Ruthenium- and Copper-Catalyzed Propargylic Substitution Reactions of Propargylic Alcohol Derivatives with Hydrazones

Ruthenium- and copper-catalyzed propargylic substitution reactions of propargylic alcohol derivatives with N-monosubstituted hydrazones as ambident nucleophiles are achieved in which N-monosubstituted hydrazones exhibit impressive different reactivities depending on different catalytic systems, behaving as carbon-centered nucleophiles to give the corresponding propargylic alkylated products in ruthenium catalysis, or as nitrogen-centered nucleophiles to afford the corresponding propargylic aminated products in copper catalysis. DFT calculations were carried out to investigate the detailed reaction pathways of these two systems. Further transformation of propargylic substituted products affords the corresponding multisubstituted pyrazoles as cyclization products in good to high yields.     

Oxidative Coupling of Terminal Alkynes with Aldehydes Leading to Alkynyl Ketones by Using Indium(III) Bromide

An indium(III)‐promoted direct acylation of terminal alkynes using aldehydes leading to ynones was developed. In contrast to the previous addition reactions of alkynes to aldehydes, which provide propargylic alcohols, the oxidative coupling proceeded exclusively to afford alkynyl ketones. The products were likely generated through an Oppenauer oxidation of the indium propargylic alkoxide species by excess amounts of aldehydes.     

Tris（2,2＇-bipyridyl） Ruthenium（Ⅱ） Doped Silica Film Modified Indium Tin Oxide Electrode and Its Electrochemiluminescent Properties

An approach was reported to synthesize silica hybridized ruthenium bipyridyl complex through amidation reaction by covalent attachment of bis（bipyridyl）-4,4＇-dicarboxy-2,2＇-bipyridyl-ruthenium to （3-aminopropyl）-triethoxysilane. The hybrid complex then was gelatinized through acid catalytic hydrolysis method and a sol-gel modified indium tin oxide electrode was prepared via spin coating technique. As prepared indium tin oxide electrode possesses good stability therein with excellent electrochemiluminescence behavior.     

Expeditious entry to novel 2-methylene-2,3-dihydrofuro[3,2-c] chromen-2-ones from 6-chloro-4-hydroxychromen-2-one and propargylic alcohols

A catalytic system consisting of the ruthenium(II) complex [Ru(η3-2-C3H4Me)(CO)(dppf)][SbF6] (dppf=1,1'-bis(diphenylphosphino)ferrocene) and trifluoroacetic acid has been used to promote the coupling of secondary propargylic alcohols with 6-chloro-4-hydroxychromen-2-one. The reactions afforded unusual 2-methylene-2,3-dihydrofuro[3,2-c]chromen-2-ones in good yields.     

Ruthenium- and gold-catalysed sequential reactions: a straightforward synthesis of substituted oxazoles from propargylic alcohols and amides

A convenient and straightforward one-pot reaction of propargylic alcohols bearing a terminal alkyne moiety with amides by the sequential action of ruthenium and gold catalysts gives the corresponding substituted oxazoles in good yields with a complete regioselectivity.     

Synthesis of a wide range of thioethers by indium triiodide catalyzed direct coupling between alkyl acetates and thiosilanes

An indium triiodide-catalyzed substitution of the acetoxy group in alkyl acetates with thiosilanes provides access to a variety of thioethers. The method is efficient for a wide scope of acetates such as primary alkyl, secondary alkyl, tertiary alkyl, allylic, benzylic, and propargylic acetates.     

Regio- and stereoselective syntheses of piperidine derivatives via ruthenium-catalyzed coupling of propargylic amides and allylic alcohols

Intermolecular selective coupling of linear allylic alcohols and propargylic amides occurs in the presence of a catalytic amount of the cationic ruthenium complex [Cp*Ru(NCCH(3))(3)]PF(6) followed by condensation to generate six-membered cyclic enamides or hemiaminal ethers with water as the only side product.     

Solvent-free synthesis of naphthopyrans under ball-milling conditions

Under solvent-free ball-milling conditions, the nucleophilic addition reactions of terminal alkynes to carbonyl compounds promoted by KOH proceeded efficiently at ambient temperature. Subsequent cyclization reactions of the synthesized propargylic alcohols with 2-naphthol catalyzed by indium trichloride tetrahydrate, leading to the formation of naphthopyrans, were then investigated. In most cases, side reactions were avoided and thus high yields were achieved.     

Expanded scope in ethylene-alkyne cross-metathesis: coordinating heteroatom functionality at the propargylic position

The Grubbs 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene-substituted ruthenium complex 1 catalyzed ethylene-alkyne cross-metathesis and was shown to tolerate free hydroxyl groups and coordinating functionality at the propargylic and homopropargylic positions. Hindered and enantiomerically enriched 1-substituted alkynes also react efficiently under the reported conditions.     

Coprecipitation Behavior of Some Metals with Chitosan and Their Determination by Graphite Furnace Atomic Absorption Spectrometry

Chitosan is derived from chitin by deacetylation. Chitosan forms a complex with metal ions and is soluble an organic acid. The metal ions were concentrated in the precipitates of chitosan when the sample solution containing metal ions was adjusted to neutral after the chitosan solution was added. These properties are applied to the preconcentration of metal ions in water samples and their determination by graphite furnace atomic absorption spectrometry. Metal ions,such as ruthenium, indium, vanadium, strontium,rhodium were collected in the chitosan precipitates.     

Metal-free access to fully substituted skipped diynes. An efficient chemodifferentiating A2BB' 4CR manifold

A metal-free chemodifferentiating A2BB' 4CR manifold for the modular synthesis of tertiary skipped diynes is described. The manifold performs a triethylamine triggered reaction of alkyl propiolates and acid chlorides to assemble two units of each component in the form of two propargylic alkynoates, a tertiary alcohol, and an ester. A differentiated incorporation of the two acid chloride components ensures functional diversity in the final structure. In addition, the presence of two connected propargylic alkynoates provides a reactive platform for complexity generation.     

A new ruthenium-catalyzed cyclopropanation of alkenes using propargylic acetates as a precursor of vinylcarbenoids

[RuCl₂(CO)₃]₂ catalyzes intermolecular cyclopropanation of various alkenes with propargylic acetates to give vinylcycloropanes in good yields. The key intermediate of this reaction is a vinylcarbene complex generated by nucleophilic attack of the carbonyl oxygen of the acetate to an internal carbon of alkyne activated by the ruthenium complex.     

New strategy for the construction of a monotetrahydrofuran ring in Annonaceous acetogenin based on a ruthenium ring-closing metathesis: application to the synthesis of Solamin

An original convergent total synthesis of Solamin (type A annonaceous acetogenin) was achieved. The central THF core was obtained by means of a ring-closing metathesis (RCM) reaction using a ruthenium imidazolylidene complex. The RCM substrate was prepared from a vinyl-substituted epoxide by reaction with an allyl alcohol, both synthesized from propargylic alcohol. The flexibility of the strategy should be useful in preparing various natural and unnatural annonaceous acetogenins.     

InBr3-catalyzed direct alkynylation of nitrones with terminal alkynes: an efficient synthesis of N-hydroxy-propargyl amines

An InBr₃-catalyzed direct and efficient alkynylation of nitrones with terminal alkynes was developed. The process enables practical synthesis of a wide range of synthetically useful N-hydroxy-propargyl amine derivatives in good yields under mild conditions. The application of this method to optically active propargylic N-hydroxyamines syntheses was also described. With chiral nitrones, good diastereoselectivities were obtained. Moreover, the first chiral indium(III) complex-catalyzed asymmetric alkynylation of nitrone was achieved with moderate enantioselectivity.     

Studies on the mechanism of intermolecular enyne metathesis: kinetic method and alkyne substituent effects

The kinetics of enyne metathesis were studied by IR spectroscopy for a variety of alkyne-alkene combinations. The rate law was determined for alkyne-ethylene and alkyne-1-hexene cross metathesis. In the cases examined, greater substitution on the alkyne accelerates the rate of metathesis, and chelation by propargylic esters was ruled out through rate comparison with hydrocarbon alkynes. The findings are discussed in terms of an alkylidene-first reaction mechanism, phosphine-bound ruthenium carbene resting states, and the rate-determining turnover of vinyl carbene intermediates (for alkyne-1-hexene metatheses).     

Separations involving sulphides: Separation of ruthenium and indium from alkaline earth metals

It has been shown that 2N sodium sulphide reagent can be efficiently used for separating ruthenium or indium from alkaline earth metals.     

Transition metal-catalyzed ring-opening, substitution, and cyclopropanation reactions via vinylcarbene complexes generated from O-propargyl thiocarbamates

We have developed various transition metal-catalyzed vinylcarbene transfer reactions, such as ring-opening, substitution, and cyclopropanation reactions, using O-propargyl thiocarbamates as carbene precursors. Platinum, ruthenium, rhodium, and gold complexes are effective for vinylcarbenoid formation. The highly nucleophilic nature and resonance effect of a thiocarbamoyl moiety readily permit the rearrangement of a thiocarbamoyl moiety from a propargylic position to an adjacent alkynyl carbon to give the intermediary vinylcarbene complexes.     

Determination of indium in high purity antimony by electrothermal atomic absorption spectrometry (ETAAS) using boric acid as a modifier

The use of boric acid as a modifier for the determination of trace amount of indium in high purity antimony by electrothermal atomic absorption is described. It was found that the negative influence of the hydrofluoric acid, used for the digestion could not be eliminated by using stabilized temperature platform furnace (STPF) alone. Due to the high dissociation energy (D₀ = 506 kJ mol⁻¹) of indium fluoride, it is difficult to dissociate in the gas phase and hence is lost. In presence of HF (used for the dissolution of antimony), the universal Pd-Mg modifier does not work satisfactorily. Additionally, rising corrosion and reduced tube lifetime were observed when the acid digested (HF-HNO₃) antimony solution was injected in to the platform. Improvement in platform life and elimination of interferences were achieved by the addition of boric acid as a chemical modifier together with ruthenium coating of the platform. Corrosive changes of the transversely heated graphite atomizer (THGA) platform surface were examined by scanning electron microscopy. The standard addition method was applied. A characteristic mass of 36 pg was obtained. The detection limit of the proposed method is around 0.04 μg g⁻¹. The developed method was applied to the determination of indium in real samples. The data obtained by this method were in good agreement with those obtained by ICP-MS.     

Enhanced diastereoselectivity in asymmetric crotylation reactions using propargylic dicobalt hexacarbonyl complexes

[reaction: see text] Hexacarbonyl dicobalt complexes of propargylic acetals undergo Lewis acid catalyzed crotylation reactions with enhanced levels of diastereoselectivity (dr 6 to >20:1, syn/anti) while efficiently producing stereochemically well-defined homoallylic ethers. These results are in contrast to uncomplexed propargylic acetals, which undergo the crotylation reactions with low selectivity (dr < 2:1, syn/anti). After removal of the cobalt complex, the reactions afford propargylic ethers in high yields.     

Light‐Triggered Release of Trapped Charges in Molecular Assemblies

We demonstrate the mediation of charge transport and release in thin films and devices by shifting the redox properties of layers of metal complexes by light. The nanoscale surface arrangement of both photo‐ and electrochemically‐active components is essential for the function of the thin films. Layers of well‐defined ruthenium complexes on indium‐tin‐oxide electrodes provide electron‐transport channels that allow the electrochemical addressing of layers of isostructural cobalt complexes. These cobalt complexes are electrochemically inactive when assembled directly on transparent metal‐oxide electrodes. The interlayer of ruthenium complexes on such electrodes allows irreversible oxidation of the cobalt complexes. However, shifting the redox properties of the ruthenium complexes by excitation with light opens up an electron‐transport channel to reduce the cobalt complexes; hence releasing the trapped positive charges.