Synthesis Of Alkenes Research Articles

Julia‐Kocienski Olefination in the Synthesis of Trisubstituted Alkenes: Recent Progress

AbstractJulia‐Kocienski olefination, a coupling reaction between a carbonyl component and a sulfone partner, has emerged as a powerful synthetic tool in the preparation of several organic compounds. A number of interesting examples involving particularly the preparation of trisubstituted alkenes along with important observations regarding the stereoselectivity of those reactions have been recently reported. This reviewing work covers the literature for the period 2016–2022 and describes in a comprehensive way the progress and developments of Julia‐Kocienski olefination application in the synthesis of trisubstituted alkenes which serve as precursors of natural products and their analogs as well of pharmaceutically interesting/biologically important compounds. Moreover, key methodology results dealing with the investigation of the optimum conditions and stereoselectivities and new modifications and approaches are discussed.

Stereoselective Synthesis of Trisubstituted Alkenes via Copper Hydride-Catalyzed Alkyne Hydroalkylation.

Alkenes are ubiquitous in organic chemistry, yet many classes of alkenes remain challenging to access by current synthetic methodology. Herein, we report a copper hydride-catalyzed approach for the synthesis of Z-configured trisubstituted alkenes with high stereo- and regioselectivity via alkyne hydroalkylation. A DTBM-dppf-supported Cu catalyst was found to be optimal, providing a substantial increase in product yield compared to reactions conducted with dppf as the ligand. DFT calculations show that the DTBM substitution leads to the acceleration of alkyne hydrocupration through combined ground and transition state effects related to preventing catalyst dimerization and enhancing catalyst-substrate dispersion interactions, respectively. Alkyne hydroalkylation was successfully demonstrated with methyl and larger alkyl tosylate electrophiles to produce a variety of (hetero)aryl-substituted alkenes in moderate to high yields with complete selectivity for the Z stereochemically configured products. In the formation of the key C-C bond, computational studies revealed a direct SN2 pathway for alkylation of the vinylcopper intermediate with in situ-formed alkyl iodides.

Comparative Study of Short-Chain Olefins Synthesis via CO2 Hydrogenation over Iron-Containing Double Metal Cyanide-Derived Catalysts

Comparative Study of Short-Chain Olefins Synthesis via CO₂ Hydrogenation over Iron-Containing Double Metal Cyanide-Derived Catalysts

Green synthesis of heterocyclic alkenes using MCM 41 supported perchloric acid catalytic system: characterization and DFT studies.

In this work, a series of heterocyclic alkenes were prepared by the reaction of 2-hydroxy-1-naphthaldehyde with various heterocyclic active methylene compounds via Knoevenagel condensation reaction using mesoporous silica, MCM 41, supported perchloric acid as an efficient green catalytic system under solvent-free conditions. A comparative study of the conventional method vs the green method was also reported with the same raw materials. 1H NMR, 13C NMR, IR, and mass spectroscopic techniques were used for the characterization of synthesized compounds. Computational study was performed for these compounds by applying density functional theory (DFT) at M06 functional and 6-311G (d,p) basis set to interpret the electronic structures and counter check the experimental findings. The frequency analysis with aforementioned levels of DFT was performed to confirm the stability associated with optimized geometries. The true minimum for the optimized geometries for 1, 2, and 3 was achieved as indicated by the absence of negative eigenvalues in all the calculated frequencies. Additionally, natural bond orbitals (NBOs) and nonlinear optical (NLO) properties were explored utilizing the aforementioned level and basis set combination via DFT, whereas the frontier molecular orbitals (FMOs) evaluation was done at time-dependent density functional theory TDDFT at M06/6-311G(d,p). The global reactivity parameters were also calculated using the FMO data. These computation-based outcomes were found in good agreement with the experimental findings.

Probing the Roles of Residual Sodium in Physicochemical Properties and Performance of FeAlNa Catalyst for Fischer–Tropsch Synthesis

Although Fe-based catalysts have made significant progress in Fischer–Tropsch synthesis, the effect of residual sodium on the structural properties and catalytic performance of Fe-based catalysts has been controversial. Herein, we report the positive role of residual sodium in the structural properties and performance of FeAlNa catalysts for olefins synthesis from syngas. Meanwhile, the as-prepared catalysts were characterized by the multiple characterization technique to reveal the positive role of residual sodium on the structural properties. The characterization results revealed that the residual sodium improved the reduction behavior of Fe species and adsorption ability of CO, and inhibited the secondary hydrogenation due to its weak adsorption ability of H2. Moreover, the residual sodium inhibited the interaction between Fe and Al. Importantly, a high olefins/paraffins ratio of 6.19 and low CH4 selectivity of 12.8% were achieved on the residual sodium modified FeAlNa catalyst. An in-depth understanding of the structural properties and catalytic performance of residual sodium on FeAl-based catalysts can provide a theoretical basis for the development of novel efficient catalysts and large-scale applications for olefins synthesis from syngas.

Stereoselective Synthesis of Multisubstituted Alkenes via Ruthenium-Catalyzed Remote Migration Arylation of Nonactivated Olefins.

Polysubstituted alkenes are an important class of organic intermediates that widely exist in various natural products and drug molecules. Herein, we reported a stereoselective synthesis of multisubstituted alkenes via ruthenium-catalyzed remote migration arylation of nonactivated olefins. This strategy exhibited wide substrate suitability and excellent functional group tolerance. In addition, we demonstrated the indispensable role of two types of ruthenium through mechanism experiments.

Switchable Direct Oxygenative Arylation of C(sp3)-H Bonds via Electrophotocatalysis.

A metal-free electrophotochemical C(sp3)-H arylation was developed under mild conditions. This method enables a switchable synthesis of diaryl alcohols and diaryl alkanes from inactive benzylic carbons. More importantly, a cheap and safe mediator N-chlorosuccinimide (NCS) was developed, which was employed for the hydrogen atom transfer (HAT) process of the benzylic C-H bond. In addition, this active radical was captured and identified by electron paramagnetic resonance (EPR).

Synthesis and Palladium-Catalyzed Cross-Coupling of an Alkyl-Substituted Alkenylboronic Acid Pinacol Ester with Aryl Bromides

The palladium-catalyzed cross-coupling reaction of alkyl-substituted alkenylboron reagents with aryl halides is a versatile method to introduce a hydrophobic hydrocarbon chain onto organic compounds of interest. The application of the cross-coupling reaction is enabled by synthetic methods for the preparation of alkenylboron reagents. The geometrically pure, alkyl-substituted alkenylboron reagent, (E)-octenylboronic acid pinacol ester, was prepared by 9-BBN-catalyzed hydroboration reaction of 1-octene with pinacolborane in refluxing 1 M THF solution. This reagent was then evaluated in palladium-catalyzed cross-coupling reactions with aryl bromides. The highest yield of the (E)-1-phenyloctene was obtained when SPhos was used as the ligand, K2CO3 was used as the base, and DMF was used as the reaction solvent. Other electron-rich, electron-poor, sterically hindered, and heteroaromatic substrates produced the corresponding (E)-1-phenyloctene derivatives in moderate to good yield. KEYWORDS: Organic synthesis; Aryl alkene synthesis; Palladium-catalyzed cross-coupling; Suzuki-Miyaura reaction; Stereocontrolled alkene preparation; Hydroboration; 9-Borobicyclo[3.3.1]nonane; Reaction optimization

Features of the deactivation of Mg/HZSM-5 catalysts for the synthesis of lower olefins from dimethyl ether in a slurry reactor

In a slurry reactor, the formation of compaction products on Mg/HZSM-5 catalysts, irrespective of the SiO2 /Al2O3 molar ratio in the zeolite, proceeds predominantly on strong acidic sites. The composition of compaction products (mostly trimethyl- and tetramethylbenzenes) virtually does not change with a growth of the molar ratio; however, their amount decreases, which is related to a growth of the mesopore volume with an increase in the SiO2 /Al2O3 ratio. This leads to a decrease in diffusion limitations and contribution of secondary reactions and enhances the removal of coke precursors from the zeolite surface, thus promoting the catalyst activity (the conversion of DME increases twofold). The composition of reaction products changes only slightly with a growth of the SiO2 /Al2O3 molar ratio, the total selectivity to lower olefins is ca. 70 wt.%. A rapid loss of the Mg/HZSM-5 activity with extending the operation time in a slurry reactor is caused not by coking, but rather by «clogging» of the catalyst with decomposition products of the dispersion medium (polydimethylsiloxane).

Enantioselective Hydroalkenylation and Hydroalkynylation of Alkenes Enabled by a Transient Directing Group: Catalyst Generality through Rigidification.

The catalytic enantioselective synthesis of α-chiral alkenes and alkynes represents a powerful strategy for rapid generation of molecular complexity. Herein, we report a transient directing group (TDG) strategy to facilitate site-selective palladium-catalyzed reductive Heck-type hydroalkenylation and hydroalkynylation of alkenylaldehyes using alkenyl and alkynyl bromides, respectively, allowing for construction of a stereocenter at the δ-position with respect to the aldehyde. Computational studies reveal the dual beneficial roles of rigid TDGs, such as L-tert-leucine, in promoting TDG binding and inducing high levels of enantioselectivity in alkene insertion with a variety of migrating groups.

Oxidative Dehydrogenation of Alkanes through Homogeneous Base Metal Catalysis.

Preparing valuable olefins from cheap and abundant alkane resources has long been a challenging task in organic synthesis, which mainly suffers from harsh reaction conditions and narrow scopes. Homogeneous transition metals catalyzed dehydrogenation of alkanes has attracted much attention for its excellent catalytic activities under relatively milder conditions. Among them, base metal catalyzed oxidative alkane dehydrogenation has emerged as a viable strategy for olefin synthesis for its usage of cheap catalysts, compatibility with various functional groups, and low reaction temperature. In this review, we discuss recent development of base metal catalyzed alkane dehydrogenation under oxidative conditions and their application in constructing complex molecules.

Bringing a Mechanistic Lens to the Development of New Transfer Hydroarylation Isodesmic Reactions for the Synthesis of Amides, Thioamides, Amidines, Alkenes and Ketones from Carboxylic Acids via Extrusion and Insertion Elementary Steps

AbstractThe wide availability, ease of handling and structural and functional diversity make carboxylic acids prized building blocks in organic synthesis. The past two decades has seen an explosion of interest in the development of new modes of reactivity of carboxylic acids and their derivatives. Of these, metal‐mediated decarboxylation reactions are attractive as they produce organometallic intermediates that can subsequently be used in C−X (where X=C, N, S etc) bond coupling reactions. Here the results of mechanistic studies integrating both gas‐ and condensed‐phase work are described for development of new extrusion‐insertion (ExIn) classes of reactions for the synthesis of amides, thioamides, amidines, alkenes and ketones from arylcarboxylic acids and suitable (hetero)cumulenes.

Aryl-to-Vinyl 1,4-Nickel Migration/Reductive Cross-Coupling Reaction for the Stereoselective Synthesis of Multisubstituted Olefins.

The aryl-to-vinyl nickel 1,4-migration (1,4-Ni migration) reaction has been reported for the first time. The generated alkenyl Ni species undergo a reductive coupling reaction with unactivated brominated alkanes affording a series of trisubstituted olefins. This tandem reaction exhibits mild conditions, a broad substrate scope, high regioselectivity, and excellent Z/E stereoselectivity. A series of controlled experiments have shown that the critical 1,4-Ni migration process is reversible. In addition, the alkenyl nickel intermediates obtained after migration are highly Z/E stereoselective and do not undergo Z/E isomerization. The obtained trace isomerization products are caused by the instability of the product.

Aryl‐to‐Vinyl 1,4‐Nickel Migration/Reductive Cross‐Coupling Reaction for the Stereoselective Synthesis of Multisubstituted Olefins

AbstractThe aryl‐to‐vinyl nickel 1,4‐migration (1,4‐Ni migration) reaction has been reported for the first time. The generated alkenyl Ni species undergo a reductive coupling reaction with unactivated brominated alkanes affording a series of trisubstituted olefins. This tandem reaction exhibits mild conditions, a broad substrate scope, high regioselectivity, and excellent Z/E stereoselectivity. A series of controlled experiments have shown that the critical 1,4‐Ni migration process is reversible. In addition, the alkenyl nickel intermediates obtained after migration are highly Z/E stereoselective and do not undergo Z/E isomerization. The obtained trace isomerization products are caused by the instability of the product.

Precise tuning of the properties of MOR-type zeolite nanoparticles to improve lower olefins selectivity in composite catalysts for CO2 hydrogenation

CO2 utilization is a key technology for carbon neutrality and is in high demand worldwide; however, many challenges need to be overcome. Composite catalysts consisting of zirconia-based catalysts for CO2 hydrogenation and zeolite-based solid acid catalysts for methanol-to-olefins reaction have been realized one-pass synthesis of olefins from CO2. High selectivity for olefins is essential for utilizing this promising process, and in this work, we precisely tuned the properties of MOR-type zeolites using multiple-step post-synthetic treatments. Miniaturization by milling and recrystallization helped realize the optimization of the zeolite composition related to the acid strength as well as enhance gas diffusion. Defect-healing treatment recently developed by us was applied, and the defects generated in the framework during these processes were successfully removed. Finally, the optimized sample showed high catalytic activity in sequential CO2 hydrogenation to hydrocarbons with the olefin selectivity with an improvement in the olefin/paraffin ratio from 0.69 to 1.4.

Synthesis of Polysubstituted Enamides by Hydrogen Atom Transfer Alkene Isomerization Using Dual Cobalt/Photoredox Catalysis.

M-HAT isomerization is a highly reliable method to access thermodynamically stable alkenes with high functional group tolerance. However, synthesis of heteroatom-substituted alkenes by M-HAT isomerization reaction is still underdeveloped. Herein, we report an enamide synthesis using M-HAT via a combination of cobalt and photoredox catalysis. This method tolerates a variety of functional groups including haloarenes, heteroarenes, free hydroxy groups, non-protected indoles, and drug derivatives. Furthermore, this method can isomerize styrene derivatives in good yield and E/Z selectivity.

Nickel-Catalyzed Hydrotrifluoroalkylation of Alkynes to Construct Allylic Trifluoromethyl Terminal Alkenes.

Herein, we describe a nickel-catalyzed hydrotrifluoroalkylation of terminal alkyne for the synthesis of a manifold allylic trifluoromethyl terminal alkene. The combination of nitrogen and phosphine ligands, especially electron-rich ones, plays an indispensable role in the course of the reaction, promoting the reactivity to a remarkable level, demonstrating high efficiency, broad substrate scope, and favorable functional group compatibility. The strategy provides a facile method for the synthesis of diversified allylic CF3-containing drugs and bioactive molecules.

Synthesis of tetra-substituted olefins by NiH-catalyzed hydroacylation of allenes

In this issue of Chem Catalysis, Cho and co-workers invent an innovative way to easily synthesize all-carbon tetra-substituted olefins through a regio- and stereoselective hydroacylation of both 1,1-disubstituted symmetric and unsymmetrical allenes with various anhydrides. This PˆN ligand-ligated NiH system reveals a complementary regioselectivity to Cu catalysis.

Base-free NiH-catalyzed regio- and stereo-selective hydroacylation of allenes: A new route to synthesis of tetra-substituted olefins

Base-free NiH-catalyzed regio- and stereo-selective hydroacylation of allenes: A new route to synthesis of tetra-substituted olefins

Effect of water and methanol concentration in the feed on the deactivation of In2O3-ZrO2/SAPO-34 catalyst in the conversion of CO2/CO to olefins by hydrogenation

On account of the superior performance of In2O3-ZrO2/SAPO-34 tandem catalyst in the direct synthesis of olefins from CO, CO2 and CO/CO2 mixture by hydrogenation, it is interesting to establish the conditions to avoid its deactivation due to the rapid coke deposition on SAPO-34. The co-feeding of H2O and/or methanol together with H2 + CO2/CO was studied in a packed bed reactor at: 400 °C, 30 bar; CO2/COx in the feed, 0–1; H2/COx in the feed, 1–3; and space time of 5 gcat h molC−1, quantifying the evolution with time on stream (up to 16 h) of CO2 and COx conversions and olefin, paraffin and CH4 yields. The effects of the co-feeding on coke content and its nature were determined by temperature programmed oxidation (TPO) analyses of the spent catalyst. The results highlighted the complex effect of the concentration of H2O and oxygenates (methanol/dimethyl ether (DME)) on the deactivation of SAPO-34 and on the products yields in the pseudo-steady state of the catalyst. Co-feeding H2O lessens coke deactivation, however, high H2O concentration leads to attenuate the acidity of SAPO-34, limiting the performance of the tandem catalyst (mainly in the CO2 conversion). Oxygenates co-feeding concentration limit value lies on its favoring effect for coke formation. In addition to this effect, the favorable attenuation of coke deactivation by the high H2 concentration (studied in runs with H2/COx ratio in the feed in the 1–3 range) plays a key role in the viability of the process, leading to a pseudo-steady catalyst state in which the activity is constant. The proven effect of H2O and methanol concentrations will be useful for establishing new catalysts and reaction conditions at which their presence in the reactor will attenuate deactivation.