Direct Aerobic Carbonylation of C(sp2)–H and C(sp3)–H Bonds through Ni/Cu Synergistic Catalysis with DMF as the Carbonyl Source

Insights into the mechanism of 3d transition-metal-catalyzed directed C(sp3)-H bond functionalization reactions

The growing interest in the catalytic activity of earth-abundant 3d transition-metals has led to the development of new and more sustainable methods for C-H bond functionalization reactions. However, this is an emerging field which involves considerable mechanistic complexity as the mode of action of 3d transition metals differs markedly from the well-studied mechanisms of precious metals. In this review, we present an overview of the research efforts in Ni-, Cu-, Fe- and Co-catalyzed directed C(sp3)-H bond functionalization reactions, covering design principles and mechanistic discussions, along with potential applications and limitations. To conclude, the unresolved challenges and future viewpoints are highlighted. We aspire for this review to serve as a relevant and valuable reference for researchers in this swiftly progressing field, helping to inspire the development of more original and innovative strategies.

Aminocarbonylation using CO surrogates

Aminocarbonylation reactions play a critical role in the synthesis of amides. Traditional aminocarbonylation processes often rely on carbon monoxide (CO) gas, a highly toxic and challenging reagent to handle. Recent advancements in CO surrogates address these challenges. This review looks at the various CO substitutes used in aminocarbonylation reactions. These include metal carbonyls, acids, formates, chloroform, and others that release CO. Use of CO surrogates not only improves safety but also broadens the substrate scope and operational simplicity of the aminocarbonylation reactions. This review provides a summary of recent progress made in aminocarbonylation reactions using different CO surrogates. We discuss key methodologies, catalytic systems, and mechanistic insights, highlighting the efficiency and versatility of CO surrogates in amide bond formation.

Reaction of Donor-Acceptor α-Diazo Esters and N,N-Dimethylformamide/γ-Lactams To Generate α-Amino-α-aroylethanoates

Herein, we present a metal-free, concise, and efficient protocol for the intermolecular reaction of amides (lactams) with donor-acceptor α-diazo esters to afford the functionalized α-amino-α-aroylethanoates. N-Methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF) are employed as both reagents and solvents, allowing for the incorporation of all units into the products. The reaction is processed by the ester group migration and compatible with a broad range of substrates up to 50 examples.

A Comprehensive Exploration of the Synergistic Relationship between DMSO and Peroxide in Organic Synthesis

In the realm of organic synthesis, reagents can serve not only as solvents but also as synthons. Dimethyl sulfoxide (DMSO) is recognized for its efficiency in this dual capacity, enabling diverse chemical transformations. DMSO can generate various synthons, including methyl, methylene, methine, oxygen, and methyl sulfoxide, broadening the accessible compound repertoire. Activation of DMSO as a reagent relies heavily on synergies with secondary agents like peroxide, persulfate, or iodine. Recent years have witnessed a surge in innovative synthetic techniques harnessing the synergistic interplay of DMSO and peroxide, leading to environmentally friendly and cost-effective reactions with mild conditions. This review highlights the synergistic effects of DMSO and peroxides (up to 2023), detailing their activation mechanisms and the generation of various synthons, along with numerous reported derivatives. Although this topic has received considerable attention in recent years, there are numerous discrepancies and a plethora of possibilities yet to be explored. We anticipate that this review will significantly support researchers in advancing their innovations to a greater extent in the future.

Organocatalyzed Carbonylation of Alkyl Halides Driven by Visible Light

Herein, we describe a new strategy for the carbonylation of alkyl halides with different nucleophiles to generate valuable carbonyl derivatives under visible light irradiation. This method is mild, robust, highly selective, and proceeds under metal-free conditions to prepare a range of structurally diverse esters and amides in good to excellent yields. In addition, we highlight the application of this activation strategy for 13C isotopic incorporation. We propose that the reaction proceeds by a photoinduced reduction to afford carbon-centered radicals from alkyl halides, which undergo subsequent single electron-oxidation to form a carbocationic intermediate. Carbon monoxide is trapped by the carbocation to generate an acylium cation, which can be attacked by a series of nucleophiles to give a range of carbonyl products.

Rhodium-catalysed additive-free carbonylation of benzamides with diethyl dicarbonate as a carbonyl source

Phthalimides are prevalent in numerous pharmaceuticals, prompting various phthalimide syntheses through C-H activation. Nevertheless, the necessity for stoichiometric additives limits their practicality and versatility. Herein, we introduced diethyl dicarbonate as a carbonyl source for an additive-free carbonylation of benzamides. This transformation signifies an operationally simple and CO-free phthalimide synthesis.

EtOS2K as a C1 Source: Solvent- and Temperature-Controlled Selective Synthesis of Quinoline-2-thione and Quinoline-2-one Derivatives

Herein, we disclosed a highly chemoselective synthesis of quinoline-2-one and quinoline-2-thione derivatives using EtOS2K as the C1 source. Quinoline-2-one derivatives were synthesized selectively with NaCl as a catalyst in the solvent DMSO/H2O, while quinoline-2-thione derivatives were produced without the need for any catalyst in an environmentally friendly solvent EtOH/H2O. The reaction conditions were mild and had good functional group tolerance.

Rh(III)-Catalyzed [4 + 1] Annulation of Benzamides with Vinyl Cyclic Carbonates for the Synthesis of Isoindolinones

A Rh(III)-catalyzed C-H bond activation and subsequent [4+1] annulation of benzamides with vinyl cyclic carbonates have been developed for the synthesis of isoindolinones, in which the electron-rich alkenes could serve as one-carbon units. This reaction proceeds smoothly with high regioselectivity under oxidant- and silver-free conditions and exhibits broad substrate scope and functional group tolerance including some biological active materials. The scale-up reaction and derivatizations of the product further demonstrate the potential synthetic utility of this transformation.

Copper-catalysed chemoselective C-OH bond activation of N-benzoyl cytosine: facile access to 2-(dimethylamino)pyrimidine

A novel method for the direct amination of N-benzoyl cytosine has been developed, giving access to 2-(dimethylamino)pyrimidine derivatives. A copper(II) catalyst and tert-butyl hydroperoxide easily promote the selective amination process that proceeds via C-OH bond activation. This practical approach can utilize different formamide molecules, N,N-dimethylformamide and N,N-diethylformamide, as efficient amino (-NMe₂, -NEt₂) sources. Moreover, the facile nature of the procedure, its broad tolerance of aliphatic and aromatic substrates, the high yields and ease of separation of the products, and the fact that it can be conducted under aerobic conditions are all notable advantages of the present protocol.

Catalytic Methylene Insertion between Amines and Terminal Alkynes via C-N Bond Cleavage of N,N-Dimethylacetamide: A Unique Route to Propargylic Amines

A copper-based system allows for the methylene insertion between an amine and a milder nucleophile, including a terminal alkyne counterpart, via C-N bond cleavage of N,N-dimethylacetamide. The method gives an expedient access to propargylic amines in good to excellent yields. A wide-ranging substrate scope and late-stage functionalization of complex molecules make the protocol practically valuable.

Palladium-Catalyzed Aminocarbonylation of Isoquinolines Utilizing Chloroform-COware Chemistry

The carbonyl group forms an integral part of several drug molecules and materials; hence, synthesis of carbonylated compounds remains an intriguing area of research for synthetic and medicinal chemists. Handling toxic CO gas has several limitations; thus, using safe and effective techniques for in or ex situ generation of carbon monoxide from nontoxic and cheap precursors is highly desirable. Among several precursors that have been explored for the generation of CO gas, chloroform can prove to be a promising CO surrogate due to its cost-effectiveness and ready availability. However, the one-pot chloroform-based carbonylation reaction requires strong basic conditions for hydrolysis of chloroform that may affect functional group tolerability of substrates and scale-up reactions. These limitations can be overcome by a two-chamber reactor (COware) that can be utilized for ex situ CO generation through hydrolysis of chloroform in one chamber and facilitating safe carbonylation reactions in another chamber under mild conditions. The versatility of this "Chloroform-COware" technique is explored through palladium-catalyzed aminocarbonylation of medicinally relevant heterocyclic cores, viz., isoquinoline and quinoline.

Application of N,N-Dimethylethanolamine as a One-Carbon Synthon for the Synthesis of Pyrrolo[1,2-a]quinoxalines, Quinazolin-4-ones, and Benzo[4,5]imidazoquinazolines via [5 + 1] Annulation

The synthesis of N-heterocycles composes a significant part of synthetic chemistry. In this report, a Cu(II)-catalyzed green and efficient synthesis of pyrrolo[1,2-a]quinoxaline, quinazolin-4-one, and benzo[4,5]imidazoquinazoline derivatives was developed, employing N,N-dimethylethanolamine (DMEA) as a C1 synthon. Green oxidant O₂ is critical in these transformations, facilitating the formation of a key intermediate─a reactive iminium ion. The method conducted under mild conditions is compatible with a diversity of functional groups, providing an appealing alternative to the previously developed protocols.

Recent Strategies in Nickel-Catalyzed C–H Bond Functionalization for Nitrogen-Containing Heterocycles

N-heterocycles are ubiquitous in natural products, pharmaceuticals, organic materials, and numerous functional molecules. Among the current synthetic approaches, transition metal-catalyzed C–H functionalization has gained considerable attention in recent years due to its advantages of simplicity, high atomic economy, and the ready availability of starting materials. In the field of N-heterocycle synthesis via C–H functionalization, nickel has been recognized as one of the most important catalysts. In this review, we will introduce nickel-catalyzed intramolecular and intermolecular pathways for N-heterocycle synthesis from 2008 to 2021.

Oxidative C-H/N-H Carbonylation of Benzamide by Nickel Catalysis with CO as the Carbonyl Source

An efficient and direct carbonylation of aminoquinoline benzamides has been developed using abundant and inexpensive Ni(OAc)₂·4H₂O as the catalyst and carbon monoxide as a cost-efficient C1 building block. This process features good functional-group tolerance and can be conducted on gram scale. The directing group can be easily removed under mild conditions.

Lewis Acid-Promoted Typical Friedel-Crafts Reactions Using DMSO as a Carbon Source

This study reports a mild and efficient synthetic protocol for the synthesis of symmetrical and unsymmetrical diarylmethanes (DAMs). Using DMSO as the C₁ source and TMSOTf as the Lewis acid promoter, a series of functionalized symmetrical and unsymmetrical DAMs were synthesized in high yields. Gratifyingly, DMSO plays a dual role as a solvent and a C₁ source and can also be replaced with its deuterated counterpart, DMSO-d₆, enabling the incorporation of the -CD₂ moiety into the diarylmethane skeleton. The developed approach has been applied to a wide range of substrates having various functional groups, and this protocol has also been extended to the synthesis of an anti-breast cancer agent and an anticoagulant agent using common feedstock compounds. In addition, the postulated mechanism has been explicitly demonstrated via control experiments.

Transition-Metal-Catalyzed Annulations Involving the Activation of C(sp3 )-H Bonds

The selective functionalization of C(sp3 )-H bonds using transition-metal catalysis is among the more attractive transformations of modern synthetic chemistry. In addition to its inherent atom economy, such reactions open unconventional retrosynthetic pathways that can streamline synthetic processes. However, the activation of intrinsically inert C(sp3 )-H bonds, and the selection among very similar C-H bonds, represent highly challenging goals. In recent years there has been notable progress tackling these issues, especially with regard to the development of intermolecular reactions entailing the formation of C-C and C-heteroatom bonds. Conversely, the assembly of cyclic products from simple acyclic precursors using metal-catalyzed C(sp3 )-H bond activations has been less explored. Only recently has the number of reports on such annulations started to grow. Herein we give an overview of some of the more relevant advances in this exciting topic.

Catalytic Direct Cyanomethylenation of C(sp3)-H Bonds via a One-Step Double C-C Bond Formation

An elegant and catalytic procedure for the one-step cyanomethylenation of C(sp³)-H bonds adjacent to benzazoles and ketones is described herein using DMF as a C-1 unit and TMSCN as the cyanide source. The copper-mediated reaction between DMF and TMSCN gives a cyanomethylene radical intermediate that reacts with 2-alkylbenzazoles or alkylketones to furnish desired cyanomethylenated compounds under palladium catalysis. Subsequent interconversion of cyanomethylenated products makes the protocol synthetically attractive.

Recent advances in Cu-catalyzed carbonylation with CO

Transition metal-catalyzed carbonylation has emerged as a powerful and versatile strategy for the efficient construction of complicated carbonyl-containing molecules from simple chemical feedstocks in the past decades.

Transition-Metal-Catalyzed, Coordination-Assisted Functionalization of Nonactivated C(sp3)-H Bonds

Transition-metal-catalyzed, coordination-assisted C(sp³)-H functionalization has revolutionized synthetic planning over the past few decades as the use of these directing groups has allowed for increased access to many strategic positions in organic molecules. Nonetheless, several challenges remain preeminent, such as the requirement for high temperatures, the difficulty in removing or converting directing groups, and, although many metals provide some reactivity, the difficulty in employing metals outside of palladium. This review aims to give a comprehensive overview of coordination-assisted, transition-metal-catalyzed, direct functionalization of nonactivated C(sp³)-H bonds by covering the literature since 2004 in order to demonstrate the current state-of-the-art methods as well as the current limitations. For clarity, this review has been divided into nine sections by the transition metal catalyst with subdivisions by the type of bond formation. Synthetic applications and reaction mechanism are discussed where appropriate.

DMF as CO Surrogate in Carbonylation Reactions: Principles and Application to the Synthesis of Heterocycles

Transition metal-catalyzed carbonylation reactions have emerged as one of the most relevant synthetic approaches for the preparation of carbonyl-containing molecules. The most commonly used protocol for the insertion of a carbonyl moiety is the use of carbon monoxide (CO) but, due to its toxic and explosive nature, this process is not suitable at an industrial scale. More recently, the chemistry of CO surrogates has received large attention as a way to use less expensive and more environmentally friendly methods. Among the various CO surrogates, N,N-dimethylformamide (DMF) has been paid greater attention due to its low cost and easy availability. This mini-review gives appealing insights into the application of DMF as a CO surrogate in metal-catalyzed carbonylations; in particular, in the first part we will give a general state of the art of these reactions for the preparation of carbonyl-containing molecules; then, we will take into account all the various synthetic approaches for the metal-catalyzed carbonylative synthesis of heterocycles using DMF as a CO surrogate. Each protocol has been discussed critically in order to screen the best synthetic method and to offer perspective on trends and future directions in this field.

A Journey from June 2018 to October 2021 with N,N-Dimethylformamide and N,N-Dimethylacetamide as Reactants

A rich array of reactions occur using N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc) as reactants, these two amides being able to deliver their own H, C, N, and O atoms for the synthesis of a variety of compounds. This account highlights the literature published since June 2018, completing previous reviews by the author.

Construction of a Pyrimidine Framework through [3 + 2 + 1] Annulation of Amidines, Ketones, and N,N-Dimethylaminoethanol as One Carbon Donor

An efficient, facile, and eco-friendly synthesis of pyrimidine derivatives has been developed. It involves a [3 + 2 + 1] three-component annulation of amidines, ketones, and one carbon source. N,N-Dimethylaminoethanol is oxidized through C(sp³)-H activation to provide the carbon donor. One C-C and two C-N bonds are formed during the oxidative annulation process. The reaction shows good tolerance to many important functional groups in air, making this methodology a highly versatile alternative, and significant improvement to the existing methods for structuring a pyrimidine framework, especially 4-aliphatic pyrimidines.

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.

The crystal structure of 5-chloro-2-(quinolin-8-yl)isoindoline-1,3-dione, C17H9ClN2O2

C17H9ClN2O2, triclinic, P 1 ‾ $P‾{1}$ (no. 2), a = 7.8944(4) Å, b = 8.0678(5) Å, c = 12.6285(9) Å, α = 74.627(6)°, β = 78.654(5)°, γ = 63.569(5)°, V = 691.58(8) Å3, Z = 2, R gt (F) = 0.0431, wR ref (F 2) = 0.1309, T = 293(2) K.

Synthesis of Cyclic Anhydrides via Ligand-Enabled C-H Carbonylation of Simple Aliphatic Acids

The development of C(sp³ )-H functionalizations of free carboxylic acids has provided a wide range of versatile C-C and C-Y (Y=heteroatom) bond-forming reactions. Additionally, C-H functionalizations have lent themselves to the one-step preparation of a number of valuable synthetic motifs that are often difficult to prepare through conventional methods. Herein, we report a β- or γ-C(sp³ )-H carbonylation of free carboxylic acids using Mo(CO)₆ as a convenient solid CO source and enabled by a bidentate ligand, leading to convenient syntheses of cyclic anhydrides. Among these, the succinic anhydride products are versatile stepping stones for the mono-selective introduction of various functional groups at the β position of the parent acids by decarboxylative functionalizations, thus providing a divergent strategy to synthesize a myriad of carboxylic acids inaccessible by previous β-C-H activation reactions. The enantioselective carbonylation of free cyclopropanecarboxylic acids has also been achieved using a chiral bidentate thioether ligand.

Metal-Free C-H [5 + 1] Carbonylation of 2-Alkenyl/Pyrrolylanilines Using Dioxazolones as Carbonylating Reagents

A novel metal-free C-H [5 + 1] carbonylative annulation of 2-alkenyl/pyrrolylanilines with dioxazolones has been established for the assembly of the privileged quinolinones and pyrrolyl-fused quinoxalinones. Entirely differing from the existing reports, the dioxazolones herein behave with an innovative chemistry and first emerge as carbonylating reagents to participate in annulation reactions. Moreover, this process features exceedingly simple operation (only solvent) and tolerates both vinyl and aryl substrates. Comprehensive mechanistic studies indicate that the formed isocyanate intermediate plays a crucial role in enabling the carbonylation annulation.

Acylation of Arenes with Aldehydes through Dual C-H Activations by Merging Photocatalysis and Palladium Catalysis

An acylation of arenes with aldehydes through dual C-H activations at room temperature is reported. The acylation was initiated by phenanthraquinone-catalyzed hydrogen atom transfer from aldehyde under visible light irradiation. The aldehyde-derived acyl radical merged with palladium-catalyzed activation of arenes to afford the cross coupling products.

Nickel-Catalyzed [4 + 2] Annulation of Nitriles and Benzylamines by C-H/N-H Activation

Nickel-catalyzed [4 + 2] annulation of benzylamines and nitriles via C-H/N-H bond activation, providing straightforward atom-economic access to a wide variety of multisubstituted quinazolines, is reported. Mechanistic investigation revealed that the in situ formed amidines from the coupling of benzylamines and nitriles direct the nickel catalyst to activate the ortho-C-H bond of the phenyl ring of the benzylamine.

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.

Beyond conventional construction of the phthalimide core: a review

This review highlights (2010–2021) different strategies for the construction of the phthalimide core apart from traditional synthetic routes.

Nickel-Catalyzed Four-Component Carbocarbonylation of Alkenes under 1 atm of CO

Transition-metal-catalyzed carbonylation is one of the most straightforward strategies to prepare carbonyl compounds. However, compared to well-established noble-metal-catalyzed carbonylation reactions, analogue coupling via base-metal, nickel catalysis has received less attention because of the easy formation of highly toxic and unreactive Ni(CO)₄ species between Ni(0) and CO. To date, the use of inexpensive and widely available carbon monoxide (CO) gas for nickel-catalyzed carbonylation reaction remains challenging, and nickel-catalyzed four-component carbonylative reaction has not been reported yet. Here, we report a highly selective nickel-catalyzed four-component carbocarbonylation of alkenes under 1 atm (1 atm) of CO gas to efficiently achieve an array of complex carbonyl compounds, including fluorinated amino acids and oligopeptides of great interest in medicinal chemistry and chemical biology. This reaction relies on a nickel-catalyzed one-pot cascade process to assemble CO, arylboronic acids, and difluoroalkyl electrophiles across the carbon-carbon double bond of alkenes, paving a new way for base-metal-catalyzed carbonylative cascade reaction.

Rh(III)-Catalyzed C(sp3)-H Acetoxylation of 8-Methylquinolines

A mild and efficient Rh(III)-catalyzed aliphatic C-H acetoxylation directed by quinolines has been developed with widespread functional groups, including various halogens, which usually can provide precursors for further organic synthesis but easily results in selectivity issues in the Pd- and Ni-catalyzed reaction. Interestingly, Ac₂O plays an essential role in promoting the transformation.