Molybdenum-Catalyzed Enantioselective Ring-Closing Metathesis/Kinetic Resolution of Racemic Planar-Chiral 1,1'-Diallylferrocenes


Metal-Free Carbazole-Thiophene Photosensitizers Designed for a Dye-Sensitized H2-Evolving Photocatalyst in Z-Scheme Water Splitting


Competitive Double Friedel-Crafts 2,5- and 1',2-Diacylation of Monophosphaferrocenes


Asymmetric Metathesis Dimerization/Kinetic Resolution of Racemic Planar-Chiral Vinylphosphaferrocenes


Diastereo- and Enantioselective Metathesis Dimerization/Kinetic Resolution of Racemic Planar-Chiral Vinylferrocenes


Application of Polysaccharide-Based Chiral HPLC Columns for Separation of Regio-, E/Z-, and Enantio-isomeric Mixtures of Allylic Compounds


Synthesis of Monophosphaferrocenes Revisited


Enantioselective Preparation of Planar-Chiral Transition Metal Complexes by Asymmetric Olefin-Metathesis Reactions in Metal Coordination Spheres


Stereodivergent Access to Trisubstituted Alkenylboronate Esters through Alkene Isomerization


C1-Symmetric Binap Derivative Featuring Single Diferrocenylphosphino-Donor Moiety


Estimating Effective Steric and Electronic Impacts of Ferrocenyl Group in Organophosphines


Oxidative Cyclization of o-(1-Hydroxy-2-alkynyl)-N-tosylanilides for Syn-thesis of 4-Quinolones


Synthesis, Characterization, and Application of Segphos Derivative Having Diferrocenylphosphino-Donor Moieties


Versatile and Enantioselective Preparation of Planar-Chiral Metallocene-Fused 4-Dialkylaminopyridines and Their Application in Asymmetric Organocatalysis


Palladium-Catalyzed Three-Component Coupling of 1,1-Dibromoalkenes, Vinylzinc Chloride, and Soft Nucleophiles: One-Pot Synthesis of 1,3-Disubstituted Allenes


Palladium-Catalyzed Sequential Twofold Nucleophilic Substitution on 3-Bromopenta-2,4-dienyl Phosphate: Preparation of C1- and C2-Symmetric Doubly Functionalized Allenes


Application of Polysaccharide-Based Chiral HPLC Columns for Separation of Non-Enantiomeric Isomeric Mixtures of Organometallic Compounds


Theoretical Investigations of Rh-Catalyzed Asymmetric 1,4-Addition to Enones using Planar-Chiral Phosphine-Olefin Ligands


Catalytic Enantioselective Aldol Reaction of Unprotected Carboxylic Acids under Phosphine Oxide Catalysis


Molybdenum-Catalyzed Enantioselective Synthesis of Planar-Chiral (5-Phosphacyclopentadienyl)manganese(I) Complexes and Application in Asymmetric Catalysis


Atropisomeric Chiral Diiododienes (Z,Z)-2,3-Di(1-iodoalkylidene)tetralins: Synthesis, Enantiomeric Resolution, and Application in Asymmetric Catalysis


Palladium-Catalyzed SN2'-Cyclization of Ambivalent (Bromoalkadienyl)malonates: Preparation of Medium- to Large-Membered Endocyclic Allenes

A palladium-catalyzed reaction for preparing various endocyclic allenes was developed. The substrates for the reaction were readily available ω-(pronucleophile-tethered)-3-bromo-1,3-alkadienes, and a palladium-catalyst facilitated their unimolecular S2'-cyclization in the presence of potassium tert-butoxide to give the corresponding 9- to 16-membered endocyclic allenes in fair yields of up to 67% together with the dimeric 16- to 32-membered endocyclic bis-allenes and other oligomeric/polymeric intermolecular reaction products. For higher yields of the monomeric endocyclic allenes, the reaction needed to be conducted under high-dilution conditions. Using a chiral palladium catalyst, axially chiral endocyclic allenes were obtained in up to 70% ee.


Isolation and Photo Transformation of Enatiomerically Pure Iridium(III) Bis[(4,6-difuorophenyl)pyridinato-N,C2]picolinate


Kinetic Resolution of Planar-Chiral (5-Bromocyclopentadienyl)manganese(I) Complexes by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis


Planar-Chiral Phosphine-Olefin Ligands Exploiting a (Cyclopentadienyl)manganese(I) Scaffold to Achieve High Robustness and High Enantioselectivity

A series of 2-methyl-1,3-propenylene-bridged (η(5)-diarylphosphinocyclopentadienyl)(phosphine)manganese(I) dicarbonyl complexes 2 have been developed as a new class of phosphine-olefin ligands based on a planar-chiral transition-metal scaffold, which show better robustness as well as higher enantioselectivity over phosphine-olefin ligands 1 with a planar-chiral (η(6)-arene)chromium(0) framework. The practical enantiospecific and scalable synthesis of 2 has been established. Phosphine-olefin ligands 2 enable construction of an effective chiral environment around a transition-metal center upon coordination, and thus their rhodium(I) complexes exhibit excellent catalytic performance in the various asymmetric addition reactions of arylboron nucleophiles. Complex 2b, which has a bis(3,5-dimethylphenyl)phosphino group on the cyclopentadienyl ring, is found to be a superior chiral ligand in the rhodium-catalyzed asymmetric 1,4-addition reactions of arylboronic acids to various cyclic/acyclic enones giving the corresponding arylation products in over 99% ee. On the other hand, 2c and 2d, which have bis[3,5-bis(trifluoromethyl)phenyl]phosphino and bis(3,5-di-tert-buthyl-4-methoxyphenyl)phosphino groups, respectively, are highly efficient chiral ligands in the rhodium-catalyzed asymmetric 1,2-addition reactions of the arylboron nucleophiles to imines or aldehydes showing up to 99.9% ee. The X-ray crystallographic studies of (R)-2b and [RhCl((S*)-2b)]2 reveal the absolute configuration of 2b and its phosphine-olefin bidentate coordination to a rhodium(I) cation. Structural comparison with [RhCl((R*)-1b)]2 postulates the origins of the higher enantioselectivity of newly developed phosphine-olefin ligands 2.

Journal of the American Chemical Society


Enantioselective Synthesis of Ferrocene- or Cymantrene-Fused Planar-Chiral Phospholes


Bithiophene with Winding Vine-Shaped Molecular Asymmetry: Preparation, Structural Characterization, and Enantioselective Synthesis

Bulletin of the Chemical Society of Japan


Kinetic Resolution of Planar-Chiral Ferrocenylphosphine Derivatives by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis and Their Application in Asymmetric Catalysis


Concise Asymmetric Construction of C2-Symmetric 1,9-Diarylnonanoids Using Hypervalent Silicon Complex: Total Synthesis of (-)-Ericanone

By using a phosphine oxide-catalyzed enantioselective double aldol reaction, we achieved the concise construction of C2 -symmetric 1,9-diarylnonanoids, enabling the synthesis of (-)-ericanone from p-hydroxybenzaldehyde in 6 steps with 65 % overall yield. The enantioselective double aldol reaction is useful for establishing C2 -symmetric 1,9-diaryl-3,7-dihydroxy-5-nonanones with a single operation. Furthermore, the use of o-nosyl-protected p-hydroxybenzaldehyde and a 4,4'-disubstituted BINAP dioxide catalyst dramatically improved the reactivity and selectivity in the double aldol reaction, enabling the total synthesis of (-)-ericanone with high yield and with excellent enantiopurity.


Ring-Closing Metathesis of (eta5-Alkenylcyclopentadienyl)(alkenylphosphine)manganese(I) Dicarbonyl Complexes


Enantioselective Synthesis of Planar-Chiral Ferrocene-Fused 4-Pyridones and Their Application in Construction of Pyridine-Based Organocatalyst Library

A couple of planar-chiral ferrocene-fused 4-pyridone derivatives 2a and 2b were synthesized in enantiomerically pure form by scalable asymmetric transformations. Pyridones 2 are versatile precursors to various ferrocene-fused pyridine derivatives, which are useful nucleophilic asymmetric organocatalysts.


Enantioselective Desymmetrization of 1,2,3-Trisubstituted Metallocenes by Molybdenum-Catalyzed Asymmetric Intraannular Ring-Closing Metathesis


Enantioselective Synthesis of Macrocyclic Heterobiaryl Derivatives of Molecular Asymmetry by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis

Winding vine-shaped molecular asymmetry is induced by enantioselective ring-closing metathesis with a chiral molybdenum catalyst. The reaction proceeds under mild conditions through an E-selective ring-closing metathesis leading to macrocyclic bisazoles with enantioselectivities of up to 96% ee.


Simultaneous Induction of Axial and Planar Chirality in Arene-Chromium Complexes by Molybdenum-Catalyzed Enantioselective Ring-Closing Metathesis

The molybdenum-catalyzed asymmetric ring-closing metathesis of the various Cs -symmetric (ϖ-arene)chromium substrates provides the corresponding bridged planar-chiral (ϖ-arene)chromium complexes in excellent yields with up to >99 % ee. With a bulky and unsymmetrical substituent, such as N-indolyl or 1-naphthyl, at the 2-positions of the η(6) -1,3-diisopropenylbenzene ligands, both biaryl-based axial chirality and ϖ-arene-based planar chirality are simultaneously induced in the products. The axial chirality is retained even after the removal of the dicarbonylchromium fragment, and the chiral biaryl/heterobiaryl compounds are obtained with complete retention of the enantiopurity.


Phosphine Oxide-Catalyzed Enantioselective Intramolecular Aldol Reaction via Regioselective Enolization of Unsymmetrical Diketones with Tetrachlorosilane

The phosphine oxide-catalyzed asymmetric intramolecular aldol reactions of diketones were investigated. The combination of tetrachlorosilane and a chiral phosphine oxide catalyst promoted the acetyl-selective enolization of diketones, and the subsequent intramolecular aldol reaction occurred in an enantioselective manner. The introduction of two trimethylsilyl groups at the 4- and 4'-positions in BINAP dioxide catalyst improved the enantioselectivity. This reaction provides an effective synthetic method to access β-tertiary-hydroxy cyclohexanones in high yields and with high enantioselectivity.


Phosphine-Olefin Ligands Based on a Planar-Chiral (pi-Arene)chromium Scaffold: Design, Synthesis, and Application in Asymmetric Catalysis

The NMR and X-ray crystallographic studies clarified that planar-chiral alkenylene-bridged (phosphino-ϖ-arene)(phosphine)chromium complexes 3 were capable of coordinating to a rhodium(I) cation in a bidentate fashion at the (ϖ-arene)-bound phosphorus atom and at the olefin moiety. The P-olefin chelate coordination of 3 constructs the effective chiral environment at the metal center, and thus, these rhodium complexes display high performances in various rhodium-catalyzed asymmetric 1,4- and 1,2-addition reactions with arylboron nucleophiles. The control experiments demonstrated that the (η(2)-olefin)-Rh interaction as well as the bridging structure in 3 played the pivotal roles in the high enantioselectivity of the Rh-catalyzed asymmetric reactions. To enhance the synthetic utilities of these phosphine-olefin ligands, an enantiospecific and scalable synthetic method was developed. The novel synthetic method is flexible in terms of the substituent variation, and a library of the planar-chiral (arene)chromium-based phosphine-olefin ligands was established by the combinatorial approach. Among the newly prepared ligand library, compound 3g, which is with a bis(3,5-dimethylphenyl)phosphino group on the η(6)-arene ring, was found to be a far better chiral ligand in the rhodium-catalyzed asymmetric reactions showing excellent enantioselectivity and high yields.

Journal of the American Chemical Society


Hybrid Sponge Comprised of Galactosylated Chitosan and Hyaluronic Acid Mediates the Co-culture of Hepatocytes and Endothelial Cells

When constructing an in vitro model of liver tissue to mimic the in vivo liver microenvironment, the major challenge is to preserve and maintain the hepatocyte phenotype. The aim of this study was to develop a novel intelligent hybrid sponge for use in a dense co-culture system designed to simulate the liver microenvironment. We prepared a galactosylated chitosan (GCs)/hyaluronic acid (HA) hybrid sponge using a freeze-drying technique for the co-culture of primary hepatocytes and endothelial cells. Subsequently, we investigated the biocompatibility of the GCs/HA scaffold with primary hepatocytes and endothelial cells in terms of cell attachment, morphology, bioactivity, and maintenance of specific liver functions. The GCs/HA-hybrid sponge demonstrated good biocompatibility not only with primary hepatocytes, but also with endothelial cells. In our model, primary hepatocytes exhibited superior bioactivity and higher levels of liver-specific functions in terms of hepatocyte-specific gene expression, urea production, and testosterone metabolism as compared to a monoculture system. We succeeded in constructing a liver tissue-like model using the GCs/HA-hybrid sponge. Therefore, we anticipate that GCs/HA-hybrid sponges may be a promising matrix for the co-culture of hepatocytes and endothelial cells in liver tissue engineering, and might be employed as a novel co-culture model for applications in toxicology and drug metabolism.

Journal of Bioscience and Bioengineering


Atropisomeric Chiral Dienes in Asymmetric Catalysis: C2-Symmetric (Z,Z)-2,3-Bis[1-(diphenylphosphinyl)ethylidene]tetralin as Highly Active Lewis-Base Organocatalyst

Diene catalysts with a twist: The title C2 -symmetric tetralin-fused 1,3-butadiene derivative is atropisomeric and can be resolved into the two helical enantiomers. The optically pure compound showed excellent enantioselectivity as well as unusually high catalytic activity as a chiral Lewis basic organocatalyst in the asymmetric allylation of various aldehydes with β-substituted allyltrichlorosilanes.


Kinetic Resolution of Planar-Chiral 1,2-Disubstituted Ferrocenes by Molybdenum-Catalyzed Asymmetric Intraannular Ring-Closing Metathesis

Planar chirality: Ring-closing metathesis of 1,2-diallylmetallocenes afforded the corresponding 4,7-dihydroindenyl species in high yields. The metallocenes are planar chiral with two different allylic substituents, and kinetic resolution of the racemic 1,2-diallylmetallocene derivatives was realized by molybdenum-catalyzed asymmetric ring-closing metathesis with excellent enantioselectivity (see scheme).


Synthesis and Characterization of Benzo[b]phosphaferrocene Derivatives


Enantioselective Morita-Baylis-Hillman Reaction Catalyzed by a Chiral Phosphine Oxide


Inter- versus Intraannular Ring-Closing Metathesis on Polyallylferrocenes: Five-Fold RCM within a Single Molecule


Asymmetric Aldol Reaction on Water using an Organocatalyst Tethered on a Thermoresponsive Block Copolymer


Preparation of C2-Symmetric Allenes by Palladium-Catalyzed Double Nucleophilic Substitution on 3-Bromopenta-2,4-dienyl Acetate

Easily accessible 3-bromopenta-2,4-dienyl acetate was applied to the palladium-catalyzed reaction with soft nucleophiles. The reaction proceeded through the stepwise 2-fold nucleophilic substitution via formal S(N)2' and S(N)2 processes giving the various doubly functionalized C(2)-symmetric allenes in good yields.


Effects of Silyl Substituents on the Palladium-Catalyzed Asymmetric Synthesis of Axially Chiral (Allenylmethyl)silanes and Their SE2' Chirality Transfer Reactions


Kinetic Resolution of Planar-Chiral (eta6-Arene)chromium Complexes by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis


Preparation of Osmium-eta5-Phospholide Complexes and Their Reactions with Acyl Electrophiles: C=O Bond Cleavage and C-C Bond Formation within Metal-Coordination Sphere


Homoannular Double Friedel-Crafts Acylation of Phosphametallocenes


Ring-Closing Metathesis within Chromium-Coordination Sphere: Facile Access to Phosphine-Chelate (pi-Arene)chromium Complexes


Palladium-Catalyzed Asymmetric Synthesis of Axially Chiral Allenylsilanes and Their Application to SE2' Chirality Transfer Reactions

Stepwise application of the Pd-catalyzed S(N)2' reaction and the desilylative S(E)2' reaction to the ambivalent 2-bromo-1-silyl-1,3-dienes provides a novel route to the highly enantioselective construction of tertiary and quaternary propargylic stereogenic centers via axially chiral allenylsilanes.


Enantioselective Synthesis of Planar-Chiral Phosphaferrocenes by Molybdenum-Catalyzed Asymmetric Interannular Ring-Closing Metathesis

Enantioselective synthesis of planar-chiral phosphaferrocenes was realized for the first time by molybdenum-catalyzed asymmetric ring-closing metathesis (ARCM) in up to 99% ee, which is the first application of ARCM to induction of chirality in molecules devoid of stereogenic centers.

Journal of the American Chemical Society


Synthesis of Fluorinated Allenes via Palladium-Catalyzed Monofluoromethylation Using FBSM

Palladium-catalyzed monofluoromethylation of substituted 2-bromo-1,3-dienes using fluorobis(phenylsulfonyl)methane (FBSM) as a pronucleophile gave previously unknown monofluoromethylated allenes in high yields, which are the isosteres of biologically attractive allenic alcohols.


Unusual Transposition of Allenic Framework in Intramolecular Cyclization of Acetal-Tethered (Allenylmethyl)silanes

Treatment of acetal-tethered (allenylmethyl)silanes, which were obtained from the corresponding 3-bromo-5-silyl-1,3-pentadienes by a Pd-catalyzed reaction with an acetal-tethered malonate, with TiCl(4) gave not only vinylcyclohexene derivatives via a standard S(E)2' pathway but also unusual allenylcyclopentane species via cyclization at the delta-position. Deuterium-labeling experiments revealed participation of a 1,2-hydride shift in a carbocation intermediate for the formation of the latter products.


Palladium-Catalyzed Synthesis of Endocyclic Allenes and Their Application in Stereoselective [2+2]Cycloaddition with Ketenes

Palladium-catalyzed reactions of various 2-bromo-3-exo-methylenecycloalkenes with a stabilized nucleophile were examined. When the carbocycles were nine-membered or larger, the corresponding endocyclic allenes were isolated in excellent yields. In a reaction of the eight-membered cyclic substrate, initial formation of a cycloocta-1,2-diene derivative was detected; however, it dimerized slowly. The seven-membered carbocycle was inert to the reaction. Using a chiral Pd-catalyst, an axially chiral endocyclic allene was obtained in 65% ee. The cyclic allenes were applied to [2 + 2]cycloaddition with ketenes, and the stereoselectivity was studied.


Asymmetric Synthesis of Planar-Chiral Ferrocenes by Mo- or Ru-Catalyzed Enantioselective Metathesis


Preparation of [4]- and [5]Ferrocenophanes by Ruthenium-Catalyzed Ring-Closing Ene-Yne Metathesis


Alkenylzirconocene-Mediated Preparation of Alkenylphosphines

Alkenylphosphines with various substituents were prepared by the reaction of an alkenylzirconocene with a chlorophosphine. Reactions of (alpha-unsubstituted alkenyl)zirconocenes with Ph2PCl or PhPCl2 gave the corresponding alkenylphosphines in good yields. On the other hand, direct reactions of (alpha-unsubstituted alkenyl)zirconocenes with iPr2PCl did not proceed. Analogously, (alpha-substituted alkenyl)zirconocenes did not react with chlorophosphines directly. However, these reactions proceeded in the presence of CuCl affording the corresponding alkenylphosphines as CuCl complexes. Treatment of the copper complexes with Na2(dtc) (dtc = N,N-diethyldithiocarbamate) or Na4(edta) liberated free alkenylphosphines from the copper centers. The overall protocol could be applicable to preparation of a variety of alkenylphosphines from alkynes via alkenylzirconocene species.


Preparation and Characterization of 1,1'-Diphosphaferrocenes with Linearly Fused Six-Membered Carbocycles


Synthesis, Structure, and Reactivity of (1,2,3-η3-Butadien-3-yl)palladium Complexes


Unprecedented Formation of μ-Vinylidene Complexes from Phospharuthenocene and Acyl Chloride via Activation of the C=O Double Bond


Palladium-Catalyzed Preparation of Vinylallenes from 2-Bromo-1,3,5-trienes via an Alkylidene-pi-allylpalladium-Mediated Formal SN2" Pathway

[Structure: see text] A novel Pd-catalyzed reaction to prepare conjugated vinylallenes from 2-bromo-1,3,5-triene and a soft nucleophile via a formal SN2" pathway was developed. The reaction proceeds via alkylidene-pi-allylpalladium and allenyl-pi-allylpalladium intermediates, and a dynamic process involving the two palladium intermediates played important roles in determining the selectivity of the Pd-catalyzed reaction. The reaction was extended to an asymmetric counterpart, and an axially chiral vinylallene was obtained with up to 81% ee.


Synthesis of 2,5-Bis(binaphthyl)-phospholes and Phosphametallocene Derivatives and Their Application in Pd-Catalyzed Asymmetric Hydrosilylation


Kinetic Resolution of Planar-Chiral Ferrocenes by Mo-Catalyzed Enantioselective Metathesis


Pd-Catalyzed Intermolecular Asymmetric Hydroamination with 4,4'-Disubstituted BINAP and SEGPHOS


Vinyl Ketones to Allenes: Preparation of 1,3-Dien-2-yl Triflates and Their Application in Pd-Catalyzed Reaction with Soft Nucleophiles

[chemical reaction: see text]. A general route of converting alkenyl ketones to functionalized allenes was developed. Substituted 1,3-dien-2-yl triflates, which were prepared from the alkenyl ketones via silyl dienol ethers, were excellent substrates for the palladium-catalyzed reaction with soft nucleophiles giving the multisubstituted allenes in high yields. Comparison between the dienyl triflates and analogous bromodienes in the Pd-catalyzed reaction was studied as well.


New Route to Methyl (R,E)-(-)-Tetradeca-2,4,5-trienoate (Pheromone of Acanthoscelides Obtectus) Utilizing a Palladium-Catalyzed Asymmetric Allene Formation Reaction

[reaction: see text] A formal total synthesis of the sex attractant of male dried bean beetle, methyl (R,E)-(-)-tetradeca-2,4,5-trienoate, was achieved by a new efficient route utilizing the Pd-catalyzed asymmetric allene synthesis reaction. It was found that the atropisomeric biaryl bisphosphine (R)-segphos showed better enantioselectivity than (R)-binap in the Pd-catalyzed reaction for preparing alkyl-substituted axially chiral allenes.


Applications of 4,4'-(Me3Si)2-BINAP in Transition-Metal-Catalyzed Asymmetric Carbon-Carbon Bond-Forming Reactions

[structure: see text] A recently developed BINAP derivative with trimethylsilyl substituents on the 4- and 4'-positions of the binaphthyl skeleton, 2,2'-bis(diphenylphosphino)-4,4'-bis(trimethylsilyl)-1,1'-binaphthyl (tms-BINAP), was used in a variety of transition-metal-catalyzed asymmetric carbon-carbon bond-forming reactions. In pi-allylpalladium-mediated reactions, tms-BINAP gave better enantioselectivity than the unsubstituted BINAP, and the origin of the improved enantioselectivity was gained from an X-ray structural study of [Pd(eta(3)-C(3)H(5))((R)-tms-BINAP)]ClO(4).


Preparation of Multi-Substituted Allenes from Allylsilanes

[reaction: see text] A three-step route of converting allylsilanes to functionalized allenes was developed. Thermal decomposition of 1,1-dibromo-2-(silylmethyl)cyclopropanes, which were quantitatively prepared by treatment of allylsilane derivatives with CHBr3/KO(t)Bu, afforded substituted 2-bromo-1,3-butadienes with elimination of bromosilanes. The Pd-catalyzed reaction of the bromodienes with soft nucleophiles gave the allene derivatives. Previously inaccessible tri- and tetrasubstituted allenes can be prepared by this method as well.


Diallene Formation by Copper(I)-Mediated Reactions of Zirconacyclopentanes with Propargyl Halides


Coordination Behavior of Phosphino-Phosphaferrocenes: Monodentate vs Bidentate Coordination to Divalent Palladium


Controlling Regiochemistry of Zirconocene-Catalyzed Hydrosilation of Styrenes. Selective Preparation of Markownikoff and anti-Markownikoff Addition Products Using Same Combination of Procatalysts


Titanocene-Catalyzed Regioselective syn-Hydrosilation of Alkynes

[reaction: see text] The titanium catalyst, which was generated in situ from titanocene dichloride and 2 equiv of butyllithium, was found to catalyze hydrosilation of a variety of alkynes with excellent regio- and syn-selectivity.


Generation of Chiral Boron Enolates by Rhodium-Catalyzed Asymmetric 1,4-Addition of 9-Aryl-9-borabicyclo[3.3.1]nonanes (B-Ar-9BBN) to ,-Unsaturated Ketones

Asymmetric 1,4-addition of 9-phenyl-9-borabicyclo[3.3.1]nonane (2m) to 2-cyclohexenone (1a) proceeded with high enantioselectivity in toluene at 80 degrees C in the presence of 3 mol % of a rhodium catalyst generated from [Rh(OMe)(cod)]2 and (S)-binap to give a high yield of boron enolate (S)-3am, which is 98% enantiomerically pure. Reaction of the boron enolate 3am with electrophiles, methanol-d, propanal, and allyl bromide, gave the corresponding 2-substituted (3S)-3-phenylcyclohexanones with perfect regio- and diastereoselectivity.


Palladium-Catalyzed Asymmetric Synthesis of Axially Chiral (Allenylmethyl)silanes and Chirality Transfer to Stereogenic Carbon Centers in SE` Reactions

[reaction: see text] Novel stereoselective reactions of 4-substituted-1-trimethylsilyl-2,3-butadienes ((allenylmethyl)silanes) were developed. The axially chiral (allenylmethyl)silanes were prepared from (3-bromopenta-2,4-dienyl)trimethylsilane by a Pd-catalyzed asymmetric reaction with soft nucleophiles with up to 88% enantioselectivity. The (allenylmethyl)silanes reacted with acetals in the presence of a TiCl(4) promoter to give 1,3-diene derivatives via an S(E)' pathway. The 1,3-dienyl products have (E)-geometry exclusively and up to 88%( )()chirality transfer from the axially chiral allenes to the centrally chiral 1,3-dienes was observed in the S(E)' reaction.


Synthesis of 1,1-Diphospha[4]ferrocenophanes by Molybdenum-Catalyzed Ring-Closing Metathesis


Induction of Atropisomeric Chirality on Heavily Substituted Phosphametallocenes


A New Type of Catalytic Tandem 1,4-Addition-Aldol Reaction Which Proceeds through an (Oxa-pi-allyl)rhodium Intermediate

The reaction of 9-aryl-9-borabicyclo[3.3.1]nonanes (B-Ar-9BBN) with alpha,beta-unsaturated ketones and aldehydes in the presence of 3 mol % [Rh(OMe)(cod)](2) in toluene at 20 degrees C for 2 h gave high yields of the tandem 1,4-addition-aldol reaction products with high syn selectivity. The reaction proceeds through the catalytic cycle consisting of 1,4-addition of an organorhodium species to an alpha,beta-unsaturated ketone and the aldol addition of the resulting (oxa-pi-allyl)rhodium intermediate to an aldehyde.

Journal of the American Chemical Society


Metathesis Route to Bridged Metallocenes

A variety of bridged metallocenes of Fe(II), Ru(II), Zr(IV), or Hf(IV) were prepared in good yield by the interannular ring-closing metathesis reaction of 1,1'-diallylmetallocenes using the Ru-carbene catalyst, and the present method was extended to diastereoselective reaction to give dl- or meso-bridged metallocenes with excellent stereoselectivity.


Asymmetric Synthesis of Metallocenes through Enantioselective Addition of Organolithium Reagents to 6-(Dimethylamino)fulvene

Enantioselective addition of aryllithiums 2a-d (Ar = Ph (a), 2-MeC(6)H(4) (b), 2-MeOC(6)H(4) (c), 1-naphthyl (d)) to 6-(dimethylamino)fulvene (1) in the presence of (-)-sparteine in toluene at -78 degrees C generated chiral cyclopentadienyllithiums (4) substituted with an N,N-dimethylamino(aryl)methyl group, where the enantioselectivities are 51, 91, 90, and 83% for 4a, 4b, 4c, and 4d, respectively. Treatment of the chiral cyclopentadienides 4 with FeCl(2) or Fe(acac)(2) gave ferrocenes, which contain an N,N-dimethylamino(aryl)methyl side chain on both of the cyclopentadienyl rings. The enantiomeric purity of the chiral ferrocenes 7 thus obtained is 99% ee or higher for those containing a 2-MeC(6)H(4) (7b) or a 2-MeOC(6)H(4) (7c) group.


Catalytic Cycle of Rhodium-Catalyzed Asymmetric 1,4-Addition of Organoboronic Acids. Arylrhodium, Oxa-pi-allylrhodium, and Hydroxorhodium Intermediates

The catalytic cycle of asymmetric 1,4-addition of phenylboronic acid to an alpha,beta-unsaturated ketone catalyzed by a rhodium-binap complex was established by use of RhPh(PPh(3))(binap) as a key intermediate. The reaction proceeds through three intermediates, phenylrhodium, oxa-pi-allylrhodium, and hydroxorhodium complexes, all of which were observed in NMR spectroscopic studies. The transformations between the three intermediates, that is, insertion, hydrolysis, and transmetalation, were also observed. On the basis of the catalytic cycle, a more active chiral catalyst, [Rh(OH)(binap)](2), was found and used successfully for the asymmetric 1,4-addition reactions.


Widening the Roof: Synthesis and Characterization of New Chiral C1-Symmetric Octahydrofluorenyl Organolanthanide Catalysts and Their Implementation in the Stereoselective Cyclizations of Aminoalkenes and Phosphinoalkenes


Synthesis and Characterization of 1,1'-Diphospharuthenocenes


Effects of Bidentate Phosphine Ligands on syn-anti Isomerization in pi-Allylpalladium Complexes


Rhodium-Catalyzed Asymmetric 1,4-Addition of Organoboron Reagents to 5,6-Dihydro-2(1H)-pyridinones. Asymmetric Synthesis of 4-Aryl-2-piperidinones

Catalytic asymmetric synthesis of 4-aryl-2-piperidinones was realized for the first time by asymmetric 1,4-addition of arylboron reagents to 5,6-dihydro-2(1H)-pyridinones in the presence of a chiral bisphosphine-rhodium catalyst. In the reaction introducing 4-fluorophenyl group, the use of 4-fluorophenylboroxine and 1 equiv (to boron) of water at 40 degrees C gave the highest yield of the arylation product with high enantioselectivity (98% ee). The (R)-4-(4-fluorophenyl)-2-piperidinone obtained here is a key intermediate for the synthesis of (-)-Paroxetine.


Rhodium-Catalyzed Hydroarylation of Alkynes with Arylboronic Acids. 1,4-Shift of Rhodium from 2-Aryl-1-alkenylrhodium to 2-Alkenylarylrhodium Intermediate


Chloroprene as a Source of Fine Chemicals: Palladium-Catalyzed Synthesis of Terminal Allenes

[reaction: see text] Several functionalized terminal allenes were prepared in moderate to excellent yield by a palladium-catalyzed reaction of chloroprene (2-chloro-1,3-butadiene) with soft nucleophiles.


Palladium-Catalyzed Asymmetric Synthesis of Axially Chiral Allenes: A Synergistic Effect of Dibenzalacetone on High Enantioselectivity


Synthesis and Characterization of a Novel Chiral Phosphole and Its Derivatives


A Novel Chiral Phosphino-Phosphaferrocene: Its Coordination Behavior and Application to Palladium-Catalyzed Asymmetric Allylic Alkylation


Novel Palladium Chiral Phosphino-Oxazoline Complexes: Crystal Structure Studies and Application to Asymmetric Heck Reaction


pi-Allylpalladium-Mediated Catalytic Synthesis of Functionalized Allenes


2,2'-Bis(diphenylphosphino)-1,1'-biphenyl: New Entry of Bidentate Triarylphosphine Ligand to Transition Metal Catalysts


Palladium-Catalyzed Asymmetric Reduction of Racemic Allylic Esters with Formic Acid; Effects of Phosphine Ligands on Isomerization of pi-Allylpalladium Intermediates and Enantioselectivity


Palladium-Catalyzed Synthesis of Butatrienes


Asymmetric 1,4-Addition of Phenylboronic Acid to 2-Cyclohexenone Catalyzed by Rh(I)/binap Complexes


Rhodium-Catalyzed Asymmetric Conjugate Addition of Organoboronic Acids to Nitroalkenes

Journal of the American Chemical Society


Design and Preparation of 3,3'-Disubstituted 2,2'-Bis(oxazolyl)-1,1'-binaphthyls (boxax): New Chiral Bis(oxazoline) Ligands for Catalytic Asymmetric Wacher-Type Cyclization


Synthetic Approaches to Fe(II) Complexes of the Bulky Phosphine PtBu2Me


Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboron Compounds Generated in situ from Aryl Bromides


Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboron Reagents to alpha,beta-Unsaturated Esters


Rhodium-Catalyzed Asymmetric 1,4-Addition to 1-Alkenylphosphonates


Synthesis and Application of Novel Chiral Phosphino-Oxazoline Ligands with 1,1'-Binaphthyl Skeleton


Rhodium-Catalyzed Asymmetric 1,4-Addition of Aryl- and Alkenylboronic Acids to Enones


Rhodium-Catalyzed Asymmetric 1,4-Addition of 2-Alkenyl-1,3,2-benzodioxaboroles to alpha,beta-Unsaturated Ketones


Is pi-Donation the Only Way ? Unprecedented Unsaturated Ru(II) Species Devoid of pi-Donor Ligands


Competition between Steric and Electronic Control of Structure in Ru(CO)2L2L' Complexes


RuX(CO)(NO)L2 and Ru(CO)(NO)L2+: Ru(0) or Ru(II) or In Between?


Structure and Characterization of 9,10-Diethyl-9,10-diphospha-9,10-dihydroanthracene as an Electron Donor

Bulletin of the Chemical Society of Japan


Characterization and Reactivity of an Unprecedented Unsaturated, Zerovalent Ruthenium Species: Isolable, Yet Highly Reactive


Estimating the Effective Steric Impact of PtBu2Me, PiPr3, and PCy3


Unexpected Coexistence of Isomeric Forms and Unusual Structures of Ru(CO)2L3


Isolable, Unsaturated Ru(0) in Ru(CO)2(PtBu2Me)2; Not Isostructural with Rh(I) in Rh(CO)2(PR3)2+

Journal of the American Chemical Society


Effects of Chelate Ring Rigidity on Intramolecular Hydrogen Exchange in Hydrido(dihydrogen)bis(diphosphine)ruthenium(II) Ions [RuH(eta2-H2)(diphosphine)2]+ (diphosphine = binap and dpbp)


Agostic Interaction and Intramolecular Hydrogen Exchange in Coordinatively Unsaturated Ruthenium Complexes: Effects of Chelate Ring Size on Intramolecular Carbon-Hydrogen Bond Activation of Diphosphine Ligands


Agostic Interaction and Hydrogen Exchange in Coordinatively Unsaturated Ruthenium Complexes


Asymmetric Hydrogenation of Prochiral Carboxylic Acids Catalyzed by Five-Coordinate Ruthenium(II)-Hydride Complex [RuH(binap)2]PF6 (binap = (R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl)


Asymmetric Transfer Hydrogenation of Prochiral Carboxylic Acids Catalyzed by a Five-Coordinate Ru(II)-binap Complex


Asymmetric Hydrogenation of Prochiral Carboxylic Acids and Functionalized Carbonyl Compounds Catalyzed by Ruthenium(II)-binap Complexes with Aryl Nitriles (binap = (R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl)