Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Monoacylation of long-chain linear diols often encounters difficulties associated with unavoidable overacylation affording the diacylate. However, several C-1- and C-2-symmetrical pyrrolidinopyridine (PPY) catalysts were found to effectively promote the chemoselective monoacylation of 1,5-pentanediol. The effects of catalyst structure on the performance for the monoacylation were investigated. The amide carbonyl group(s) in the pyrrolidine ring in both C-1- and C-2-symmetrical catalysts was(were) suggested to play the key role in selective monoacylation. On the other hand, the indolyl NH group in the amide side chain of the catalysts was found to be critically important for further increasing the chemoselectivity of monoacylation only when the catalyst has a C-2-symmetrical structure. The effects of the catalyst structure on the chemoselective monoacylation were elucidated by DFT calculations, and the origin of the precise molecular recognition for 1,5-pentanediol by the catalysts and transition state (TS) stabilization effects by these functionalities were disclosed.

DOI： 10.1002/adsc.201600010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The amaryllidaceae alkaloid (+)-trans-dihydrolycoricidine (1) was synthesized by asymmetric organocatalytic Friedel-Crafts reaction of sesamol with nitro-olefin followed by an intramolecular Henry reaction for construction of the C ring system. Construction of the B ring was achieved by a microwave-assisted palladium-catalyzed CO insertion reaction. Finally, regio- and stereoselective introduction of the third hydroxyl group (at C3) on the C ring afforded 1.

DOI： 10.1002/ajoc.201500469

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Catalytic discrimination between inequivalent formyl groups was achieved using an aniline-type acid-base catalyst for the regio-, diastereo-, and enantioselective intramolecular cross-aldol reactions of enolizable dials. Although L-proline gave a mixture of the regio-and stereoisomeric products in the presence of an N-containing 1,6-dial, the aniline-type catalyst afforded anti-3,4-disubstituted pyrrolidine in high regio-, and stereoselectivity beyond the background reaction, which led to the regioisomeric 2,3-disubstituted products. The mild reactivity of the aniline-type amine facilitated catalytic discrimination between the inequivalent formyl groups. Kinetic isotope effect studies and reductive amination experiments suggested that the regioselectivity was controlled under the enamine-forming steps.

DOI： 10.1039/c5sc04594k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Differential activation entropy (Delta Delta S-not equal) is revisited as an important parameter that governs catalytic stereodiscrimination processes by investigating temperature effects on the basis of the Eyring theory. However, correlating the Delta Delta S-not equal effect and the molecular structure of the asymmetric catalyst is still an underdeveloped area. Efforts to identify factors (including catalyst structure, reactants, and reaction conditions) that contribute to the attainment of large Delta Delta S-not equal values for enantioselective 1,2-type Friedel-Crafts reactions of phenols with N-tert-butoxycarbonyl aldimines catalyzed by conformationally flexible guanidine bisthioureas are described. First, we uncover an interesting property of the Delta Delta S-not equal-driven stereodiscrimination process: maximum enantioselectivity is obtained at around room temperature. Second, a plausible transition-state model accounting for the characteristic Delta Delta S-not equal effect and the structural dynamics of the conformationally flexible organocatalyst in the stereodiscrimination process is discussed.

DOI： 10.1002/chem.201503280

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A newly developed aminoiminophenoxy copper carboxylate (L7-Cu-OAc)-catalyzed asymmetric iodocyclization of N-Tosyl alkenamides gave O-cyclized products in good yields with high enantioselectivity. From the O-cyclized products, a skeletal transformation was succeeded in the synthesis of biologically important chiral 8-oxa-6-azabicyclo[3.2.1] octanes. DFT calculations suggested that the acetoxy anion of the [L7-Cu-OAc] acts as a base to generate the anion of N-Tosyl alkenamide substrates. The exchanged acetic acid reconstructs a new hydrogen-bonding network between the catalyst and the substrates to accomplish the highly efficient asymmetric O-iodocyclization of N-Tosyl alkenamides.

DOI： 10.1002/anie.201505748

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Novel guanidine-bisurea bifunctional organocatalysts 5 bearing a chiral pyrrolidine moiety on guanidine were designed with the guidance of DFT calculations. The resulting organocatalysts 5 were examined for alpha-hydroxylation of tetralone-derived beta-keto esters, and good selectivity was obtained with 5j bearing a methoxymethyl ether-containing chiral pyrrolidine moiety.

DOI： 10.3390/molecules200712590

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have developed 4-pyrrolidinopyridine catalysts for the geometry-selective (E-selective) acylation of tetrasubstituted alpha,alpha'-alkenediols. To elucidate the major factors of the high geometry selectivity, experimental and computational studies were carried out. The control experiments with respect to the substituent of the substrate indicated the fundamental hydrogen bonding of the acidic hydrogen of NHNs and the Z-OH in the substrate. Comparison between C-2- and C-1-symmetric catalysts exhibited the necessity of the C-2-symmetric catalyst structure. The computationally proposed transition state (TS) model well explained the experimental results. Whereas the fundamental NH/amide-CO and the two-point free-OH/acetate anion hydrogen bonds stabilize the transition state (TS), affording the E-product, the steric repulsion between the N-protecting group and the amide side chain destabilizes TS, affording the Z-product. The role of the two amide side chains of the catalyst in a C-2-symmetric fashion is the enhancement of the molecular recognition ability through the additional hydrogen bond in a cooperative manner.

DOI： 10.1021/jo5029453

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The asymmetric reduction of ketimines is an important method for the preparation of amines in optically pure form. Inspired by the biological system using NAD(P)H, Hantzsch ester has been extensively employed as a hydrogen donor in combination with chiral phosphoric acid for the transfer hydrogenation of ketimines to furnish amines with high to excellent enantioselectivities.
We focused on 2-substituted benzothiazoline as a hydrogen donor in the phosphoric acid catalyzed transfer hydrogenation reaction of ketimines for the following reasons: (1) benzothiazoline is readily prepared just by mixing 2-aminobenzenethiol and aldehyde, (2) both reactivity (hydrogen donating ability) and enantioselectivity would be controlled by tuning the 2-substituent of benzothiazoline, and (3) benzothiazoline can be stored in a refrigerator under inert atmosphere without conceivable decomposition. Both the 2-position of benzothiazoline and the 3,3'-position of phosphoric acid are tunable in order to achieve excellent enantioselectivity.
Benzothiazoline proved to be useful hydrogen donor in combination with chiral phosphoric acid for the transfer hydrogenation reaction of ketimine derivatives to afford the corresponding amines with high to excellent enantioselectivities by tuning the 2-substituent of benzothiazoline. Ketimines derived from acetophenone, propiophenone, a-keto ester, trifluoromethyl ketone, and difluoromethyl ketone derivatives proved to be suitable substrates. Benzothiazoline could be generated in situ starting from 2-aminobenzenethiol and aromatic aldehyde in the presence of ketimine and chiral phosphoric acid and successfully worked in the sequential transfer hydrogenation reaction. The reductive amination of dialkyl ketones also proceeded with high enantioselectivities. Use of 2-deuterated benzothiazoline led to the formation of a-deuterated amines with excellent enantioselectivities. The kinetic isotope effect (k(H)/k(C) = 3.8) was observed in the competitive reaction between H- and D-benzothiazoline, which explicitly implies that the cleavage of the CH (CD) bond is the rate-determining step in the transfer hydrogenation reaction.
Benzothiazoline yielded products with higher enantioselectivity in the transfer hydrogenation reaction of ketimines, particularly ketimines derived from propiophenone derivatives, than Hantzsch ester. DFT study elucidated the mechanism, as well as the difference in selectivity, between benzothiazoline and Hantzsch ester. The chiral phosphoric acid activates ketimines and benzothiazoline by means of the Bronsted acidic site (proton) and the Bronsted basic site (phosphoryl oxygen), respectively, to accelerate the hydride transfer reaction.

DOI： 10.1021/ar500414x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The mechanism of asymmetric a-hydroxylation of tetralone-derived beta-ketoesters with guanidine-bisurea bifunctional organocatalyst in the presence of cumene hydroperoxide (CHP) was examined by means of DFT calculations to understand the origin of the stereocontrol in the reaction. The identified transition-state model was utilized to design an enantioselective synthesis of beta- or gamma-substituted tetralones by catalytic oxidative kinetic resolution reaction of tetralone-derived beta-ketoesters. This kinetic resolution reaction proceeded with high selectivity, and selectivity factors (s value) of up to 99 were obtained. The potential utility of this oxidative kinetic resolution method for synthesis of natural products was confirmed by applying it to achieve an enantioselective synthesis of (+)-linoxepin (13) from beta-substituted tetralone rac-7 in only six steps.

DOI： 10.1021/ja511149y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A bis(imidazolidine)pyridine (PyBidine)-Cu(OTf)(2) complex catalyzing the endo-selective [3+2] cycloaddition of nitroalkenes with imino esters was applied to the reaction of methyleneindolinones with imino esters to afford spiro[pyrrolidin-3,3'-oxindole]s in up to 98% ee. X-ray crystallographic analysis of the PyBidine-Cu(OTf)(2) complex and DFT calculations suggested that an intermediate Cu enolate of the imino ester reacts with nitroalkenes or methyleneindolinones, which are activated by NH-hydrogen bonding with the PyBidine-Cu(OTf)(2) catalyst.

DOI： 10.1002/anie.201410782

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Chiral phosphoric acids have emerged as promising asymmetric Bronsted acid catalysts that harness hydrogen bonding interactions as key stereocontrolling elements. A new approach to chiral phosphoric acid catalysis through ion-pairing interactions between the anionic conjugate base of the catalyst and a cationic electrophile has recently attracted attention. However, the mechanism of stereocontrol through ion-pairing interactions is still elusive. As a probe reaction for studying the stereocontrolling element involved in such catalytic reactions, we investigated the Petasis-Ferrier-type rearrangement of a 7-membered cyclic vinyl acetal catalyzed by chiral phosphoric acids. DFT calculations suggested that non-classical C-H center dot center dot center dot O hydrogen bonds between the catalyst and the substrate play an important role in determining the stereosetectivity. In addition, pi-pi stacking interactions were found to be a key factor for stereocontrol when using a 9-anthryl group-bearing catalyst.

DOI： 10.1039/c4sc00611a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A 3,3'-bis(aminoimino)BINOL ligand was newly designed and synthesized for the formation of a trinuclear Zn complex upon reaction with Zn(0Ac)2. Using the harmony of the tri-zinc atoms, 1 mol% Zn3(0Ac)4-3,3'-bis(aminoimino)binaphthoxide catalyzed asymmetric iodolactonization in up to 99.9% ee.

DOI： 10.1039/c4cc02415j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Pd-catalyzed cyclotrimerization reactions of enantiopure halonorbornene derivatives furnished C-3 or C-3v symmetric syn-tris(norborneno)benzenes with high syn selectivity. To elucidate the reaction mechanism as well as the stereoselectivity of the present Pd-catalyzed cyclotrimerization, DFT calculations were carried out. The promising reaction pathway consists of (1) sequential olefin insertion followed by an HX elimination reaction of halonorbornene with the norbornenylpalladium intermediate, (2) electrocyclization of the trienylpalladium intermediate with a lower activation barrier than a triene compound, and (3) the beta-elimination of HPdX of the cyclohexadienylpalladium intermediate. In addition, the stereoselectivity would be controlled by the regioselectivity in the olefin insertion process (homo and hetero positions) and the symmetry breaking in the palladacyclic intermediate.

DOI： 10.1021/om500322b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Chiral phosphoric acid catalyzed transfer hydrogenation of ketimines derived from propiophenone derivatives and reductive amination of alkyl ethyl ketone derivatives were extensively examined in the presence of two representative hydrogen donors. The excellent enantioselective transfer hydrogenation was achieved by use of benzothiazoline as a hydrogen donor. The theoretical studies elucidated that the unsymmetrical structure of benzothiazoline plays an important role in high enantioselective hydrogenation.

DOI： 10.1002/chem.201402763

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC SYNTHETIC ORGANIC CHEM JPN  

The chiral BINOL-phosphoric acid is a well-designed asymmetric organocatalyst because it features the bifunctionality of the Bronsted acid (proton)/base (phosphoryl oxygen) and the conformational rigidity of the 3,3-substituents of the BINOL unit controlling the stereoselectivity through the hydrogen bonding network. Though the bifunctional activation has emerged as an important paradigm of chiral phosphoric acid catalyzed asymmetric reactions, it has remained elusive in most cases. Recently, we revealed the reaction mechanism as well as the stereocontrol mechanism by our computational two-step approach using (1) simplified chemical model and (2) realistic chemical model.

DOI： 10.5059/yukigoseikyokaishi.72.580

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A highly enantioselective Michael addition of -ketoesters to enones was achieved by using the salt of a readily available primary -amino acid as the catalyst. The obtained Michael adducts were converted into enantioenriched 1,5-diketones in high yields through a common decarboxylation reaction under acidic conditions. A plausible reaction mechanism for the Michael addition reaction, which is supported by results of mechanistic studies that include DFT calculations, is also described.

DOI： 10.1002/ajoc.201400024

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Described herein are two novel types of double C(sp(3))-H bond functionalizations triggered by a sequential hydride shift/cyclization process: (1) construction of a bicyclo[3.2.2]nonane skeleton by a [1,6]- and [1,5]-hydride shift sequence and (2) sequential [1,4]- and [1,5]-hydride shift mediated construction of a linear tricyclic skeleton.

DOI： 10.1021/ja412706d

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A mechanistic study was carried out for the asymmetric Michael addition reaction of malonates to enones catalyzed by a primary amino acid lithium salt to elucidate the origin of the asymmetric induction. A primary beta-amino acid salt catalyst, O-TBDPS beta-homoserine lithium salt, exhibited much higher enantioselectivity than that achieved with the corresponding catalysts derived from alpha- and gamma-amino acids for this reaction. Detailed studies of the transition states with DFT calculations revealed that the lithium cation and carboxylate group of the beta-amino acid salt catalyst have important roles in achieving high enantioselectivity in the Michael addition reaction of malonates to enones. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2013.09.066

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Language：English   Publishing type：Research paper (scientific journal)  

We describe herein the “1H NMR-assisted catalyst screening method,” which enables us to find the suitable catalyst easily and predict enantioselectivity with the same accuracy as the computational method. Based on this method, we constructed multisubstituted biaryls that occur frequently in many biologically active compounds, chiral ligands, and organocatalysts, with excellent enantioselectivities via chiral phosphoric acid-catalyzed asymmetric bromination. © 2013 The Royal Society of Chemistry.

DOI： 10.1039/c3sc52142g

Scopus

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The oxidative kinetic resolution of 2-substituted indoline derivatives was achieved by hydrogen transfer to imines by means of a chiral phosphoric acid catalyst. The oxidative kinetic resolution was applicable to racemic alkyl- or aryl-substituted indolines, and the remaining indolines were obtained in good yields with excellent enantioselectivities.

DOI： 10.1021/ja406004q

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Language：English   Publishing type：Research paper (scientific journal)  

Benzothiazoline is an efficient reducing agent for the chiral BINOL-phosphoric acid catalyzed enantioselective transfer hydrogenation of ketimines and α-imino esters to afford the corresponding amines with high enantioselectivities. DFT studies (M05-2X/6-31G*//ONIOM(B3LYP/6- 31G*:HF/3-21G)) revealed the reaction mechanism and the origin of the high enantioselectivity in the present BINOL-phosphoric acid catalyzed transfer hydrogenation of ketimines and α-imino esters using benzothiazoline. The reaction mechanism is similar to that reported in the asymmetric transfer hydrogenation of ketimines using Hantzsch ester. Phosphoric acid simultaneously activates ketimine (α-imino ester) and benzothiazoline to form cyclic transition structures. The high enantioselectivity is attributed to the steric interaction between the substituents at the 3,3′-positions of BINOL-phosphoric acid and substrates. In contrast to the C2- symmetrical Hantzsch ester, the readily tunable 2-aryl substituent of unsymmetrical benzothiazoline plays a significant role in the steric interaction, influencing the asymmetric induction. This feature is responsible for the advantage of benzothiazoline over Hantzsch ester. © 2013 American Chemical Society.

DOI： 10.1021/jo4002195

Scopus

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Described herein is the enantioselective synthesis of multisubstituted biaryl derivatives by chiral phosphoric acid catalyzed asymmetric bromination. Two asymmetric reactions (desymmetrization and kinetic resolution) proceeded successively to afford chiral biaryls in excellent enantioselectivities (up to 99% ee). Both experimental and computational studies suggested that this excellent selectivity could be achieved via a highly organized hydrogen bond network among a substrate, a catalyst (chiral phosphoric acid), and a brominating reagent (N-bromophthalimide).

DOI： 10.1021/ja311902f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201300665

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The origin of the regioselectivity of the Baeyer Villiger reaction of alpha-Me-, -F-, and -CF3-cyclohexanones was investigated theoretically (MPWB1K/6-311++G**-PCM(CH2Cl2)//MPWB1K/6-311G**-Onsager-(CH2Cl2)). Investigation of the energy profiles of the rearrangement step revealed the reality of the importance of conventional migratory aptitude based on the stabilization capability of partial positive charge generated during the migration step. We have divided the origin of the regioselectivity into two factors: (1) structural stability (steric repulsion, dipole interaction, etc.) and kinetic reactivity (energy barrier from the intermediate, i.e., cation stabilization capability). For alpha-CF3-cyclohexanone, the migration tendency was mostly dependent on the kinetic reactivity; CF3 substitution greatly increased the energy barrier. Noteworthy is the orientation of the CF3 group at the transition state. The CF3 group possessed the axial orientation overcoming the 1,3-diaxial repulsion, probably because of the strong dipole interaction between the CF3 group and the leaving acid moiety. Striking results in the case of alpha-F- and -Me-cyclohexanone were that no difference in the energy barriers by the substituents could be observed. Especially in the case of alpha-Me substitution, structural stability operates in determining the most stable transition state, which is in contrast to the conventional understanding of the migratory aptitude based on the ability to stabilize partial positive charge.

DOI： 10.1021/jo302151r

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Focusing on the steric and electronic properties of the resonance-stabilized amidine framework, a cationic metal-bisamidine complex was designed as a conjugated combined Lewis-Bronsted acid catalyst. The chiral Zn(II)-bisamidine catalyst prepared from the 2,2'-bipyridyl derived bisamidine ligand, ZnCl2, and AgSbF6 promoted asymmetric Mukaiyama aldol reaction of alpha-ketoester and alpha,alpha-disubstituted silyl enol ether to afford the alpha-hydroxyester having sequential quarternary carbons in good yield, albeit with low enantioselectivity. Addition of 1.0 equivalent of the fluoroalcohol having suitable acidity and bulkiness dramatically increased the enantioselectivity (up to 68% ee). DFT calculations suggested that this additive effect would be caused by self-assembly of the fluoroalcohol on the Zn(II)-bisamidine catalyst.

DOI： 10.3390/molecules17089010

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/ange.200901127

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The enantioselective Friedel-Crafts reaction of indoles with nitroalkenes proceeds catalytically by means of a chiral-phosphoric-acid catalyst to afford products with high enantioselectivities (up to 91% ee). The use of a 3,3'-SiPh3-substituted (R)-binol-derived (binol=1,1'-binaphthyl-2,2'-diol) catalyst and a free indole that bears an N-H moiety is essential to achieving high enantioselectivity as well as high yield. To elucidate the reaction mechanism and the origin of the high enantioselectivity, DFT calculations were carried out. The reaction proceeded through a cyclic transition state formed by the two-point binding of both substrates to the conjugated O-P-O moiety of the catalyst, in which indoles and nitroalkenes could be simultaneously activated by Bronsted acidic (proton) and basic (phosphoryl oxygen) sites, respectively. The enantioselectivity was entirely controlled by the steric effect between the 3,3'-substituent group on the (R)-binol-derived phosphoric acid catalyst and the indole ring. When the sterically demanding SiPh3 group was used as the 3,3'-substituent group, the energy difference between the moststable diastereomeric transition states that afforded the S and R products was increased to lead to the high enantioselectivity in agreement with the experimental results.

DOI： 10.1002/asia.201000596

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The enantioselective hydrophosphonylation reaction of diisopropyl phosphite with aldimine furnished alpha-amino phosphonates with high enantioselectivities by means of a chiral phosphoric acid. DFT calculation of the effect of 3,3'-substituents of the phosphoric acid revealed the reason for the high enantioselectivities. (C) 2009 Elsevier Ltd. All rights reserved,

DOI： 10.1016/j.tet.2009.03.023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Asymmetric hydrophosphonylation reaction of aldimines with dialkyl phosphites proceeds catalytically by means of a phosphoric acid diester, derived from (R)-BINOL, as a chiral Bronsted acid to afford a-amino phosphonates with good to high enantioselectivities (up to 90% ee). The use of the aldimines derived from cinnamaidehyde derivatives and sterically demanding dialkyl phosphites was essential for achieving high enantioselectivity as well as high yield. To elucidate the reaction mechanism and the origin of the high enantioselectivity, DFT calculation (BHandHLYP/6-31G*) was carried out. The reaction proceeds via the nine-membered zwitterionic transition state (TS) with the chiral phosphoric acid, where aldimine and phosphite could be activated by the Bronsted acidic site and Lewis basic site, respectively. The si-facial attacking TS could be less favored by the steric repulsion of 3,3'-aryl groups on the chiral phosphoric acid with the bulky phosphite. When using the aldimine derived from benzaldehyde, the re-facial attacking TS is destabilized to decrease the enantioselectivity in agreement with the experimental results.

DOI： 10.1021/jo900404b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200905271

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Mannich-type reaction of ketene silyl acetals with aldimines proceeded catalytically by means of a phosphoric acid diester, derived from (R)-BINOL, as a chiral Bronsted acid to afford beta-amino esters with good diastereoselectivity in favor of the syn isomer and high enantioselectivity (up to 96% ee). The highest enantioselectivity was achieved by the phosphoric acid diester bearing 4-nitrophenyl groups on the 3,3'-positions of BINOL. The N-2-hydroxyphenyl group of aldimine was found to be essential for the present Mannich-type reaction. In combination with these experimental investigations, two possible monocoordination and dicoordination pathways were explored using density functional theory calculations (BHandHLYP/6-31G*). The present reaction proceeds via a dicoordination pathway through the zwitterionic and nine-membered cyclic transition state (TS) consisting of the aldimine and the phosphoric acid. The re-facial selectivity was also well-rationalized theoretically. The nine-membered cyclic structure and aromatic stacking interaction between the 4-nitrophenyl group and N-aryl group would fix the geometry of aldimine on the transition state, and the si-facial attacking TS is less favored by the steric hindrance of the 3,3'-aryl substituents.

DOI： 10.1021/ja0684803

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Theoretical studies of the organic base-catalyzed 5-exo intramolecular cyclization of o-alkynylbenzoic acid were documented. The acidic fragment participating in the transition states was shown to reduce the activation energy significantly on the basis of hybrid DFT (BHandHLYP) calculation of 5-exo and 6-endo transition states. Furthermore, preference for the 5-exo cyclization mode was rationalized by natural population analysis of optimized structures of the transition states and the reactants.

DOI： 10.3987/COM-07-S(W)73

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A series of ruthenium complexes [ Ru( OAc)( dioxolene)( terpy)] having various substituents on the dioxolene ligand ( dioxolene) 3,5-t-Bu2C6H2O2 ( 1), 4-t-BuC6H3O2 ( 2), 4-ClC6H3O2 ( 3), 3,5-Cl2C6H2O2 ( 4), Cl4C6O2 ( 5); terpy) 2,2': 6'2 ''-terpyridine) were prepared. EPR spectra of these complexes in glassy frozen solutions ( CH2Cl2: MeOH = 95: 5, v/v) at 20 K showed anisotropic signals with g tensor components 2.242 > g(1) > 2.104, 2.097 > g(2) > 2.042, and 1.951 > g(3) > 1.846. An anisotropic value, < g > = g(1) - g(3), and an isotropic g value, < g > [( g(1)(2) + g(2)(2) + g(3)(2))/3](1/2), increase in the order 1 < 2 < 3 < 4 < 5. The resonance between the Ru-II( sq) ( sq = semiquinone) and RuIII( cat) ( cat) catecholato) frameworks shifts to the latter with an increase of the number of electron-withdrawing substituents on the dioxolene ligand. DFT calculations of 1, 2, 3, and 5 also support the increase of the Ru spin density ( RuIII character) with an increase of the number of Cl atoms on the dioxolene ligand. The singly occupied molecular orbitals ( SOMOs) of 1 and 5 are very similar to each other and stretch out the Ru - dioxolene frameworks, whereas the lowest unoccupied molecular orbital ( LUMO) of 5 is localized on Ru and two oxygen atoms of dioxolene in comparison with that of 1. Electron-withdrawing groups decrease the energy levels of both the SOMO and LUMO. In other words, an increase in the number of Cl atoms in the dioxolene ligand results in an increase of the positive charge on Ru. Successive shifts in the electronic structure between the RuII( sq) and RuIII( cat) frameworks caused by the variation of the substituents are compatible with the experimental data.

DOI： 10.1021/ic060696i

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A cobalt-rhodium mixed-metal carbonyl complex Co2Rh2(CO)(12) effects efficient catalytic silylformylation of an alkyne that adds silyl and formyl groups across the C-C triple bond. A bimetallic synergism in this reaction was elucidated with density functional calculations. The catalytic cycle consists of oxidative addition of hydrosilane, alkyne insertion, CO insertion, and reductive elimination. While major bond-forming events take place only at the rhodium center, the cobalt also plays an important role; it fixes the metal cluster on the organic substrate, keeps the hydride ligand temporarily on the metal center, and suppresses hydrosilylation, which would otherwise be preferred over the silylformylation. The Rh and Co atoms exchange electrons with each other, giving rise to a unique bimetallic reaction pathway that is related to but different from the conventional pathways of hydroformylation and hydrosilylation.

DOI： 10.1021/om060478x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report on the singlet ground and singlet/triplet excited-state features of a series of bucky ferrocenes, bucky ruthenocenes, and respective reference compounds. In the bucky ferrocene conjugates, intimate contacts between the fullerenes and ferrocenes result in appreciable ground-state interactions-suggesting a substantial shift of charge density from the electron donor (i.e., ferrocene) to the electron acceptor (i.e., fullerene). In contrast, no prominent charge-transfer features were observed for the bucky ruthenocene conjugates. An arsenal of experimental techniques, ranging from fluorescence (i.e., steady state and time-resolved) and pump probe experiments (i.e., femtosecond and nanoseconds) to pulse radiolysis, were employed to examine excited-state interactions. In the excited states, bucky ferrocene conjugates are dominated by rapid charge separation reactions (0.8 +/- 0.1 ps) to yield metastable radical ion pairs. The radical ion pair lifetimes vary between 27 and 39 ps. No charge separation was, however, found in the corresponding bucky ruthenocence. Instead, an intrinsically faster excited-state deactivation (similar to 200 ps) evolves from the heavier ruthenium center-relative to iron. This effect is further augmented by the unfavorably shifted oxidation potential in ruthenocene of about 0.61 V, which in ruthenocene (-Delta G(ET) = -0.26 eV), in contrast to ferrocene (-Delta G(ET) = 0.35 eV), renders charge separation thermodynamically unfeasible.

DOI： 10.1021/ja061120v

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Not only the reaction rate but also the regioselectivity in the scandium bis(perfluorooctanesulfonyl)amide-catalyzed Baeyer-Villiger reaction is remarkably increased by the development of the fluorous nanoflow microreactor system continuously controlled by the nanofeeder DiNaS (Direct Nanoflow System) even in the lowest concentration of the catalyst (<< 0.1 mol%). The Baeyer-Villiger reaction completes within few seconds as a contact time in the nanoflow microreactor to give the lactone products with high regioselectivity without hydrolysis. (C) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jfluchem.2006.03.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The facility of axial chirality control of the Pd(II) complex bearing a chirally flexible (tropos) biphenylphosphine (BIPHEP) ligand with combination of diphenylethylenediamine (DPEN) or diaminobinaphthyl (DABN) was theoretically studied by the B3L'YP methods and the paired interacting orbital (PIO) analysis. The simple Pd(II) complex models PR3Pd(II) and PR3Pd(II)NMe3 (R = H, Ph), were also employed to probe the bonding interaction of the phosphine-Pd(II) moiety and the trans influence of NMe3 coordination. The PIO analysis of the PPh3Pd(II) complex indicates that the sigma-donation to the vacant Pd 4d orbital is amplified, keeping the pi-back-donation to the P-C sigma* orbital by NMe3 coordination. A similar tendency of the trans influence of the simple model was also observed in the BIPHEP-Pd(II) models. The origin of the strong atropos nature of BIPHEP-Pd(II)/DPEN can be caused by enhancement of the sigma-interactions with Pd 4d(xz), and 4d(x2-y2),which are relatively amplified by coordination of a strongly donative DPEN ligand in comparison with the DABN ligand.

DOI： 10.1021/om050249v

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Since the proposal of the dummy ligand concept by Corey, it has been widely accepted that the ligand transfer selectivity of a mixed organocuprate (Me(X)CuLi) depends on the Cu-X bond strength. The present B3LYP density functional studies on the Me(2)(X)Cu(III)-OMe(2),pi-allyl Cu(III), and Me(X)-Cu(III)LiCI(.)LiCI reacting with acrolein showed that the ligand transfer selectivity of the conjugate addition depends on two factors, thermodynamic stability (X =tert-butyl, ethynyl, cyano, and thiomethyl groups) and kinetic reactivity ((trimethylsilyl)methyl and vinyl groups) of the Cu(III) intermediate formed by complexation of the cuprate and the alpha,beta-unsaturated carbonyl compound. For the typical dummy ligands (X = alkynyl, cyano, and heteroatom ligands), the trans effect and the strong Li-X affinity are the reasons why these ligands stay on the copper atom. In contrast, for the (trimethylsilyl)methyl and vinyl groups, the selectivity depends on the kinetics of reductive elimination of the Cu(III) intermediate. The (trimethylsilyl)methyl transfer is retarded by repulsive four-electron interaction between the lone pair Cu 3d(Xy) orbital and the C-Si a-orbital.

DOI： 10.1021/ja049401v

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

A new orbital interaction analysis system, "LUMMOX", is based on two theories of "Paired Interacting Orbital (PIO)" and "Localized Frontier Orbital (LFO)", which have been developed by Fujimoto et al LUMMOX can readily estimate the reactivity of an interacting system A-B of various sizes with the same A by comparing with the same number of the interacting orbitals. By applying LUMMOX, we report herein the primary orbital interaction on the phosphine-palladium complexes (PF3Pd, PH3Pd, PMe3Pd, PPh3Pd) continuously changes from the donative to back-donative interaction.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Organocuprate (R2Cu-) reagents react with a carbon electrophile to form a new C-C bond, yet their silver and gold counterparts seldom serve for such purposes. The origin of this striking difference is discussed with the aid of the quantum mechanical calculations using hybrid density functional method. The copper reaction takes place through two steps, the nucleophilic reaction of the ate complex R2Cu(I)(-) with an electrophile E+ and the decomposition of the resulting R-2(E)Cu(III) intermediate. These two steps were examined for Cu, Ag, and Au to find the reasons for the superiority of organocopper compounds to the silver and the gold counterparts. The first reaction is favored because of the higher-lying d-orbitals that directly participate in the nucleophilic reaction. The second reaction is faster with copper because of the intrinsic instability of the high valent copper species.

DOI： 10.1021/ja045659+

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja046518a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Reductive elimination of a pi-allylcopper(III) compound leading to the formation of a C-C bond on an allylic terminal has been considered to occur via the corresponding sigma-allylcopper(III) species. The present B3LYP density functional study has shown however that the C-C bond formation occurs directly from the pi-allyl complex via an enyl[sigma+pi]-type transition state, which has structural features different from a simple sigma-allylcopper(III) intermediate. In the case of unsymmetrically substituted pi-allylcopper(III) compound that has a partial sigma-allylcopper(III) structure, the reductive elimination occurs preferentially at the a-bonded allylic terminal since, in this way, the copper atom can recover most effectively its cl-electrons shared with the allyl system. The regioselectivity of the reductive elimination of a substituted pi-allylcopper(III) intermediate is mainly controlled by the electronic effect, and correlated well to the Hammett sigma(p)(+) constant. The analyses revealed mechanistic kinship between the allylic substitution and the conjugate addition reaction of organocopper reagents.

DOI： 10.1021/ja049211k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The scandium bis(perfluorooctanesulfonyl)amide-catalyzed Baeyer-Villiger reaction significantly increased the regioselectivity as well as the reaction rate by nanoflow system continuously controlled by a nanofeeder even in the lowest concentration of the catalyst (much less than0.1 mol %), The Baeyer-Villiger reaction completed within few seconds as a contact time in the microcell to afford the lactone products high regioselectively without hydrolysis. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2004.02.157

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1351/pac200476030537

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/cr030685w

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

[GRAPHICS]
The stereoselectivity of a reaction is generally determined by minimizing steric repulsion. However, the aldol reaction of alpha-CF3-ketone (Z)-enolate with fluoral anomalously gave an anti-aldol through a sterically demanding transition state, because of the strong dipole interaction of the two CF3 groups. We have thus disclosed a paradigm shift from steric to electronic control of reaction stereoselectivity.

DOI： 10.1021/ol0358307

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

'Fluorous nanoflow' system is extremely effective for the lanthanide bis(perfluorooctanesulfonyl)amide-catalyzed Mukaiyama aldol reaction with dramatic increase in the reaction rate by the continuously controlled nano feeder. Thus, the acceleration of the aldol reaction was achieved even in the lowest concentration ( < 0.0001 M) of the lanthanide fluorous catalyst and, hence, the reaction completed within seconds as a bi-phase contact time in the micro cell. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2003.10.036

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The reactivity of the Mukaiyama aldol reaction is significantly increased by 'fluorous nano flow' system even in the low concentration (<0.0001 M) of a lanthanide fluorous catalyst and the reaction completes within seconds as a contact time in the micro cell. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/S0040-4039(03)01835-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Systematic evaluation of method and basis set on the structure and energetics of organocuprate(l) and organocopper(III) species has been carried out. Various structures of organocuprate(l) and organocuprate(III) complexes were optimized with the HF, MP2, and B3LYP methods, and compared with the structures determined by X-ray crystallography (i.e., Me2Cu(I)(-), (CF3)(4)Cu(III)(-)). Both the MP2 and B3LYP methods reasonably reproduce the X-ray structures while the HF method does not. Using larger basis set and incorporating the relativistic effects for Cu afford the best results. In the studies on the energetics of a Li-Cu cluster model (Me2CuLi (.) LiCI) and Me3Cu model with the MP2, MP3. MP4DQ, MP4SDQ, CCSD(T), and B3LYP methods, the B3LYP method gives energetics similar to those obtained with the CCSD(T) method with much less cost, and hence, is judged to be the best practical method. The studies have shown that B3LYP method with the basis set incorporating the relativistic effective core potentials for Cu and the 6-31G* basis set for the rest is the theoretical method that is the most cost-effective for the studies of the structure and energetics of organocuprate(I) and organocopper(III) species. (C) 2003 Wiley Periodicals, Inc.

DOI： 10.1002/jcc.10132

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/cr000260z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A highly effective Cl-symmetric gem-dimethyl N,P-ligand has been developed for enantioselective palladium(II)-catalyzed carbocyclization of 1,6-enynes, in which the N/C trans mode is established for the first time in the "Mizoroki-Heck-type" transition state by virtue of the Cl-symmetric N,P-ligand. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

DOI： 10.1002/ejoc.200300196

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

(2,5)-Ene reactions catalyzed by mesoporous solid acids are reported from the mechanistic point of view. The continuum (2,5)-ene mechanism from the concerted to the cationic cyclization followed by 1,2-hydride shift is evaluated. The solid-acid-catalyzed cyclization of the oxonium. ion intermediate 4 derived from cyclic allylic lactol ether 3 bearing allylic hydroxy group affords the (2,5)-ene product as the enol form, eventually tautomerizing to the corresponding aldehyde 6. The continuum from the concerted to stepwise mechanism is experimentally and theoretically verified in the present ene cyclization of the oxonium ion intermediate such as 4. The stepwise cyclization leading to aldehyde 6 is thus shown to associate with the concerted version as a result of the stabilization of the beta-hydroxycarbenium ion intermediate.

DOI： 10.1021/jo020634j

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ol0358298

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Asymmetric activation and deactivation of racemic catalysts are two extremes in asymmetric catalysis. In a combination of these two protocols, higher enantioselectivity can be achieved by maximizing the difference in catalytic activity between the enantiomers of racemic catalysts through selective activation and deactivation of enantiomeric catalysts. 3,3'-Dimethyl-2,2'-diamino-1,1'-binaphthyl (DM-DABN) is thus designed as a chiral poison (deactivator) for complete enantiomer resolution of racemic BINAP-Ru(II) catalysts. The catalyst System of DM-DABN, 1,2-diphenylethylenediamine (DPEN), and racemic BINAP-Ru(II) led to great success in highly enantioselective hydrogenation irrespective of the ketonic substrates. The lower catalytic activity of the BINAP-Ru(II)/DM-DABN complex stems from the electron delocalization from the Ru center to the diamine moiety in contrast to the BINAP-Ru(II)/DPEN complex where the highest electron densities are localized on the Ru-N region. The present 'asymmetric activation/deactivation protocol' can provide a guiding principle for the rational design of a molecule for enantiomeric discrimination between racemic catalysts.

DOI： 10.1002/adsc.200390019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The mechanism of tropo-inversion of the Ru(II) complex bearing a chirally flexible biphenylphosphine (BIPHEP) ligand has been studied by the B3LYP and the ONIOM(B3LYP: HF) methods. The relative energy difference between the favorable (S)I(SS) and the less favorable (R)I(SS) pairs of BIPHEP-RuCl2/DPEN complexes is well comparable to the experimental results. The tropo-inversion of the (S)I(SS) pair to the (R)I(SS) pair is found to be achieved by solvent-assisted rotation around the biphenyl single bond and subsequent recoordination of phosphine to the Ru center. The sterically demanding phenyl groups attached to phosphorus atoms in the BIPHEP-RuCl2 moiety prevented the internal rotation without dissociation of P-Ru coordination.

DOI： 10.1021/om02015c

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEORG THIEME VERLAG KG  

While non-racemic catalysts can generate non-racemic products with or without the non-linear relationship in enantiomeric excesses between catalysts and products, racemic catalysts inherently give only a racemic mixture of chiral products. Racemic catalysts can be enantioselectively evolved into highly activated catalysts by association with chiral activators. Asymmetric activation strategy can produce greater enantiomeric excess in the products, even when using a catalytic amount of chiral activator per chiral or racemic catalysts bearing atropisomeric (atropos: from Greek a meaning not, and tropos meaning turn) ligands, than the enantioselectivity attained by the enantiomerically pure catalyst on its own. Some recent applications of the asymmetric activation catalysis that employ not only atropos and racemic ligands but also tropos ligands without enantiomeric resolution are herein reported. The great success of the asymmetric catalysts with tropos ligands clearly illustrate that chirally rigid atropos ligands can be replaced by chirally flexible tropos ligands to give preferentially the thermodynamically favorable diastereomer of catalysts with higher chiral efficiency than does the minor isomer. The asymmetric activation concept now progress toward the use of racemic but tropos ligands rather than the use of atropos ones.

DOI： 10.1002/chin.200301252

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

There is a frequently used organocuprate species that was introduced by Lipshutz and possesses a molecular structure written as CuLi2R2(CN). This species was previously called "higher order cuprate", but is now considered to exist as an equilibrating mixture of various isomers of R2CuLi.LiCN and R(CN)CuLi-LiR, among which R2Cu-.Li2CN+ is known to be dominant in solution. The present studies on the kinetic reactivity of these species in the addition reaction to acetylene suggest that the minor species R(CN)CuLi.LiR may be more reactive than the major species, thereby making it equally possible that addition reaction products may arise through both the major and the minor reactive species. The reason for the high reactivity of the minor species has been ascribed to the anisotropic and multi-coordination capability of the cyanide ligand to metals; such capability is not available for a halide or alkyl anion ligand.

DOI： 10.1246/bcsj.75.1815

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The B3LYP density functional studies on the dirhodium tetracarboxylate-catalyzed C-H bond activation/C-C bond formation reaction of a diazo compound with an alkane revealed the energetics and the geometry of important intermediates and transition states in the catalytic cycle. The reaction is initiated by complexation between the rhodium catalyst and the diazo compound. Driven by the back-donation from the Rh 4d(xz) orbital to the C-N sigma*-orbital, nitrogen extrusion takes place to afford a rhodium-carbene complex. The carbene carbon of the complex is strongly electrophilic because of its vacant 2p orbital. The C-H activation/C-C formation proceeds in a single step through a three-centered hydride transfer-like transition state with a small activation energy. Only one of the two rhodium atoms works as a carbene binding site throughout the reaction, and the other rhodium atom assists the C-H insertion reaction. The second Rh atom acts as a mobile ligand for the first one to enhance the electrophilicity of the carbene moiety and to facilitate the cleavage of the rhodium-carbon bond. The calculations reproduce experimental data including the activation enthalpy of the nitrogen extrusion, the kinetic isotope effect of the C-H insertion, and the reactivity order of the C-H bond.

DOI： 10.1021/ja017823o

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/hlca.200290011

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ja026069j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Conjugate addition of lithium diorganocuprate to acrolein, cyclohexenone, and 4,4-dimethylcyclohexenone has been studied in the presence of Me(2)O molecules coordinated on the lithium atoms. Solvation does not change the mechanism of the conjugate addition but increases the activation energy of the C-C bond-forming step through attenuation of the Lewis acidity of the lithium atoms. The substituent on the enone electrophile was found to have considerable influence on the activation energy. Computed activation energy of the conjugate addition of lithium dimethylcuprate to 4,4-dimethyleyclohexenone is DeltaE(double dagger) = 15.5 kcal/mol, which is close to the experimental data (E(a) = 18.2 +/- 1.7 kcal/mol). The (12)C/(13)C kinetic isotope effects were found to be susceptible to substituent effects. The (13)C NMR chemical shift values qualitatively agree with experimental data.

DOI： 10.1021/om0105270

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/1521-3757(20010518)113:10<1989::AID-ANGE1989>3.0.CO;2-C

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ja005565+

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ja993124o

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

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Synthesis of n-membered medium and macrocarbocycles through intramolecular sp(2)-sp(2) C-C bond formation was achieved with the aid of CuOTf or AgOTf by intramolecular coupling reaction of cyclopropenone acetals tethered by a methylene chain of (n - 4) carbon atoms, The reaction has proved to be useful for the synthesis of large carbocycles (n &gt; 13) in yields as high as 78%, and most notably also for an eight-membered carbocycle in 88% yield.

DOI： 10.1021/ol990053p

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ja991324u

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Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1016/S0040-4039(98)01748-1

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Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1055/s-1996-5692

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