Photoinduced Decatungstate Anion-Catalyzed 1,4-Difunctionalization of 1,3-Butadienes via C-H Activation.

This paper outlines an innovative three-component coupling strategy for the 1,4-difunctionalization of 1,3-butadiene, utilizing sodium decatungstate (NaDT) as a hydrogen atom transfer (HAT) photocatalyst. The photoinduced process efficiently generates homoallylic amino acid esters with 100% atom economy, employing readily available components under mild reaction conditions. This light-induced protocol eliminates the need for an additional transition metal catalysts, additives, or equivalent reducing agents. The study explored various C(sp3)-H bearing partners, butadienes, and α-iminoesters, demonstrating the versatility and synthetic utility of this method.

Photoinduced Pd-Catalyzed Enantioselective Carboamination of Dienes via Aliphatic C-H Bond Elaboration.

Three-component diene carboaminations offer a potent means to access synthetically valuable allylic amines with rapid molecular complexity escalation. The existing literature primarily discloses racemic examples, necessitating the use of halides/pseudohalides as substrates. This paper introduces a photoinduced Pd-catalyzed enantioselective three-component carboamination of aryl-substituted 1,3-dienes, leveraging aliphatic C-H bonds for rapid synthesis. The reaction employs 10 mol % of chiral palladium catalyst and an excess aryl bromide as the HAT reagent. This approach yields diverse chiral allylamines with moderate to excellent enantioselectivities. Notably, it stands as the first instance of an asymmetric three-component diene carboamination reaction, directly utilizing abundant C(sp3)-H bearing partners, such as toluene-type substrates, ethers, amines, esters, and ketones. The protocol exhibits versatility across amines, encompassing aliphatic, aromatic, primary, and secondary derivatives. This method could serve as a versatile platform for stereoselective incorporation of various nucleophiles, dienes, and C(sp3)-H bearing partners.

Asymmetric construction of phosphono dihydropyranones from α-ketophosphonates enabled by Pd/chiral isothiourea relay catalysis.

A highly enantio- and diastereoselective approach has been developed for the synthesis of chiral phosphono dihydropyranones. This approach is enabled by Pd/chiral isothiourea relay catalysis under mild reaction conditions, starting from readily available benzyl bromides, CO, and α-ketophosphonates. The cascade reaction involves the generation of a ketene intermediate from Pd-catalyzed carbonylation of benzyl bromide and subsequent chiral Lewis base catalyzed formal [4 + 2] reaction. Phosphono lactone products can also be transformed to chiral 1,5-diester products in good yield and high stereoselectivity.

Chiral Bisphosphoric Acids and Their Applications in Asymmetric Catalysis.

Asymmetric Brønsted acid catalysis has been recognized as a powerful concept for asymmetric synthesis. In the process of pursuing more robust and highly effective chiral Brønsted acid catalysts, chiral bisphosphoric acids have received much attention in the last two decades. Their unique catalytic properties are mainly attributed to the inherent intramolecular hydrogen bonding interactions that could increase the overall acidity and tune the conformation property. Integrating hydrogen bonding into the catalyst design, quite a few structurally unique and effective bisphosphoric acids have been synthesized, which frequently exhibited superior selectivity in a broad range of asymmetric transformations. This review summarizes the status quo of chiral bisphosphoric acid catalysts and their applications in catalyzing asymmetric transformations.

Asymmetric Cascade Carbonylation/Annulation of Benzyl Bromides, CO, and Vinyl Benzoxazinanones Enabled by Pd/Chiral Lewis-Base Relay Catalysis.

A highly enantioselective cascade carbonylation/annulation of benzyl bromides, CO, and vinyl benzoxazinanones under mild conditions has been established by Pd/chiral Lewis base relay catalysis, providing an efficient method to assemble chiral quinolinones from readily available starting materials in good yields with excellent diastereo- and enantioselectivities. The palladium catalyst plays two roles in this reaction, enabling both the carbonylation process and the generation of the zwitterionic π-allyl palladium intermediate.

Redox-Neutral 1,4-Dicarbonfunctionalization of 1,3-Butadiene by Merging Photoredox and Nickel Catalysis.

The diverse functionalization of 1,3-butadiene provides wide applicability toward the synthesis of abundant and useful allylic compounds. Here, we describe a three-component and redox-neutral assembly of readily available C═X compounds, 1,3-butadiene, and various nucleophiles by merging photoredox and nickel catalysis, enabling the rapid synthesis of structurally diverse homoallyl amines and homoallylic alcohols.

Palladium-Catalyzed and Photoinduced Benzylic C-H Carbonylation/Annulation under Mild Conditions.

A Pd-catalyzed and photoinduced benzylic cascade benzylic C-H carbonylation/annulation reaction is realized under mild conditions (35 °C, 2 bar CO). The use of a catalytic amount of base is crucial for the reaction to achieve high yields. The reaction consists of a Pd-catalyzed generation of amidyl radical from O-benzyl hydroxylamide substrates and 1,5-HAT to give a benzylic radical, followed by carbonylation and annulation. Various homophthalimides, which could be readily converted to a number of bioactive compounds, could be obtained with up to 96% yield.

Palladium-Catalyzed Cascade C-H Functionalization/Asymmetric Allylation Reaction of Aryl α-Diazoamides and Allenes: Lewis Acid Makes a Difference.

A Pd-catalyzed cascade C-H functionalization/asymmetric allylation reaction with aryl α-diazoamides and allenes has been developed. The reaction provides an efficient approach to construct chiral 3,3-disubstituted oxindole derivatives in high levels of yield and enantioselectivity (up to 93 % ee). Notably, the chromium complex works as Lewis acid to facilitate the formation of palladium carbene and to enhance acidity of carboxylic acid, allowing for higher stereochemical control and efficiency.

Asymmetric Counteranion Directed Catalytic Heck/Tsuji-Trost Annulation of Aryl Iodides and 1,3-Dienes.

A chiral anion-mediated asymmetric Heck/Tsuji-Trost reaction of aryl iodides and 1,3-dienes is presented. Chiral indoline derivatives could be afforded with remarkably higher yields and enantioselectivities than our previous chiral ligand-based method. Silver carbonate is employed as both base and halide scavenger to ensure fast and recyclable exchange of the catalytic amount of chiral anions. Fast salt metathesis, as well as the acceleration effect of the chiral anion, could both benefit the stereocontrol of the reaction.

Chiral-Anion-Mediated Asymmetric Heck-Matsuda Reaction of Acyclic Alkenyl Alcohols.

Acyclic internal alkenes are a class of challenging substrates in asymmetric Heck-type reactions due to difficulties related to both reactivity and selectivity control. Employing acyclic alkenyl alcohols, an asymmetric Heck-Matsuda reaction is developed through the strategy of chiral anion phase transfer. Various chiral ketones could be obtained in high levels of enantioselectivity. A catalytic amount of dimethyl sulfoxide (DMSO) as an additive is crucial for the reaction to suppress the palladium-hydride-mediated side reactions.

Asymmetric α-Pentadienylation of Aldehydes with Cyclopropylacetylenes.

By employing readily available cyclopropylacetylene and its derivatives as the pentadienylation reagent, an asymmetric regioselective asymmetric α-pentadienylation reaction of aldehydes is developed by cooperative catalysis of a chiral Pd(0) catalyst and a chiral Brønsted acid in the presence of a subschoichmetric amount of an achiral amine. α-Pentadienylated aldehydes are afforded with high yields and enantioselectivities as well as excellent E/Z ratios.

Synthesis of Chiral Esters via Asymmetric Wolff Rearrangement Reaction.

The first asymmetric Wolff rearrangement reaction that directly converts α-diazoketones into broadly useful chiral α,α-disubstituted carboxylic esters with high enantioselectivities (up to 97.5:2.5 er) is reported. The cascade reaction proceeds through the seamless combination of visible-light-induced formation of the ketene intermediate and asymmetric ketene esterification using a readily available benzotetramisole-type catalyst.

Catalytic Generation of C1 Ammonium Enolates from Halides and CO for Asymmetric Cascade Reactions.

A general strategy for the design of asymmetric cascade reactions using readily available halides and carbon monoxide (CO) as substrates is developed. The key is the catalytic generation of C1-ammonium enolates for the subsequent asymmetric cascade reactions through the combination of palladium-catalyzed carbonylation and chiral Lewis base catalysis. Utilizing this strategy, we have established asymmetric formal [1+1+4] and [1+1+2] reactions to afford chiral dihydropyridones and ß-lactams with high yields and high enantio- and diastereoselectivities.

Access to chiral tetrahydrofluorenes through a palladium-catalyzed enantioselective tandem intramolecular Heck/Tsuji-Trost reaction.

A palladium-catalyzed enantioselective coupling of 2,5-cyclohexadienyl-substituted aryl iodides and carbon or heteroatom nucleophiles is described. The reaction proceeded via a tandem asymmetric Heck insertion and Tsuji-Trost allylation, enabling the rapid construction of valuable chiral tetrahydrofluorenes by using a chiral H8-BINOL-based phosphoramidite ligand.

Pd(II)-Catalyzed Asymmetric Oxidative Annulation of N-Alkoxyheteroaryl Amides and 1,3-Dienes.

The first Pd(II)-catalyzed asymmetric oxidative annulation of N-alkoxyaryl amides and 1,3-dienes is reported, which features particular applicability for quick assembly of different types of chiral heterocycles with high yields and enantioselectivities. A novel chiral pyridine-oxazoline bearing a methoxyl group at the C-5 position and a gem-dimethyl group on the oxazoline moiety was found to be crucial for conversion.

Enantioselective Synthesis of 5-Alkylated Thiazolidinones via Palladium-Catalyzed Asymmetric Allylic C-H Alkylations of 1,4-Pentadienes with 5 H-Thiazol-4-ones.

A palladium-catalyzed, enantioselective allylic C-H alkylation of 1,4-pentadienes with 5 H-thiazol-4-ones has been developed. Under the cooperative catalysis of a palladium complex of chiral phosphoramidite ligand and an achiral Brønsted acid, a broad range of substituted 5 H-thiazol-4-ones bearing sulfur-containing tertiary chiral centers were accessed from the allylic C-H alkylation in high levels of yields and enantioselectivities. Alkyl and aryl 1,4-pentadienes led to linear and branched allylation products, respectively.

[Adsorption of Methylene Blue and Cu(â ¡) by Activated Carbon/Macromolecule Composite Hydrogel].

Activated carbon/alginate/poly(vinyl alcohol) composite macromolecule hydrogels (CAP) were prepared as adsorbents to study their adsorption performance for methylene blue (MB) and Cu2+ in aqueous solution. The effect of dosage, pH, temperature, contact time, and initial concentrations of MB and Cu2+ on the adsorption process was investigated. SEM, FTIR, and BET analyses were conducted to identify the physicochemical properties of CAP. The results indicated that activated carbon was successfully loaded into the interconnected 3D porous network and CAP had rich -COOH and -OH groups. The surface area of the composite hydrogel was 112.7 m2·g-1. With the dosage and temperature increase, the adsorbed amount of MB and Cu2+ on CAP decreased, while with the increase in pH, the adsorbed amount increased. The adsorption isotherm was fitted to the Langmuir equation and the maximum monolayer adsorption capacities of MB and Cu2+ on CAP were 1940.75 and 190.48 mg·g-1, respectively. The adsorption was a fast process and 90% of the maximum adsorption capacity could be reached in 5 h. The kinetic data were fitted to the pseudo-second-order kinetic model reasonably well. CAP had excellent adsorption properties after five times of regeneration.

[Treating Simulated Dye Wastewater by an In Situ Copper Ferrite Process].

Four types of simulated dye wastewater containing methylene blue, tartrazine, Congo red, and crystal violet were treated by an in situ copper ferrite process, and the influencing factors of the operational parameters in this process were studied. The main mechanism of dye removal was suggested by reaction thermodynamics and solid products characterization for methylene blue removal. The results showed that an in situ copper ferrite process could effectively remove four kinds of simulated dyes by adjusting reaction conditions appropriately. The maximum capacities of the in situ copper ferrite process for methylene blue, crystal violet, tartrazine, and Congo red were 349.2, 382.2, 402.5 and 831.8 mg·g-1, respectively, under reaction condition of c(Cu2+) of 0.01 mol·L-1, c(Fe2+) of 0.025 mol·L-1, c(OH)/c(M)=1.7 (hydroxyl and metal molar ratio), reaction temperature of 40℃, and reaction time of 60 min. Comprehensive physical interactions, including a sweeping effect, encapsulation, and high active surface adsorption of the in situ Fe-Cu precipitates were the dominant mechanisms in dye removal by the process. Copper ferrite, as an effective magnetic adsorbent and a highly efficient environmental catalyst, was regenerated by magnetic separation, catalytic oxidation, and high temperature calcination.

Pd(II)-Catalyzed Asymmetric Oxidative 1,2-Diamination of Conjugated Dienes with Ureas.

A palladium(II)-catalyzed asymmetric 1,2-diamination of 1,3-dienes with readily available dialkylureas was established by using a chiral pyridine-oxazoline ligand. The diamination reaction exclusively occurs at the terminal C-C double bond of the 1,3-dienes to give 4-vinylimidazolidin-2-ones in high yields and with excellent levels of enantioselectivity (up to 99% yield, 97% ee). The reaction could feasibly be applied for gram-scale synthesis with a 1:1 ratio of the diene and the urea.