Synthesis Of Alkenes Research Articles

Fischer-tropsch synthesis of fuels and olefins in 3D printed SS microreactor using iron/graphene oxide catalysts with Mn- and Na-metal promoters

The effects of adding Mn and Na promoter metals to graphene oxide (GO)-supported iron-based catalysts for Ficher-Tropsch Synthesis (FTS) reactions to olefins at 20 bars were investigated in a 3D-printed stainless steel (SS) Microreactor. While promoter metals encourage reduction of iron oxide to iron to form iron carbide, the active metal catalysts in GO allow hydrogenation of CO. These catalysts were synthesized by layer deposition method and characterized by different techniques. The TEM images show the integration of graphene oxide into the catalysts. The XRD and XPS studies confirmed the crystal structure and oxidation states of the metals. The catalytic activity and product selectivity were studied in the temperature range of 200–350°Cwith a 2:1 M ratio of H2: CO. Higher CO conversion with greater selectivity for olefins was observed in the presence of the promoters. FeMnNa@GO showed better stability than both Fe@GO and FeMn@GO catalysts in time-on-stream studies.

A Neutral PCNHCP Co(I)-Me Pincer Complex as a Catalyst for N-Allylic Isomerization with a Broad Substrate Scope.

Earth-abundant-metal catalyzed double bond transposition offers a sustainable and atom-economical route toward the synthesis of internal alkenes. With an emphasis specifically on internal olefins and ethers, the isomerization of allylic amines has been particularly under represented in the literature. Herein, we report an efficient methodology for the selective isomerization of N-allylic organic compounds, including amines, amides, and imines. The reaction is catalyzed by a neutral PCNHCP cobalt(I) pincer complex and proceeds via a π-allyl mechanism. The isomerization occurs readily at 80-90 °C, and it is compatible with a wide variety of functional groups. The in situ formed enamines could additionally be used for a one-pot inverse-electron-demand Diels-Alder reaction to furnish a series of diversely substituted heterobiaryls, which is further discussed in this report.

Synthesis of substituted (trifluoromethyl)alkenes: (Trifluoromethyl)alkylidenation of thioketones via CF3-thiiranes

The synthesis of (trifluoromethyl)alkenes, including fully substituted variants, was achieved from thioketones with in situ-generated (trifluoromethyl)diazoalkanes [CF3C(R)=N2] (the Barton–Kellogg reaction). In the presence of sodium methoxide and a catalytic amount of tetrabutylammonium chloride, trifluoromethylated N-tosylhydrazones [CF3C(R)=NNHTs] derived from trifluoroacetaldehyde hemiacetal (R = H) or trifluoromethyl ketones (R = aryl or alkyl) were employed in the reactions with thioketones. The resulting (trifluoromethyl)diazoalkanes reacted with thioketones, forming (trifluoromethyl)thiirane intermediates. Treatment of these intermediates with trimethyl phosphite readily afforded the substituted (trifluoromethyl)alkenes. Theoretical calculations (DFT, B3LYP/6-31G*) showed that (trifluoromethyl)thiiranes, with less distortion than 2,2-difluorothiiranes, exhibited lower reactivity. Consequently, the involvement of a reducing agent was deemed necessary for the desulfurization step.

Silver-catalyzed direct conversion of epoxides into cyclopropanes using N-triftosylhydrazones

Epoxides, as a prominent small ring O-heterocyclic and the privileged pharmacophores for medicinal chemistry, have recently represented an ideal substrate for the development of single-atom replacements. The previous O-to-C replacement strategy for epoxides to date typically requires high temperatures to achieve low yields and lacks substrate range and functional group tolerance, so achieving this oxygen-carbon exchange remains a formidable challenge. Here, we report a silver-catalyzed direct conversion of epoxides into trifluoromethylcyclopropanes in a single step using trifluoromethyl N-triftosylhydrazones as carbene precursors, thereby achieving oxygen-carbon exchange via a tandem deoxygenation/[2 + 1] cycloaddition. The reaction shows broad tolerance of functional groups, allowing routine cheletropic olefin synthesis in a strategy for the net oxygen-carbon exchange reaction. The utility of this method is further showcased with the late-stage diversification of epoxides derived from bioactive natural products and drugs. Mechanistic experiments and DFT calculations elucidate the reaction mechanism and the origin of the chemo- and stereoselectivity.

Mass Transfer Modulation by Hollow Multi‐Shelled Structures for High Space‐Time Yield Synthesis of Light Olefins from Syngas

AbstractThe separation of CO activation and C─C coupling enables oxide–zeolite catalyzed tandem reaction toward direct conversion of syngas into light olefins to be a promising alternative for the traditional Fischer–Tropsch process with elevated selectivity. Utilizing controlled mass transfer to match the activation of reactants and the coupling of intermediates presents an appealing strategy to break the limitation on space‐time yield in this tandem process. In this work, ZnCrOx hollow multi‐shelled structures (HoMS) are fabricated to enhance the adsorption and enrichment ability of syngas, thereby strengthening the rate‐determining activation step of reactants and resulting in an accelerated generation of intermediates. When coupled with SAPO zeolite, quintuple‐shelled ZnCrOx HoMS‐based catalysts exhibit a record high C2 = ‐C4 = space‐time yield of 559 mg·gcat−1·h−1 with a selectivity of 90%. This work demonstrates the advantages of precise nanostructure sculpturing on the mass transfer behavior in the microenvironment and provides a new strategy for highly selective direct conversion of syngas to light olefins, based on efficient activation of reactants and sufficient feeding of intermediates through enrichment effects within HoMS.

Deactivation of Mg/HZSM-5 Catalysts for the Synthesis of Lower Olefins from Dimethyl Ether in a Slurry Reactor

Deactivation of Mg/HZSM-5 Catalysts for the Synthesis of Lower Olefins from Dimethyl Ether in a Slurry Reactor

Stereospecific Assembly of Trisubstituted Alkenes via Photoinduced Nitrogen‐Centered Radical‐Triggered C—C Bond Cleavage/Functionalization of Oxime Esters

Comprehensive SummaryA general and convenient photoredox‐catalyzed acylation and alkylcyanation of MBH acetates has been established, enabling the assembly of the C(sp2)–C(sp3) bond by a nitrogen‐centered radical strategy for the synthesis of trisubstituted alkenes in moderate to excellent chemical yields (48 examples in total). The reaction of MBH acetates with acyl (indanone) oxime esters afforded trisubstituted alkenes containing 1,4‐dicarbonyl groups. Interestingly, the use of Eosin Y as a photocatalyst in the catalytic system resulted in the formation of distal cyano group‐anchored trisubstituted alkenes via deconstructive functionalization of cycloketone oxime esters. Notably, these resulting 1,4‐dicarbonyl compounds could be applied to late‐stage transformations, providing important methods for the synthesis of dihydropyridazin‐3(2H)‐one.

Facile Access of Olefins from Ketones and Arylboroxines Enabled by Rhodium Catalysis

AbstractOlefination of carbonyl compounds is a typical strategy for the synthesis of olefins. Herein, we reported a rhodium‐catalyzed cross‐coupling reaction of ketones with arylboroxines for straightforward access of olefins. The reaction displays a good functional group tolerance and affords the corresponding products in good to excellent yields. Addition and elimination are suggested as the indispensable steps in catalytic cycle by preliminary mechanistic experiments. This reaction provided a complementary method in catalytic construction of olefins from ketones and organoboron compounds.

Remote-carbonyl-directed sequential Heck/isomerization/C(sp2)–H arylation of alkenes for modular synthesis of stereodefined tetrasubstituted olefins

Modular and regio-/stereoselective syntheses of all-carbon tetrasubstituted olefins from simple alkene materials remain a challenging project. Here, we demonstrate that a remote-carbonyl-directed palladium-catalyzed Heck/isomerization/C(sp2)–H arylation sequence enables unactivated 1,1-disubstituted alkenes to undergo stereoselective terminal diarylation with aryl iodides, thus offering a concise approach to construct stereodefined tetrasubstituted olefins in generally good yields under mild conditions; diverse carbonyl groups are allowed to act as directing groups, and various aryl groups can be introduced at the desired position simply by changing aryl iodides. The stereocontrol of the protocol stems from the compatibility between the E/Z isomerization and the alkenyl C(sp2)–H arylation, where the vicinal group-directed C(sp2)–H arylation of the Z-type intermediate product thermodynamically drives the reversible E to Z isomerization. Besides, the carbonyl group not only promotes the Pd-catalyzed sequential transformations of unactivated alkenes by weak coordination, but also avoids byproducts caused by other possible β-H elimination.

Tailoring the product distribution of CO2 hydrogenation via engineering of Al location in zeolite

Even though tremendous progress has been made on modified Fischer-Tropsch synthesis (FTS) multifunctional catalyst that composed of Fe-based component and acidic zeolite H-ZSM-5 for CO2 hydrogenation into value-added chemicals, the structure-function relationship between the acidic zeolite H-ZSM-5 and product distribution is still under debate. Herein, a series of H-ZSM-5 zeolites with different Al locations and acidic properties are fabricated by varying the synthesis raw agents and conditions. After combining with the carbon-encapsulated Fe-based catalyst for alkenes synthesis from CO2 hydrogenation, aromatics are directionally produced from the ellipsoidal H-ZSM-5 with Al species mainly located at the intersection of straight and sinusoidal channels, while the main products shift to iso-paraffins for the H-ZSM-5 with pillared nanosheet morphology owing to its Brønsted acid site-rich property. The Al location in H-ZSM-5 and the corresponding acidic property are systematically investigated, and the theoretical simulations illustrate that the Al species at the intersection channels could lower the energy barrier of key aromatization step. The Al richly located at straight/sinusoidal would boost the isomerization reaction. Our work not only clarifies the structure-function relationship of acidic zeolite H-ZSM-5 in valuable chemicals synthesis from CO2 hydrogenation but also provides a novel protocol for controlled synthesis.

Homologation reactions for olefin synthesis

Homologation reactions for olefin synthesis

Direct Intramolecular Coupling of Primary/Secondary Alcohols with Secondary Alcohols for Macrocyclic Alkenylation Using Ni‐Zeolite Catalyst Under Continuous‐Flow Conditions

AbstractHerein, we report the direct intramolecular coupling of primary and secondary alcohols for the selective synthesis of macrocyclic olefins in the presence of Ni‐zeolite catalyst under continuous flow. This reaction proceeds via dehydration of secondary alcohols to alkenes, which subsequently undergo intramolecular dehydrative coupling reaction with a primary alcohol to obtain moderate yields of macrocyclic olefins. This reaction is also effective for the coupling of secondary‐secondary alcohols and alkene‐alcohols to produce diverse macrocyclic olefin products. This unique approach has various advantages including step‐economy, no additives and pre‐functionalization required, inexpensive and reusable catalyst, and exemplification with 23 macrocycles in different ring sizes. The continuous flow macrocyclisation afforded higher productivity and space‐time yield than the batch reaction conditions.

Oxidative construction of unusual indole-derived intermediates en route to conodusine A

We describe several approaches to the tricyclic core of conodusine A. Synthesis of a macrocyclic alkene set the stage for 1,2-olefin difunctionalization with conodusine’s pendent amine. Unanticipated reactivity of an unusually labile indole mitigated the desired olefin manipulation. Efforts to pre-install the oxidation state at C19 before macrocyclic ring closure were met with unexpected results. Additionally, late stage allylic oxidation of the complete carbon skeleton of Conodusine was fraught with unforeseen challenges.

Toward sustainable production of N-containing products via nonthermal plasma-enhanced conversion of natural gas resources

Nonthermal plasmas can directly activate and cleave the strong chemical bonds in molecular nitrogen and methane to facilitate the transformation of these inherently stable molecules through the application of electrical energy. Here, we report a low temperature, atmospheric pressure, nonthermal plasma for the “one-pot” synthesis of olefins, alkynes, higher molecular weight hydrocarbons, ammonia, and nitrogen-containing liquids from a representative shale gas feed enriched with nitrogen. We reproducibly observe a wide range of valuable and synthetically challenging gas-phase and liquid-phase products containing C–N, C–C, and N–H bonding by controlling the N2 concentration in the inlet feed stream. In nitrogen-lean regimes, hydrocarbon products dominate (e.g., ethylene, acetylene, etc.), while nitrogen-rich regimes promote incorporation of nitrogen into the products, leading to the formation of ammonia and liquid products containing a variety of functionalities (e.g., nitriles, amines, heterocycles). High resolution electrospray ionization mass spectrometry was used to measure molecular weights and identify the chemical formulas of the liquid products. Van Krevelen diagrams were created and showed many products with compositions around H/C= 2 and N/C= 0.5, indicating the potential importance of intermediate species with these ratios for liquid formation (e.g., CH3CN + H).

Synthesis of green light olefins from direct hydrogenation of CO2. Part I: Techno-economic, decarbonization, and sustainability analyses based on rigorous simulation

BackgroundsConverting CO2 into light olefins through direct hydrogenation is a promising pathway to achieve net-zero emissions. This part aims to present a detailed layout and the analysis results of the process through rigorous simulation. MethodologyThe process encompasses three sections (reaction, CO2 removal, and olefin recovery). Two alternatives for handling the off-gas were proposed, including sending it for additional hydrogen recovery (Scheme 1) or direct combustion (Scheme 2). The minimum required selling price (MRSP), the indirect CO2 emissions per kg of olefins produced (CO2-e), and the carbon efficiency are demonstrated for process evaluation. Significant FindingsScheme 1 demonstrates better economic performance but less decarbonization ability compared to Scheme 2 (i.e. Scheme 1: MRSP = 2327 USD/kg and CO2-e = -2.036 kg/kg; Scheme 2: MRSP = 2366 USD/kg and CO2-e = -2.247 kg/kg). To achieve carbon neutrality, the carbon footprint for the hydrogen feedstock should not exceed 6.92 and 7.08 kg-CO2/kg-H2 for Schemes 1 and 2, respectively. Considering the trade-offs between MRSP and CO2-e, using biomass-based hydrogen is currently the most viable option. Finally, the entire process has a 99.7 % carbon efficiency. In summary, the proposed process is effective in CO2 fixation, with minimal impact on the process economics and sustainability.

Study on the catalytic performance of ZnCrAl co-precipitated oxides washed with ammonium carbonate solution in the synthesis of light olefins from syngas

Ammonium carbonate solution was used instead of water to wash the impurities in the coprecipitation method, and oxides with increased oxygen vacancy content and catalytic effect were obtained.

A new method for synthesizing terminal olefins from esters using the Corey-Chaykovsky reagent.

A new method for the synthesis of terminal olefins was developed through the reaction of the Corey-Chaykovsky reagent (dimethyl-sulfonium methylide) with readily available esters. After the domino process of nucleophilic addition, elimination and rearrangement in one pot, the terminal olefins were synthesized in high yields (up to 84%) under mild conditions. The synthetic method was well tolerated by many functional groups and a new route for the synthesis of various terminal olefin derivatives is provided. In the end, a possible reaction mechanism is proposed, which is supported by DFT calculations.

Microfluidic Microreactor Device with Integrated Heaters for Temperature Assisted Synthesis of Gold Nanoparticles and Alkene

Microfluidic Microreactor Device with Integrated Heaters for Temperature Assisted Synthesis of Gold Nanoparticles and Alkene

Photoredox Suzuki coupling using alkyl boronic acids and esters

Herein, we report a novel methodology for the one-step synthesis of olefins via a transition metal-free pathway.

Transition metal-free decarboxylative olefination of carboxylic acid salts.

The cost-effective and efficient synthesis of alkenes is highly significant due to their extensive applications in both synthetic and polymer industries. A transition metal-free approach has been devised for the chemoselective olefination of carboxylic acid salts. This modular approach provides direct access to valuable electron-deficient styrenes in moderate to good yields. Detailed mechanistic studies suggest anionic decarboxylation is followed by halogen ion transfer. This halogen transfer leads to an umpolung of reactant electronics, allowing for a rate-limiting rebound elimination.