Nickel-catalyzed allylic carbonylative coupling of alkyl zinc reagents with tert-butyl isocyanide

Electrochemical Synergistic Ni/Co-Catalyzed Carbonylative Cross-Electrophile Coupling of Aryl and Alkyl Halides with CO

Accessing unsymmetric ketones and achieving their carbon isotope labeling are crucial yet challenging tasks in both synthetic and medicinal chemistry. We report here an efficient electrochemical nickel-/cobalt-catalyzed carbonylative cross-electrophile coupling reaction. This method allows for the modular synthesis of a library of unsymmetric ketones from simple building blocks, including aryl halides, alkyl halides, and gaseous CO. The simultaneous use of nickel and cobalt salts as concerted catalysts ensures the high efficiency of this three-component carbonylative coupling. Furthermore, electrochemical reduction avoids the use of stoichiometric reductants, making this protocol more sustainable and attractive. The broad substrate scope and late-stage 13C isotope labeling of complex molecules derived from biologically active compounds highlight the practicality of this method.

Pd-Catalyzed Coupling of Aryl Chloride, Isocyanides, and Thiocarboxylate To Synthesize Thioamides

Although aryl chlorides are among the most abundant and stable aromatic electrophiles, the coupling of aryl chlorides with isocyanides has remained an unsolved challenge. Herein, we report a general transformation of aryl chlorides, isocyanides, and thiocarboxylates to synthesize thioamides. The sterically hindered and electron-rich Josiphos ligand significantly facilitates the rate-determining oxidative addition step and reduces the toxicity of isocyanides toward the metal center. The combination of thiocarboxylate as the nucleophile and Josiphos as the ligands enabled the coupling-tolerated various 1°, 2°, and 3° isocyanides, which provides a rapid, efficient, and versatile method for the synthesis of large quantities of thioamides, including those of pharmaceutical relevance.

Electrochemical stereoselective borylation of Morita-Baylis-Hillman adducts to functionalized allylic boronates

Herein, we disclose a highly efficient and facile electrochemical borylation of Morita-Baylis-Hillman adducts without using any metal catalyst. This methodology demonstrates excellent regio- and stereo-selectivity, leading to a wide range of functionalized E-allylic boronates, including derivatives of ibuprofen and menthol. Under mild and straightforward conditions, this redox-neutral reaction, combined with the scalability and synthetic applications of the allylic boronate esters, underscores its potential for a wide range of applications in organic synthesis.

Nickel-Catalyzed Four-Component Carbonylation of 1,3-Butadiene To Access β,γ-Unsaturated Ketones

A new strategy to obtain β,γ-unsaturated ketones via the cross-coupling of 1,3-butadiene, alkyl bromides, and arylboronic acids under 1 bar of CO with nickel as the catalyst has been developed. This newly developed four-component carbonylation procedure features advantages including using a cheap catalytic system, high step economy, mild reaction conditions, and excellent 1,4-regioselectivity, thereby providing a sustainable and alternative tool for β,γ-unsaturated ketones production compared to the present tactics. To elucidate the application potential of this method, olefin synthons are derived from the representative coupling product.

Nickel-Catalyzed Carbonylative Negishi Cross-Coupling of Unactivated Secondary Alkyl Electrophiles with 1 atm CO Gas

We describe a nickel-catalyzed carbonylative cross-coupling of unactivated secondary alkyl electrophiles with the organozinc reagent at atmospheric CO gas, thus allowing the expedient construction of unsymmetric dialkyl ketones with broad functional group tolerance. The leverage of a newly developed NN2-pincer type ligand enables the chemoselective three-component carbonylation by overcoming the competing Negishi coupling, the undesired β-hydride elimination, and dehalogenation of alkyl iodides side pathways. Both alkyl iodides and alkyl tosylates are compatible in the single electron transfer involved mechanism.

Palladium-catalyzed allylation and carbonylation: access to allylhydrazones and allyl acylhydrazones

A palladium-catalyzed allylation of hydrazines with allyl alcohols and aldehydes was developed, enabling the syntheses of a series of allylhydrazones in good to excellent yields with high regioselectivity. Furthermore, the four-component tandem allylation carbonylation of hydrazines with allyl alcohols and aldehydes was established using the catalytic system, producing various allyl acylhydrazones. Additionally, the functionalized allyl acylhydrazones could be smoothly constructed with the catalytic system employing allylhydrazones as a partner. The catalytic system exhibited good functional tolerance with excellent regioselectivities and scaled-up capability, overcoming the limitations of chemoselectivity of the multicomponent transformation and poor conversion of the weak nucleophile.

Nickel-catalyzed acylzincation of allenes with organozincs and CO

Transition metal-catalyzed carbonylative reaction with CO gas are among the central task in organic synthesis, enabling the construction of highly valuable carbonyl compound. Here, we show an earth-abundant nickel-catalyzed three-component tandem acylzincation/cyclization sequence of allene and alkylzinc reagent with 1 atm of CO under mild conditions. This protocol is featured by broad functional group tolerance with high reaction selectivity, providing a rapid and convenient synthetic method for the construction of diverse fully substituted benzotropone derivatives. Mechanistic studies reveal that the installation of a cyano group tethered to allene moiety enables the high regio- and stereoselectivity of this acylzincation of allene, allowing the selective formation of three consecutive C-C bonds in a highly efficient manner.

Nickel-Catalyzed Aminocarbonylation of Aryl Iodides with 1 atm CO

Reported here is a nickel-catalyzed aminocarbonylation of aromatic iodides with (hetero)aryl anilines and alkyl amines under atmospheric CO pressure. The reaction features with broad substrate scope with excellent functional group tolerance, providing an expedient method for the construction of amide analogues. Notably, amino alcohols can be selectively transformed into the corresponding amides successfully without interfering the hydroxyl group under the current standard conditions.

Nickel-catalyzed alkoxycarbonylation of aryl iodides with 1 atm CO

A nickel-catalyzed alkoxycarbonylation of aromatic iodides with alcohols under atmospheric pressure of carbon monoxide is presented here. This operationally simple protocol allows the facile synthesis of (hetero)aromatic esters, exhibiting broad substrate scope with excellent functional group tolerance. Various primary and secondary aliphatic alcohols as well as phenols are suitable for this transformation.

Nickel-Catalyzed Carbonylation of Cyclopropanol with Benzyl Bromide for Multisubstituted Cyclopentenone Synthesis

Herein, we reported a Ni-catalyzed carbonylation of cyclopropanol with benzyl bromide to afford multisubstituted cyclopentenone under 1 atm of CO. The reaction proceeds through cascade carbonylation of benzyl bromides, followed by generation of nickel homoenolate from cyclopropanols via β-C elimination to afford 1,4-diketones, which undergoes intramolecular Aldol condensation to furnish highly substituted cyclopentenone derivatives in moderate to good yields. The reaction exhibits high functional group tolerance with broad substrate scope.

Synthesis of unprotected glyco-alkynones via molybdenum-catalyzed carbonylative Sonogashira cross-coupling reaction

Herein we report a novel Mo-catalyzed carbonylative Sonogashira cross-coupling between 2-iodoglycals and terminal alkynes. The reaction displays major improvements compared to a related Pd-catalyzed procedure previously published by our group, such as utilizing unprotected sugar derivatives as starting materials and tolerance to substrates bearing chelating groups. In this work we also demonstrate the utility of the glyco-alkynone products as platform for further functionalization by synthesizing glyco-flavones via Au-catalyzed 6-endo-dig cyclization.

Nickel/Photo-Cocatalyzed C(sp2)-H Allylation of Aldehydes and Formamides

Herein we report a nickel/photo-cocatalyzed C(sp²)-H allylation of aldehydes and formamides wherein both allyl acetates and allyl alcohols can be used as the allylating agents. In this reaction, radical-type umpolung of the formyl moiety is enabled by tetrabutylammonium decatungstate as a hydrogen-atom-transfer photocatalyst, whereas nickel serves to cleave the C-O bond of allyl acetates or allyl alcohols. The synergistic effect of these two catalysts provides new access to various β,γ-unsaturated ketones and amides with high selectivities.

Divergent synthesis of α-functionalized amides through selective N-O/C-C or N-O/C-C/C-N cleavage of aza-cyclobutanone oxime esters

Herein, a novel sequential ring opening reaction of aza-cyclobutanone oxime esters with isocyanides is described. The reaction proceeded smoothly under redox-neutral and mild conditions, leading to a divergent synthesis of α-cyanomethylaminoamides, α-acyloxyamides and α-acylaminoamides. In these transformations, a selective N-O/C-C or N-O/C-C/C-N cleavage was achieved only by changing the iron-catalyst system. Among them, a rare sequential N-O/C-C/C-N cleavage process with a classical Passerini or Ugi multicomponent reaction can be executed in a single step. To the best of our knowledge, this work creates a novel reaction mode of cycloketone oximes and provides new opportunities for reaction design.

Nickel-Catalyzed Multicomponent Coupling: Synthesis of α-Chiral Ketones by Reductive Hydrocarbonylation of Alkenes

A nickel-catalyzed, multicomponent regio- and enantioselective coupling via sequential hydroformylation and carbonylation from readily available starting materials has been developed. This modular multicomponent hydrofunctionalization strategy enables the straightforward reductive hydrocarbonylation of a broad range of unactivated alkenes to produce a wide variety of unsymmetrical dialkyl ketones bearing a functionalized α-stereocenter, including enantioenriched chiral α-aryl ketones and α-amino ketones. It uses chiral bisoxazoline as a ligand, silane as a reductant, chloroformate as a safe CO source, and a racemic secondary benzyl chloride or an N-hydroxyphthalimide (NHP) ester of a protected α-amino acid as the alkylation reagent. The benign nature of this process renders this method suitable for late-stage functionalization of complex molecules.

Nickel-Catalyzed Arylation of C(sp3)-O Bonds in Allylic Alkyl Ethers with Organoboron Compounds

A nickel-catalyzed cross-coupling of allylic alkyl ethers with organoboron compounds through the cleavage of the inert C(sp³)-O(alkyl) bonds is described. Several types of allylic alkyl ethers can be coupled with various boronic acids or their derivatives to give the corresponding products in good to excellent yields with wide functional group tolerance and excellent regioselectivity. The gram-scale reaction and late-stage modification of biologically active compounds further prove the practicality of this synthetic method.

Nickel Nanoparticles Immobilized over Mesoporous SBA-15 for Efficient Carbonylative Coupling Reactions Utilizing CO2: A Spotlight

Ecofriendly routes for the synthesis of carbamates and carbonylative coupling products such as benzyl formate derivatives are very demanding for both academia and industries. Foreseeing a sustainable green future, we systematically analyzed the synthesis history of both these chemicals, mentioning their pros and cons. As a step towards green chemistry, here we have optimized the reaction conditions for the synthesis of various benzyl formates from corresponding benzyl halides and carbamates from substituted anilines and alkyl halides catalyzed by Ni(0) nanoparticles (NPs) immobilized over amine-functionalized ordered mesoporous SBA-15 material in the presence of CO₂ as C1 source. This spotlight on applications is aimed to provide a clear outlook to date regarding the gradual progress in the synthesis of both these aforementioned chemicals and finally addresses further efforts for overcoming the current challenges.

Nickel-promoted oxidative domino Csp3-H/N-H bond double-isocyanide insertion reaction to construct pyrrolin-2-ones

The first nickel-catalyzed oxidative domino C_sp3-H/N-H double isocyanide insertion reaction of acetamides with isocyanides has been developed for the synthesis of pyrrolin-2-one derivatives. A wide range of acetamides bearing various functional groups are compatible with this reaction system by utilizing Ni(acac)₂ as a catalyst. In this transformation, isocyanide could serve as a C1 connector and insert into the inactive C_sp3-H bond, representing an effective way to construct heterocycles.

Direct C-H aminocarbonylation of N-heteroarenes with isocyanides under transition metal-free conditions

A C-C bond forming amide synthesis through direct C-H aminocarbonylation of N-heteroarenes with isocyanides was developed. The reaction was mediated by an inorganic persulfate salt under transition metal-free conditions. Mechanistic studies suggested a radical pathway for this reaction without the participation of H₂O and O₂. This method also showed merits of substrate availability, easy operation and atom economy. It provided an efficient route for straightforward synthesis of N-heteroaryl amides.

Palladium-catalyzed [2 + 2 + 1] annulation: access to chromone fused cyclopentanones with cyclopropenone as the CO source

A variety of chromone fused cyclopentanones are efficiently generated in good to high yields via palladium-catalyzed [2 + 2 + 1] annulation, in which cyclopropenone was utilized for the first time as the sole CO surrogate in the carbonylation process.

Palladium-Catalyzed Secondary Benzylic Imidoylative Reactions

Reported herein is a palladium-catalyzed secondary benzylic imidoylative Negishi reaction leveraging the sterically bulky aromatic isocyanides as the imine source. This method allows the facile access of alkyl-, (hetero)aryl-, and alkynylzinc reagents to afford various α-substituted phenylacetone products under mild acidic hydrolysis, which are ubiquitous motifs in many pharmaceuticals and biologically active compounds. The diastereoselective reduction of imine can be accomplished to provide the expedient conversion of secondary benzylic halide into α-substituted phenethylamine derivatives with high atom economy.

Nickel-Catalyzed Formal Aminocarbonylation of Secondary Benzyl Chlorides with Isocyanides

Phenylacetamides represent versatile feedstocks in synthetic chemistry, widely existing in drug molecules and natural products. Herein, we disclose a nickel-catalyzed formal aminocarbonylation of secondary benzyl chlorides with isocyanides yielding α-substituted phenylacetamide with steric hindrance, which is synthetically challenging via palladium-catalyzed aminocarbonylation. The reaction features wide functional group tolerance under mild conditions, highlighted by the tolerance of various aromatic halide (-Cl, -Br, -I) and heteroaromatic rings (pyridine and pyrazine).

Nickel-Catalyzed Formal Aminocarbonylation of Unactivated Alkyl Iodides with Isocyanides

Herein, we disclose a Ni-catalyzed formal aminocarbonylation of primary and secondary unactivated aliphatic iodides with isocyanides to afford alkyl amide, which proceeds via the selective monomigratory insertion of isocyanides with alkyl iodides, subsequent β-hydride elimination, and hydrolysis process. The reaction features wide functional group tolerance under mild conditions. Additionally, the selective, one-pot hydrolysis of reaction mixture under acid conditions allows for expedient synthesis of the corresponding alkyl carboxylic acid.

Palladium-catalyzed carbonylations of highly substituted olefins using CO-surrogates

CO surrogate chemistry: General protocols for alkoxycarbonylations of highly substituted olefins with paraformaldehyde and methyl formate are reported, allowing the performance of carbonylation reactions in all labs and for all kinds of substrates.