Unsaturated Carbon-carbon Bonds Research Articles

Fluoroalkanesulfinate Salts as Dual Fluoroalkyl and SO2 Sources: Atom-Economical Fluoroalkyl-Sulfonylation of Alkenes and Alkynes by Photoredox Catalysis.

We disclose that fluoroalkanesulfinate salts ((RFSO2)nM) such as the Langlois reagent, CF3SO2Na, serve as dual fluoroalkyl (RF) and sulfur dioxide (SO2) sources by the action of photoredox catalysis. An operationally simple strategy for the vicinal installation of RF and SO2 groups onto unsaturated carbon-carbon bonds, i.e., fluoroalkyl-sulfonylation, has been developed. In particular, the present photocatalytic trifluoromethyl-sulfonylation can be applied to aromatic alkynes in addition to aliphatic and aromatic alkenes bearing various functional groups.

Bifunctional N-Heterocyclic Carbenes Derived from l-Pyroglutamic Acid and Their Applications in Enantioselective Organocatalysis.

In nature, enzymes are a powerful medium for the construction of enantiomerically pure chemicals, which always inspires synthetic chemists to explore new catalysts to imitate the enzyme machinery for asymmetric transformations. Vitamin B1, a bifunctional thiazolium N-heterocyclic carbene (NHC) precursor, is the coenzyme for transketolase. In the past two decades, a series of chiral NHCs, including monocyclic, bicyclic, tetracyclic, and even bridged ones, have been synthesized and successfully utilized as efficient organocatalysts for a wide variety of asymmetric organic reactions. The utility of bifunctional catalysts can enhance catalytic activity and improve stereochemical control through their synchronous activation of both reaction partners. However, the NHCs possessing multiple activation sites are far less developed.This Account gives an overview of our research on the design, development, and applications of bifunctional NHCs in organocatalysis. We synthesized a series of l-pyroglutamic acid-derived bifunctional NHCs bearing a free hydroxyl group which can interact with carbonyl or imino groups via hydrogen-bonding. Further studies revealed that these bifunctional catalysts worked well for a variety of reactions. We have developed bifunctional NHC-catalyzed aza-benzoin reactions, [2 + 2], [2 + 3], and [2 + 4] cycloadditions of ketenes, [3 + 2] and [3 + 4] annulations of enals, and aza-MBH and Rauhut-Currier reactions of Michael acceptors. In addition to these reactions via nucleophilic Breslow intermediates, enolates, homoenolates, and zwitterionic azolium intermediates, the bifunctional NHC-catalyzed [3 + 3] annulation via 1,3-biselectrophilic α,β-unsaturated acyl azolium intermediates was also developed.In these reactions, bifunctional NHCs showed amazing effects compared to normal nonbifunctional NHCs. In some cases, the bifunctional NHCs facilitated reactions which did not work under normal NHC catalysis, possibly due to additional activation via H-bonding. More interestingly, the bifunctional NHCs could not only improve but also switch the enantioselectivity to get products with opposite stereochemistry through H-bond controlled stereochemical directing. Furthermore, the reaction mode could be totally changed from [3 + 2] to [3 + 4] annulation to give kinetically favored products when bifunctional NHCs were employed. In future, the applications of bifunctional NHCs in other challenging reactions, such as asymmetric reactions with carbon-carbon unsaturated bonds, and the reactions involving alkyl or heteroatom radicals will be the major focus in our group.

Influence of the Capping Agent PVP of the Outer Layer of Pd Nanocubes Surface on the Catalytic Hydrogenation of Unsaturated C−C Bonds

The excess of capping agents used during the synthesis of nanoparticles is usually removed by solvent washing. The influence of the amount of polyvinylpyrrolidone (PVP) capping agent in the catalytic activity of palladium nanocubes was evaluated, after different numbers of washing cycles in the purification step performed after the syntheses of the nanoparticles. The effect of PVP amount on the hydrogenation of unsaturated carbon-carbon bonds was evaluated in terms of kinetic analysis and diffusion experiments. Five different catalysts were prepared utilizing the washing off procedure. All catalysts were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, small angle X-ray scattering spectroscopy and dynamic light scattering. The reaction presented strong influence by the amount of PVP, which was determined to be due to a balance between the amount of capping agent and the structure of the substrate.

Oxalic Acid Monothioester for Palladium-Catalyzed Decarboxylative Thiocarbonylation and Hydrothiocarbonylation.

Oxalic acid monothioester (OAM), an easily accessible and storable reagent, was reported herein as a thioester synthetic equivalent for palladium-catalyzed decarboxylative thiocarbonylation of organohalides and hydrothiocarbonylation of unsaturated carbon-carbon bonds at room temperature with high chemo- and regioselectivity. The reaction is applicable to the synthesis of cysteine-derived thioesters, thus allowing chemical modification of cysteine-containing peptides. Decarboxylation of OAM proceeds through oxidative addition of Pd(0) to the acyl-S bond, which accounts for the very mild reaction conditions.

Cobaloxime Catalysis: Selective Synthesis of Alkenylphosphine Oxides under Visible Light.

Direct activation of H-phosphine oxide to react with an unsaturated carbon-carbon bond is a straightforward approach for accessing alkenylphosphine oxides, which shows significant applications in both synthetic and material fields. However, expensive metals and strong oxidants are typically required to realize the transformation. Here, we demonstrate the utility of earth-abundant cobaloxime to convert H-phosphine oxide into its reactive radical species under visible light irradiation. The radical species thus generated can be utilized to functionalize alkenes and alkynes without any external photosensitizer and oxidant. The coupling with terminal alkene generates E-alkenylphosphine oxide with excellent chemo- and stereoselectivity. The reaction with terminal alkyne yields linear E-alkenylphosphine oxide via neutral radical addition, while addition with internal ones generates cyclic benzophosphine oxides and hydrogen. Mechanistic studies on radical trapping experiments, electron spin resonance studies, and spectroscopic measurements confirm the formation of phosphinoyl radical and cobalt intermediates that are from capturing the electron and proton eliminated from H-phosphine oxide. The highlight of our mechanistic investigation is the dual role played by cobaloxime, viz., both as the visible light absorber to activate the P(O)-H bond as well as a hydrogen transfer agent to influence the reaction pathway. This synergetic feature of the cobaloxime catalyst preforming multiple functions under ambient condition provides a convergent synthetic approach to vinylphosphine oxides directly from H-phosphine oxides and alkenes (or alkynes).

High activity Pd-Fe bimetallic catalysts for aqueous phase hydrogenations

Palladium-iron bimetallic catalysts were synthesized using carbon-coated silica supports that provided high hydrogenation activity relative to monometallic palladium under condensed-phase hydrothermal conditions. The catalysts were applied to the hydrogenation of carbonyl groups in acetone, 2-pentanone, and propionaldehyde. While Fe incorporation independent of Pd-to-Fe ratio gave enhanced activity, the catalysts having more Fe than Pd gave more than a three-fold increase in hydrogenation activity relative to the Pd only counterpart. The activity enhancement appeared to be related to the influence of Fe on the Pd as Fe under the condensed-phase reaction conditions was inert. The catalysts were also tested for hydrogenation of unsaturated carbon-carbon double bond and aromatic rings in which more moderate activity enhancement was observed. Through evaluating the influence of Pd-to-Fe ratio on catalyst properties and catalytic performance for the range of molecules, it is proposed that the turnover frequency enhancement can be attributed to the formation of Pdδ− via Pd-Fe interaction.

ω-3 fish oil fat emulsion preconditioning mitigates myocardial oxidative damage in rats through aldehydes stress

ω-3 fish oil fat emulsions contain a considerable quantity of unsaturated carbon-carbon double bonds, which undergo lipid peroxidation to yield low-dose aldehydes. These aldehydes may stimulate the production of antioxidant enzymes, thereby mitigating myocardial oxidative damage. This study aims to (1) verify the cardioprotective effect of ω-3 fish oil fat emulsion in vivo and in vitro, and (2) determine whether aldehyde stress is a protective mechanism. For modeling purposes, we pretreated rats with 2 ml/kg of a 10% ω-3 fish oil fat emulsion for 5 days in order to generate a sufficient aldehyde stress response to trigger the production of antioxidant enzymes, and we obtained similar response with H9C2 cells that were pretreated with a 0.5% ω-3 fish oil fat emulsion for 24 h. ω-3 fish oil fat emulsion pretreatment in vivo reduced the myocardial infarct size, decreased the incidence of arrhythmias, and promoted the recovery of cardiac function after myocardial ischemia/reperfusion injury. Once the expression of nuclear factor E2-related factor 2 (Nrf2) was silenced in H9C2 cells, aldehydes no longer produced enough antioxidant enzymes to reverse the oxidative damage caused by tert-butyl hydroperoxide (TBHP). Our results demonstrated that ω-3 fish oil fat emulsion enhanced the inhibition of oxidation and production of free radicals, and alleviated myocardial oxidative injury via activation of the Nrf2 signaling pathway.

Ready access to organoiodides: Practical hydroiodination and double-iodination of carbon-carbon unsaturated bonds with I2

By using I2 or I2/H3PO3 system, various alkenes and alkynes were converted to the corresponding alkyl and alkenyl iodides in good yields. In the presence of I2, alkynes could be di-iodinated using H2O as the solvent in air at room temperature. This method also features the simple work-up procedure since the pure product could be obtained by extraction. Additionally, for the first time, combining with the non-toxic and cheap phosphonic acid H3PO3, alkenes and alkynes were also hydroiodinated successfully, which provides a simple and practical approach for synthesis of organoiodides.

Controlling the surface chemistry towards unsaturated carbon-carbon bonds over non-oxide transition metal ceramics: Trends in adsorption and distortion energies and adsorbate “activation”

Controlling the surface chemistry of catalysts towards unsaturated carbon-carbon bonds is vital to achieving many contemporary chemical transformations. Transition metal (TM) ceramics are promising materials that exhibit lower and tunable surface reactivity towards C=C bonds. Herein, we have employed an analysis of the adsorption of benzene over a large suite of TM ceramic and pure metal surfaces to benchmark a large selection of materials to isolate trends. Results showed a wide range of surface reactivity as a function of the constituent elements, surface composition, TM-to-p-element ratio, surface ensemble size, electronic structure, etc. The 1st row TM ceramics exhibited lower surface reactivity and more stable surface composition than the 2nd/3rd TM ceramics suggesting that orbital-size match could be a simple marker for predicting general surface chemistry and surface composition stability in TM solid compounds. The TM-to-p-element ratio also generally dictated metal-like or markedly-modified reactivity of the constituent elements at the ceramic surface. Electronic analysis further quantified the correlation between the density and type of electronic states near the Fermi level and the reactivity of surface-lattice elements. Structural and energetic analysis of the adsorbed benzene indicated the activation of the adsorbate could be better quantified beyond simple adsorption energy.

Superlithiated Polydopamine Derivative for High-Capacity and High-Rate Anode for Lithium-Ion Batteries.

Organic electrode materials, with low-cost synthesis and environmental friendliness, have gained significant research interest in lithium-ion batteries (LIBs). Polydopamine (PDA), as a bioderived organic electrode material, exhibits a low capacity of ∼100 mAh g-1, greatly limiting the practical application in LIBs. In this work, we find that a simple heat treatment at 300 °C can endow PDA-derived material (PDA300) with superior electrochemical performance. The obtained PDA300 electrode exhibits an ultrahigh capacity of 977 mAh g-1 at 50 mA g-1. Further combining the PDA300 with highly conductive Ti3C2T x MXene, the obtained PDA300/Ti3C2T x composite is demonstrated by high capacity (1190 mAh g-1, 50 mA g-1), excellent rate capability (remaining 552 mAh g-1 at 5 A g-1), and good cycling stability (82% retaining after 1000 cycles). The outstanding lithium storage performance is highly associated with the superlithiation process of the unsaturated carbon-carbon bonds in the PDA derivative and the introduction of the highly conductive Ti3C2T x substrate with a unique two-dimensional nanostructure. This work will provide new opportunities for the expansion of high-performance organic anodes for LIBs.

Regiodivergent Copper Catalyzed Borocyanation of 1,3-Dienes.

Copper catalyzed multi-functionalization of unsaturated carbon-carbon bonds is a powerful tool for the generation of complex molecules. We report a regiodivergent process that allows a switch between 1,4-borocupration and 4,1-borocupration of 1,3-dienes upon a simple change in ligand. The subsequently generated allyl coppers are trapped in an electrophilic cyanation to selectively generate densely functionalized and synthetically versatile 1,2- or 4,3-borocyanation products.

On the road towards tailor-made rhamnolipids: current state and perspectives.

Rhamnolipids are biosurfactants with an enormous potential to replace or complement classic surfactants in industrial applications. They consist of one or two L-rhamnose residues linked to one or two 3-hydroxyfatty acids of various chain lengths, which can also contain unsaturated carbon-carbon bonds, yielding a wide variety of different structures each with its specific physicochemical properties. Since different applications of surfactants require specific tenside characteristics related to surface tension reduction, emulsification, and foaming etc., rhamnolipids represent a platform molecule which harbors an enormous potential to adopt tailor-made properties to meet a huge variety of demands of surfactants for food-, healthcare-, and biotechnological applications. We are here giving an overview on current technology to synthesize tailor-made rhamnolipids based on the biotechnological use of different enzymes responsible for rhamnolipid biosynthesis originating from different naturally rhamnolipid-producing microorganism. Furthermore, we present future strategies to determine the number of L-rhamnose and 3-hydroxyfatty acids as well as their specific chain lengths and unsaturations to produce customized rhamnolipids perfectly tuned for every application.

Recent Advances of Phosphorus-Centered Radical Promoted Difunctionalization of Unsaturated Carbon-Carbon Bonds

Recent Advances of Phosphorus-Centered Radical Promoted Difunctionalization of Unsaturated Carbon-Carbon Bonds

Hydroarylation of unsaturated carbon-carbon bonds in cross-conjugated enynones under the action of superacid CF3SO3H or acidic zeolite HUSY. Reaction mechanism and DFT study on cationic intermediate species.

Reactions of cross-conjugated enynones,1,5-diarylpent-1-en-4-yn-3-ones, with arenes in the system TfOH-pyridine or under the action of acidic zeolite HUSY lead regioselectively to products of hydroarylation of the acetylene bond only,1,1,5-triarylpent-1,4-dien-3-ones, in yields up to 98%. These dienones add one more arene molecule to the double carbon-carbon bond in neat TfOH forming 1,1,5,5-tetraarylpent-1-en-3-ones in high yields. Cationic reaction intermediates have been studied by means of DFT calculations to elucidate plausible reaction mechanisms.

Intramolecular structural parameters are key modulators of the gel-liquid transition in coarse grained simulations of DPPC and DOPC lipid bilayers

The capability of coarse-grained models based on the MARTINI mapping to reproduce the gel-liquid phase transition in saturated and unsaturated model lipids was investigated. We found that the model is able to reproduce a lower critical temperature for 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with respect to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Nonetheless, the appearance of a gel phase for DOPC is strictly dependent on the intramolecular parameters chosen to model its molecular structure. In particular, we show that the bending angle at the coarse-grained bead corresponding to the unsaturated carbon-carbon bond acts as an order parameter determining the temperature of the phase transition. Structural analysis of the molecular dynamics simulations runs evidences that in the gel phase, the packing of the lipophilic tails of DOPC assume a different conformation than in the liquid phase. In the latter phase, the DOPC geometry resembles that of the relaxed free molecule. DPPC:DOPC mixtures show a single phase transition temperature, indicating that the observation of a phase separation between the two lipids requires the simulation of systems with sizes much larger than the ones used here.

Visible Light-Mediated Installation of Halogen Functionalities into Multiple Bond Systems

Photoredox catalysis has emerged as a useful tool for organic, synthetic, and material chemists to approach target molecules with new functionalities and structural complexity. This review focuses on the recent advances in the visible light-promoted halogenation and trifluoromethylation/difluoromethylation of multiple bonds. Halogen functionalities are important chemical handles and building blocks in organic synthesis. Both electrophilic addition of halogens and radical halogenations are widely utilized in organic synthesis to install halogen functionalities. However, harsh conditions and low regioselectivity could present challenges. Despite these concerns, recent efforts have led to obvious advances in the visible light-promoted halogenation of multiple bonds. In this context, we address the recent achievements in the visible light-mediated installation of different types of halogen-containing functionalities, which include (i) halogenation of unsaturated carbon-carbon bonds, (ii) trifluoromethylation and difluoromethylation of π-systems, and (iii) photoredox cyclization by insertion of fluorine sources. A variety of active catalytic species in the photoredox halogenations are also discussed in terms of their unique reactivity for the future development of highly practical and efficient processes.

New feats of alkene and alkyne asymmetric hydroamination catalyzed by copper and rhodium hydrides

Abstract Hydroamination of unsaturated carbon-carbon bonds is a useful C-N bond forming reaction as it leads to products (amines, imines, enamines) of high synthetic value. While the hydroamination of terminal alkenes and alkynes under metal catalysis has been widely developed, the corresponding reactions with internal substrates remain a challenge. Two recent studies by Buchwald and by Dong which focus on enantioselective hydroamination of internal alkenes and alkynes respectively are of significant importance. [43,44] The results reported broaden the scope of hydroamination as a useful C-N bond forming process and allow acess to chiral amines which are difficult to synthesize by other methods.

Radical Promoted Difunctionalization of Unsaturated Carbon-Carbon Bonds in the Presence of Dioxygen

The difunctionalization of unsaturated carbon-carbon bonds is a powerful strategy for the synthesis of various organic compounds. Recently, the remarkable progress has been made in difunctionalization of unsaturated carbon-carbon bonds with dioxygen and radicals. The present protocol, which utilizes dioxygen as oxygen source, provides a green and atom economy approach to alcohols or ketones. This review will summarize the recent development in this area on the basis of different types of radicals.

User-Friendly Platinum Catalysts for the Highly Stereoselective Hydrosilylation of Alkynes and Alkenes.

With a view to addressing the shortcomings of traditional catalysts, a new generation of outstanding N-heterocyclic carbene platinum(0) complexes for the hydrosilylation of unsaturated carbon-carbon bonds is reported. Their discovery and application to the stereoselective addition of various silanes to silylated alkynes, terminal acetylenes, and olefins is presented. Insights into the catalytic cycle and the origin of the stereoselectivity are also discussed.

The Retro-Hydroformylation Reaction.

Hydroformylation, a reaction that adds carbon monoxide and dihydrogen across an unsaturated carbon-carbon multiple bond, has been widely employed in the chemical industry since its discovery in 1938. In contrast, the reverse reaction, retro-hydroformylation, has seldom been studied. The retro-hydroformylation reaction of an aldehyde into an alkene and synthesis gas (a mixture of carbon monoxide and dihydrogen) in the presence of a cyclopentadienyl iridium catalyst is now reported. Aliphatic aldehydes were converted into the corresponding alkenes in up to 91% yield with concomitant release of carbon monoxide and dihydrogen. Mechanistic control experiments indicated that the reaction proceeds by retro-hydroformylation and not by a sequential decarbonylation-dehydrogenation or dehydrogenation-decarbonylation process.