Alkyl Coupling Research Articles

Rh(III)‐Catalyzed Selective C−H Alkylation and Alkenylation of 1,2,3‐Benzotriazinones with Maleimides

AbstractHerein, we describe a reaction conditions‐based switchable Rh(III)‐catalyzed C−H alkylation and alkenylation of 1,2,3‐benzotriazinones with maleimides, where the triazinone serves as a directing group rather than its traditional role denitrogenative precursor. This strategy enables the selective synthesis of diverse 3‐arylated succinimides and 3‐arylated maleimides in up to 99% yield and a broad substrate scope (48 examples). Furthermore, for the first time, a tandem C−H alkylation and denitrogenative coupling of 1,2,3‐benzotriazinones has been achieved by slightly modifying the reaction conditions. Additionally, gram‐scale reactions and product derivatizations were conducted to demonstrate the synthetic utility.

Enantioselective alkyl–alkyl coupling by Ni-catalysed asymmetric cross-hydrodimerization of alkenes

Enantioselective alkyl–alkyl coupling by Ni-catalysed asymmetric cross-hydrodimerization of alkenes

PdFe Alloy-Fe5C2 interfaces for efficient CO2 hydrogenation to higher alcohols

Direct CO2 hydrogenation to higher alcohols (HA) is a promising route for high-value utilization of waste CO2, but developing active and stable catalysts remains a grand challenge. For this reaction, constructing multifunctional interfaces as active sites is required to fulfill controllable C-C coupling of alkyl and CO*/CHxO* species. Herein, we report a PdFe catalyst with abundant PdFe alloy-Fe5C2 interfaces via a PdFe alloy induced FeOx carbidization process, which can achieve HA yield of 86.5 mg gcat−1 h−1 with 26.5% selectivity at 300 ºC, 5 MPa, and 6000 mL gcat−1 h−1. The accelerated deactivation test unveils the PdFe catalyst exhibits better durability than the widely studied CuFe based catalysts against harsh conditions. Multiple in-situ characterization results unveil a synergetic mechanism for HA synthesis at the PdFe alloy-Fe5C2 interfaces, where PdFe alloy is responsible for CO formation and non-dissociative activation, while Fe5C2 phase promotes CO dissociation and chain propagation.

Nickel/Photoredox Dual-Catalyzed Regiodivergent Aminoalkylation of Unactivated Alkyl Halides.

A mild and regiodivergent aminoalkylation of unactivated alkyl halides is disclosed via a dual photoredox/nickel catalysis. Bipyridyl-type ligands without an ortho-substituent control the site-selective coupling at the original position, while ortho-disubstituted ligands tune the site-selectivity at a remote, unprefunctionalized position. Mechanistic studies combined with DFT calculations give insight into the mechanism and the origins of the ligand-controlled regioselectivity. Notably, this redox-neutral, regiodivergent alkyl-alkyl coupling features mild conditions, broad substrate scope for both alkyl coupling partners, and excellent site-selectivity and offers a straightforward way for α-alkylation of tertiary amines to synthesize structurally diverse alkylamines and value-added amino acid derivatives.

Controlled Partial Linker Thermolysis in Metal‐Organic Framework UiO‐66‐NH2 to Give a Single‐Site Copper Photocatalyst for the Functionalization of Terminal Alkynes

AbstractMetal–organic frameworks (MOFs) with expanding porosity and tailored pore environments are intriguing for catalytic applications. We report herein a straightforward method of controlled partial linker thermolysis to introduce desirable mesopores into mono‐ligand MOFs, which is different from the classical thermolyzing method that starts from mixed‐linker MOFs. UiO‐66‐NH2, after partial ligand thermolysis, exhibits significant mesoporosity, retained crystal structure, improved charge photogeneration and abundant anchoring sites, which is ideal to explore single‐site photocatalysis. Atomically dispersed Cu is then accommodated in the tailored pore. The resulting single‐site Cu catalyst exhibits excellent performance for photocatalytic alkylation and oxidation coupling for the functionalization of terminal alkynes. The study highlights the advantage of controlled partial linker thermolysis to synthesize hierarchical MOFs to achieve the advanced single‐site photocatalysis.

Controlled Partial Linker Thermolysis in Metal-Organic Framework UiO-66-NH2 to Give a Single-Site Copper Photocatalyst for the Functionalization of Terminal Alkynes.

Metal-organic frameworks (MOFs) with expanding porosity and tailored pore environments are intriguing for catalytic applications. We report herein a straightforward method of controlled partial linker thermolysis to introduce desirable mesopores into mono-ligand MOFs, which is different from the classical thermolyzing method that starts from mixed-linker MOFs. UiO-66-NH2 , after partial ligand thermolysis, exhibits significant mesoporosity, retained crystal structure, improved charge photogeneration and abundant anchoring sites, which is ideal to explore single-site photocatalysis. Atomically dispersed Cu is then accommodated in the tailored pore. The resulting single-site Cu catalyst exhibits excellent performance for photocatalytic alkylation and oxidation coupling for the functionalization of terminal alkynes. The study highlights the advantage of controlled partial linker thermolysis to synthesize hierarchical MOFs to achieve the advanced single-site photocatalysis.

Copper‐Catalyzed Coupling Reaction of Secondary Alkyl 2‐Pyridinesulfonates with Alkyl Lithium‐Based Reagents

AbstractThe Cu(OTf)2‐catalyzed alkyl–alkyl coupling reaction of a secondary substrate MeCH(OSO2Py)CH2CH2C6H4(4‐OMe) with a nBuLi‐based reagent prepared by transmetalation with MgBr2 ⋅ THF3 in THF produced a coupling product in 74 % yield. The use of soluble MgBr2 ⋅ THF3 in THF was required for this reaction. This method was applied to sBuLi and Ph(CH2)4Li. In contrast, transmetalation of MeLi with soluble MgCl2 ⋅ THF2 in THF produced the Me reagent, which was reactive for the coupling reaction. The reaction proceeded with inversion of the stereogenic carbon. Furthermore, (S)‐14‐methyloctadecan‐2‐one, a sex pheromone produced by lichen moths, was synthesized.

Visible-Light-Driven Organocatalytic Alkoxylation of Benzylic C-H Bonds.

A variety of strategies for direct alkoxylation of the benzyl C-H bond have been developed toward the construction of benzyl ethers. The light-induced benzyl C-H bond alkoxylation provides an alternative strategy for the synthesis of these important intermediates. The photocatalyzed alkoxylation of the benzyl C-H bond has dominated by metal-catalyzed methods. Herein, we reported a light-driven organocatalytic approach for alkoxylation of the benzyl C-H bond by the use of 9,10-dibromoanthracene as a photocatalyst and employing N-fluorobenzenesulfonimide as an oxidant. This reaction proceeds at room temperature and is capable of converting a variety of alkyl biphenyl and coupling partners, including a variety of alcohol and carboxylic acid, as well as peroxide, to the desired products under 400 nm light irradiation.

Stable Immobilization of DNA to Silica Surfaces by Sequential Michael Addition Reactions Developed with Insights from Confocal Raman Microscopy.

The immobilization of DNA to surfaces is required for numerous biosensing applications related to the capture of target DNA sequences, proteins, or small-molecule analytes from solution. For these applications to be successful, the chemistry of DNA immobilization should be efficient, reproducible, and stable and should allow the immobilized DNA to adopt a secondary structure required for association with its respective target molecule. To develop and characterize surface immobilization chemistry to meet this challenge, it is invaluable to have a quantitative, surface-sensitive method that can report the interfacial chemistry at each step, while also being capable of determining the structure, stability, and activity of the tethered DNA product. In this work, we develop a method to immobilize DNA to silica, glass, or other oxide surfaces by carrying out the reactions in porous silica particles. Due to the high specific surface area of porous silica, the local concentrations of surface-immobilized molecules within the particle are sufficiently high that interfacial chemistry can be monitored at each step of the process with confocal Raman microscopy, providing a unique capability to assess the molecular composition, structure, yield, and surface coverage of these reactions. We employ this methodology to investigate the steps for immobilizing thiolated-DNA to thiol-modified silica surfaces through sequential Michael addition reactions with the cross-linker 1,4-phenylene-bismaleimide. A key advantage of employing a phenyl-bismaleimide over a comparable alkyl coupling reagent is the efficient conversion of the initial phenyl-thiosuccinimide to a more stable succinamic acid thioether linkage. This transformation was confirmed by in situ Raman spectroscopy measurements, and the resulting succinamic acid thioether product exhibited greater than 95% retention of surface-immobilized DNA after 12 days at room temperature in aqueous buffer. Confocal Raman microscopy was also used to assess the conformational freedom of surface-immobilized DNA by comparing the structure of a 23-mer DNA hairpin sequence under duplex-forming and unfolding conditions. We find that the immobilized DNA hairpin can undergo reversible intramolecular duplex formation based on the changes in frequencies and intensities of the phosphate backbone and base-specific vibrational modes that are informative of the hybridization state of DNA.

Two Facile Aniline-Based Hypercrosslinked Polymer Adsorbents for Highly Efficient Iodine Capture and Removal

Effective capture and safe disposal of radioactive iodine (129I or 131I) during nuclear power generation processes have always been a worldwide environmental concern. Low-cost and high-efficiency iodine removal materials are urgently needed. In this study, we synthesized two aniline-based hypercrosslinked polymers (AHCPs), AHCP-1 and AHCP-2, for iodine capture in both aqueous and gaseous phases. They are obtained by aniline polymerization through Friedel-Crafts alkylation and Scholl coupling reaction, respectively, with high chemical and thermal stability. Notably, AHCP-1 exhibits record-high static iodine adsorption (250 wt%) in aqueous solution. In the iodine vapor adsorption, AHCP-2 presents an excellent total iodine capture (596 wt%), surpassing the most reported amorphous polymer adsorbents. The rich primary amine groups of AHCPs promote the rapid physical capture of iodine from iodine water and iodine vapor. Intrinsic features such as low-cost preparation, good recyclability, as well as excellent performance in iodine capture indicate that the AHCPs can be used as potential candidates for the removal of iodine from radioactive wastewater and gas mixtures.

Ni/Photoredox-Catalyzed C(sp3)-C(sp3) Coupling between Aziridines and Acetals as Alcohol-Derived Alkyl Radical Precursors.

Aziridines are readily available C(sp3) precursors that afford valuable β-functionalized amines upon ring opening. In this article, we report a Ni/photoredox methodology for C(sp3)-C(sp3) cross-coupling between aziridines and methyl/1°/2° aliphatic alcohols activated as benzaldehyde dialkyl acetals. Orthogonal activation modes of each alkyl coupling partner facilitate cross-selectivity in the C(sp3)-C(sp3) bond-forming reaction: the benzaldehyde dialkyl acetal is activated via hydrogen atom abstraction and β-scission via a bromine radical (generated in situ from single-electron oxidation of bromide), whereas the aziridine is activated at the Ni center via reduction. We demonstrate that an Ni(II) azametallacycle, conventionally proposed in aziridine cross-coupling, is not an intermediate in the productive cross-coupling. Rather, stoichiometric organometallic and linear free energy relationship studies indicate that aziridine activation proceeds via Ni(I) oxidative addition, a previously unexplored elementary step.

Diverse Synthesis of Chiral Trifluoromethylated Alkanes via Nickel-Catalyzed Enantioconvergent Reductive Hydroalkylation of Unactivated Olefins.

Here, we report a nickel-catalyzed enantioconvergent hydroalkylation of olefins with trifluoromethyl-containing α-alkyl halides for the synthesis of enantioenriched trifluoromethylated alkanes. This reaction employs readily available and bench-stable alkenes as alkyl coupling partners, featuring mild conditions, a broad substrate scope, and high functional group tolerance. The synthetic utility of this method is further demonstrated in the late-stage functionalization of a range of drug molecules and natural products.

DFT insight into asymmetric alkyl-alkyl bond formation via nickel-catalysed enantioconvergent reductive coupling of racemic electrophiles with olefins.

A DFT study has been conducted to understand the asymmetric alkyl–alkyl bond formation through nickel-catalysed reductive coupling of racemic alkyl bromide with olefin in the presence of hydrosilane and K3PO4. The key findings of the study include: (i) under the reductive experimental conditions, the Ni(ii) precursor is easily activated/reduced to Ni(0) species which can serve as an active species to start a Ni(0)/Ni(ii) catalytic cycle. (ii) Alternatively, the reaction may proceed via a Ni(i)/Ni(ii)/Ni(iii) catalytic cycle starting with a Ni(i) species such as Ni(i)–Br. The generation of a Ni(i) active species via comproportionation of Ni(ii) and Ni(0) species is highly unlikely, because the necessary Ni(0) species is strongly stabilized by olefin. Alternatively, a cage effect enabled generation of a Ni(i) active catalyst from the Ni(ii) species involved in the Ni(0)/Ni(ii) cycle was proposed to be a viable mechanism. (iii) In both catalytic cycles, K3PO4 greatly facilitates the hydrosilane hydride transfer for reducing olefin to an alkyl coupling partner. The reduction proceeds by converting a Ni–Br bond to a Ni–H bond via hydrosilane hydride transfer to a Ni–alkyl bond via olefin insertion. On the basis of two catalytic cycles, the origins for enantioconvergence and enantioselectivity control were discussed.

A relay catalysis strategy for enantioselective nickel-catalyzed migratory hydroarylation forming chiral α-aryl alkylboronates

A relay catalysis strategy for enantioselective nickel-catalyzed migratory hydroarylation forming chiral α-aryl alkylboronates

Synthetic Approaches to N‐Methoxy‐N‐methylamides

N‐Methoxy‐N‐methylamides were prepared by the acylation of acid halides, acyl cyanides, esters, lactones, activated amides, and mesyl carboxylates with N,O‐dimethylhydroxylamine hydrochloride. The reaction of carboxylic acids with alkyl chloroformates, phosphonate reagents, or coupling agents afforded the activated esters, which were converted to N‐methoxy‐N‐methylamides by (CH3O)NHCH3. N‐Methoxy‐N‐methylamides were also prepared by the oxidative amidation of benzyl alcohols and palladium‐catalyzed aminocarbonylation of organoboronic acids or aryl halides with (CH3O)NHCH3 under CO equivalents. Furthermore, N‐methoxy‐N‐methylamides were produced by the selective substitution of N,O‐dimethylcarbamoylation agents with organometallic reagents.

Transition-Metal-Free Reductive Cross-Coupling Employing Metabisulfite as a Connector: General Construction of Alkyl–Alkyl Sulfones

Transition-Metal-Free Reductive Cross-Coupling Employing Metabisulfite as a Connector: General Construction of Alkyl–Alkyl Sulfones

Germatranes and carbagermatranes: (hetero)aryl and alkyl coupling partners in Pd-catalyzed cross-coupling reactions.

In the past few decades, palladium-catalyzed cross-coupling reactions have taken root in the construction of a complex synthetic community. The development of organometallics has been an important objective in this field. Our group has focused on exploiting new germanium-based reagents and the corresponding catalytic processes. In the past three years, we have established new methods for the synthesis of structure-modified (hetero)aryl germatranes and alkyl carbagermatranes. Particularly for alkyl carbagermatranes, the stability to be compatible with various derivatization reactions and the high activity for transmetallation (e.g. base/additive-free for primary alkyl carbagermatranes) distinguish them from many reported nucleophiles. In this article, we would introduce (1) the development process of organogermanium reagents in palladium-catalyzed cross-couplings; (2) the history of germatrane-type systems and the breakthrough we have made in the field; (3) the outlook for (carba)germatranes and alkyl-GeMe3.

Enantioselective C(sp3)-C(sp3) cross-coupling of non-activated alkyl electrophiles via nickel hydride catalysis.

Cross-coupling of two alkyl fragments is an efficient method to produce organic molecules rich in sp3-hybridized carbon centers, which are attractive candidate compounds in drug discovery. Enantioselective C(sp3)–C(sp3) coupling is challenging, especially of alkyl electrophiles without an activating group (aryl, vinyl, carbonyl). Here we report a strategy based on nickel hydride addition to internal olefins followed by nickel-catalyzed alkyl-alkyl coupling. This strategy enables enantioselective cross-coupling of non-activated alkyl halides with alkenyl boronates to produce chiral alkyl boronates. Employing readily available and stable olefins as pro-chiral nucleophiles, the coupling proceeds under mild conditions and exhibits broad scope and high functional group tolerance. Applications for the functionalization of natural products and drug molecules, as well as the synthesis of chiral building blocks and a key intermediate to (S)-(+)-Pregabalin, are demonstrated.

Facile synthesis of highly porous hyper‐cross‐linked polymer for light hydrocarbon separation

AbstractLight hydrocarbon separation is a crucial process associated with high energy expenditure in the petrochemical industry. The utilization of porous organic materials as solid porous adsorbents for light hydrocarbon separation has found widespread attention because of the advantages of low cost, excellent stability, and good recyclability. Here, we present the facile synthesis of a porous organic material, constructed from pyridine‐triphenylborane by using a Friedel‐Crafts alkylation coupling reaction, affording the hyper‐cross‐linked polymer, HCP‐B. HCP‐B features significant thermal stability, and high surface area. Gas adsorption experiments show that this material adsorbs much larger amounts of ethane, ethylene, and acetylene than that of methane. Ideal adsorbed solution theory (IAST) calculations also predict that HCP‐B selectively adsorbs ethane, ethylene, and acetylene over methane. Both are indicative of the great potential of HCP‐B in light hydrocarbon separation.

Decarboxylative Alkyl Coupling Promoted by NADH and Blue Light.

Photoexcited dihydronicotinamides like NADH and analogues have been found to generate alkyl radicals upon reductive decarboxylation of redox-active esters without auxiliary photocatalysts. This principle allowed aliphatic photocoupling between redox-active carboxylate derivatives and electron-poor olefins, displaying surprising water and air-tolerance and unusually high coupling rates in dilute conditions. The orthogonality of the reaction in the presence of other carboxylic acids and its utility in the functionalization of DNA is presented, notably using visible light in combination with NADH, the ubiquitous reductant of life.