Terminal Alkenes Research Articles

Enzymatic Synthesis of a Polyketide/Nonribosomal Peptide Hybrid Antibiotic, Salivabactin.

Salivabactin is a newly identified polyketide/nonribosomal peptide (PK/NRP) from a human oral probiotic, possessing a unique chemical structure and outstanding antibiotic activities. Although the biosynthetic gene cluster for salivabactin is known, the enzymatic logic that governs the synthesis of salivabactin has not yet been fully studied. In this work, we dissected the biosynthetic pathway for salivabactin using biochemical analysis. We successfully reconstituted the enzymatic synthesis of salivabactin in vitro, identified the minimal set of enzymes required for its biosynthesis, and revealed an unusual thioesterase domain involved in terminal olefin formation.

Covalent bidentate ligand-enabled regioselective Wacker-type oxidation of olefins.

The utilization of Pd(ii)-catalyzed oxidation for the transformation of terminal olefins into methyl ketones has emerged as a particularly intriguing and versatile strategy in organic synthesis. Herein we report a novel Pd(ii)-catalyzed Wacker-type oxidation with covalent bidentate ligands. The ligand, 1-(pyridin-2-yl)-1,2-dihydro-3H-indazol-3-one, exhibits excellent performance in converting olefins to ketones. The optimized reaction conditions include the use of TBHP as oxidant, EtOH or MeCN as solvent and short reaction time. The substrate scope includes various substituted olefins, which undergo the desired oxidation reaction with high efficiency.

Synthesis of 2,4,5-vinylic-trisubstituted oxazoles via a Palladium-catalyzed cascade coupling reaction

A novel one-step synthesis of valuable 2,4,5-vinylic-trisubstituted oxazoles is described. This reaction, utilizing readily available β,β-dibrominated secondary enamides and terminal alkenes as starting materials, occurs via a ligand-free Palladium-catalyzed cascade intramolecular CO coupling/intermolecular Heck reaction.

Promotion of Metal‐Free Catalytic Coupling of Fluorinated Halogenated Hydrocarbons By a Base for the Synthesis of Difluoromethyl Heterocyclic Amines

The selective functionalization of difluoromethyl groups (‐CF2) is a promising approach and an attractive synthetic route for accessing fluorine‐containing moieties with medicinal benefits. Here, we report a case of a C‒N coupling reaction between bromodifluoropropene with heterocyclic amines, such as indole, pyrrole, and imidazole, promoted by an alkali without the use of transition metal catalysis. This reaction differs from existing methods in that it does not undergo a difluoromethylation isomerization reaction but directly retains the structure of the terminal olefin. This chemical conversion process has a wide substrate range, good functional group tolerance, and an ideal reaction conversion rate, making it an effective new method for the difluoropropenation of heterocyclic amines.

Ambient Pressure Hydroformylation – A Key Step to Meso‐Alkyl BODIPYs

AbstractHerein, a highly efficient five‐step reaction sequence to meso‐alkyl BODIPYs is presented. In our previous work, the hydroformylation of terminal alkenes was used to generate an aldehyde from an alkene via rhodium catalysis and use them in a subsequent tandem reaction to obtain BODIPY dyes. However, the use of higher pressures and therefore autoclaves as well as their necessary equipment might limit others to use this method. The refined approach in this work employs ambient pressure hydroformylation, done in a simple Schlenk tube and using a CO/H2 balloon, as key step towards an easier meso‐alkyl BODIPY synthesis. Additionally, the use of MTBE instead of chloroform as reaction solvent results in a greener approach. Readily available and easily synthesizable alkenes as well as different pyrrole building blocks can be used to extend the range of known alkyl‐BODIPYs. The synthesis of 23 derivatives with overall yields of up to 67 % demonstrates the wide applicability and advantages of the refined method.

Photoinduced Pd-Catalyzed Direct Sulfonylation of Allylic C-H Bonds.

Allylic sulfones are valuable motifs due to their medicinal and biological significance and their versatile chemical reactivities. While direct allylic C-H sulfonylation represents a straightforward and desirable approach, these methods are primarily restricted to terminal alkenes, leaving the engagement of the internal counterparts a formidable challenge. Herein we report a photocatalytic approach that accommodates both cyclic and acyclic internal alkenes with diverse substitution patterns and electronic properties. Importantly, the obtained allylic sulfones can be readily diversified into a wide range of products, thus enabling formal alkene transposition and all-carbon quaternary center formation through the sequential C-H functionalization.

Photoinduced Pd‐Catalyzed Direct Sulfonylation of Allylic C−H Bonds

AbstractAllylic sulfones are valuable motifs due to their medicinal and biological significance and their versatile chemical reactivities. While direct allylic C−H sulfonylation represents a straightforward and desirable approach, these methods are primarily restricted to terminal alkenes, leaving the engagement of the internal counterparts a formidable challenge. Herein we report a photocatalytic approach that accommodates both cyclic and acyclic internal alkenes with diverse substitution patterns and electronic properties. Importantly, the obtained allylic sulfones can be readily diversified into a wide range of products, thus enabling formal alkene transposition and all‐carbon quaternary center formation through the sequential C−H functionalization.

Platinum-Catalyzed Regio- and Enantioselective Diboration of Unactivated Alkenes with (pin)B-B(dan).

Asymmetric diboration of terminal alkenes is well established, and subsequent selective functionalization of the less hindered primary boronic ester is commonly achieved. Conversely, selective functionalization of the sterically less accessible secondary boronic ester remains challenging. An alternative way to control chemoselective functionalization of bis(boron) compounds is by engendering different Lewis acidity to the two boryl moieties, since reactivity would then be dictated by Lewis acidity instead of sterics. We report herein the regio- and enantioselective Pt-catalyzed diboration of unactivated alkenes with (pin)B-B(dan). A broad range of terminal and cyclic alkenes undergo diboration to furnish the differentiable 1,2-bis(boron) compounds with high levels of regio- and enantiocontrol, giving access to a wide variety of novel building blocks from a common intermediate. The reaction places the less Lewis acidic B(dan) group at the less hindered position and the resulting 1,2-bisboryl alkanes undergo selective transformations of the B(pin) group located at the more hindered position. The regioselectivity of the diboration has been studied by DFT calculations and is believed to originate from the trans influence, which lowers the activation barrier for formation of the regioisomer that places the weaker electron donor [B(pin) vs B(dan)] opposite the strong electron donor (alkyl group) in the platinum complex.

Platinum‐Catalyzed Regio‐ and Enantioselective Diboration of Unactivated Alkenes with (pin)B−B(dan)

AbstractAsymmetric diboration of terminal alkenes is well established, and subsequent selective functionalization of the less hindered primary boronic ester is commonly achieved. Conversely, selective functionalization of the sterically less accessible secondary boronic ester remains challenging. An alternative way to control chemoselective functionalization of bis(boron) compounds is by engendering different Lewis acidity to the two boryl moieties, since reactivity would then be dictated by Lewis acidity instead of sterics. We report herein the regio‐ and enantioselective Pt‐catalyzed diboration of unactivated alkenes with (pin)B−B(dan). A broad range of terminal and cyclic alkenes undergo diboration to furnish the differentiable 1,2‐bis(boron) compounds with high levels of regio‐ and enantiocontrol, giving access to a wide variety of novel building blocks from a common intermediate. The reaction places the less Lewis acidic B(dan) group at the less hindered position and the resulting 1,2‐bisboryl alkanes undergo selective transformations of the B(pin) group located at the more hindered position. The regioselectivity of the diboration has been studied by DFT calculations and is believed to originate from the trans influence, which lowers the activation barrier for formation of the regioisomer that places the weaker electron donor [B(pin) vs B(dan)] opposite the strong electron donor (alkyl group) in the platinum complex.

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.

Photoredox Catalyzed Tandem Denitrogenative [4 + 2] Annulation of 1,2,3-Benzotriazin-4(3H)-ones with Terminal Olefins.

The dihydroisoquinolones skeleton is ubiquitous in natural products and biological molecules. Reported strategies for constructing dihydroisoquinolones usually require noble metal catalysts or stoichiometric oxidants, which limit their wide applications. Herein, we developed a photoredox catalyzed tandem denitrogenative [4 + 2] annulation reaction of 1,2,3-benzotriazin-4(3H)-ones with terminal olefins. A variety of dihydroisoquinolones can be accessed in moderate to excellent yield. This protocol features high atom-economy, mild reaction conditions, and is external oxidant-free, enabling the synthesis of various substituted dihydroisoquinolones.

A Novel Reusable Polymer Supported Palladium Catalyst for HeckReaction

With the rapid development of “green” chemistry; researchers are highly interested towards more sustainable approaches and prefer to choose eco-friendly synthetic routes and materials. This paper deals with the development of a novel reusable heterogeneous palladium catalyst for Heck reaction. The catalyst (mPAN-Pd) was developed by a simple procedure via synthetic modification of polyacrylonitrile (PAN) with monoethanolamine (MEA) followed by complexation with palladium chloride (PdCl2). After detailed characteristic studies, the catalytic efficiency of mPAN-Pd in Heck coupling reaction was systematically evaluated and optimised the reaction condition through a set of experiments. This heterogeneous catalytic system was found be applicable over a series of aryl halides and terminal alkenes leading to corresponding coupling products in good yields. Furthermore, this catalyst offers easy recyclability by simple filtration and reused for at least 5 cycles of Heck reaction without losing much of its activity.

Site Specific C3‐Alkenylation of Indoles Mediated by in situ C‐H Iodination

Text. The C3‐alkenylation of indoles have been developed by means of a novel in situ iodination tactic which is capable of mediating the Heck coupling with alkenes. The method features specific site‐selectivity oriented by the C‐I bond, high‐step efficiency without pre‐functionalization for C‐halogen bond construction, as well as the highly general tolerance to different terminal alkenes, including unactivated alkenes, acrylates, acrylic acid, vinyl sulfone as well as different vinyl functionalized natural products.

Hydrocarboxylation of Terminal Alkenes with Formate by a ZnIn2S4 Photocatalyst

Hydrocarboxylation of Terminal Alkenes with Formate by a ZnIn2S4 Photocatalyst

Multifunctional Polymer Synthesis via Sequential Postpolymerization Modification Using a Single Aldehyde Repeat Unit: Allylation and Orthogonal Esterification and Thiol-ene Reaction.

Herein, we present a highly efficient method for synthesizing multifunctional polymers. This method involves the sequential postpolymerization modification (PPM) of a highly reactive aldehyde polymer. We introduce an allylic alcohol functionality into the polymer backbone via Barbier-type allylation, a process facilitated by easy-to-handle indium(0) powder. This step enables the formation of orthogonal pendants, secondary alcohol, and terminal alkene, which can be further functionalized through esterification and thiol-ene click reactions. All of these processes are carried out under mild conditions, ensuring high efficiency and a wide range of functional groups. Our study underscores PPM's operational simplicity and versatility in developing advanced polymer materials and expanding the scope of multifunctional polymer design.

Unlocking Oxetane Potential: Modular Synthetic Platform for the Concise Synthesis of Acyclic Oligo-Isoprenoids and Terpenoids.

Terpenes occupy a unique place among the secondary metabolites due to their broad utility and extraordinary structural diversity. Their synthesis via polyene cyclization, either biomimetic or enzymatic, represents the cutting edge of modern synthetic chemistry. However, these endeavors have been inherently tied to the availability of natural and non-natural acyclic polyene starting materials. Herein, we report an oxetane-based platform for the modular construction of oxygenated polyolefins with precise geometric control. This "tail-to head" iterative method leverages the site-selective cross-metathesis of terminal olefins to form an alkylidene oxetane moiety and the regioselective ring opening of alkenyl-oxetanes for chain elongation. In addition, the unique and peculiar propensity of alkylidene oxetane fragment in various reactions was also revealed and exploited for site-selective functionalization, cyclization, and as a protecting group in polyenes.

Methoxide‐Enabled Zirconium‐Catalyzed Migratory Alkene Hydrosilylation

AbstractA zirconocene dichloride‐catalyzed alkene hydrosilylation is reported that can be applied to non‐activated and conjugated terminal and internal alkenes. It involves a catalytic Zr‐walk process and leads to a selective conversion to the linear product. Lithium methoxide serves as mild catalyst activating agent, which significantly increases the applicability and operational simplicity in comparison to earlier zirconium(II)‐based protocols. Supported by additional experiments and calculations, a mechanism via zirconium(IV) intermediates is proposed. Due to the benign nature and ready‐availability of the zirconium catalyst, the reaction is an attractive alternative to established alkene hydrosilylation methods.

Methoxide-Enabled Zirconium-Catalyzed Migratory Alkene Hydrosilylation.

A zirconocene dichloride-catalyzed alkene hydrosilylation is reported that can be applied to non-activated and conjugated terminal and internal alkenes. It involves a catalytic Zr-walk process and leads to a selective conversion to the linear product. Lithium methoxide serves as mild catalyst activating agent, which significantly increases the applicability and operational simplicity in comparison to earlier zirconium(II)-based protocols. Supported by additional experiments and calculations, a mechanism via zirconium(IV) intermediates is proposed. Due to the benign nature and ready-availability of the zirconium catalyst, the reaction is an attractive alternative to established alkene hydrosilylation methods.

Defluorinative Haloalkylation of Unactivated Alkenes Enabled by Dual Photoredox and Copper Catalysis.

A three-component defluorinative haloalkylation of alkenes with trifluoromethyl compounds and TBAX (X = Cl, Br) via dual photoredox/copper catalysis is reported. The mild conditions are compatible with a wide array of activated trifluoromethyl aromatics bearing diverse substituents, and various nonactivated terminal and internal alkenes, enabling straightforward access to synthetically valuable γ-gem-difluoroalkyl halides with high efficiency. Mechanistic studies indicate that the [Cu] complexes not only serve as XAT catalysts but also facilitate the SET reduction of trifluoromethyl groups by photocatalysts. Additionally, the resulting alkyl halide products can serve as versatile conversion intermediates for the synthesis of a diverse range of γ-gem-difluoroalkyl compounds.

Alkene Isomerization Catalyzed by a Mn(I) Bisphosphine Borohydride Complex.

An additive-free manganese-catalyzed isomerization of terminal alkenes to internal alkenes is described. This reaction is implementing an inexpensive nonprecious metal catalyst. The most efficient catalyst is the borohydride complex cis-[Mn(dippe)(CO)2(κ2-BH4)]. This catalyst operates at room temperature, with a catalyst loading of 2.5 mol %. A variety of terminal alkenes is effectively and selectively transformed into the respective internal E-alkenes. Preliminary results show chain-walking isomerization at an elevated temperature. Mechanistic studies were carried out, including stoichiometric reactions and in situ NMR analysis. These experiments are flanked by computational studies. Based on these, the catalytic process is initiated by the liberation of "BH3" as a THF adduct. The catalytic process is initiated by double bond insertion into an M-H species, leading to an alkyl metal intermediate, followed by β-hydride elimination at the opposite position to afford the isomerization product.