Triangular Halogen Bond and Hydrogen Bond Supramolecular Complex Consisting of Carbon Tetrabromide,Halide, and Solvent Molecule： A Theoretical and Spectroscopic Study

The theoretical calculation and spectroscopic experiments indicate a kind of triangular three bonding supramolecular complexes CBr4…X^-…-H-C, which consist of carbon tetrabromide, halide, and protic solvent molecule （referring to dichloromethane, chloroform and acetonitrile）, can be formed in solution. The strength of halogen and hydrogen bonds in the triangular complexes using halide as common acceptor obeys the order of iodide〉bromide〉chloride. The halogen and hydrogen bonds work weak-cooperatively. Charge transfer bands of halogen bonding complexes between CBra and halide are observed in UV-Vis absorption spectroscopy in three solvents, and then the stoichiometry of 1：1, formation constants K and molar extinction coefficients ε of the halogen bonding complexes are obtained by Benesi-Hildebrand method. The K and ε show a dependence on the solvent dielectric constant and, on the whole, obey an order of iodide〉bromide〉chloride in the same solvents. Furthermore, the C-H vibrational frequencies of solvent molecules vary obviously with the addition of halide, which indicates the C-H…X- interaction. The experimental data indicate that the halogen bond and hydrogen bond coexist by sharing a common halide acceptor as predicted by calculation.     

Theoretical study on the reaction mechanism of CN radical with ketene

The bimolecular single collision reaction potential energy surface of CN radical with ketene (CH2CO) was investigated by means of B3LYP and QCISD(T) methods. The calculated results indicate that there are three possible channels in the reaction. The first is an attack reaction by the carbon atom of CN at the carbon atom of the methylene of CH2CO to form the intermediate NCCH2CO followed by a rupture reaction of the C-C bond combined with -CO group to the products CH2CN CO. The second is a direct addition reaction between CN and CH2CO to form the intermediate CH2C(O)CN followed by its isomerization into NCCH2CO via a CN-shift reaction, and subsequently, NCCH2CO dissociates into CH2CN CO through a CO-loss reaction. The last is a direct hydrogen abstraction reaction of CH2CO by CN radical. Because of the existence of a 15.44 kJ/mol reaction barrier and higher energy of reaction products, the path can be ruled out as an important channel in the reaction kinetics. The present theoretical computation results, which give an available suggestion on the reaction mechanism, are in good agreement with previous experimental studies.     

Regioselective introduction of vinyl trifluoromethylthioether to remote unactivated C(sp~3)–H bonds via radical translocation cascade

Described herein is an efficient protocol for the regioselective introduction of a vinyl trifluoromethylthioether to remote unactivated C(sp~3)–H bonds. The cascade process involves the vinyl radical-mediated 1,5-hydrogen atom transfer(HAT) and remote vinyl migration. During the transformation, inert C–H and C–C bonds are consecutively cleaved under mild conditions.The reaction features good functional group tolerance, broad substrate scope, and high regio-/stereo-selectivity.     

Selective nickel-electrocatalyzed benzylic C–H oxygenation of functionalized alkyl arenes

Herein, a site-selective paired electrochemical C–H oxidation of functionalized alkyl arenes promoted by nickel catalyst is disclosed. A Ni(Ⅱ)-dioxygen species formed in situ efficiently enable the oxidation process under mild conditions with a broad substrate scope with excellent functional group compatibilities,such as free carboxylic acid, aldehyde, halogen(including aryl iodide), amide and amino acid. The use of the nickel catalyst in combination with water provides a safe, green and economi...     

All-at-once arrangement of both oxygen atoms of dioxygen into aliphatic C(sp~3)–C(sp~3) bonds for hydroxyketone difunctionalization

Both β-and γ-hydroxyketone structures are important units in biologically active molecules, synthetic drugs and fine chemicals.Although there are some routes available for their manufacture from pre-functionalized groups on one or two matrix molecule(s),the approaches to simply and simultaneously deposit two oxygen atoms from dioxygen into two specific C(sp~3) positions of pure saturated hydrocarbons have rarely succeeded because they are involved in the targeted activation of three inert C–H σ bonds all at once. Here, we show that a TiO_2-CH_3CN photocatalytic suspension system enables the insertion of dioxygen into one C(sp~3)–C(sp~3) bond of strained cycloparaffin derivatives, by which difunctionalized hydroxyketone products are obtained in a one-pot reaction. With the cleavage event to release strain as the directional driving force, as-designed photocatalytic reaction systems show 21 examples of β-hydroxyketone products with 31%–76% isolated yields for three-membered ring derivatives and 5 examples of γ-hydroxyketone products with 30%–63% isolated yields for four-membered ring substrates.~(18)O isotopic labeling experiments using ~(18)O_2, Ti~(18)O_2 and intentionally added H_2~(18)O, respectively, indicated that both oxygen atoms of hydroxyketone products were exclusively from dioxygen, suggesting a previously unknown H+/TiO_2-e-catalyzed arrangement pathway of the hydroperoxide intermediate to convert dioxygen into hydroxyketone units.     

Fabrication of polymersomes with controllable morphologies through dewetting w/o/w double emulsion droplets

In this work, monodisperse giant polymersomes are fabricated by dewetting of water-in-oil-in-water double emulsion droplets which are assembled by amphiphilic block copolymer molecules in a microfluidic device. The dewetting process can be tuned by solvation between solvent and amphiphilic block copolymer to get polymersomes with controllable morphology. Good solvent(chloroform and toluene) hinders dewetting process of double emulsion droplets and gets acornlike polymersomes or patched polymersomes. On the other hand, poor solvent(hexane) accelerates the dewetting process and achieves complete separation of inner water phase from oil phase to form complete bilayer polymersomes. In addition, twin polymersomes with bilayer membrane structure are formed by this facile method. The formation mechanism for different polymersomes is discussed in detail.     

Mechanism of rhodium(Ⅲ)-catalyzed formal C(sp~3)-H activation/spiroannulation of a-arylidene pyrazolones with alkynes:A computational study

The rhodium-catalyzed formal C(sp~3)-H activation/spiroannulation of a-arylidene pyrazolones with alkynes was investigated by means of density functional theory calculations. The calculations indicate that the spiroannulation through the proposed C—C reductive elimination is kinetically unfeasible.Instead, the C—C coupling from the eight-membered rhodacycle was proposed to account for the experimental results. The overall catalytic cycle consists of six steps:(1) the keto-enol isomerization;(2)the O—H deprotonation,(3) the C(sp~2)—H bond cleavage;(4) the migratory insertion of alkyne into the Rh—C bond;(5) the C—C coupling and(6) the regeneration of the active catalyst.     

Generation of sulfonylureas under photoredox catalysis and their biological evaluations

Traditional synthesis of sulfonylureas largely depends on nucleophilic addition of arylsulfonamides to presynthesized isocyanates.Now we report a new access to alkylsulfonylureas with good yields and broad substrate scope.With the insertion of commercialized chlorosulfonyl isocyanate under photoredox catalysis,alkylsulfonylureas are synthesized in one-pot from the corresponding anilines and silyl enolates.A reaction mechanism is proposed showing the transformation undergoes a radical process,and...     

Transformations of N-arylpropiolamides to indoline-2,3-diones and acids via C≡C triple bond oxidative cleavage and C(sp^2)–H functionalization

A new palladium-catalyzed oxidative conversion of N-arylpropiolamides and H2O to various indoline-2,3-diones and acids through the C≡C triple bond cleavage and C(sp2)–H functionalization is described,which is promoted by a cooperative action of catalytic CuBr2,2,2,6,6-tetramethyl-1-piperidinyloxy(TEMPO)and O2.The method provides a practical tool for transformations of alkynes by means of a C–H functionalization strategy,which enables the formation of one C–C bond and multiple C–O bonds in a single reaction with high substrates compatibility and excellent functional group tolerance.     

Catalyst-free,radical-mediated intermolecular 1,2-arylheteroarylation of alkenes by cleaving inert C–C bond

A novel photoinduced intermolecular 1,2-arylheteroarylation of alkenes and the efficient synthesis of valuable polyarylalkanes are reported. The reaction is operationally simple, proceeds under mild conditions and with no additional catalyst and reagents.The strategically designed radical cascade reaction is enabled by electron transfer, and involves cleavage of an inert C–C bond.The process features broad functional group compatibility as well as high product transformability.     

C–F bond activation under transition-metal-free conditions

The unique properties of fluorine-containing organic compounds make fluorine substitution attractive for the development of pharmaceuticals and various specialty materials, which have inspired the evolution of diverse C–F bond activation techniques.Although many advances have been made in functionalizations of activated C–F bonds utilizing transition metal complexes,there are fewer approaches available for nonactivated C–F bonds due to the difficulty in oxidative addition of transition metals to the inert C–F bonds. In this regard, using Lewis acid to abstract the fluoride and light/radical initiator to generate the radical intermediate have emerged as powerful tools for activating those inert C–F bonds. Meanwhile, these transition-metal-free processes are greener, economical, and for the pharmaceutical industry, without heavy metal residues. This review provides an overview of recent C–F bond activations and functionalizations under transition-metal-free conditions. The key mechanisms involved are demonstrated and discussed in detail. Finally, a brief discussion on the existing limitations of this field and our perspective are presented.     

Investigation of Quantitative Relationship between Adsorbed Amount of Solute and Solvent Concentration at Relatively High Solute Con－centration by Frontal Analysis in RPLC

In previous paper a new adsorption isotherm which relates the amount of solute absorbed to the solvent concentration is pro-posed and simplified, and it only can be used at lower solute concentration. In this article the scope of the new adsorption isotherm is extended and the expressions with three and four parameters are obtained. The equations with multi-parameters are valid when the adsorbed mounts are larger and show non-linear logarithmic relationships. Tests with a homologue of are-matic alcohols by frontal analysis in reversed phase liquid chro-matography demonstrate that the experimental results fit those equations well. In addition, the predicted values by the multi-parameters were found to fit the experimental values well also. The parameters have physical meaning only for the two-param-eter equation for the aromatic alcohols.     

Palladium-catalyzed oxidative cyclopropanation of enamides and norbornenes initiated by C–H activation

A novel palladium-catalyzed oxidative cyclopropanation of enamides and norbornenes has been developed. The reaction proceeded through palladium-catalyzed vinyl C–H bond activation of enamides followed by two migratory insertions, β-(N)H elimination and hydrolyzation cascade steps. The reaction tolerates a range of functional groups and provides an effective method for the synthesis of cyclopropane-fused norbornanes in good yields under mild conditions.     

C(sp~3)–H bond functionalization of non-cyclic ethers by decarboxylative oxidative coupling with α,β-unsaturated carboxylic acids

A copper-catalyzed decarboxylative oxidative coupling of α,β-unsaturated carboxylic acids with non-cyclic ethers is developed.This method provides a new approach for C(sp~3)–H bond functionalization of non-cyclic ethers. Mechanism study shows the reaction involves a radical process.     

Metallaphotoredox⁃Catalyzed O⁃Arylation of Serine北大核心CSCD

A metallaphotoredox catalyzed hydroxyl aromatization of serine is developed to achieve rapid synthesis of aryl ethers of various serine derivatives. Under the catalytic system of ethylene glycol dimethyl ether nickel bromide （NiBr2 （dme））/4,4'-dimethoxy-2,2'-bipyridine/zinc powder and synergistic iridium photoredox catalysis, nickel is catalyzed and inserted into the C—Br bond, and then followed by transmetalation with the hydroxyl group of serine. The resulting Ni（Ⅱ）species are oxidized by the excited Ir（Ⅲ）species to a Ni（Ⅲ）intermediate. This intermediate is unstable and reductive elimination takes place rapidly to give the target product O-arylated serine in the yields from 65% to 39%. Through a metallaphotoredox catalysis strategy,the reaction features mild,efficient,clean and broad scope of substrate, providing a new way for the synthesis of various serine derivatives with medicinal value. © 2022, Science Press (China). All rights reserved.     

Putting aniline radical cations in a bottle

Salts containing aniline radical cations have been isolated and characterized by electron paramagnetic resonance(EPR)spectroscopy, UV-Vis absorption spectroscopy and single crystal X-ray diffraction. The EPR spectra and theoretical calculations indicate the unpaired electron is delocalized on phenyl rings and nitrogen atoms. Both radical cations feature a quinoidal geometry with a partially double C–N bond, but are distinct in that the C–N bond is coplanar to the phenyl plane in one cation while deviates from the plane in the other due to steric crowding. The work provides the first unequivocal examples of stable aniline radical cations.     

Regioselective 1,2-Addition of Ti(IV)-enolate to α, β–Unsaturated Compounds

The nucleophilic addition to α, β-unsaturated carbonyl compounds is a fundamental C-C bond forming reaction in organic chemistry1. Since there are two reaction sites in the α, β–unsaturated carbonyl group, the regioselectivity of the nucleophilic addition (1, 2 vs. 1, 4 addition) is of primary importance when applying this type of reaction in organic synthesis. Factors that control the regioselectivity include the softness and hardness of the attacking nucleophiles2, solvent and temperatu…     

DFT Study on the Germanium Ion Activated C–H Bond in Methane

Thermal reactions of methane with the main group metal cations Ge~+,GeO~+,GeOH~+ and OGeOH~+ were investigated by state-of-the-art quantum chemical calculations.For GeO~+/CH_4,a H atom in CH_4 abstracted by the O atom in GeO~+ to form GeOH~+ and CH_3˙constitutes the channel mainly.The barrier-free process,combined with a large exothermicity,suggested a fast and efficient reaction in agreement with the experiment.For OGeOH~+ and CH_4,the intermediates and products of the most favorable path were below the reactant asymptote,and the reaction was easy to take place,while for Ge~+ and GeOH~+,the activation of C–H bond in methane was hard to happen under ambient temperature.The results showed,in contrast to the inertness of Ge~+ and Ge OH~+,the GeO~+ and OGeOH~+ can activate the H_3C–H bond.The NBO natural charge and molecular electrostatic potential were used to analyze the four main group metal germanium constructions.The phenomenon suggested that ligands affect the electronic character and tune the chemical features of metal germanium center.     

Recent advances in synthesis of organosilicons via radical strategies

Organosilicon compounds play an important role in the fields of materials science,pharmacy,and organic synthesis.The development of effective approaches for the preparation of these compounds have also become a research focus in organic synthesis.In recent years,free radical synthesis of organosilicons has been vigorously developed,which generally has the advantages of milder synthesis conditions,higher yields and selectivity,and free of precious metal catalysts compared with traditional strategies.This article reviews research progresses in the synthesis of organosilico n compounds by free radical pathways since 2016.In most cases,the radical silylation is achieved based on the reaction of silyl radicals,which are triggered by four routes including peroxide,transition-metal-induced peroxide decomposition,alkali,photocatalysis.The alkyl radicals can also initiate the radical silylation for the generation of C(sp~3)—Si bonds.     

Scission of C–O and C–C linkages in lignin over RuRe alloy catalyst

The performance of lignin depolymerization is basically determined by the interunit C–O and C–C bonds.Numerous C–O bond cleavage strategies have been developed, while the cleavage of C–C bond between the primary aromatic units remains a challenging task due to the high dissociation energy of C–C bond.Herein, a multifunctional Ru Re alloy catalyst was designed, which exhibited exceptional catalytic activity for the cleavage of both C–O and C–C linkages in a broad range of lignin model compounds(β...