Palladium-Catalyzed Carbonylative [3+2+1] Annulation ofN-Aryl-Pyridine-2-Amines with Internal Alkynes by CH Activation: Facile Synthesis of 2-Quinolinones

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.

Palladium-Catalyzed Carbonylative Cyclization of 1-Alkynyl-2-iodo-d-glucal

Cascade reactions are important synthetic tools for the synthesis of heterocyclic molecules, particularly those catalyzed by palladium. Herein, we report a palladium-catalyzed aminocarbonylative cyclization of new 1-alkynyl-2-iodo-d-glucals, which undergo a tandem carbonylative cyclization in the presence of various amine nucleophiles. A broad range of aromatic and aliphatic amines were applied as coupling partners, resulting in the selective and high-yield synthesis of glycosides fused to pyridinones. A plausible mechanism is proposed, proceeding via a tandem palladium aminocarbonylation followed by a palladium-catalyzed endo-dig cyclization.

Transition-Metal-Catalyzed Carbonylative Multifunctionalization of Alkynes

Currently, the construction of new carbon-carbon bonds and value-added structures in an atom- and step economical manner has become a continuous pursuit in the synthetic chemistry community. Since the first transition-metal-catalyzed hydroformylation of ethylene was reported by Otto Roelen in the 1930s, impressive progress has been achieved in the carbonylative functionalization of unsaturated C-C bonds. In contrast to alkenes, the carbonylative functionalization of alkynes offers tremendous potential for the construction of multisubstituted carbonyl-containing derivatives because of their two independently addressable π-systems. This review provides a timely and necessary investigation of transition-metal-catalyzed carbonylative mutifunctionalization of alkynes with the exclusion of carbonylative hydrofunctionalizations. Different transition metals including palladium, rhodium, iridium, ruthenium, iron, copper, etc. were applied to the development of novel carbonylative transformation. Various C-C, C-N, C-O, C-S, C-B, C-Si, and carbon-halogen bonds were formed efficiently and give the corresponding tri- or tetrasubstituted α,β-unsaturated ketones, diesters, and heterocycles.

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.

Recent advances in directed sp2 C-H functionalization towards the synthesis of N-heterocycles and O-heterocycles

Heterocyclic compounds are widely present in the core structures of several natural products, pharmaceuticals and agrochemicals, and thus great efforts have been devoted to their synthesis in a mild and simpler way. In the past decade, remarkable progress has been made in the field of heterocycle synthesis by employing C-H functionalization as an emerging synthetic strategy. As a complement to previous protocols, transition metal catalyzed C-H functionalization of arenes using various directing groups has recently emerged as a powerful tool to create different classes of heterocycles. This review is mainly focussed on the recent key progress made in the field of the synthesis of N,O-heterocycles from olefins and allenes by using nitrogen based and oxidizing directing groups.

Radical Annulation of 2-Cyanoaryl Acrylamides via C═C Double Bond Cleavage: Access to Amino-Substituted 2-Quinolones

A novel annulation of 2-cyanoaryl acrylamides via C═C double bond cleavage has been developed for facile and efficient access to a broad spectrum of functionalized 4-amino-2-quinolones, which are important N-heterocycles. In this transformation, the solvent THF is demonstrated to play a crucial role, and the addition of alkyl radicals to nitrile, 1,5-hydride shift, and cleavage of the C-C bond are involved in the mechanism.

Recent Advances in One-Pot Modular Synthesis of 2-Quinolones

It is known that 2-quinolones are broadly applicable chemical structures in medicinal and agrochemical research as well as various functional materials. A number of current publications about their synthesis and their applications emphasize the importance of these small molecules. The early synthetic chemistry originated from the same principle of the classical Friedländer and Knorr procedures for the preparation of quinolines. The analogous processes were developed by applying new synthetic tools such as novel catalysts, the microwave irradiation method, etc., whereas recent innovations in new bond forming reactions have allowed for novel strategies to construct the core structures of 2-quinolones beyond the bond disconnections based on two classical reactions. Over the last few decades, some reviews on structure-based, catalyst-based, and bioactivity-based studies have been released. In this focused review, we extensively surveyed recent examples of one-pot reactions, particularly in view of modular approaches. Thus, the contents are categorized as three major sections (two-, three-, and four-component reactions) according to the number of reagents that ultimately compose atoms of the core structures of 2-quinolones. The collected synthetic methods are discussed from the perspectives of strategy, efficiency, selectivity, and reaction mechanism.

Ligand-Enabled Ni-Al Bimetallic Catalysis for Nonchelated Dual C-H Annulation of Arylformamides and Alkynes

A bifunctional secondary phosphine oxide (SPO) ligand-controlled method was developed for Ni-Al-catalyzed nonchelated dual C-H annulation of arylformamides with alkynes, providing a series of substituted amide-containing heterocycles in ≤97% yield. The SPO-bound bimetallic catalysis proved to be critical to the reaction efficiency.

Carbonylative synthesis of heterocycles involving diverse CO surrogates

Recent advances in the carbonylative synthesis of heterocycles by using diverse CO surrogates as sources of CO are summarized and discussed.

Cobaltaelectro-Catalyzed C-H Activation with Carbon Monoxide or Isocyanides

Electrochemical oxidative C-H/N-H activations with isocyanides have been realized with a versatile cobalt catalyst. The widely applicable cobalt catalysis manifold further enabled electrooxidative C-H/N-H carbonylations with carbon monoxide under ambient conditions. The C-H functionalizations were efficiently realized with ample scope and outstanding functional group tolerance in a user-friendly undivided cell setup.

Electrochemical Transition-Metal-Catalyzed C-H Bond Functionalization: Electricity as Clean Surrogates of Chemical Oxidants

Transition-metal-catalyzed C-H activation has attracted much attention from the organic synthetic community because it obviates the need to prefunctionalize substrates. However, superstoichiometric chemical oxidants, such as copper- or silver-based metal oxidants, benzoquinones, organic peroxides, K₂ S₂ O₈ , hypervalent iodine, and O₂ , are required for most of the reactions. Thus, the development of environmentally benign and user-friendly C-H bond activation protocols, in the absence of chemical oxidants, are urgently desired. The inherent advantages and unique characteristics of organic electrosynthesis make fill this gap. Herein, recent progress in this area (until the end of September 2018) is summarized for different transition metals to highlight the potential sustainability of electro-organic chemistry.

Base-catalyzed thio-lactamization of 2-(1-arylvinyl)anilines with CS2 for the synthesis of quinoline-2-thiones

Quinoline-2-thiones were prepared through a base-catalyzed thio-lactamization of 2-(1-arylvinyl)anilines with CS₂.

Base-controlled chemoselectivity reaction of vinylanilines with isothiocyanates for synthesis of quinolino-2-thione and 2-aminoquinoline derivatives

Quinolino-2-thione and 2-aminoquinoline derivatives were obtained by a base-controlled chemo-selective reaction of vinylanilines with alkyl/aryl isothiocyanates.

Rh-catalyzed aerobic oxidative cyclization of anilines, alkynes, and CO

We describe a novel Rh-catalyzed C–H cyclization of a wide range of anilines with alkynes and CO. Particularly, simple primary anilines and readily prepared tertiary anilines can be easily converted to quinolin-2(1H)-ones via C–N bond cleavage.

Transition-metal-catalyzed oxidative C–H cyclization of anilines has been an attractive and powerful strategy for the efficient construction of N-heterocycles. However, primary and tertiary anilines are rarely employed in this strategy due to the relative instability with strong oxidants or the presence of three C–N bonds. We describe here a novel Rh-catalyzed C–H cyclization of a wide range of anilines with alkynes and CO, using an aerobic oxidative protocol. Particularly, the simple primary anilines and readily prepared tertiary anilines could be easily converted to quinolin-2(1H)-ones, which are high value-added, biologically significant N-heterocycles, via C–N bond cleavage.

Carbon annulation of ortho-vinylanilines with dimethyl sulfoxide to access 4-aryl quinolines

A palladium-catalyzed annulation of ortho-vinylanilines with dimethyl sulfoxide was developed to access 4-aryl quinolines in moderate to good yields.

A palladium-catalyzed intramolecular carbonylative annulation reaction for the synthesis of 4,5-fused tricyclic 2-quinolones

A new method for the synthesis of 4,5-fused tricyclic 2-quinolones via a palladium-catalyzed intramolecular carbonylative annulation reaction is described.

Pd-catalyzed aminocarbonylation of alkynes with amines using Co2(CO)8 as a carbonyl source

A facile protocol for aminocarbonylation of alkynes with amines at room temperature was developed using a metal carbonyl source.

Intramolecular cyclization of diarylmethanols and α,β-unsaturated amides promoted by KOt-Bu/DMF: a metal-free approach towards 3,4-disubstituted quinolinones

A facile synthesis of 3,4-disubstituted quinolinones had been developed via KOt-Bu/DMF promoted intramolecular addition of diarylmethanols to α,β-unsaturated amides.