Ene Reaction Research Articles

Access to CF3-benzofulvenes via palladium-catalyzed cascade arylation/Trost-Oppolzer cyclization/double-bond isomerization.

Herein, we demonstrated a Pd-catalyzed cascade reaction that involves arylation, Trost-Oppolzer type Alder ene reaction, and double bond isomerization using the 4-(2-alkynylphenyl)-allylcarbonates and aryl boronic acids. This cascade process delivers a wide array of distinctive functionalized CF3-benzofulvenes in good yields with high stereoselectivity (E). A single palladium catalyst orchestrates the two individual reactions in a single operation. Trost-Oppolzer type Alder ene reaction is the key in this transformation, also called a rare acid-free iso-Nazarov type cyclization.

Access to indenofluorene skeletons via Pd-catalyzed sequential reaction involving cyclization of indenone–allenyne intermediates

The rapid construction of 7,12-dihydroindeno[1,2-a]fluorene skeletons is achieved via a tandem palladium-catalyzed cross-coupling, Alder–ene isomerization and cyclization sequence from 1-(2-iodophenyl)-3-arylprop-2-yn-1-ones and diynylic ethers.

Post-synthetic modification of a covalent organic framework via a thiol–ene reaction for improving fluorescence detection and removal of cationic crystal violet carcinogenic dye

Based on a thiol–ene reaction, a covalent organic framework containing olefins (COF-A) is modified with 2-mercaptoacetic acid to prepare COF-S-COOH for the first time, which greatly improves the sensing and adsorption capacity for crystal violet.

Recent advances in ligand-enabled palladium-catalyzed divergent synthesis.

Developing efficient and straightforward strategies to rapidly construct structurally distinct and diverse organic molecules is one of the most fundamental tasks in organic synthesis, drug discovery and materials science. In recent years, divergent synthesis of organic functional molecules from the same starting materials has attracted significant attention and has been recognized as an efficient and powerful strategy. To achieve this objective, the proper adjustment of reaction conditions, such as catalysts, solvents, ligands, etc., is required. In this review, we summarized the recent efforts in chemo-, regio- and stereodivergent reactions involving acyclic and cyclic systems catalyzed by palladium complexes. Meanwhile, the reaction types, including carbonylative reactions, coupling reactions and cycloaddition reactions, as well as the probable mechanism have also been highlighted in detail.

Efficient synthesis of glycerol carbonate by doping metallic copper in palladium-catalyzed glycerol system for carbonylation reaction

The synergistic effect between copper and palladium promotes electron transport by using ZIF-8-derived Cu–NC materials to support palladium nanoparticles, which plays a crucial role in the ringing of glycerol carbonate.

“Honeycomb catalytic strategy” for carbonylation reaction based on the structural evolution of cobalt species

A catalytic strategy based on the structural evolution of cobalt species successfully reconcile catalytic efficiency and facile active metal recovery.

Visible light-promoted oxycarbonylation of unactivated alkenes

We developed an intermolecular oxygen-centered radical addition carbonylation reaction of unactivated alkenes under visible light irradiation which provides a new intermolecular strategy of oxygen-centered radical addition to alkenes.

Access to carbamates and o-aminobenzoates via oxidative carbonylation of amines with CO and alcohols under rhodium/copper catalysis

Approaches to access carbamates and o-aminobenzoates via Rh/Cu catalytic system-enabled oxidative carbonylative reactions from amines, alcohols and CO have been demonstrated, featuring good functional group tolerance and a broad substrate scope.

Palladium-catalyzed carbonylation of activated alkyl halides via radical intermediates

In this review, we summarize and discuss recent achievements in palladium-catalyzed carbonylative reactions of activated alkyl halides. Aliphatic carboxylic acid derivates were prepared effectively with various nucleophiles.

Supported Pd-catalyzed decarboxylative carbonylation reaction of 2-alkynoic acids and aryl iodides

A tandem polystyrene-supported Pd catalyzed decarboxylative carbonylation reaction between 2-alkynoic acids and aryl iodides using oxalic acid as a CO source under milder reaction conditions with vast substrate scope has been developed.

Photoinduced radical alkylation of aldehydes with potassium alkyltrifluoroborates

A method for radical addition at aldehydes is described. The reaction is based on the interplay of radical attack and cleavage processes occurring at a boron complexed carbonyl group.

Inside Back Cover

Compounds containing carbonyl‐derived functional groups have received intensive attention owing to their widespread applications. As a complementary to the palladium catalysts, the use of nickel catalysts in carbonylative reactions has a great potential. We discussed the nickel catalyzed carbonylative reactions reported during 2017 to March 2023 in this review by Lian et al. on page 177—189. image

Synchronous and zwitter-ion channels of (<i>R</i>)-5-methyl2-(1-methylethylidene)-cyclohexanone reaction with 4-phenyl-4<i>H</i>-1,2,4-triazoline-3,5-dione

The interaction of pulegone with enophil - 4-phenyl-4 H -1,2,4-triazoline-3,5-dione leads to the formation of two described earlier epimers: 1-[(1 R ,4 R )-4-methyl-1-(1-methylethenyl)-2-oxocyclohexyl]-4-phenyl-1,2,4-triazolidine-3,5-dione ( RR -isomer) and 1-[(1 S ,4 R )-4-methyl-1-(1-methylethenyl)-2-oxocyclohexyl]-4-phenyl-1,2,4-triazolidine-3,5-dione ( SR -isomer). Along with these epimers, we found another isomer - 1-{1-methyl-1-[(4 R )-4methyl-6-oxocyclohex-1-en-1-yl]ethyl}-4-phenyl-1,2,4-triazolidine-3,5-dione. Quantum chemical modeling has established that isomeric products of hydrogen substitution in pulegone by enophil are formed along three routes. In the SR -isomer formation route, the ene reaction proceeds consistently. The other two routes are implemented with the enophil approach from the R -side of the pulegon. These routes consist of two consecutive stages. At the first stage, an intermediate of the type of asymmetric cyclic aziridine cation is formed. Elimination of a proton from one of the geminal methyl groups of the intermediate leads to an RR -isomer with a terminal double bond. When a proton is eliminated from the methylene group of the pulegog ring, an internal unsaturated compound is formed. The ratio of the yield of the isomer with an internal double binding and the RR -isomer depends on the polarity of the aprotic solvents.

Synthesis of Spiro[4.5]ecanes by Au(I)‐Catalyzed Vinylogous Conia Ene Reaction

AbstractAu(I) catalysed vinylogous Conia ene reaction was developed to construct the densely functionalized spiro[4.5]‐deca‐1,6‐diene‐8‐ones from easily available 4‐alkyne tethered cyclohex‐2‐enones. 17 substrates with multiple substitutes on the cyclohex‐2‐enone ring were explored to afford the corresponding spiro[4.5]in 52–81 % yields. This reaction features mild conditions, wide substrate scope and atom economic characters.

Regioselective and Stereoselective Synthesis of Parthenolide Analogs by Acyl Nitroso-Ene Reaction and Their Biological Evaluation against Mycobacterium tuberculosis.

Historically, natural products have played a major role in the development of antibiotics. Their complex chemical structures and high polarity give them advantages in the drug discovery process. In the broad range of natural products, sesquiterpene lactones are interesting compounds because of their diverse biological activities, their high-polarity, and sp3-carbon-rich chemical structures. Parthenolide (PTL) is a natural compound isolated from Tanacetum parthenium, of the family of germacranolide-type sesquiterpene lactones. In recent years, parthenolide has been studied for its anti-inflammatory, antimigraine, and anticancer properties. Recently, PTL has shown antibacterial activities, especially against Gram-positive bacteria. However, few studies are available on the potential antitubercular activities of parthenolide and its analogs. It has been demonstrated that parthenolide's biological effects are linked to the reactivity of α-exo-methylene-γ-butyrolactone, which reacts with cysteine in targeted proteins via a Michael addition. In this work, we describe the ene reaction of acylnitroso intermediates with parthenolide leading to the regioselective and stereoselective synthesis of new derivatives and their biological evaluation. The addition of hydroxycarbamates and hydroxyureas led to original analogs with higher polarity and solubility than parthenolide. Through this synthetic route, the Michael acceptor motif was preserved and is thus believed to be involved in the selective activity against Mycobacterium tuberculosis.

Platform for the Immobilizing of Ultrasmall Pd Clusters for Carbonylation: In Situ Self-Templating Fabrication of ZIF-8 on ZnO.

Incorporating metal clusters into the confined cavities of metal-organic frameworks (MOFs) to form MOF-supported catalysts has attracted considerable research interest with regard to carbonylation reactions. Herein, a self-templating method is used to prepare the zinc oxide (ZnO)-supported core-shell catalyst ZnO@Pd/ZIF-8. This facile strategy controls the growth of metal sources on the ZIF-8 shell layer and avoids the metal diffusion or aggregation problems of the conventional synthesis method. The characteristics of the catalysts show that the palladium (Pd) clusters are highly dispersed with an average particle size of ≈1.2nm, making them excellent candidates as a catalyst for carbonylation under mild conditions. The optimal catalyst (1.25-ZnO@Pd/ZIF-8) exhibits excellent activity in synthesizing α, β-alkynyl ketones under 1 atm of carbon monooxide (CO), and the conversion rate of 1, 3-diphenylprop-2-yn-1-one is 3.09 and 3.87 times more than those of Pd/ZIF-8 and Pd2+, respectively, for the first 2h. Moreover, the 1.25-ZnO@Pd/ZIF-8 is recyclable, showing negligible metal leaching, and, under the conditions used in this investigation, can be reused at least five times without considerable loss in its catalytic efficiency. This protocol can also be applied with other nucleophile reagents to synthesize esters, amides, and acid products.

Adaptable Networks with Semiorthogonal Two-Stage Polymerizations Enabled by Sequential Photoinitiated Thiol–Ene and Disulfide–Ene Reactions

Adaptable Networks with Semiorthogonal Two-Stage Polymerizations Enabled by Sequential Photoinitiated Thiol–Ene and Disulfide–Ene Reactions

Synthetic studies toward Swinhoeisterol A: Synthesis of the 6/6/5/7 tetracyclic core

6/6/5/7 Tetracyclic core of Swinhoeisterol A was constructed starting from Wieland-Miescher ketone and silylated ethyl 5–hydroxyvalerate. After modification, the bicyclic and linear subunits were assembled by means of cross-metathesis reaction. Then, cyclopentane C ring was formed by the intramolecular aldol condensation. C17-stereocenter was constructed using Claisen rearrangement followed by the decarbonylation step. Finally, ene reaction was applied for the simultaneous formation of cycloheptane d-ring and tetrasubstituted double bond between rings B and C.

Recent Advances in Catalytic Carbonylation Reactions in Alternative Reaction Media

Comprehensive SummarySince the discovery of the hydroformylation (oxo‐synthesis or Roelen reaction) and the Reppe‐reaction, the transition metal‐catalyzed carbonylation reactions, providing versatile, facile, and even atom‐economic methods for the selective incorporation of C=O functionality to various skeletons, have gained tremendous importance in synthetic organic chemistry from laboratories to industrial applications. The carbonylation of carbon‐carbon multiple bonds, aromatic halides, triflates, etc., in the presence of various nucleophiles has led the way to produce aldehydes, carboxylic acids, esters, amides, etc., in the fine chemical industry. However, these protocols usually proceed in conventional, fossil‐based, and usually toxic reaction environments. Thus, several attempts have been directed to developing efficient carbonylation methods in alternative, less harmful, non‐fossil‐based and even in renewable reaction media. In this review, we overview the recent applications of alternative solvents such as water, biomass‐based alcohols, γ‐valerolactone (GVL), 2‐methyltetrahydrofuran (2‐MeTHF), ionic liquids (ILs), deep eutectic solvents (DES), alkyl levulinates, limonene, α‐pinene, and dimethyl carbonate as well as fluorous media to improve efficiency, safety and environmentally benign nature of carbonylation protocols.

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.