Olefination Reaction Research Articles

Trifluoromethylthiolation Carbonylation of Unactivated Alkenes via Distal Migration.

Sulfur-containing compounds represent a significant category of organic compounds, and the introduction of sulfur groups into organic compounds can effectively enhance their biological activity and synthetic diversity. Although a variety of difunctionalization reactions of alkenes based on sulfur radicals have been documented, significant challenges remain in the carbonylative difunctionalization of unactivated alkenes by the addition of a sulfur radical. Herein, we present a trifluoromethylthiolative carbonylation reaction of unactivated alkenes, which goes through the addition of a trifluoromethylthiol radical to unactivated alkenes and then carbonylation of the newly generated carbon radical intermediate. A heterocyclic/aryl migration in the presence of carbon monoxide is crucial for the success of this methodology and finally resulted in the formation of sulfur-containing carbonylated products in good yields.

Catalytic Asymmetric Cycloaddition of Olefins with In Situ Generated N-Boc-Formaldimine.

Chiral 1,3-amino alcohols are ubiquitous structural motifs in natural products and active pharmaceutical ingredients. We present a highly enantioselective, inverse-electron-demand hetero-Diels-Alder reaction of olefins with in situ generated N-Boc-formaldimine catalyzed by strong and confined Bro̷nsted acids. This transformation provides direct access to valuable 1,3-amino alcohols from styrenes and 1,1-disubtituted alkenes. Isotope labeling studies and kinetic analysis reveal an unusual mechanism involving an oxazinium intermediate and a catalyst order greater than one.

Cu-Catalyzed Asymmetric Three-Component Radical Acylarylation of Vinylarenes with Aldehydes and Aryl Boronic Acids.

The direct use of readily available aldehydes as acyl radical precursors has facilitated diverse three-component acylative difunctionalization reactions of alkenes, offering a powerful route to synthesize β-branched ketones. However, asymmetric three-component acylative difunctionalization of alkenes with aldehydes still remains elusive. Here we report a copper-catalyzed asymmetric three-component radical acylarylation of vinylarenes with aldehydes and aryl boronic acids. This method begins with acyl radical formation from an aldehyde via hydrogen atom transfer. The acyl radical adds to the alkene, forming a new benzylic radical that then undergoes copper-catalyzed enantioselective arylation. A chiral binaphthyl-tethered bisoxazoline ligand is essential for achieving high stereocontrol. This strategy enables the direct synthesis of a range of synthetically valuable chiral β,β-diaryl ketones from aldehydes and vinylarenes.

Synthesis of pyrrole-fused dibenzoxazepine/dibenzothiazepine/triazolobenzodiazepine derivatives via isocyanide-based multicomponent reactions.

An efficient and facile synthesis of pyrrole-fused dibenzoxazepine/dibenzothiazepine/triazolobenzodiazepine derivatives was developed through the isocyanide-based multicomponent reaction of isocyanides, gem-diactivated olefins, and cyclic imines such as dibenzoxazepine, dibenzothiazepine, and triazolobenzodiazepine under solvent- and catalyst-free conditions. Purposefully, this approach produced various bioactive scaffolds using environmentally friendly, mild, and simple conditions. Due to their bioactive moieties, these compounds with exclusive fluorescence properties may attract great attention in biomedical applications, clinical diagnostics, and conjugate materials.

Rare-Earth-Metal-Catalyzed Regioselective Hydrosilylation of Internal Alkenes and Alkynes

AbstractA highly regioselective hydrosilylation reaction of internal alkenes was achieved by using commercially available lanthanum hexamethyldisilazane (La(HMDS)3). Notably, the Z- or E-configuration of internal alkenes has negligible influence on either the reactivity or regioselectivity. Internal alkynes could also be used, affording the mono di-hydrosilylation product in the presence of La(HMDS)3 or mono-hydrosilylation product with Y(HMDS)3 as the promoter.

Photochemical Defluorinative Alkenylation of Trifluoromethyl Alkenes with Organoboronic Acids

AbstractWe have developed a photo‐catalyzed defluorinative two‐component coupling reaction of trifluoromethyl alkenes and organoboronic acids, providing a straightforward and efficient route for the synthesis of functionalized gem‐difluorinated 1,4‐dienes. Both the chemical yields and functional group tolerance are generally good.

Catalytic Asymmetric Reactions of Ketimines and Alkenes via [2 + 2] Cycloaddition: Chemical Reactivity Controlled by Switching a Heteroatom.

Azetidine units are commonly found in natural products and biologically active drugs. The [2 + 2] cycloaddition of imines and alkenes has been extensively used in the synthesis of such structures, while enantioselective approaches remain elusive. Herein, an efficient B(C6F5)3/chiral phosphoric acid-catalyzed asymmetric [2 + 2] cycloaddition of ketimines and aryl vinyl selenides was presented, delivering valuable chiral azetidines with excellent stereoselectivities (>20:1 dr and up to 96:4 er). What's even more interesting was that when a "Se" atom was switched to an "S" atom, the reaction proceeded through a [2 + 2] cycloaddition/ring-opening cascade process, affording a range of chiral thioacetals with high enantioselectivities (up to 98:2 er), which were also important organic sulfur compounds. Mechanistic experiments, coupled with density functional theory (DFT) calculations, shed light on a mechanism involving stepwise [2 + 2] cycloaddition and ring-opening processes, with the initial alkenylation step identified as crucial for achieving stereoselective control.

Nano-Pd/SiO2 aerogel catalyst prepared via ambient pressure drying process using perlite powder in hydrogenation and cross-coupling reactions

Perlite, a cheap silica source with abundant reserves in countries such as Türkiye, China, and Greece, was used to produce nano Pd-doped silica aerogel powder for the first time in this study. The microstructure and morphology of the prepared silica aerogel powder were examined using SEM, FE-SEM, and TEM. The phases of the silica aerogel powders were analyzed via XRD (X-ray Diffraction) technique. The chemical bonding of the surface modifier with aerogels was analyzed by Fourier transform infrared spectroscopy (FTIR, Spectrum RX-1, Perkin Elmer). Surface areas, pore volumes, distributions, and particle sizes of the alumina-silica-based aerogel powders with a porous structure were measured using a Micromeritics/ASAP 2020 brand BET (Brunauer, Emmet, and Teller) device in a liquid nitrogen gas environment at 77K.The efficiency of this nano Pd-doped silica aerogel powder was investigated as a heterogeneous catalyst for well-known transformations in organic synthesis, such as alkene hydrogenation and cross-linking reactions. The results indicated that the developed method is chemoselective, reducing only carbon-carbon multiple bonds without affecting C-N or C-O multiple bonds, such as carbonyl and nitrile. The effectiveness of the newly developed catalyst was also investigated in Heck and Suzuki-Miyaura reactions, yielding the targeted products with high efficiency.Thus, an inexpensive, economical, and environmentally friendly method has been developed that is potentially applicable in the hydrogenation and cross-coupling reactions of alkenes.

Visible-Light-Mediated Vicinal Dihalogenation of Unsaturated C-C Bonds Using Dual-Functional Group Transfer Reagents.

The growing demand for chemical production continues to drive the development of sustainable and efficient methods for introducing molecular complexity. In this context, the exploration of unconventional functional group transfer reagents (FGTRs) has led to significant advancements in practical and atom-efficient synthetic protocols. Aiming to advance the field of valuable organic synthesis, herein we report the successful development of carbon-based, bench-stable, modular, and inexpensive reagents implemented in dual halogen transfer to unsaturated hydrocarbons via photocatalytic activation of reagents based on a radical-polar crossover mechanism. This method beneficially enables vicinal dichlorination, dibromination, and bromo-chlorination reactions of olefins, offering practical alternatives to the use of toxic binary halogens. Detailed mechanistic studies, combining experimental, spectroscopic, and theoretical investigations, revealed a distinctive photocatalytic single-electron transfer reduction of FGTR. This process triggers mesolytic carbon-halogen bond cleavage, followed by a radical 1,2-halide rearrangement, leading to the continuous generation of dihalogen species in the reaction medium. The wide applicability of the developed protocol is demonstrated through an extensive scope of unsaturated molecules, including additional operations on strain-release dihalogenation.

Efficient construction of a quinoline framework from alcohols, nitroarenes, and alkenes promoted by a trimetallic catalyst system

A Pd/Fe/In-trimetallic catalyst system promotes the three-component coupling reaction of primary alcohols, nitroarenes, and terminal alkenes to construct quinoline frameworks in a single operation. These consecutive coupling reactions proceed via an oxidative Povarov reaction of alkenes and aldimines derived from primary alcohols and nitroarenes by a redox hydrogen transfer system. This reaction may contribute to the efficient development of pharmaceuticals and medicinal products.

Regioselective Synthesis of Cycloalkane-fused Pyrazolo[4,3-e]pyridines through Tandem Reaction of 5-aminopyrazoles, Cyclic Ketones and Electron-rich Olefins.

Pyrazolopyridines are interesting fused heterocyclic pharmacophores that combine pyrazole and pyridine; two privileged nuclei extensively studied and with a wide range of applications. They can be obtained by a broad variety of synthetic methods among which multicomponent reactions have gained importance, especially from 5-aminopyrazoles and dielectrophilic reagents. However, the search for new approaches more in tune with sustainable chemistry and the use of unconventional heating in three-component synthesis are open and highly relevant study fields. A novel, practical and efficient three-component synthesis of cycloalkane-fused pyrazolo[ 4,3-e]pyridines was developed through a tandem reaction of 5-aminopyrazoles, cyclic ketones and electron-rich olefins, using microwave induction in perfluorinated solvent and iodine as catalyst. The microwave-induced three-component approach applied in this work promoted the construction of 10 new pyrazolopyridines with high speed and excellent control of regioselectivity, favoring the linear product with good yields; where the versatility of electron-rich olefins in iodine-catalyzed cascade heterocyclizations, granted the additional benefit of easy isolation and the possibility to reuse the fluorous phase. Although pyrazolopyridines have been synthetically explored because of their structural and biological properties, most of the reported synthetic methods use common or even toxic organic solvents and conventional heating or multi-step processes. In contrast, this study applied a multicomponent methodology in a single step by microwave induction and with the versatility provided in this case by the use of perfluorinated solvent, which allowed easy isolation of the final product and recovery of the fluorous phase.

Theoretical kinetics study of hydrogen abstraction reactions of O2(X3Σg/a1Δg) + CnH2n+2 (n ≤ 4)

The chain-initial reactions of small-molecule alkane (CnH2n+2(n ≤ 4)) oxidation participated by electronically excited oxygen O2(a1Δg) are crucial for understanding the role of O2(a1Δg) in plasma-assisted combustion and fuel reforming. Accordingly, in the present work, the energy barriers for the reactions O2(X3Σg/a1Δg) + alkane (n ≤ 4) → products were investigated by using high-precision quantum calculations. Rate constants for each reaction channel within the temperature range of 300–1500 K were predicted based on transition state theory (TST), supplementing plasma kinetics parameters. The energy barriers and rate constants for methane and ethane oxidation dehydrogenation reactions showed good agreement with literature data, validating the accuracy of the computational method employed in this work. The calculations revealed that the dehydrogenation sites have vital impacts on the reaction system. The energy barriers of the reaction channels involved in O2(a1Δg) were reduced at different dehydrogenation sites. Specifically, the change rate of each reaction energy barrier at primary, secondary and tertiary site was about 40 %, 65 % and 65 %, respectively. The reactions involving O2(a1Δg) significantly increased the reaction rate coefficient, especially for single hydrogen abstraction at the secondary and tertiary sites. The effect of O2(a1Δg) on ignition promotion and its regularity were further studied through kinetic simulations. The results suggested that adding O2(a1Δg) reduces the ignition delay time (IDT) of small molecular alkanes by approximately one order of magnitude, attributed to variations in energy barrier and branching ratios of different reaction channels. Notably, the H-atom abstraction reaction on primary site showed the largest sensitivity in IDT at 800 K, particularly for propane and isobutane, with IDT change rates of 98.0 % and 96.3 %, respectively. This study provided reasonable rate coefficients for kinetic modeling of plasma-assisted alkane ignition.

Can Metal Promotion of SAPO-34 Genuinely Improve Its Catalytic Performance in Methanol Conversion to Light Olefins Reaction?

To genuinely assess the effect of secondary metal promotion on improving the SAPO-34 catalytic performance in MTO reaction, a broad spectrum of metals from different groups of the periodic table (alkali and alkaline earth metals, transition metals, rare earth metals, and basic metals) were investigated. Metals were added through a direct incorporation route with Me/Al2O3 molar ratio of 0.05. Some metals seamlessly incorporated into the SAPO-34 framework and replaced the Si and Al atoms, while others partially merged or even failed to be combined with SAPO and emerged as amorphous phases. Although, in some cases, the surface area of the metal-promoted samples increased due to enhanced nucleation rate and smaller particle formation, the majority of the promoted samples suffered from a severe loss in crystallinity that resulted in inferior catalytic performance. It was also illustrated that hydrogen co-feeding with methanol (H2/MeOH molar ratio of 1.5) at ambient pressure could extend the catalyst lifetime by 27 % due to hydrogenation and cracking of the coke species and improve the light olefins selectivity.

Photoinduced Copper‐Catalyzed Three‐Component Radical Carboamination of Styrene Derivatives

AbstractThe catalytic three‐component radical carboamination of alkenes has recently emerged as an alternative and robust platform for the rapid construction of diverse and valuable amines. Despite great advances in this field, new methods that enable highly selective access to new chemical space surrounding the amine functional groups are still in high demand. Herein, we report a generally applicable visible light‐induced copper‐catalyzed three‐component radical cyanoalkylamination reaction of alkenes, oxime carbonates, and benzoyloxycarbamates. This protocol demonstrates high chemo‐selectivity, broad substrate scope, and good functional group tolerance, providing access to a variety of cyanoalkylated aliphatic amines with good yields.

A Teaching Design with Ideological-Political Element on Reactions of Alkanes in College Chemistry II

College chemistry II is a basic course for normal college students majoring in science education in our university, and it is of practical significance to integrate ideological and political education into the teaching of the course to achieve the teaching purpose effectively. Taking the part “reactions of alkanes” as a case of teaching design, this paper discussed the teaching design ideas and methods of integrating ideological-political elements into the specialized course specifically in the setting of the three learning objectives, the introduction of the new lesson, the teaching of the three knowledge points, etc., and carried on the teaching reflection. By fully excavating the ideological-political elements in this course, and integrating the ideological and political education with cases related to reactions of alkanes in daily life and production practice into, it can arouse the students' attention and thinking, stimulate the students' interest in learning, and enhance the effectiveness of students' learning.

Consolidated Description of Explosion Limits and Ignition Delays: Hydrogen and C1-C7 N-Alkanes

ABSTRACT This study computationally investigates the auto-ignition delay times and explosion limits of H2/O2 and C1-C7 n-alkanes/O2 mixtures based on detailed chemical kinetics. Comprehensive ignition responses are consolidated through three-dimensional response surfaces of the ignition delay time as function of the system temperature and pressure, yielding the essential kinetic characteristics governing ignition. The intersection curves of the ignition surface with the cross-section perpendicular to the three coordinate axes are the characteristic response curves of the ignition delay time and explosion limit. Therefore, the ignition delay time and explosion limit are the changing characteristics of the three-dimensional ignition surface observed from different perspectives. Sensitivity analysis demonstrates that while the significant variations of the reaction pathways among different fuels are the primary reason of the wide spreading of the explosion limits curves for the various fuels in the low-temperature regime, their chain branching reactions tend to be similar in the intermediate temperature regime such that the explosion limit curves of different fuels are closely coalesced. Furthermore, in the high-temperature regime, the chain branching reactions of alkanes are primarily governed by small radicals, such as CH3, while it is still dominated by the H+O2=OH+O for H2.

Modular Synthesis of gem-Difluorotetrahydrocarbazolone Scaffolds via Copper-Catalyzed Cascade Reaction of Bromodifluoroacetyl Indoles and Olefins.

A novel and efficient modular synthesis of gem-difluorotetrahydrocarbazolone scaffolds via copper-catalyzed radical cascade cyclization of bromodifluoroacetyl indoles and olefins has been reported. This operationally simple protocol provides straightforward and practical access to a series of privileged gem-difluorotetrahydrocarbazolone scaffolds from readily available starting materials, with the feature of broad functional group tolerance and mild reaction conditions. Moreover, the method could be used for the late-stage functionalization of bioactive molecules, which opens up the possibility for practical applications.

Cyano-Fluorosulfonylation of Unactivated Alkenes by Photoredox and Copper Dual Catalysis.

Both fluorosulfonyl and cyano groups are important structural motifs in bioactive molecules. Herein, we report a new difunctionalization reaction of alkenes based on fluorosulfonyl radicals, which allows for the introduction of the fluorosulfonyl and cyano groups into unactivated alkenes in one step. This transformation is enabled by merging photoredox and copper catalysis, featuring visible light catalysis, mild conditions, and good functional group tolerance. Further transformation of products via SuFEx reactions is also demonstrated.

Molecular Architecture @ MOFs: Designing a Multifunctional Catalyst for the Cascade Reaction of Olefins via Epoxides to Cyclic Carbonates

Employing enzymatic reaction cascade principles to synthesize artificial materials with multiple autonomously operating active sites is one of the holy grails in modern catalysis research. In this regard, metal‐organic frameworks (MOFs) are promising host platforms. Yet, applying MOFs as enzyme‐mimicking catalysts is synthetically challenging. Herein, we present a design strategy for the synthesis of porphyrin‐based MOFs for the cascade catalysis of the conversion of olefins to epoxides and their cycloaddition with CO2 to cyclic carbonates. The MOFs feature tunable dual active sites with synthetically controllable metal variations. A clear dependence of the metal combination on the catalytic performance of the MOF catalysts is shown. This work advances the understanding essential for designing sophisticated, multifunctional porphyrin MOFs for efficient one‐pot cascade catalysis.

Visible-light-promoted one-pot synthesis of β-keto sulfones from aryldiazo tetrafluoroborate salts via aerobic multicomponent reaction

β-Keto sulfone is a useful structure in organic chemistry and pharmaceuticals. In the present study, we developed a highly efficient visible-light-promoted reaction to prepare β-keto sulfones under mild conditions. Synthesis was achieved via one-pot multi-component reaction of aryldiazo tetrafluoroborate salts, alkenes, and DABSO in the presence of air (O2) with rhodamine B serving as the photocatalyst. A variety of β-keto sulfones were obtained at high yields by this one-pot operation under aerobic atmosphere. This oxysulfonylation procedure has benefits such as mild reaction conditions, a wide tolerance of functional groups, and simplicity, making it a promising choice for preparing valuable β-keto sulfones.