Showing papers on "Double bond published in 2016"
TL;DR: In this article, a steric bulky ligand was used to promote the reductive elimination steps from the Pd(II) center and impeding the β-hydride elimination reactions, which are beyond the scope of this Account.
Abstract: ConspectusDifunctionalization of alkenes to incorporate two functional groups across a double bond has emerged as a powerful transformation to greatly increase molecular complexity in organic synthesis with improved efficiency. Historically, palladium-catalyzed difunctionalization of alkenes has suffered from difficulties with introducing a second functional group through reductive elimination of a Pd(II) intermediate and competing β-hydride elimination reactions. To overcome these challenges, one strategy involves utilizing a steric bulky ligand to promote the reductive elimination steps from the Pd(II) center and impeding the β-hydride elimination reactions, which are beyond the scope of this Account. Alternatively, strong oxidants have been utilized to generate high-valent palladium species, which are prone to undergo reductive elimination to form a second C–X bond. This new strategy has been extensively applied to explore the difunctionalization of alkenes with enriched functional group diversity over...
462 citations
TL;DR: The pairwise interactions of the constituent components of the choline chloride-urea DES are examined and it is found that the covalency of doubly ionic H-bonds can be greater than, or comparable with, neutral and ionic examples.
Abstract: Deep eutectic solvents (DESs) are exemplars of systems with the ability to form neutral, ionic and doubly ionic H-bonds. Herein, the pairwise interactions of the constituent components of the choline chloride-urea DES are examined. Evidence is found for a tripodal CHCl doubly ionic H-bond motif. Moreover it is found that the covalency of doubly ionic H-bonds can be greater than, or comparable with, neutral and ionic examples. In contrast to many traditional solvents, an "alphabet soup" of many different types of H-bond (OHO[double bond, length as m-dash]C, NHO[double bond, length as m-dash]C, OHCl, NHCl, OHNH, CHCl, CHO[double bond, length as m-dash]C, NHOH and NHNH) can form. These H-bonds exhibit substantial flexibility in terms of number and strength. It is anticipated that H-bonding will have a significant impact on the entropy of the system and thus could play an important role in the formation of the eutectic. The 2 : 1 urea : choline-chloride eutectic point of this DES is often associated with the formation of a [Cl(urea)2](-) complexed anion. However, urea is found to form a H-bonded urea[choline](+) complexed cation that is energetically competitive with [Cl(urea)2](-). The negative charge on [Cl(urea)2](-) is found to remain localised on the chloride, moreover, the urea[choline](+) complexed cation forms the strongest H-bond studied here. Thus, there is potential to consider a urea[choline](+)·urea[Cl](-) interaction.
253 citations
TL;DR: The ability of CD-MOF to separate a wide variety of mixtures, including ethylbenzene from styrene, haloaromatics, terpinenes, pinenes and other chiral compounds is reported, which could lead to cheaper and easier-to-prepare stationary phases for HPLC separations when compared with otherChiral stationary phases, such as CD-bonded silica particles.
Abstract: Porous metal-organic frameworks (MOFs) have been studied in the context of a wide variety of applications, particularly in relation to molecular storage and separation sciences. Recently, we reported a green, renewable framework material composed of γ-cyclodextrin (γ-CD) and alkali metal salts--namely, CD-MOF. This porous material has been shown to facilitate the separation of mixtures of alkylaromatic compounds, including the BTEX mixture (benzene, toluene, ethylbenzene, and the regioisomers of xylene), into their pure components, in both the liquid and gas phases, in an energy-efficient manner which could have implications for the petrochemical industry. Here, we report the ability of CD-MOF to separate a wide variety of mixtures, including ethylbenzene from styrene, haloaromatics, terpinenes, pinenes and other chiral compounds. CD-MOF retains saturated compounds to a greater extent than their unsaturated analogues. Also, the location of a double bond within a molecule influences its retention within the extended framework, as revealed in the case of the structural isomers of pinene and terpinine, where the isomers with exocyclic double bonds are more highly retained than those with endocyclic double bonds. The ability of CD-MOF to separate various mono- and disubstituted haloaromatic compounds appears to be controlled by both the size of the halogen substituents and the strength of the noncovalent bonding interactions between the analyte and the framework, an observation which has been confirmed by molecular simulations. Since CD-MOF is a homochiral framework, it is also able to resolve the enantiomers of chiral analytes, including those of limonene and 1-phenylethanol. These findings could lead to cheaper and easier-to-prepare stationary phases for HPLC separations when compared with other chiral stationary phases, such as CD-bonded silica particles.
240 citations
TL;DR: A phosphorus analog of carbenes, namely a phosphinidene, was synthesized by irradiation-induced elimination of carbon monoxide from the corresponding (phosphino)phosphaketene as discussed by the authors.
214 citations
TL;DR: The high levels of enantioselectivity obtained in the isomerization of a small set of α-substituted α,β-unsaturated ketones augur well for the successful development of an enantiOSElective version of this unconventional isomerizations.
Abstract: The long-range deconjugative isomerization of a broad range of α,β-unsaturated amides, esters, and ketones by an in situ generated palladium hydride catalyst is described. This redox-economical process is triggered by a hydrometalation event and is thermodynamically driven by the refunctionalization of a primary or a secondary alcohol into an aldehyde or a ketone. Di-, tri-, and tetrasubstituted carbon–carbon double bonds react with similar efficiency; the system is tolerant toward a variety of functional groups, and olefin migration can be sustained over 30 carbon atoms. The refunctionalized products are usually isolated in good to excellent yield. Mechanistic investigations are in support of a chain-walking process consisting of repeated migratory insertions and β-H eliminations. The bidirectionality of the isomerization reaction was established by isotopic labeling experiments using a substrate with a double bond isolated from both terminal functions. The palladium hydride was also found to be directly...
142 citations
TL;DR: Initial mechanistic studies suggest that this process occurs via a concerted carbo-palladation across the thiophene double bond, followed by a base-assisted anti-elimination, resulting in a highly efficient catalytic system.
Abstract: The first example of a regioselective β-arylation of benzo[b]thiophenes and thiophenes at room temperature with aryl iodides as coupling partners is reported. This methodology stands out for its operational simplicity: no prefunctionalization of either starting material is required, the reaction is insensitive to air and moisture, and it proceeds at room temperature. The mild conditions afford wide functional group tolerance, often with complete regioselectivity and high yields, resulting in a highly efficient catalytic system. Initial mechanistic studies, including 13C and 2H KIEs, suggest that this process occurs via a concerted carbo-palladation across the thiophene double bond, followed by a base-assisted anti-elimination.
111 citations
TL;DR: This Minireview summarizes the efforts reported to date on the use of double bonds as partners in [2+2-2] cyclotrimerizations.
Abstract: Participation of alkenes and allenes in [2+2+2] cycloaddition reactions has attracted much attention recently. This version of the well-established alkyne cyclotrimerization renders interesting products, such as cyclohexadienes and other polycycles, through cascade processes. Many mechanistic variations are observed when using certain metal complexes as catalysts. The frequent generation of stereogenic centers has prompted the development of efficient asymmetric versions. This Minireview summarizes the efforts reported to date on the use of double bonds as partners in [2+2+2] cyclotrimerizations.
98 citations
TL;DR: A new method for the AgSCF3-mediated radical cascade difunctionalizing trifluoromethythiolation of alkynes with dearomatization is developed, which provides a novel route to SCF 3-substituted spirocyclic compounds via the formation of one C- SCF3 bond, one C -C bond, and oneC-O double bond in a single step.
97 citations
TL;DR: In this article, a bis(phosphino)amine pincer ligand was used for selective hydrogenation of C═C double bonds in the presence of other reducible functionalities such as −CO2Me, −CN, and N-heterocycles.
Abstract: Hydrogenation of alkenes containing polarized C═C double bonds has been achieved with iron-based homogeneous catalysts bearing a bis(phosphino)amine pincer ligand. Under standard catalytic conditions (5 mol % of (PNHPiPr)Fe(H)2(CO) (PNHPiPr = NH(CH2CH2PiPr2)2), 23 °C, 1 atm of H2), styrene derivatives containing electron-withdrawing para substituents reacted much more quickly than both the parent styrene and substituted styrenes with an electron-donating group. Selective hydrogenation of C═C double bonds occurs in the presence of other reducible functionalities such as −CO2Me, −CN, and N-heterocycles. For the α,β-unsaturated ketone benzalacetone, both C═C and C═O bonds have been reduced in the final product, but NMR analysis at the initial stage of catalysis demonstrates that the C═O bond is reduced much more rapidly than the C═C bond. Although Hanson and co-workers have proposed a nonbifunctional alkene hydrogenation mechanism for related nickel and cobalt catalysts, the iron system described here operat...
92 citations
TL;DR: Under H2 pressure, Co(II)(dmgBF2)2L2 (L = H2O, THF) generates a low concentration of an H• donor that can be transferred back to the metal, generating an isomerized olefin, or added intramolecularly to a double bond, generating a cyclized radical.
Abstract: Under H2 pressure, CoII(dmgBF2)2L2 (L = H2O, THF) generates a low concentration of an H• donor. Transfer of the H• onto an olefin gives a radical that can either (1) transfer an H• back to the metal, generating an isomerized olefin, or (2) add intramolecularly to a double bond, generating a cyclized radical. Transfer of an H• back to the metal from the cyclized radical results in a cycloisomerization. Both outcomes are favored by the low concentration of the cobalt H• donor, whereas hydrogenation and cyclohydrogenation are more likely with other catalysts (when the concentration of the H• donor is high).
90 citations
TL;DR: These are the first molecular examples of Si2H2 characterized by single crystal X-ray structural analysis and the structure of compound 1 explains equally well its structure with coordinate bonds as with classical double bonds of a 2,3-disila-1, 3-butadiene.
Abstract: The cyclic alkyl(amino) carbene stabilized Si2H2 has been isolated in the molecular form of composition (Me-cAAC:)2Si2H2 (1) and (Cy-cAAC:)2Si2H2 (2) at room temperature. Compounds 1 and 2 were synthesized from the reduction of HSiCl3 using 3 equiv of KC8 in the presence of 1 equiv of Me-cAAC: and Cy-cAAC:, respectively. These are the first molecular examples of Si2H2 characterized by single crystal X-ray structural analysis. Moreover, electrospray ionization mass spectrometry and 1H as well as 29Si NMR data are reported. Furthermore, the structure of compound 1 has been investigated by theoretical methods. The theoretical analysis of 1 explains equally well its structure with coordinate bonds as with classical double bonds of a 2,3-disila-1,3-butadiene.
TL;DR: In this paper, hole-transport materials (HTMs) were used to replace the central spiro-linkage inspiro-OMeTAD by a CC bond in H11 and a CC double bond (CC double bond) in H12.
Abstract: This study presents new hole-transport materials (HTMs) to replace the central spiro linkage inspiro-OMeTAD by a CC bond in H11 and CC double bond in H12. This structural change results in a facile ...
TL;DR: This review covers free radical additions, which are initiated by the formal addition of a hydrogen atom to a C[double bond, length as m-dash]C double bond.
Abstract: This review covers free radical additions, which are initiated by the formal addition of a hydrogen atom to a CC double bond. These reactions originated in the realms of inorganic chemistry, polymer chemistry, and organic chemistry, whereby barriers between these disciplines impeded the rapid implementation of the findings.
TL;DR: The C-H polyaddition of dimethoxyarene moieties and 4,4'-dimethoxybiphenyl to unconjugated dienes such as norbornadiene and 1,4-divinylbenzene has been achieved for the first time by using cationic half-sandwich rare earth alkyl catalysts.
Abstract: The C–H polyaddition of dimethoxyarenes such as 1,4-dimethoxybenzene and 4,4′-dimethoxybiphenyl to unconjugated dienes such as norbornadiene and 1,4-divinylbenzene has been achieved for the first time by using cationic half-sandwich rare earth alkyl catalysts. This protocol afforded novel polymer materials consisting of dimethoxyarene moieties and nonpolar hydrocarbon structure motifs (cyclic, linear, and aromatic) in perfectly alternating sequences that are otherwise difficult to make. The reaction proceeded via C═C double bond insertion into a C–H bond ortho to each of the two methoxy groups in a step-growth polymerization fashion.
TL;DR: The reactions of a diborene with elemental selenium or tellurium are shown to afford adiboraselenirane or diboratellurirane, respectively, reminiscent of the sequestration of subvalent oxygen and nitrogen in the formation of oxiranes and aziridines.
Abstract: The reactions of a diborene with elemental selenium or tellurium are shown to afford a diboraselenirane or diboratellurirane, respectively. These reactions are reminiscent of the sequestration of subvalent oxygen and nitrogen in the formation of oxiranes and aziridines; however, such reactivity is not known between alkenes and the heavy chalcogens. Although carbon is too electronegative to affect the reduction of elements with lower relative electronegativity, the highly reducing nature of the B-B double bond enables reactions with Se(0) and Te(0) . The capacity of multiple bonds between boron atoms to donate electron density is highlighted in reactions where diborynes behave as nucleophiles, attacking one of the two Te atoms of diaryltellurides, forming salts consisting of diboratellurenium cations and aryltelluride anions.
TL;DR: One-pot polycondensation reaction of triethoxyvinylsilane (A-151) with excessive neopentyl glycol (NPG) is employed as an efficient and facile methodology for the synthesis of novel hyperbranched polysiloxanes contemporaneously bearing plenty of unconjugated carbon-carbon double bonds and hydroxyl groups as discussed by the authors.
TL;DR: A detailed comparison of the adsorption behavior of long straight chain saturated and unsaturated fatty acids at the iron oxide/oil interface has been considered using a combination of surface study techniques, which indicate chemisorbed monolayer adsorbed layer formed at higher concentrations.
Abstract: A detailed comparison of the adsorption behavior of long straight chain saturated and unsaturated fatty acids at the iron oxide/oil interface has been considered using a combination of surface study techniques. Both depletion isotherms and polarized neutron reflectometry (PNR) show that the extent of adsorption decreases as the number of double bonds in the alkyl chains increases. Sum frequency generation spectroscopic measurements demonstrate that there is also an increase in chain disorder within the adsorbed layer as the unsaturation increases. However, for the unsaturated analogues, a decrease in peak intensity is seen for the double bond peak upon heating, which is thought to arise from isomerization in the surface-bound layer. The PNR study of oleic acid adsorption indicates chemisorbed monolayer adsorption, with a further diffuse reversible adsorbed layer formed at higher concentrations.
TL;DR: 1,2-Diketones were synthesized by the oxidation of corresponding alkynes using air as the oxidant under metal-free conditions upon irradiation of blue light to give the dicarbonylation products in moderate to good yields.
Abstract: 1,2-Diketones were synthesized by the oxidation of corresponding alkynes using air as the oxidant under metal-free conditions upon irradiation of blue light. A cheap and readily available organic dye, eosin Y, was used as the photocatalyst. For various substituents on the aryl ring, the reaction proceeded smoothly to give the dicarbonylation products in moderate to good yields. Some oxidation-sensitive groups, such as formyl and the carbon–carbon double bond, were tolerated under the developed reaction conditions.
TL;DR: The heterogeneous reaction between SO2 and unsaturated compounds results in the efficient production of organosulfates for several fatty acids and long-chain alkenes through high-resolution mass spectrometry.
Abstract: The heterogeneous reaction between SO2 and unsaturated compounds results in the efficient production of organosulfates for several fatty acids and long-chain alkenes. The presence of an acid group, the physical state of the reactants (solid or liquid), the nature of the double bond (cis, trans, terminal), and the use of light irradiation all have an impact on the reaction rate. The reaction was investigated using different set-ups (coated flow tube, aerosol flow tube, and diffuse reflectance infrared Fourier transform cell). The reaction products were identified by high-resolution mass spectrometry and the impact of this reaction on organosulfate formation in the atmosphere is discussed.
TL;DR: The utility of coupling the PB reaction with infusion ESI-MS/MS was demonstrated by analyzing a yeast polar lipid extract where C[double bond, length as m-dash]C bond locations were revealed for 35 glycerophospholipids (GPs).
Abstract: Tandem mass spectrometry (MS/MS) coupled with soft ionization is established as an essential platform for lipid analysis; however, determining high order structural information, such as the carbon-carbon double bond (C[double bond, length as m-dash]C) location, remains challenging. Recently, our group demonstrated a method for sensitive and confident lipid C[double bond, length as m-dash]C location determination by coupling online the Paterno-Buchi (PB) reaction with nanoelectrospray ionization (nanoESI) and MS/MS. Herein, we aimed to expand the scope of the PB reaction for lipid analysis by enabling the reaction with infusion ESI-MS/MS at much higher flow rates than demonstrated in the nanoESI setup (∼20 nL min(-1)). In the new design, the PB reaction was effected in a fused silica capillary solution transfer line, which also served as a microflow UV reactor, prior to ESI. This setup allowed PB reaction optimization and kinetics studies. Under optimized conditions, a maximum of 50% PB reaction yield could be achieved for a standard glycerophosphocholine (PC) within 6 s of UV exposure over a wide flow rate range (0.1-10 μL min(-1)). A solvent composition of 7 : 3 acetone : H2O (with 1% acid or base modifier) allowed the highest PB yields and good lipid ionization, while lower yields were obtained with an addition of a variety of organic solvents. Radical induced lipid peroxidation was identified to induce undesirable side reactions, which could be effectively suppressed by eliminating trace oxygen in the solution via N2 purge. Finally, the utility of coupling the PB reaction with infusion ESI-MS/MS was demonstrated by analyzing a yeast polar lipid extract where C[double bond, length as m-dash]C bond locations were revealed for 35 glycerophospholipids (GPs).
TL;DR: In this article, the cascade reactions between enaminones and o-aminothiophenols have been implemented to provide unprecedented vicinal diketones containing benzothiazole structures.
TL;DR: The reaction results in the formation of a new carbon–magnesium bond and a new fluorine–mag magnesium bond and is analogous to Grignard formation in homogeneous solution.
Abstract: Addition of the carbon–fluorine bond of a series of perfluorinated and polyfluorinated arenes across the Mg–Mg bond of a simple coordination complex proceeds rapidly in solution. The reaction results in the formation of a new carbon–magnesium bond and a new fluorine–magnesium bond and is analogous to Grignard formation in homogeneous solution.
TL;DR: Recent advances in carbonyl-generation reactions based on alkene C=C double oxygenation as well as related cascade reactions in the synthesis of diverse organic products are reviewed.
Abstract: Carbonyl-forming reactions are a class of fundamental transformations in organic chemistry. Guided by the current importance of environmentally benign metal-free catalysis and synthesis, herein we review recent advances in carbonyl-generation reactions based on alkene C=C double oxygenation as well as related cascade reactions in the synthesis of diverse organic products. The content of this focus review consists of two important but different reaction models: oxygenation based on full C=C double-bond cleavage and oxygenation based on partial C=C double-bond cleavage.
TL;DR: Graphene obtained by pyrolysis of alginate at 900 °C under inert atmosphere and exfoliation is used as a metal-free catalyst for reduction of nitro to amino groups with hydrogen as a reagent.
Abstract: Graphene obtained by pyrolysis of alginate at 900 °C under inert atmosphere and exfoliation is used as a metal-free catalyst for reduction of nitro to amino groups with hydrogen as a reagent. The process is general for aromatic and aliphatic, conjugated and isolated nitro groups, and occurs with low selectivity over hydrogenation of carbon-carbon double bonds.
TL;DR: The diazoester is transformed into tetrasubstituted alkenes, whereas the diazo-oxindole delivers the quinolinone products, and the 13C-labeling experiments were also conducted to elucidate a possible mechanism.
TL;DR: In sharp contrast to tetraphenyldiphosphine, its monoxide, [Ph2 P(O)PPh2 ] can engage in a radical addition to various alkenes, thus affording the corresponding 1-ph phosphinyl-2-phosphinoalkanes regioselectively, and they can be converted into their sulfides by treatment with elemental sulfur.
Abstract: In sharp contrast to tetraphenyldiphosphine, which does not add to carbon–carbon double bonds efficiently, its monoxide, [Ph2P(O)PPh2] can engage in a radical addition to various alkenes, thus affording the corresponding 1-phosphinyl-2-phosphinoalkanes regioselectively, and they can be converted into their sulfides by treatment with elemental sulfur. The phosphinylphosphination proceeds by the homolytic cleavage of the PV(O)−PIII single bond of Ph2P(O)PPh2, followed by selective attack of the phosphinyl radical at the terminal position of the alkenes, and selective trapping of the resulting carbon radical by the phosphino group. Furthermore, the phosphinylphosphination product could be converted directly into its platinum complex with a hemilabile P,O chelation.
TL;DR: In this article, a new protocol for the synthesis of 2,2′-((1S,1′S)-ethane-1,2-diylbis(phenylphosphanediyl))dibenzaldehyde ((SP,SP)-5) was described.
TL;DR: Kinetic and isotope labeling studies suggest that a concerted 4-centred addition across the Ni=C bond is operative rather than a mechanism involving Si-H oxidative addition, which constitutes an example of Si- H bond activation via ligand cooperativity.
TL;DR: All novel complexes were characterized by multinuclear NMR spectroscopy, and the structures of 5, 9, and 10 were confirmed by X-ray diffraction analysis and the nature of the Al=S bond in 5 was also probed by DFT calculations.
Abstract: The treatment of cyclic thioureas with the aluminum(I) compound NacNacAl (1; NacNac=[ArNC(Me)CHC(Me)NAr]−, Ar=2,6-Pri2C6H3) resulted in oxidative cleavage of the C=S bond and the formation of 3 and 5, the first monomeric aluminum complexes with an Al=S double bond stabilized by N-heterocyclic carbenes. Compound 1 also reacted with triphenylphosphine sulfide in a similar manner, which resulted in cleavage of the P=S bond and production of the adduct [NacNacAl=S(S=PPh3)] (8). The Al=S double bond in 3 can react with phenyl isothiocyanate to furnish the cycloaddition product 9 and zwitterion 10 as a result of coupling between the liberated carbene and PhN=C=S. All novel complexes were characterized by multinuclear NMR spectroscopy, and the structures of 5, 9, and 10 were confirmed by X-ray diffraction analysis. The nature of the Al=S bond in 5 was also probed by DFT calculations.
01 Jan 2016
TL;DR: In this paper, the effects of ancillary ligands on metal-Carbon bond strength were determined via C-H Activation and catalytic organometallic C(sp3)-H bond functionalization of cyclopropane derivatives.
Abstract: Iron-Catalyzed C-H Bond Activation.- Nickel-catalyzed C-H bond functionalization.- Copper-Mediated Intermolecular C-H/C-H and C-H/N-H Couplings via Aromatic C-H cleavage.- The Effects of Ancillary Ligands on Metal-Carbon Bond Strengths as Determined via C-H Activation.- Catalytic C-H bond functionalization of cyclopropane derivatives.- Silver-Mediated Direct sp3 C-H Transformations.- Applications of catalytic organometallic C(sp3)-H Bond functionalization.- New concepts of C-H and C-C bond activation via surface organometallic chemistry.- Transfer Dehydrogenations of Alkanes and Related Reactions using Iridium Pincer Complexes.