Showing papers on "Bond cleavage published in 2006"
TL;DR: Experimental and computational evidence indicates that the pivalate anion is a key component in the palladium-pivalic acid cocatalyst system, that it lowers the energy of C-H bond cleavage and acts as a catalytic proton shuttle from benzene to the stoichiometric carbonate base.
Abstract: A palladium−pivalic acid cocatalyst system has been developed that exhibits unprecedented reactivity in direct arylation This reactivity is illustrated with the first examples of high yielding direct metalation−arylation reactions of a completely unactivated arene, benzene Experimental and computational evidence indicates that the pivalate anion is a key component in the palladation/C−H bond breaking event, that it lowers the energy of C−H bond cleavage and acts as a catalytic proton shuttle from benzene to the stoichiometric carbonate base Eight examples of substituted aryl bromides are included which undergo direct arylation with benzene in 55−85% yield
839 citations
TL;DR: Penta-, tetra-, tri-, and difluorobenzenes undergo direct arylation with a wide range of arylhalides in high yield and utilize commercially available, air-stable catalyst precursors.
Abstract: Penta-, tetra-, tri-, and difluorobenzenes undergo direct arylation with a wide range of arylhalides in high yield. Inverse reactivity is observed compared to the common electrophilic aromatic substitution pathway since electron-deficient, C−H acidic arenes react preferentially. Computational studies indicate that C−H bond cleavage occurs via a concerted carbon−palladium and carbon−hydrogen bond cleaving event involving a carbonate or a bromide ligand. The reactions are rapid, require only a slight excess of the perfluoroarene reagent, and utilize commercially available, air-stable catalyst precursors.
716 citations
Journal Article•
TL;DR: The reactivity of polyphenols is due to the position of the hydroxyl groups on their aromatic nuclei as mentioned in this paper, and the reaction of the A and C rings are pH-dependent.
Abstract: The reactivity of polyphenols is due to the position of the hydroxyl groups on their aromatic nuclei. Ortho-hydroxyl groups promote oxidation while meta-hydroxyl groups induce electrophilic aromatic substitution. Both hydroxylation patterns are encountered in flavonoid structures, on the B and A rings, respectively. In addition to oxidation and electrophilic aromatic substitution, flavonoids undergo nucleophilic addition on the central C ring when it is positively charged. Reactions of the A and C rings are pH-dependent. The A ring of flavonoids undergoes a polycondensation reaction mediated by an aldehyde. The products are anthocyanin and flavanol polymers and copolymers constituted of both. Flavanol polymers are not stable and rearrange into vinyl flavanols and xanthylium pigments. Vinyl flavanols can react with the positively charged C ring of anthocyanins, yielding pyranoanthocyanins, which can also be formed from components that have a reactive double bond, such as carbonyl and ethylene bonds. The positively charged C ring primarily undergoes direct reactions. Since the positive charge on the C ring of anthocyanins and flavanols is pH-dependent, their dehydration and interflavan bond cleavage reactions are also pH-dependent. This leads to flavanol–anthocyanin (F-A + ) adducts at lower pH values and anthocyanin–flavanol (A + -F) adducts above pH 3.8. Temperature seems to favor formation of the latter.
278 citations
TL;DR: This work provides the first direct evidence that methanol dissociates on oxygen vacancies via O-H bond scission rather than C-O scission, and for CH3OH coverages lower than the oxygen vacancy concentration, stationary methoxy-hydroxyl pairs form.
Abstract: We investigated methanol adsorption and dissociation on bridge-bonded oxygen vacancies of the TiO2(110)-(1×1) surface using in situ scanning tunneling microscopy. We provide the first direct evidence that methanol dissociates on oxygen vacancies via O−H bond scission rather than C−O scission. For CH3OH coverages lower than the oxygen vacancy concentration, stationary methoxy−hydroxyl pairs form. At CH3OH coverages close to the oxygen vacancy concentration undissociated mobile CH3OH interacts with methoxy−hydroxyl pairs and facilitates the movement of hydroxyl away from the methoxy group.
198 citations
TL;DR: In this article, a comparison of product ion mass spectra of protonated and deprotonated molecules of kaempferol-3-O-glucoside, quercitin-3 O-galactoside (hyperoin), apigenin-7-Oglucuside (orientin), luteolin-8-C-glocoside(orientin) together with the product ion spectrum of depro-tonated 6-C-, 7-O-, and 4-O glycosides was presented.
177 citations
TL;DR: A highly efficient carbon-carbon triple bond cleavage reaction of (Z)-enynols was developed, which offered a new route to highly substituted butenolides.
Abstract: A highly efficient carbon−carbon triple bond cleavage reaction of (Z)-enynols was developed, which offered a new route to highly substituted butenolides. The methodology is realized by a tandem rea...
172 citations
TL;DR: In this article, water dissociation on clean and oxygen-preadsorbed transition metal surfaces was investigated by the DFT-GGA method, and the total energy change and the reaction barrier were calculated with respect to the direct and oxygen assisted cleavage of O H bonds of water.
170 citations
156 citations
TL;DR: The 1H and 31P NMR studies of the reaction of Ru(CO)(PPh3)3 with o-aryloxy pivalophenone revealed that the C-H bond cleavage is a kinetically favorable process but theC-O bond cleaving is a thermodynamic one.
Abstract: When RuH2(CO)(PPh3)3 was reacted with 2,2-dimethyl-1-(2-p-tolylphenyl)propan-1-one (2), the ruthenium-aryloxy complex 3 was obtained in 76% yield. The structure of this complex was determined from 1H and 31P NMR and X-ray data. Complex 3 showed the catalytic activity for the coupling of 2 with the phenylboronate 4. The 1H and 31P NMR studies of the reaction of Ru(CO)(PPh3)3 with o-aryloxy pivalophenone revealed that the C-H bond cleavage is a kinetically favorable process but the C-O bond cleavage is a thermodynamic one. The reaction of 2'-methoxyacetophenone with vinylsilane and organoboronate resulted in chemoselective C-C bond formation.
152 citations
TL;DR: Greeley and Mavrikakis as mentioned in this paper presented a microkinetic model for methanol decomposition on platinum, which incorporates competitive decomposition pathways, beginning with both O-H and C-H bond scission in methanOL, using results from density functional theory (DFT) calculations.
Abstract: A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT) calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004) 3910]. Results from reaction kinetics experiments show that the rate of H2 production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by the presence of CO or H2 with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH3OH→H2COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species.
148 citations
TL;DR: The results of studies with radical inhibitors and light suggest that the reaction does not proceed by a radical chain mechanism and a second-order rate law is observed for the reaction.
Abstract: Insertion of molecular oxygen into a palladium(II) hydride bond to form an (η1-hydroperoxo)palladium(II) complex is reported. The hydroperoxo palladium(II) product has been crystallographically characterized. A second-order rate law (first-order in palladium and first-order in oxygen) is observed for the reaction and a large kinetic isotope effect implicates Pd−H bond cleavage in the rate-determining step. The results of studies with radical inhibitors and light suggest that the reaction does not proceed by a radical chain mechanism.
TL;DR: The asymmetric reaction was successfully applied to a synthesis of sesquiterpene, (-)-alpha-herbertenol, which involves enantioselective beta-carbon elimination from a symmetrical rhodium cyclobutanolate.
TL;DR: The reversible oxidative cyclization of dienes and aldehydes with nickel(0) proceeded to give eta(3):eta(1)-allylalkoxynickel complexes, which were made easier by the use of heavier butadiene and ketone, such as 2, 3-dibenzyl-1,3-butadienes and benzophenone or by theUse of cyclobutanone.
Abstract: The reversible oxidative cyclization of dienes and aldehydes with nickel(0) proceeded to give η3:η1-allylalkoxynickel complexes. The treatment of these complexes with carbon monoxide led to the formation of the corresponding lactone and/or the regeneration of a butadiene and an aldehyde concomitant with the formation of Ni(CO)3(PCy3). The scission of the nickel−oxygen bond of the allylalkoxy complexes with ZnMe2 leading to η3-allyl(methyl)nickel was very efficient to suppress the reverse reaction of the oxidative cyclization. The methylated η3-allylnickel compound underwent the reductive elimination. The carbonylative coupling reaction of the η3-allyl(methyl)nickel proceeded as well under a carbon monoxide atmosphere. Similarly, the addition of Me3SiCl to η3:η1-allylalkoxynickel complexes was also efficient for the inhibition of the reverse reaction. The resulting η3-1-siloxyethylallylnickel complex was treated with carbon monoxides followed by the addition of MeOH to give the expected hydroxyester. This ...
TL;DR: The results indicate that the pyrimidine nucleotides are able to capture electrons characterized by near-0-eV energy to form electronically stable radical anions in both the gas phase and aqueous solution.
Abstract: To elucidate the mechanism of DNA strand breaks by low-energy electrons (LEE), theoretical investigations of the LEE attachment-induced C5′ O5′ σ bond breaking of pyrimidine nucleotides (5′-dCMPH and 5′-dTMPH) were performed by using the B3LYP/DZP++ approach. The results indicate that the pyrimidine nucleotides are able to capture electrons characterized by near-0-eV energy to form electronically stable radical anions in both the gas phase and aqueous solution. The mechanism of the LEE-induced single-strand bond breaking in DNA might involve the attachment of an electron to the bases of DNA and the formation of base-centered radical anions in the first step. Subsequently, these radical anions undergo either C O or glycosidic bond breaking, yielding neutral ribose radical fragments and the corresponding phosphoric anions or base anions. The CO bond cleavage is expected to dominate because of its low activation energy. In aqueous solutions, the significant increases in the electron affinities of pyrimidine nucleotides ensure the formation of electronically more stable radical anions of the nucleotides. The low activation energy barriers for the C5′ O5′ bond breaking predicted in this work are relevant when the counterions are close enough to the phosphate moiety of DNA.
TL;DR: In this article, a bisphosphine-ligated rhodium-aryl complex was shown to be stabilized by Rh-Cphenyl interactions, as evidenced by an X-ray structure with a metal-aryl interaction likely illustrates the pathway for C-C bond cleavage.
Abstract: beta-Aryl eliminations from a series of rhodium(I) alkoxides to form rhodium aryl complexes and free ketones are reported. Tertiary phenylmethoxide complexes [Rh(PEt3)n(OCPhRR')] (n = 2, 3) were prepared via alcoholysis of {Rh(PEt3)2[N(SiMe3)2} by the corresponding alcohols HOCPhRR' in the presence and absence of added PEt3. Heating of these complexes in the presence of added PEt3 generated the rhodium phenyl complex, (PEt3)3RhPh, and the corresponding ketones in good to high yields. Kinetic results are most consistent with irreversible beta-phenyl elimination from a bisphosphine-ligated rhodium alkoxide complex. Such bisphosphine complexes result from ligand dissociation from the trisphosphine complexes and have been isolated in some cases. The bisphosphine complexes are stabilized by Rh-Cphenyl interactions, as evidenced by an X-ray structure, and this structure with a metal-aryl interaction likely illustrates the pathway for C-C bond cleavage.
09 May 2006
TL;DR: In this article, a series of recent advances are discussed, focusing on the interactions between the fragments formed upon bond cleavage, and applications of dissociative electron transfer concepts and models to mechanistic analysis in this class of enzymes will be discussed.
Abstract: After a reminder of concerted/stepwise mechanistic dichotomy and other basic concepts and facts in the field, a series of recent advances is discussed. Particular emphasis is laid on the interactions between the fragments formed upon bond cleavage. These interactions may persist even in polar solvents and have important consequences on dissociative electron transfer kinetics and on the competition between concerted and stepwise pathways. Cleavage of ion radicals and its reverse reaction are examples of single electron transfer reactions concerted with bond cleavage and bond formation, respectively. The case of aromatic carbon–heteroatom bonds is particularly worth examination since symmetry restrictions impose circumventing a conical intersection. Reductive dehalogenases are involved in ‘dehalorespiration’ of anaerobic bacteria in which the role of dioxygen in aerobic organisms is played by major polychloride pollutants such as tetrachloroethylene. They offer an interesting illustration of how the coupling of electron transfer with bond breaking may be an important issue in natural processes. Applications of dissociative electron transfer concepts and models to mechanistic analysis in this class of enzymes will be discussed.
TL;DR: This paper reconciles existing anomalies between theory and experiment with the hypothesis that the local stress at the Kolmogorov scale generates the molecular tension leading to polymer covalent bond breakage and yields a universal scaling for polymer scission in turbulent flows.
Abstract: We report that previous polymer chain scission experiments in strong flows, long analyzed according to accepted laminar flow scission theories, were in fact affected by turbulence. We reconcile existing anomalies between theory and experiment with the hypothesis that the local stress at the Kolmogorov scale generates the molecular tension leading to polymer covalent bond breakage. The hypothesis yields a universal scaling for polymer scission in turbulent flows. This surprising reassessment of over 40 years of experimental data simplifies the theoretical picture of polymer dynamics leading to scission and allows control of scission in commercial polymers and genomic DNA.
TL;DR: The structural changes occurring in these reactions have been followed by X-ray powder diffraction, including Rietveld refinement, of the crystal structures and are fully reversible upon exposure of the blue coordination compound to vapor from a concentrated aqueous solution of HCl.
Abstract: Yellow crystalline salts (3-XpyH)2[CuCl4] (3-XpyH = 3-halopyridinium, X = Cl, Br) lose HCl upon exposure to air in an open vessel, yielding quantitatively blue crystalline coordination compounds [CuCl2(3-Xpy)2]. The reaction is prevented if the vessel is sealed, but can be driven forward under such conditions by providing a trapping agent for HCl, such as an aqueous solution of AgNO3. The reaction requires cleavage of Cu-Cl and N-H bonds and formation of Cu-N bonds. The metal coordination geometry also changes from distorted tetrahedral to square planar. Remarkably, the reaction is fully reversible upon exposure of the blue coordination compound to vapor from a concentrated aqueous solution of HCl, and the initial yellow crystalline salt results. The structural changes occurring in these reactions have been followed by X-ray powder diffraction, including Rietveld refinement, of the crystal structures.
TL;DR: Experimental and theoretical evidence is provided and an attractive mechanism for the role of ABLM in double-strand cleavage is proposed, which would generate a reactive Fe(IV)=O species, capable of a second DNA strand cleavage, as observed in vivo.
Abstract: Bleomycin (BLM), a glycopeptide antibiotic chemotherapy agent, is capable of single- and double-strand DNA damage. Activated bleomycin (ABLM), a low-spin FeIII−OOH complex, is the last intermediate detected prior to DNA cleavage following hydrogen-atom abstraction from the C-4‘ of a deoxyribose sugar moiety. The mechanism of this C−H bond cleavage reaction and the nature of the active oxidizing species are still open issues. We have used kinetic measurements in combination with density functional calculations to study the reactivity of ABLM and the mechanism of the initial attack on DNA. Circular dichroism spectroscopy was used to directly monitor the kinetics of the ABLM reaction. These experiments yield a deuterium isotope effect, kH/kD ≈ 3 for ABLM decay, indicating the involvement of a hydrogen atom in the rate-determining step. H-atom donors with relatively weak X−H bonds accelerate the reaction rate, establishing that ABLM is capable of hydrogen-atom abstraction. Density functional calculations were...
TL;DR: Spectroscopic and reactivity studies are consistent with DNA oxidation mediated by formation of a side-on peroxodicopper(II) (Cu(2)-O(2)) complex.
Abstract: A homologous series of binuclear copper(II) complexes [CuII2(Nn)(Y)2]2+ (1−3) (n = 3−5 and Y = (ClO4)- or (NO3)-) were studied to investigate the intermediate(s) responsible for selective DNA strand scission in the presence of MPA/O2 (MPA = 3-mercaptopropanoic acid). While the N3 complex does not react, the N4 and N5 analogues show comparable activity with strand scission occurring at a single-strand/double-strand junction. Identical reactivity is also observed in the alternate presence of H2O2. Spectroscopic and reactivity studies with [CuII2(N4)(Y)2]2+ (2) and H2O2 are consistent with DNA oxidation mediated by formation of a side-on peroxodicopper(II) (Cu2−O2) complex.
TL;DR: A nonradical mechanism for methane hydroxylation by the bare FeO+ complex, Fe-ZSM-5 zeolite, and soluble methane monooxygenase is proposed from quantum chemical calculations.
Abstract: A nonradical mechanism for methane hydroxylation by the bare FeO+ complex, Fe-ZSM-5 zeolite, and soluble methane monooxygenase is proposed from quantum chemical calculations. This mechanism is applicable when a metal-oxo species is coordinatively unsaturated. Direct interaction between methane and a metal active center can form a weakly bound methane complex in the initial stages of this reaction. Subsequent C-H bond cleavage to form an intermediate with an HO-Fe-CH3 moiety in a nonradical manner and recombination of the resultant OH and CH3 ligands take place at a metal active center to form a final methanol complex. Thus, this is a nonradical, two-step reaction. The fact that methyl radical is 10-20 kcal/mol less stable than secondary and tertiary carbon radicals and benzyl radicals leads us to propose this mechanism.
TL;DR: Di(2-pyridyl)methanesulfonate ligand allows for facile aerobic oxidation of a PtIIMe complex into PtIVMe(OH)2 species and clean C-O reductive elimination of methanol from the latter in either acidic or basic aqueous solutions.
Abstract: Di(2-pyridyl)methanesulfonate ligand allows for facile aerobic oxidation of a PtIIMe complex into PtIVMe(OH)2 species and clean C-O reductive elimination of methanol from the latter in either acidic or basic aqueous solutions.
TL;DR: A flavonol iron(III) complex, [Fe(flavonolato)(2)Cl(MeOH)], has been prepared and mechanisms of the oxidative cleavage have been proposed when DNA strand scission is performed both with and without ascorbate/hydrogen peroxide activation.
TL;DR: The high selectivity of periodate and lead tetraacetate as glycol-cleaving oxidants is attributed mainly to the ability of the central atom of the reagent to complex with a 1,2-diol and effect a two-electron transfer.
Abstract: Publisher Summary This chapter provides an overview of glycol-cleavage oxidation. Carbohydrates provide a profusion of compounds that contain hydroxyl groups on two or more adjacent carbon atoms, and the fact that this type of carbon–carbon bond generally undergoes oxidative scission selectively and quantitatively has been a major factor contributing to the current status of carbohydrate chemistry. The fact that periodate functions best in water and leads tetra-acetate in organic solvents, makes glycol-cleavage oxidation possible with all types of carbohydrates and derivatives. The high selectivity of periodate and lead tetraacetate as glycol-cleaving oxidants is attributed mainly to the ability of the central atom of the reagent to complex with a 1,2-diol and effect a two-electron transfer. Formation of an intermediate complex has been shown for periodate by pH and ultraviolet spectral changes, and, for both oxidants, less directly by the consideration of the reaction kinetics. The glycol-cleaving action of periodate is generally more consistent with the concept of a five-membered ring intermediate than is the action of lead tetraacetate. The characteristics of periodate and lead tetra-acetate oxidations are explained in the chapter. It also discusses the properties of glycosides and related alicyclic compounds and explains the oxidation patterns and end-group analysis of polysaccharides.
TL;DR: The potent nucleofugacity of the triflate moiety is channeled through the sigma-bond framework of 1, providing direct access to the fragmentation pathway without denying other typical reactions of cyclic vinylogous esters.
Abstract: A thorough analysis of the chemistry of vinylogous acyl triflates provides insight into important chemical processes and opens new directions in synthetic technology. Tandem nucleophilic addition/C−C bond cleaving fragmentation reactions of cyclic vinylogous acyl triflates 1 yield a variety of acyclic acetylenic compounds. Full details are disclosed herein. A wide array of nucleophiles, such as organolithium and Grignard reagents, lithium enolates and their analogues, hydride reagents, and lithium amides, are applied. The respective reactions produce ketones 2, 1,3-diketones and their analogues 3, alcohols 4, and amides 5. The present reactions are proposed to proceed through a 1,2-addition of the nucleophile to the carbonyl group of starting triflates 1 to form tetrahedral alkoxide intermediates C, followed by Grob-type fragmentation, which effects C−C bond cleavage to yield acyclic acetylenic compounds 2−5 and 7. The potent nucleofugacity of the triflate moiety is channeled through the σ-bond framework ...
TL;DR: A systematic investigation of fluoride anion binding properties as a function of chelate backbone has been carried out for ferrocene functionalised boronic esters of the types FcB( OR)2 and fc[B(OR)2]2, finding no binding of potentially competitive anions.
Abstract: A systematic investigation of fluoride anion binding properties as a function of chelate backbone has been carried out for ferrocene functionalised boronic esters of the types FcB(OR)2 and fc[B(OR)2]2 [Fc = ferrocenyl = (η5-C5H5)Fe(η5-C5H4); fc = ferrocendiyl = Fe(η5-C5H4)2]. Cyclic boronic esters containing a saturated five- or six-membered chelate ring are readily synthesized from ferrocene, and selectively bind fluoride via Lewis acid/base chemistry in chloroform solution. The resulting complexes are characterized by relatively weak fluoride binding (e.g.K = 35.8 ± 9.8 M−1 for FcBO2C2H2Ph2–S,S), and by cathodic shifts in the ferrocene oxidation potential that form the basis for electrochemical or colorimetric fluoride detection. The fluoride selectivity of these systems is attributed to relatively weak Lewis acidity, resulting in weak F− binding, and essentially no binding of potentially competitive anions. By contrast, more elaborate Lewis acid frameworks based on calix[4]arene (calixH4), such as (FcB)2calix or fcB2calix, do not survive intact exposure to standard fluoride sources (e.g. [nBu4N]F·xH2O solutions in chloroform or acetonitrile). Instead B–O bond cleavage occurs yielding the parent calixarene; the differences between alkoxo- and aryloxo-functionalised derivatives can be rationalised, at least in part, by consideration of the differences in electron donating capabilities of RO− (R = alkyl, aryl).
TL;DR: ONIOM calculations have provided novel insights into the mechanism of homolytic Co-C5' bond cleavage in the 5'-deoxyadenosylcobalamin cofactor catalyzed by methylmalonyl-CoA mutase, and it is shown that it is a stepwise process in which conformational changes in the5'-de oxygenadenosine moiety precede the actual homolysis step.
Abstract: ONIOM calculations have provided novel insights into the mechanism of homolytic Co−C5‘ bond cleavage in the 5‘-deoxyadenosylcobalamin cofactor catalyzed by methylmalonyl-CoA mutase. We have shown that it is a stepwise process in which conformational changes in the 5‘-deoxyadenosine moiety precede the actual homolysis step. In the transition state structure for homolysis, the Co−C5‘ bond elongates by ∼0.5 A from the value found in the substrate-bound reactant complex. The overall barrier to homolysis is ∼10 kcal/mol, and the radical products are ∼2.5 kcal/mol less stable than the initial ternary complex of enzyme, substrate, and cofactor. The movement of the deoxyadenosine moiety during the homolysis step positions the resulting 5‘-deoxyadenosyl radical for the subsequent hydrogen atom transfer from the substrate, methylmalonyl-CoA.
TL;DR: Thin molecular films of the short single strand of DNA, GCAT, were bombarded under vacuum by electrons with energies between 4 and 15 eV, and ex vacuo analysis by high-pressure liquid chromatography of the samples exposed to the electron beam revealed the formation of a multitude of products.
Abstract: Thin molecular films of the short single strand of DNA, GCAT, were bombarded under vacuum by electrons with energies between 4 and 15 eV Ex vacuo analysis by high-pressure liquid chromatography of the samples exposed to the electron beam revealed the formation of a multitude of products Among these, 12 fragments of GCAT were identified by comparison with reference compounds and their yields were measured as a function of electron energy For all energies, scission of the backbone gave nonmodified fragments containing a terminal phosphate, with negligible amounts of fragments without the phosphate group This indicates that phosphodiester bond cleavage by 4–15 eV electrons involves cleavage of the C–O bond rather than the P–O bond The yield functions exhibit maxima at 6 and 10–12 eV, which are interpreted as due to the formation of transient anions leading to fragmentation Below 15 eV, these resonances dominate bond dissociation processes All four nonmodified bases are released from the tetramer, by c
TL;DR: Complex OsH2Cl2(PiPr3)2 promotes the C-H activation of 2-vinylpyridine and subsequently couples the activated substrate with a second 2- Marvinidine and two acetylene molecules to afford a 2-butadienyl pyridine derivative.
Abstract: Complex OsH2Cl2(PiPr3)2 promotes the C−H activation of 2-vinylpyridine and subsequently couples the activated substrate with a second 2-vinylpyridine and two acetylene molecules. In the absence of 2-vinylpyridine, the activated substrate is coupled with an acetylene unit to afford a 2-butadienylpyridine derivative.