Iron-catalyzed carbonylation: selective and efficient synthesis of succinimides

Ligand-Free Iron-Catalyzed Carbonylation of Aryl Iodides with Alkenyl Boronic Acids: Access to α,β-Unsaturated Ketones

The application of earth-abundant and low-toxicity iron catalysts as replacements for palladium in carbonylative coupling reactions remains challenging and largely unexplored. Reported here is a highly efficient iron-catalyzed carbonylation of aryl iodides with alkenyl boronic acids under ligand-free conditions, enabling the synthesis of α,β-unsaturated ketones even at atmospheric CO pressure. The broad applicability, including its effectiveness with α-branched enones and biologically active molecules, along with high yields and selectivity, underlines the general applicability of this catalytic system.

Single-Pd-Site Catalyst Induced by Different Dimensional Nitrogen of N-Doping Carbon for Efficient Hydroaminocarbonylation of Alkynes

The unsaturated amides are traditionally synthesized by acylation of carboxylic acids or hydration of nitrile compounds but are rarely investigated by hydroaminocarbonylation of alkynes using heterogeneous single-metal-site catalysts (HSMSCs). Herein, single-Pd-site catalysts supported on N-doping carbon (NC) with different nitrogen dimensions inherited from corresponding metal-organic-framework precursors are successfully synthesized. 2D NC-supported single-Pd-site (Pd1/NC-2D) exhibited the best performance with near 100% selectivity and 76% yield of acrylamide for acetylene hydroaminocarbonylation with better stability, superior to those of Pd1/NC-3D, single-metal-site/nanoparticle coexisting catalyst, and nanoparticle catalyst. The coordination environment and molecular evolution of the single-Pd-site during the process of acetylene hydroaminocarbonylation on Pd1/NC-2D are detailly illuminated by various characterizations and density functional theoretical calculations (DFT). DFT also showed the energy barrier of rate-determining step on Pd1/NC-2D is lower than that of Pd1/NC-3D. Furthermore, Pd1/NC-2D catalyst illustrated the general applicability of the hydroaminocarbonylation for various alkynes.

On the Question of Uncatalyzed CO Insertion into a Hydrazone Double Bond: A Comparative Study Using Different CO Sources and Substrates

Because of endogenous signaling roles of carbon monoxide (CO) and its demonstrated pharmacological effects, there has been extensive interests in developing fluorescent CO probes. Palladium-mediated CO insertion has been successfully used for such applications. However, recent years have seen many publications of using uncatalyzed CO insertion into a hydrazone double bond as a way to sense CO. Such chemistry has no precedents otherwise. Further, the rigor of the CO-sensing work was largely based on using ruthenium-carbonyl complexes such as CORM-3 as CO surrogates, which have been reported to have extensive chemical reactivity and to release largely CO2 instead of CO unless in the presence of a strong nucleophile such as dithionite. For all of these, it is important to reassess the feasibility of such a CO-insertion reaction. By studying two of the reported "CO probes" using CO gas, this study finds no evidence of CO insertion into a hydrazone double bond. Further, the chemical reaction between CO gas and a series of eight hydrazone compounds was conducted, leading to the same conclusion. Such findings are consistent with the state-of-the-art knowledge of carbonylation chemistry and do not support uncatalyzed CO insertion as a mechanism for developing fluorescent CO probes.

Iron-Catalyzed Aminoalkylative Carbonylative Cyclization of Alkenes toward α-Tetralones

Carbonylative multifunctionalization of alkenes is an efficient approach to introduce multiple functional groups into one molecule from easily available materials. Herein, we developed an iron-catalyzed radical relay carbonylative cyclization of alkenes with acetamides. Various α-tetralones can be constructed in moderate yields from readily available substrates with an earth-abundant iron salt as the catalyst.

Palladium-Catalyzed Tandem Cyclization of Bromoalkynes, Anilines and CO: Access to 1,3-Substituted Maleimides

A novel palladium-catalyzed three-component carbonylation reaction for the assembly of various 1,3-substituted maleimide derivatives from haloalkynes and simple anilines. The nucleophilic addition reaction of haloalkynes, anilines and CO, and insertion of carbonyl have been achieved sequentially in this reaction. The high chemo- and regioselectivities, as well as no need of expensive ligands or additives further illustrate the synthetic value of this approach.

Metal-free, I2-promoted direct synthesis of 2-cyano-substituted maleimides via a unique 3,3-dicyano-2-arylacrylic acid intermediate

A robust, I₂-mediated cyclization reaction was developed for the synthesis of 2-cyano-substituted maleimides from arylethylidene malononitriles and amines via unique a 3,3-dicyano-2-arylacrylic acid intermediate. The reaction duration was short and devoid of an expensive transition-metal catalyst, ligands or toxic carbon monoxide. We executed an I₂/DMSO-mediated desirable oxidation of the C(sp³)-H bond of the carbonyl precursor followed by the formation of a 3,3-dicyano-2-arylacrylic acid intermediate. Use of readily available starting materials under mild and operationally simple reaction conditions are the major advantages of this strategy.

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.

Antioxidant Molecules Isolated from Edible Prostrate Knotweed: Rational Derivatization to Produce More Potent Molecules

Prostrate knotweed also called Polygonum aviculare is an important edible plant. The polygonum is majorly known for the phenolics and antioxidants. The antioxidants combat the excessive free radicals within the body. The excessive free radicals are implicated in various other diseases like diabetes, Alzheimer's, and inflammation. This study was aimed at exploring the antioxidant bioactives and their derivatizations to produce new molecules with advanced pharmacological features. We have isolated six compounds (1–6) from Polygonum aviculare. Furthermore, rational-based chemical derivatives for compound 5 have been formed for the management of diabetes, Alzheimer's, and inflammation. In preliminary antioxidant studies, all the isolated compounds (1–6) showed potential results against DPPH and ABTS free radicals. Based on the IC₅₀ and chemical nature of the compounds, compound 5 was subjected to derivatization. Keeping the phenolic part of compound 5 unaffected, hydroxy succinimide (5A) and thiazolidinedione (5B) were synthesized. The compound 5A was found to be a potent inhibitor of AChE, BChE, COX-1, COX-2, 5-LOX, and DPPH giving IC₅₀ values of 10.60, 15.10, 13.91, 1.08, 0.71, and 1.05 μM, respectively. The COX-2 selectivity of compound 5A was found at 12.9. The compound 5B was found to be a potent multitarget antidiabetic agent giving IC₅₀ values of 15.34, 21.83, 53.28, and 1.94 μM against α-glucosidase, α-amylase, protein tyrosine phosphatase 1B, and DPPH. Docking studies were performed to manipulate the binding interactions. The docking pose of all the tested compounds was found to have increased binding affinity against all tested targets that supported the in vitro results. Our results showed that Polygonum aviculare is a rich source of antioxidant compounds. The two new derivatives have enhanced pharmacological features to treat diabetes, inflammation, and Alzheimer's disease.

Divergent Aminocarbonylations of Alkynes Enabled by Photoredox/Nickel Dual Catalysis

A metallaphotoredox-catalyzed strategy for the selective and divergent aminocarbonylation of alkynes with amines and 1 atm of CO is reported. This synergistic protocol not only enables the Markovnikov-selective hydroaminocarbonylation of alkynes to afford α,β-unsaturated amides, but also facilitates a sequential four-component hydroaminocarbonylation/radical alkylation in the presence of tertiary and secondary alkyl boronate esters, which allows for straightforward conversion of alkynes into corresponding amides. Preliminary mechanistic studies disclose that a photoinduced oxidative insertion of aniline and CO into nickel followed by a migratory insertion of (carbamoyl)nickel species could be involved.

Palladium-Catalyzed Domino Aminocarbonylation of Alkynols: Direct and Selective Synthesis of Itaconimides

The first direct and selective synthesis of substituted itaconimdes by palladium-catalyzed aminocarbonylation of alkynols is reported. Key to the success of this transformation is the use of a novel catalyst system involving ligand L11 and appropriate reaction conditions. In the protocol here presented, easily available propargylic alcohols react with N-nucleophiles including aryl- and alkylamines as well as aryl hydrazines to provide a broad variety of interesting heterocycles with high catalyst activity and excellent selectivity. The synthetic utility of the protocol is demonstrated in the synthesis of natural product 11 with aminocarbonylation as the key step. Mechanistic studies and control experiments reveal the crucial role of the hydroxyl group in the substrate for the control of selectivity.

Methanesulfonic Acid Catalyzed Friedel–Crafts Reaction of Electron-Rich Arenes with N-Arylmaleimides: A Highly Efficient Metal-Free Route To Access 3-Arylsuccinimides

Friedel–Crafts reaction is widely used for the C–C bond forming reaction to enable the direct connection of electron-rich arenes to electron-deficient olefins with high regioselectivity. Herein, a highly efficient, metal-free, and environmentally benign F–C strategy of electron-rich arenes with N-arylmaleimides has been developed for the construction of 3-arylsuccinimides in the presence of a green reagent methanesulfonic acid under mild reaction conditions. This highly facile and high-yielding protocol has compatibility with different electron-rich arenes.

Synthesis of Succinimides via Intramolecular Alder-Ene Reaction of 1,6-Enynes

A novel and convenient method has been developed for the facile synthesis of functionalized succinimide derivatives via intramolecular Alder-ene reaction of 1,6-enynes. This reaction features mild and metal-free reaction conditions, which offers a green and efficient entry to synthetically important succinimide scaffolds. Preliminary mechanistic studies suggest that a diradical intermediate might be involved in this transformation.

"On water" nano-Cu2O-catalyzed CO-free one-pot multicomponent cascade cyanation-annulation-aminolysis reaction toward phthalimides

An efficient nano-Cu2O-catalyzed cascade multicomponent reaction of 2-halobenzoic acids and trimethylsilyl cyanide with diverse amines was developed using water as a solvent, affording versatile N-substituted phthalimide derivatives in moderate to excellent yields. This novel strategy features carbon monoxide gas-free, environmentally benign, one-pot multistep transformation, commercially available reagents, a cheap catalyst without any additives, wide functional group tolerance, and operational convenience.

Organic synthesis with the most abundant transition metal–iron: from rust to multitasking catalysts

The promising aspects of iron in synthetic chemistry are being explored for three-four decades as a green and eco-friendly alternative to late transition metals. This present review unveils these rich iron-chemistry towards different transformations.

Synthesis of α,β-unsaturated carbonyl compounds by carbonylation reactions

Carbonylation reactions represent one of the most important tool box for the synthesis of α,β-unsaturated carbonyl compounds which are key building blocks in organic chemistry. This paper summarizes the most important advances in this field.

Preparation of cyclic imides from alkene-tethered amides: application of homogeneous Cu(ii) catalytic systems

A Cu-based homogeneous catalytic system was proposed for the preparation of imides from alkene-tethered amides. Here, O₂ acted as a terminal oxidant and a cheap and easily available oxygen source. The cleavage of C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds and the formation of C–N bonds were catalyzed by Cu(ii) salts with proper nitrogen-containing ligands under 100 °C. The synthesis approach has potential applications in pharmaceutical syntheses. Moreover, scaled-up experiments confirmed the practical applicability.

A catalytic system comprising Cu(ii) and a nitrogen-based ligand for the oxygenation and cyclization of alkene-tethered amides.

Visible-Light-Mediated Dearomatisation of Indoles and Pyrroles to Pharmaceuticals and Pesticides

Dearomatisation of indole derivatives to the corresponding isatin derivatives has been achieved with the aid of visible light and oxygen. It should be noted that isatin derivatives are highly important for the synthesis of pharmaceuticals and bioactive compounds. Notably, this chemistry works excellently with N-protected and protection-free indoles. Additionally, this methodology can also be applied to dearomatise pyrrole derivatives to generate cyclic imides in a single step. Later this methodology was applied for the synthesis of four pharmaceuticals and a pesticide called dianthalexin B. Detailed mechanistic studies revealed the actual role of oxygen and photocatalyst.

Cu-catalyzed oxygenation of alkene-tethered amides with O2 via unactivated C[double bond, length as m-dash]C bond cleavage: a direct approach to cyclic imides

An efficient aerobic unactivated C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bond cleavage process was achieved, in which the succinimide or glutarimide derivatives could be prepared directly from alkenyl amides.

The transformations of unactivated alkenes through C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bond double cleavage are always attractive but very challenging. We report herein a chemoselective approach to valuable cyclic imides by a novel Cu-catalyzed geminal amino-oxygenation of unactivated C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds. O₂ was successfully employed as the oxidant as well as the O-source and was incorporated into alkenyl amides via C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bond cleavage for the efficient preparation of succinimide or glutarimide derivatives. Moreover, the present strategy under simple conditions can be used in the late-stage modification of biologically active compounds and the synthesis of pharmaceuticals, which demonstrated the potential application.

Carbonylation of C-N Bonds in Tertiary Amines Catalyzed by Low-Valent Iron Catalysts

The first iron catalysts able to promote the formal insertion of CO into the C-N bond of amines are reported. Using low-valent iron complexes, including K₂ [Fe(CO)₄ ], amides are formed from aromatic and aliphatic amines, in the presence of an iodoalkane promoter. Inorganic Lewis acids, such as AlCl₃ and Nd(OTf)₃ , have a positive influence on the catalytic activity of the iron salts, enabling the carbonylation at a low pressure of CO (6 to 8 bars).

Zn(OAc)2-catalyzed tandem cyclization of isocyanides, α-diazoketones, and anhydrides: a general route to polysubstituted maleimides

A zinc-catalyzed three-component reaction of isocyanides, α-diazoketones, and anhydrides has been realized as a novel and efficient method for the synthesis of polysubstituted maleimides.

Non-noble metal-catalysed carbonylative transformations

The main achievements on non-noble metal (Mn, Fe, Cu, Co, Ni) catalysed carbonylative transformations have been summarized and discussed.

Palladium-catalyzed aerobic oxidative carbonylation of alkynes with amines: a general access to substituted maleimides

A catalytic oxidative carbonylation reaction was developed for the synthesis of polysubstituted maleimides from alkynes and amines with air as a green oxidant.

Regioselectivity inversion tuned by iron(iii) salts in palladium-catalyzed carbonylations

We disclose the Pd-catalyzed carbonylation of alkenes and alcohols, with the regioselectivity tuned by the anion of Fe(iii) salts.

Palladium-catalyzed regiodivergent hydroaminocarbonylation of alkenes to primary amides with ammonium chloride

A new and efficient process for transferring NH₄Cl to both linear and branched primary amides has been achieved via palladium-catalyzed hydroaminocarbonylation of alkenes.

Palladium-catalyzed hydroaminocarbonylation of alkenes for the synthesis of primary amides has long been an elusive aim. Here, we report an efficient catalytic system which enables inexpensive NH₄Cl to be utilized as a practical alternative to gaseous ammonia for the palladium-catalyzed alkene-hydroaminocarbonylation reaction. Through appropriate choice of the palladium precursors and ligands, either branched or linear primary amides can be obtained in good yields with good to excellent regioselectivities. Primary mechanistic studies were conducted and disclosed that electrophilic acylpalladium species were capable of capturing the NH₂-moiety from ammonium salts to form amides in the presence of CO with NMP as a base.