Reductive Coupling Reaction Research Articles

Characterization of a Paramagnetic, Mononuclear Pt(III)–Alkyl Complex Intermediate in Carbon–Halogen Bond Coupling Reactions

Addition of Br(2) or I(2) to 14-electron, cationic Pt(II)-alkyl complexes led to the formation of the corresponding carbon-halogen Pt(II) coupling products. Low temperature experiments with Br(2) allowed us to isolate and characterize crystallographically a very unusual mononuclear, paramagnetic Pt(III)-alkyl intermediate with a seesaw structure that can be further oxidized to a transient Pt(IV) species before reductive carbon-halogen coupling reaction takes place.

ChemInform Abstract: Synthesis, Reactivity and Applications of Zinc—Zinc Bonded Complexes

AbstractReview: 83 refs.

ChemInform Abstract: Nickel‐Catalyzed Diastereoselective Reductive Coupling Reaction of Norbornene with Aldehydes in the Presence of Triethylborane.

AbstractAliphatic and aromatic aldehydes (II) and (V) undergo a reductive coupling reaction with norbornene (I) and norbornadiene (IV) in the presence of triethylborane as reducing agent and a Ni—phosphine catalytic system to provide the secondary alcohols (III) and (VI), resp., in a smooth and highly diastereoselective fashion.

Evolution of Late Transition‐Metal‐Catalyzed Intermolecular Reductive Coupling Reaction of [60]Fullerene and N‐Sulfonylaldimines: Competing Formation of Hydrobenzylated [60]Fullerenes and 1,2‐Dihydrofullerene

AbstractA system based on late transition‐metal halides, phosphanes, water, and reducing agents in 1,2‐dichlorobenzene can efficiently catalyze the intermolecular reductive coupling of [60]fullerene with N‐sulfonylaldimines to afford novel 1,2‐hydrobenzylated [60]fullerene derivatives. We found that both group VII B metals (cobalt, rhodium, iridium) and group VIII B metals (nickel, palladium, platinum) perform this coupling reaction. A control experiment in the absence of aldimines produced C60H2, which showed that the reaction might proceed via a [60]fullerene metal complex [M(η2‐C60)(ligand)]. An isotope labeling experiment with D2O as deuterium source resulted in deuterioaryzilation with deuterium bonded to the sp3‐carbon of C60, providing evidence of a five‐membered azametallacycle intermediate. Evaluation of the scope of reductive coupling reaction with versatile aldimines gave access to the hydroaryzilation products. All the reductive coupling products were completely characterized by IR and NMR spectroscopy and ESI mass spectrometry. A possible reaction mechanism based on these results is proposed. This discovery of the formation of reductive coupling compounds and metal‐catalyzed formation of C60H2 are both new to metal catalysis and fullerene chemistry.

Nickel‐Catalyzed Regio‐ and Stereoselective Reductive Coupling between Methylenecyclopropanes, Aldehydes, and Triethylborane with Retention of the Cyclopropane Ring

Running rings: The first regio- and stereoselective reductive coupling between methylenecyclopropanes, aldehydes, and triethylborane with retention of the cyclopropane ring was achieved using a nickel-phosphine catalyst (see scheme). The reductive coupling reaction constructed a stereo-defined cyclopropane ring with formation of a quaternary stereogenic carbon center.

Reductive Coupling of Aldehydes by H2S in Aqueous Solutions, a CC Bond Forming Reaction of Prebiotic Interest

We report here a novel reductive coupling reaction of conjugated, non- or poorly enolizable aldehydes induced by H(2) S and operative in aqueous solutions under prebiotically relevant conditions. This reaction leads from retinal to β-carotene, and from benzylic aldehydes to the corresponding diarylethylenes. This novel reaction also opens a new potentially prebiotic pathway leading from glyoxylic acid to various compounds that are involved in the reductive tricarboxylic acid cycle. This C--C bond forming reaction of prebiotic interest might have been operative, notably, in the sulfide-rich environments of hydrothermal vents, which have been postulated as possible sites for the first steps of organic chemical evolution.

Access to functionalized 4-benzylidene-4H-benzo[d][1,3]thiazines via tandem addition-cyclization/cross-coupling reactions

Tandem addition-cyclization reactions of various 2-alkynylbenzenamines with CS2 lead to the formation of 2-mercapto-4-benzylidene-4H-benzo[d][1,3]thiazines under mild conditions. The reactions showed moderate to excellent yields and were highly regiospecific, and only the six-membered ring was generated via 6-exo-dig S-cyclization. The reaction can be transferred to highly functionalized 4-benzylidene-4H-benzo[d][1,3]thiazines via CuI-catalyzed crossing-coupling and reductive coupling reactions.

ChemInform Abstract: Triflic Acid Catalyzed Reductive Coupling Reactions of Carbonyl Compounds with O‐, S‐, and N‐Nucleophiles.

AbstractHighly efficient metal‐free reductive coupling reactions of aldehydes and ketones with a range of nucleophiles in the presence of triflic acid as catalyst are presented.

Nickel-catalyzed Diastereoselective Reductive Coupling Reaction of Norbornene with Aldehydes in the Presence of Triethylborane

Abstract Highly diastereoselective reductive coupling reaction was achieved between an aldehyde and a norbornene to afford an alcohol compound using a nickel/phosphine catalyst system in the presence of a reducing agent. The combination of a PCy3 ligand and triethylborane as the reducing agent proved effective for the reaction. A wide range of aldehydes were found to participate in the reaction with high diastereoselectivities.

0価ニッケル錯体触媒を用いたC-HおよびC-C結合活性化を含む3成分カップリング反応の開発

The studies on nickel(0)-catalyzed three-component reactions via C-H and C-C bond activation were described. Highly regio- and stereoselective cross-trimerization of alkynes proceeded to give the corresponding 1,3-diene-5-yne by combination of triisopropylsilylacetylene and identical or distinct two alkynes via selective terminal C-H bond activation of triisopropylsilylacetylene in the presence of Ni(cod)2/phosphine catalyst. The methodology could be also extended toward the three-component reaction among two alkynes and a norbornene to give the 1,5-enyne. On the other hand, our interest also focused on three-component reductive coupling reaction between ring-strained cyclic alkene, aryl aldehyde and silane. Using methylenecyclopropane, reductive coupling reaction with aryl aldehyde and triisopropylsilane proceeded to yield silylated allylic alcohols via C-C bond cleavage of methylenecyclopropane ring in the presence of Ni(cod)2/NHC catalyst. We also found an unprecedented three-component reductive coupling via aromatic C-H bond activation of aryl aldehyde at the ortho position by combination with norbornene and triisopropylsilane leading to silylated indanol using Ni(cod)2/NHC catalyst.

Synthesis, reactivity and applications of zinc–zinc bonded complexes

The discovery of decamethyldizincocene [Zn(2)(η(5)-Cp*)(2)] (Cp* = C(5)Me(5)), the first complex containing a covalent zinc-zinc bond, by Carmona in 2004 initiated the search for this remarkable class of compounds. Low-valent organozinc complexes can either be formed by ligand substitution reactions of [Zn(2)(η(5)-Cp*)(2)] or by reductive coupling reactions of Zn(ii) compounds. To the best of our knowledge, until now 25 low-valent Zn-Zn bonded molecular compounds stabilized by a variety of sterically demanding, very often chelating, organic ligands have been synthesized and characterized. There are two major reaction pathways of [Zn(2)(η(5)-Cp*)(2)]: it can either react with cleavage of the Zn-Zn bond or by ligand substitution. In addition, upon reaction with late transition metal complexes, [Zn(2)(η(5)-Cp*)(2)] was found to form novel intermetallic complexes with Cp*Zn and Cp*Zn(2) acting as unusual one-electron donor ligands. Very recently, the potential capability of [Zn(2)(η(5)-Cp*)(2)] to serve as a suitable catalyst in hydroamination reactions was demonstrated. Finally, the recent work on Cd-Cd bonded coordination compounds is reviewed.

トリエチルホウ素と後周期遷移金属の相乗効果を利用した炭素‐炭素結合形成および切断反応

Ni catalyzes homoallylation of aldehydes with 1,3-dienes in the presence of triethylborane to provide bishomoallyl alcohols. Triethylborane serves as reducing agent and Lewis acid to promote the homoallylation via oxanickelacycles. Under similar conditions, Rh catalyzes the reductive coupling reaction of aldehydes and 1,3-dienes to provide homoallyl alcohols while Pd catalyst promotes the ene-type reaction to provide dienyl homoallyl alcohols.Triethylborane also activates allylic alcohols to form π-allylpalladium key intermediates by oxidative addition of Pd(0) toward allylic C-O bonds and achieves amphiphilic allylations. A combination of Pd catalyst and triethylborane effectively promotes 3-hydroxy-4-pentenoic acid to undergo β-decarboxylative C-C bond cleavage reaction via β-vinyloxapalladacyclopentanone to provide conjugated diene and carbon dioxide.

Novel photo-switchable polymers based on calix[4]arenes

5,17-Dinitrocalix[4]arenes with varying lower rim substituents (butyl, dodecyl chains), locked in the cone conformation, were synthesized and further subjected to reductive coupling reactions to yield a new type of photoswitchable polymers—poly(azocalix[4]arenes). These rigid polymers can undergo reversible photoswitching between the trans and cis form upon irradiation with specific wavelengths, as well as slow thermal isomerisation back to the preferred trans form.

Mechanistic Study of Half-titanocene-based Reductive Pinacol Coupling Reaction

E-mail: sungjinpark@inha.ac.krReceived July 13, 2011, Accepted September 14, 2011The reductive pinacol coupling reaction of aldehydes or ketones creating a new C-C bond has been a major toolto produce 1,2-diol compounds. The reaction mechanism is known to be composed of sequential three steps(activation, coupling, and dissociation). In this work, we studied the dissociation step of half-titanocene-basedcatalytic systems. Cp and Cp* derivatives of the pinacolato-bridged dinuclear complex were synthesized andevaluated as possible models for intermediates from the coupling step. We monitored

Luminophore charge effects in water-based oxygen sensor films

The neutral luminophore [Ir(ppy) 2(fppy)], where fppy = 4-(2-pyridyl)benzaldehyde and ppy = 2-phenylpyridine were prepared and bound to the water soluble amine-functionalized polymer Silamine D208-EDA by either reductive amination or coupling reactions. Pressure sensitive paint (psp) formulations were made by blending microcrystalline cellulose (MC) with these polymer-luminophores and the psp photophysical properties, oxygen sensitivities and luminescent microscopies were compared to psps made from the charged luminophore [Ir(fppy) 2( t-Bu-iCN) 2]CF 3SO 3, where t-Bu-iCN = tert-butyl isocyanide, attached by reductive amination to Silamine D208-EDA. The excited-state lifetime for the neutral luminophore in psp blends was almost independent of MC concentration whereas those of the charge luminophore increased with MC concentration. The nearly 30% increase in oxygen sensitivity of psps made with the charged compared to neutral polymer luminophores is ascribed to the association of charged luminophores with polar groups on the surface of MC.

Triflic Acid Catalyzed Reductive Coupling Reactions of Carbonyl Compounds with O‐, S‐, and N‐Nucleophiles

Highly efficient metal-free reductive coupling reactions of aldehydes and ketones with a range of nucleophiles in the presence of triflic acid (1-5 mol%) as the catalyst are presented. The reactions can be performed at ambient temperature without exclusion of moisture or air. A range of symmetrical and unsymmetrical ethers were obtained by this method in high yields and short reaction times. For the first time, the influence of additional functionalization has been studied. Furthermore, the formation of thioethers from ketones (by addition of unmodified thiols) and of sulfonamides from either aldehydes or ketones has been achieved under catalytic conditions.

A Concise Total Synthesis of (−)-Maoecrystal Z

The first total synthesis of (-)-maoecrystal Z is described. The key steps of the synthesis include a diastereoselective Ti(III)-mediated reductive epoxide coupling reaction and a diastereoselective Sm(II)-mediated reductive cascade cyclization reaction. These transformations enabled the preparation of (-)-maoecrystal Z in only 12 steps from (-)-γ-cyclogeraniol.

Fourier-transform infrared spectroscopic studies of pristine polysilanes as precursor molecules for the solution deposition of amorphous silicon thin-films

Pristine polysilane containing only Si and H is considered as a potential precursor material that allows the solution-based deposition of hydrogenated amorphous Si (a-Si:H) thin-films reducing manufacturing cost of Si thin-film photovoltaic devices. This study explored three different synthetic routes including Würtz-type reductive coupling reaction, hydrogenation of Si anionic compound, and the dehydrocoupling reaction in order to realize the soluble polysilane molecules. While Würtz-type reaction of diiodosilane presented us a direct synthetic scheme for hydrogenated polysilane, the results indicated that an extremely controlled air-free system for the synthesis and sample handling would be necessary to prevent the formation of siloxane bonds from the spontaneous reaction between silane-based molecules and water in the air. While the hydrogenation of CaSi2 and the dehydrocoupling reaction of phenylsilane provided more stable forms of polysilane, dissolution of the polysilane from CaSi2 in dichlorobenzene was not successful possibly due to its layered structure succeeded from CaSi2 and the removal of the phenyl groups from the synthesized polyphenylsilane remains as a challenge to realize the polysilane precursor necessary for the solution-based thin-film process of a-Si:H.

Ligand steric contours to understand the effects of N-heterocyclic carbene ligands on the reversal of regioselectivity in Ni-catalyzed reductive couplings of alkynes and aldehydes.

The regioselectivities of N-heterocyclic carbene (NHC) ligands in Ni-catalyzed alkyne-aldehyde reductive coupling reactions with silane reducing agents are investigated using density functional theory. Reversal of regioselectivity can be achieved by varying the steric bulkiness of the ligand. The steric influences of NHC ligands are highly anisotropic. Regioselectivity is primarily controlled by the steric hindrance at the region of the ligand close to the alkyne. Analysis of 2D contour maps of the NHC ligands indicates that the regioselectivities are directly affected by the shape and orientation of the N-substituents on the ligand.

31P NMR Studies Demonstrating the Assembly of catena-Phosphorus Frameworks from Chlorophosphinochlorophosphonium Cations

New examples of chlorophosphinochlorophosphonium (4) and chlorophosphinodichlorophosphonium (5) cations have been prepared and spectroscopically characterized. These bifunctional phosphinophosphonium cations offer a new approach to the development of phosphinophosphonium frameworks using reductive coupling reactions and have been exploited as synthons to assemble larger catena-phosphorus cations. The reactions of 4 and 5 with stibine reducing agents have been studied using (31)P NMR spectroscopy and have been shown to produce a variety of new and known frameworks in a facile manner, depending on the reducing agent selection and the stoichiometry of the reaction. New derivatives of frameworks containing three, four, and five phosphorus atoms have been identified by (31)P NMR spectroscopy. Crystals of the [GaCl(4)](-) salt of the five-membered dication 11((i)Pr) have been isolated from the reaction of [4((i)Pr)][GaCl(4)] with SbBu(3), and the solid state structural features and solution state dynamics are comprehensively described in the context of (31)P{(1)H} NMR spectroscopic observations.