist gezeigt).

Deuterium isotope effects on the enantioselectivity in the rhodium‐catalyzed asymmetric hydrogenation of enamides and related substrates have been studied. Distinct deuterium isotope effects were observed in the hydrogenation of aryl‐substituted enamides having an orthosubstituent that is capable of forming a hydrogen bond. The observed isotope effects are interpreted in terms of the competitive reactions of two dihydride intermediates and dideuteride intermediates that exist in equilibrium in the catalytic cycle.

Complete chiral crystallization and absolute chiral synthesis are both fascinating phenomena shedding light on the possible origins of homochirality in nature and opening perspectives for efficient preparations of optically pure materials. Originally these two phenomena have been considered mechanistically quite different belonging to the hetero- and homogeneous systems, respectively. However, the results of the active research in both fields undertaken in the last few years suggest that there may be a much closer likeness of the most important mechanistic features of these two phenomena. In the present review, we bring together the latest data on the complete chiral crystallization and absolute chiral synthesis including our own data on the mechanism and spontaneous break of chirality in the Soai asymmetric autocatalysis.

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A new class of chiral C2-symmetric bis(trialkyl)phosphine ligands has been prepared and used in Rh(I)-catalyzed asymmetric hydrogenation reactions. The ligands, 1,2-bis(alkylmethylphosphino)ethanes 1a-g (abbreviated as BisP*, alkyl = t-butyl, 1-adamantyl, 1-methylcyclohexyl, 1,1-diethylpropyl, cyclopentyl, cyclohexyl, isopropyl) and 1,2-bis(alkylmethylphosphino)methanes 2a-d (abbreviated as MiniPHOS, alkyl = t-butyl, cyclohexyl, isopropyl, phenyl) are prepared by a simple synthetic approach based on the air-stable phosphine–boranes. These new ligands give the corresponding Rh(I) complexes, which are effective catalytic precursors for the asymmetric hydrogenation of a representative series of dehydroamino acids and itaconic acid derivatives. Enantioselectivities observed in these hydrogenations are universally high and in many cases exceed 99%. X-Ray characterization of four precatalysts, study of the pressure effects, deuteration experiments, and characterization of the wide series of intermediates in the catalytic cycle are used for the discussion of the possible correlation between the structure of the catalysts and the outcome of the catalytic asymmetric hydrogenation.

A new class of chiral C2-symmetric bis(trialkyl)phosphine ligands has been prepared and used in Rh(I)-catalyzed asymmetric hydrogenation reactions. The ligands, 1,2-bis(alkylmethylphosphino)ethanes 1a-g (abbreviated as BisP*, alkyl = t-butyl, 1-adamantyl, 1-methylcyclohexyl, 1,1-diethylpropyl, cyclopentyl, cyclohexyl, isopropyl) and 1,2-bis(alkylmethylphosphino)methanes 2a-d (abbreviated as MiniPHOS, alkyl = t-butyl, cyclohexyl, isopropyl, phenyl) are prepared by a simple synthetic approach based on the air-stable phosphine–boranes. These new ligands give the corresponding Rh(I) complexes, which are effective catalytic precursors for the asymmetric hydrogenation of a representative series of dehydroamino acids and itaconic acid derivatives. Enantioselectivities observed in these hydrogenations are universally high and in many cases exceed 99%. X-Ray characterization of four precatalysts, study of the pressure effects, deuteration experiments, and characterization of the wide series of intermediates in the catalytic cycle are used for the discussion of the possible correlation between the structure of the catalysts and the outcome of the catalytic asymmetric hydrogenation.

A new enantiomerically pure P‐chiral phosphine, (S)‐cyclohexylmethyl‐ (1‐naphthyl)phosphine (1) was prepared by phosphine–borane methodology and used in a mechanistic study of the Mitsunobu reaction. Enantiomerically enriched (S)‐cyclo‐ hexylmethyl(1‐naphtyl)phosphine oxide (8) is obtained if the reaction proceeds through the phosphonium salt 4, whereas the intermediate dialkoxyphosphorane 5leads to racemic phosphine oxide 8. The results of the experiments including the variation of the reaction conditions and the natures of alcohol and carboxylic acid used in the Mitsunobu reaction prove the competition of two alternative mechanisms (reaction via 4or 5) on the second stage of the Mitsunobu reaction. Chirality 12:346–351, 2000. © 2000 Wiley‐Liss, Inc.

A new enantiomerically pure P-chiral phosphine, (S)-cyclohexylmethyl- (1-naphthyl)phosphine (1) was prepared by phosphine–borane methodology and used in a mechanistic study of the Mitsunobu reaction. Enantiomerically enriched (S)-cyclo- hexylmethyl(1-naphtyl)phosphine oxide (8) is obtained if the reaction proceeds through the phosphonium salt 4, whereas the intermediate dialkoxyphosphorane 5 leads to racemic phosphine oxide 8. The results of the experiments including the variation of the reaction conditions and the natures of alcohol and carboxylic acid used in the Mitsunobu reaction prove the competition of two alternative mechanisms (reaction via 4 or 5) on the second stage of the Mitsunobu reaction. Chirality 12:346–351, 2000. © 2000 Wiley-Liss, Inc.

Molecular orbital control or the least‐motion principle—what determines sigmatropic shifts in cyclopolyolefins? This question can be answered by a synergistic combination of two‐dimensional NMR techniques and density functional theory computations which reveal the intricacies of the degenerate [1,9]‐SnMe3sigmatropic shifts in the title compound as well as in related structures.

A convenient method for isomerization of trans-2-allyl-6-alkyl(aryl)-1,2,3,6-tetrahydropyridines into the corresponding cis-isomers is presented.

A convenient method for the preparation of the title compounds involving the sequential treatment of pyridine with RLi ( R= Alk, Ar), triallylborane and methanol is developed.

Two sequential [1,3] boron shifts in 1-(dipropylboryl)cyclohepta-2,4-diene 1 result in a degenerate rearrangement (EA=98.9±3.3.kJ mol−1, ln A=39.3±1.4, ΔG298≠=118.3±0.3 kJ mol−1); reaction of 1 with acetone affords non-conjugated alcohol 2.

Reaction of [2.2]paracyclophane with K/Na alloy in THF gives a p-xylylenyl dianion together with its dimer and trimer which are relatively stable at low temperatures; at ambient temperatures further polymerization takes place.

Reaction of 2.2paracyclophane with KNa alloy in THF gives a p-xylylenyl dianion together with its dimer and trimer which are relatively stable at low temperatures; at ambient temperatures further polymerization takes place.

Both possible [1,3]-B sigmatropic shifts are observed in the title compound; benzylic rearrangement to position 9 is much faster than allylic migration to position 3.

Review: 35 refs.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.