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The effects of the number of imidazoline ring and the length of alkyl group chain of imidazoline derivatives were investigated using quantum chemical calculation, molecular dynamics simulation and experimental techniques. Three corrosion inhibitors including Symmetrical lauric acid imidazoline (SAI), Tetracyclic lauric acid imidazoline (LAI), and Symmetric stearic acid imidazoline (SPI) were synthesized and their inhibition performance was evaluated using weight loss measurement, electrochemical techniques and surface characterization. The results show that SAI and LAI with the same length of alkyl group chain, LAI with more imidazoline rings could supply a better inhibition performance since the increase of active sites. The increase of active sites attached to the metal surface may also change the distribution of corrosion inhibitor, which could limit inhibition performance improvement. While, SAI and SPI with the same number of imidazoline rings, SPI with longer alkyl group chain shows a better inhibition efficiency due to the better hydrophobic performance of alkyl groups. Among the three inhibitors, SPI show the best inhibition performance, indicating that the alkyl group chain length affects the inhibition performance more obvious than the number of the imidazoline rings.

A Pd-catalyzed carbonylative double cyclization approach to a novel class of S,O-bicyclic heterocycles is presented. It is based on the reaction between readily available 5-(methylthio)pent-1-yn-3-ols with CO in the presence of the PdI2/KI catalytic system carried out under oxidative conditions with oxygen as external oxidant. The process takes place through an ordered sequence of steps involving an initial 5-exo-dig S-cyclization (by intramolecular nucleoplilic attack by the thiomethyl group to the triple bond activated by coordination to the palladium center), followed by S-demethylation (by attack by the iodide anion), carbon monoxide insertion, O-cyclization (by intramolecular nucleophilic displacement of the hydroxyl group to the ensuing acylpalladium intermediate), and Pd(0) reoxidation. The method allows the construction of previously unreported 6,6a-dihydrothieno[3,2-b]furan-2(5H)-ones starting from simple substrates (5-(methylthio)pent-1-yn-3-ols and CO) with the formation of 3 new bonds and two cycles in one step, and has been successfully applied to the synthesis of variously substituted products (57–81 %, 17 examples).

Migratory insertion is a fundamental organometallic transformation that enables the functionalization of an unsaturated bond. Recent reports on catalytic hydroamination provide evidence that supports an intermolecular migratory insertion pathway featuring alkene insertion into metalnitrogen (M-N) bonds. This article presents factors influencing the rate of migratory insertion in latetransition metal-catalyzed hydroamination, including steric and electronic effects from ligands, alkenes, and metal centers, along with stabilization from coordinated amine intermediates and ordered transition states.

The first intermolecular electrophilic dearomatization of halonaphthols with benzyl/allyl bromides is described. Halonaphthols are used as carbon-nucleophiles in dearomatization to form three-dimensional cyclic enones with excellent chemoselectivity, in which etherification of phenolic hydroxyl group could be restrained well by using cesium carbonate as the base. A wide range of cyclic enones is directly prepared from various substituted benzyl/allyl bromides and halonaphthols. Mechanistic investigations suggest a direct SN2 reaction pathway.

The tandem reaction of photoinduced double hydrogen-atom transfer and deoxygenative transborylation for chemo- and site-selective reduction of nitroarenes into aryl amines under catalyst-free, room temperature conditions was disclosed in excellent yields. In this reaction, isopropanol (iPrOH) was used as hydrogen donor and tetrahydroxydiboron [B2(OH)4] as deoxygenative reagent with green, cheap, and commercially available credentials. In particular, a wide range of reducible functional groups such as halogen (-Cl, -Br, and even -I), alkenyl, alkynyl, aldehyde, ketone, carboxyl, and cyano are tolerated. Moreover, the reaction preferentially reduces the nitro group at the electron-deficient site over another nitro group in the same molecule. A detailed mechanistic investigation in combination of experiments and theoretical calculations gave a reasonable explanation for the reaction pathway.

Abstract: A facile methodology has been developed to build carbon nitrogen double bond from ketones promoted by the hydroxyl groups in β-phenol hydroxy ketone. It is noteworthy that the halogenated β-phenol hydroxy ketone can chemoselectively react with the amine to afford halogenated phenol imine. It is suitable for certain natural products and also suitable for water-based heteroamines. The method possesses low toxicity and is widely applicable. This strategy is usually used to obtain moderate to good yields of aromatic amine Schiff base.

A Lewis acid-catalyzed [4 + 2] cycloaddition of 3-alkyl-2-vinylindoles with β,γ-unsaturated α-ketoesters has been established in the presence of Sc(OTf)3, which afforded a series of indole-containing pyran derivatives in generally good yields (up to 90% yield) with excellent diastereoselectivities (up to >95:5 dr) under mild conditions. This approach not only enriches the chemistry of 3-alkyl-2-vinylindoles, but also has provided an atom-economic method for the synthesis of indole-containing pyran derivatives with potential bioactivity.

The selective synthesis of N2-sulfonyl and N2-H 1,2,3-triazoles via organocatalytic annulation of enaminone/enaminoester with sulfonyl azide has been realized. The unconventional selectivity providing N2-sulfoyl 1,2,3-triazoles takes place in pure water, wherein the hydrogen bond effect between water and the intermediate resulting from enamine-azide corporation accounts for the novel reaction selectivity. On the other hand, the reactions conducted in DMSO specifically afford N2-H 1,2,3-triazoles in the absence of such hydrogen bond effect.

In this paper, we developed an electrophilic ring-opening reaction, which is beyond the strained small ring system. Under reductive nickel catalysis, ring-opening of diverse benzofurans via endocyc...

Three bench-stable difluoromethylene phosphonate hydrazones were prepared from simple diethyl(difluoromethyl)phosphonate within two steps in good yields. The [3 + 2] cycloaddition reaction of these diazo precursors with aryl diazonium salts has been accomplished under metal-free conditions with exclusive regioselectivity. This transformation provides practical access to a broad panel of 2-aryl-2H-tetrazol-5-yl difluoromethylene phosphonates, including the corresponding derivatives of amino acid (phenylalanine) and drug cores (Pomalidomide and Lapatinib fragment).

A straightforward synthesis of indolizines and pyrrolo[1,2-a]pyrazines was performed through a cascade condensation/cyclization/aromatization reaction of substituted 2-formyl-N-propargylpyrroles with active methylene compounds such as nitromethane, alkyl malonates, methyl cyanoacetate and malononitrile. Under basic conditions, the reaction proceeded satisfactorily to provide the corresponding 6,7-disubstituted indolizines. The condensation of the pyrrolic analogues with ammonium acetate gave rise to pyrrolo[1,2-a]pyrazines in high yields. N-Allenyl-2-formylpyrroles behaved as more reactive substrates than 2-formyl-N-propargylpyrroles, furnishing the expected indolizines in higher yields. Hence, an allenyl-containing intermediate was probably generated as the reactive species in the reaction mechanism of some N-propargyl pyrroles prior to the cyclization reaction.

Already 1 mol-% of subvalent [Ga(PhF)2]+[pf]– ([pf]– = [Al(ORF)4]– , RF = C(CF3)3) initiates the hydrosilylation of olefinic double bonds under mild conditions. Reactions with HSiMe3 and HSiEt3 as substrates efficiently yield anti-Markovnikov and anti-addition products, while bulkier substrates like HSiiPr3 are less reactive. Investigating the underlying mechanism by gas chromatography and STEM analysis, we unexpectedly found that H2 and metallic Ga0 formed. Without addition of the olefin, the formation of R3Si–F–Al(ORF)3 (R = alkyl) was observed, a typical degradation product of the [pf]– anion in the presence of a small silylium ion. Electrochemical analysis revealed a surprisingly high oxidation potential of univalent [Ga(PhF)2]+[pf]– in the weakly coordinating, but polar ortho-difluorobenzene of E1/2(Ga+/Ga0; oDFB) = +0.26–0.37 V vs. Fc+ /Fc (depending on the scan rate). Apparently, the subvalent Ga+, mainly known as reductant, initially oxidizes the silane, and generates a highly electrophilic, silane-supported, silylium ion representing the actual catalyst. Consequently, the [Ga(PhF)2]+[pf]– /HSiEt3 system also hydrodefluorinates C(sp3)–F bonds in 1-fluoroadamantane, 1-fluorobutane and PhCF3 at room temperature. In addition, both catalytic reactions may also be initiated by using only 0.2 mol-% of [Ph3C]+[pf]– as silylium ion generating initiator. These results indicate that silylium ion-catalysis is possible with the straight forward accessible weakly coordinating [pf]– anion. Apparently, the kinetics of hydrosilylation and hydrodefluorination are faster than that of anion degradation under ambient conditions. These findings open new windows for main group catalysis.

Compound dimethyl pyridine-2,6-dicarboxylate (1) was synthesized via the reaction of pyridine-2,6-dicarboxylic acid with methanol. Pyridine-2,6-dicarbohydrazide (2) was synthesized via the reaction of compound (1) with hydrazine hydrate compounds of N,N-bis-(sub. benzylidine) pyridine-2,6-dicarbohydrazide (3–8) were synthesized Via the reaction of compound (2) with aromatic aldehyde compounds of N,N-bis(3-chloro(sub,phenyl)-4-oxoazetine-1-yl-pyridine)-2,6-dicarboxamide (9–14) were synthesized via the reaction of compounds (3–8) with chloro acetyl chloride the biological activity for some compounds were tested the synthesized compounds were identified by I.R, C13.N.M.R, H1.N.M.R and melting point.

A silver-catalyzed, K2S2O8-mediated protocol to access regioselective acylarylation of unactivated alkenes was developed. The reaction between N-allyl-indoles and α-oxocarboxylic acids proceeded smoothly and involved an acyl radical addition/C–H cyclization cascade. The protocol showed a broad substrate scope and good tolerance of functional groups. The reaction proceeded with both internal and terminal alkenes to furnish many functional pyrrolo[1,2-a]indoles bearing the ketone carbonyl group, and this feature also provides the potential to construct structurally complex N-containing heterocycles.

In this work, cyclic (alkyl)(amino)carbene copper ((CAAC)Cu) catalyzed aerobic oxidation of aldehydes in water at room temperature has been reported. Good to excellent yields were obtained using different substrates. A possible reaction mechanism was proposed, in which (CAAC)Cu dioxygen activates the C-H bond of aldehyde with a low barrier of 10.6 kcal mol-1.

Density functional theory calculations were performed on a prototype of three-component reactions involving aryl iodides, 2,6-substituted aryl bromides, and acrylates to understand the construction of axially chiral biaryls through the palladium/chiral norbornene cooperative catalysis (Nat. Catal. 2020, 3, 727733). The reaction is established to occur in sequence through oxidative addition of aryl iodide to Pd(0), norbornene insertion, CH activation, oxidative addition of aryl bromide to Pd(II), CC reductive elimination, norbornene extrusion, alkene insertion, and -H elimination. The CH activation is characterized as the rate-determining step, and the oxidative addition of aryl bromide on Pd(II) control the enantioselectivity of the reaction. The construction of more favorable (S)-CC axial chirality is attributed to the smaller steric repulsion between the ortho-methyl group of aryl bromide and the norbornene moiety. The theoretical results rationalize the reaction sequence of aryl iodide and aryl bromide on both Pd(0) and Pd(II) and clarify the substantial role of the ortho-ester group in the aryl bromide.

Here in we report Ag(I)-promoted homo-dimerization of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes for the synthesis of structurally novel and functionalized naphthalene derivatives. This transformation has exhibited a broad scope for the alkyl as well as aryl groups present on alkynes. Observations made from the control experiments, had suggested the possible mechanism as i) homo-dimerization of in situ generated benzopyrylium ion intermediates through a head–tail [4+2] cycloaddition, followed by ii) the competitive aromative ring-opening vs. decarbonylative aromatization of the adduct to give the formylated and deformylated naphthalenes respectively.

A series of heterobimetallic PdII/MII complexes (MII = Mn, Co) were synthesised and tested as precatalysts for sequential Sonogashira coupling–alkyne semi-hydrogenation reactions to form Z-aryl alkenes. The carbometalated heterobimetallic PdII/CoII complex CoPdL3’ demonstrated an apparent cooperative effect compared to the corresponding monometallic counterparts. This compound was identified as a potent single-molecule catalyst for the one-pot Cu-free Sonogashira coupling of aryl bromides with terminal alkynes followed by chemo- and stereoselective semi-hydrogenation of the alkyne intermediate using NH3·BH3 as a hydrogen source. Furthermore, different aromatic substrates have been tested to show the generality of the reaction for the synthesis of Z-alkenes, including biologically active combretastatin A-4. In addition, the homogeneous nature of the catalytically active species was demonstrated.

Die enantiomerenreinen Valenzisomere (+)-und(−)−1 sowie (+)- und (−)−2 konnten als erste ihrer Art isoliert werden. Diese Verbindungen mit nichtplanaren, cyclisch konjugierten π-Elektronensystem und lokalisierten π-Bindungen im Grundzustand stehen miteinander im dynamischen Gleichgewicht. Die kinetischen Daten der dynamischen Prozesse - Ringinversion und Doppelbindungsverschiebung -wurden ebenfalls bestimmt (R=H, Me).

We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10-phenanthroline), formed as an intermediate during the Zn(OAc)2 /phen-catalyzed synthesis of organic carbamates from CO2 , amines, and the reusable reactant Si(OMe)4 . Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe)4 proceeds via a five-coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe)4 as the reaction solvent and additives like KOMe and KF, which promote the formation of the five-coordinated silicon species. This sustainable and effective method can be used to synthesize various N-aryl and N-alkyl carbamates, including industrially important polyurethane raw materials, starting from CO2 under atmospheric pressure.

We report here an iridium-catalyzed hydroalkynylation of allylic alcohols protected by an oxime group. Catalytic alkynylation occurs exclusively at the distal position of the alkene. This method generates γ-alkynyl alcohol oximes directly from internal alkenes and terminal alkynes. The oxime group can be readily removed to afford a free alcohol, thus providing an indirect route for the catalytic hydroalkynylation of allylic alcohols.

The title complex, systematic name catena-poly[[[acetatochloridozinc(II)]-μ-(5R,6R,7S)-5-(furan-2-yl)-7-phenyl-4,5,6,7-tetrahydro[1,2,4]triazolo[1,5-a]pyrimidin-6-amine] monohydrate], {[Zn(C2H3O2)Cl(C15H15N5O)]·H2O} n , is the first coordination complex in which the neutral tetrahydrotriazolopyrimidine derivative acts as bridging ligand between two zinc molecules. As a result, polymeric chains of the coordination complex are found. The coordination of the zinc metal atom occurs with the lone pairs of the triazolo nitrogen atom and amino group. The positive charge of the zinc atom is compensated by the chlorine anion and deprotonated acetic acid. The coordination complex exists as a monohydrate in the crystalline phase. The water molecules bind neighbouring polymeric chains by the formation of O—H...O, O—H...Cl and N—H...O hydrogen bonds.

Remote ether groups could be used as directing groups to prepare fully substituted 5-ether-1,2,3-triazoles with exclusive 1,5-regioselectivities and excellent chemoselectivities. Ether group could coordinate with iridium catalyst by lone-pair electron at a distance (up to four σ bonds) away from alkyne to control the regioselectivity by weak coordination effect. The cycloaddition reaction chemoselectively occurred at the propargyl ether moiety of diyne to give unique fully substituted 4-alkynyl-triazole.

Background: 4,4′-isopropylidenediphenol (BPA) hydrogenated to 2,2-bis(4-hydroxycyclohexyl) propane (HBPA) is a simple way to reduce its toxicity and environmental impact. In addition, the higher trans/trans HBPA moiety in polymer will has better mechanical properties. Therefore, how to prepare trans/trans HBPA via hydrogenation is an important issue. Method: One-dimensional nickel-palladium catalyst was successfully synthesized via reduction by an external magnetic field. The high ratio of trans/trans HBPA was characterized by FTIR, GC/MS, and NMR, respectively. The adsorption behavior of BPA and its half-hydrogenated intermediates was studied by Material Studio software. Significant findings: The pd nanoparticles immobilized on the magnetization of 1-D Ni catalyst with high amount of Ni(111) plane is the novelty of this research. The conversion of BPA was high to 100% and the ratio of trans/trans HBPA was over than 75% at 180 °C and 70 kgf/cm2 in isopropanol medium. The trans/trans ratio of HBPA was slightly increasing as increasing hydrogen pressure and decreasing reaction temperature. Reaction intermediate was selected with the aid of molecular simulation. Moreover, the reaction path of BPA hydrogenated by one-dimensional nickel-palladium catalyst was proposed that BPA was firstly hydrogenated to tetrahydro intermediate and followed roll-over mechanism to obtain trans/trans HBPA product.

The alkyl substituent(s) in the scaffold of the alkylphosphanyl PNP ligands of the form Ph2PN(cyclopentyl)PPhR, Ph2PN(cyclopentyl)PR2, and RPhPN(cyclopentyl)PPhR have been observed to have a marked impact on the catalytic performance of Cr(III) catalysts in ethylene oligomerization reactions. Precatalyst 6, bearing diisopropylphosphanyl substituent, afforded the highest catalytic activity of 4490 kg(product)·g(Cr)−1·h−1 and 51.0% C8 selectivity with good product purity under suitable conditions. Precatalyst 7, having diethylphosphanyl substituent in the PNP scaffold, exhibited 72.0% high C8 selectivity with 1717 kg(product)·g(Cr)−1·h−1 improved catalytic activity. Precatalysts based on monoalkylphosphanyl PNP (2–4) and symmetrical alkylphosphanyl PNP (9–10) exhibited poor catalytic performance toward selective ethylene oligomerization. Single crystal analysis suggested that the alkyl substituents in the scaffold of the alkylphosphanyl PNP ligands may effectively induce the complex structure and consequently the catalytic performance. Density functional theory (DFT) calculations revealed that in comparison to the trimerization pathway, the rate-determining states in the tetramerization pathways of precatalysts 6–7 may face low energy barriers and therefore may offer high C8 selectivity.

Methylation of aromatic compounds is a key reaction step in various industrial processes such as the aromatic cycle of methanol-to-hydrocarbons chemistry. The study of isolated methylation reactions and of the influence of catalyst acidity on their kinetics is a challenging task. Herein, we have studied unidirectional metal-substituted H-MeAlPO-5 materials to evaluate the effect of acid strength on the kinetics of benzene methylation with DME. First-principle simulations showed a direct correlation between the methylation barrier and acid site strength, which depends on the metal substituent. Three H-MeAlPO5 catalysts with high (Me = Mg), moderate (Me = Si) and low acidity (Me = Zr) were experimentally tested, confirming a linear relationship between the methylation activation energy and acid strength. The effects of temperature and reactant partial pressure were evaluated, showing significant differences in the byproduct distribution between H-MgAlPO-5 and H-SAPO-5. Comparison with propene methylation suggested that the Mg substituted catalyst is also the most active for the selective methylation of alkenes. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The anionic tetrakis-complex of lanthanum(III) NMe4LaL 4 with the CAPh-ligand dimethyl (2,2,2-trichloroacetyl)phosphoramidate (HL), namely, tetramethylammonium tetrakis{2,2,2-trichloro-1-[(dimethoxyphosphoryl)imino]ethanolato}lanthanum(III), (C4H12N)[La(C4H6Cl3NO4P)4], has been synthesized, crystallized and structurally characterized by X-ray diffraction. The lanthanide ion is surrounded by four anionic, bis-chelating CAPh ligands forming the complex anion with a coordination number of eight for La3+ and NMe4 + as the counter-ion. The coordination polyhedron of the La3+ ion was interpreted as a triangular dodecahedron.

Pyridinium 1,4-zwitterionic thiolates were applied to a formal [3 + 2] annulation reaction with modified activated alkynes, affording various tetrasubstituted thiophenes with aryl, alkenyl, alkyl or silyl group at the special position. The structural modification of alkyne substrates enabled the synthesis of diverse thiophenes to be achieved using the pyridinium 1,4-zwitterionic thiolates as the sulfur-containing building blocks. This approach is metal-free and catalyst-free.

Cu-catalyzed endo-selective asymmetric 1,3-dipolar cycloaddition of azomethine ylides with ethenesulfonyl fluorides (ESFs) was successfully developed, this protocol provided an efficient and facile method to a wide range of chiral pyrrolidine-3-sulfonyl fluorides with good to excellent results (up to 87% yield, >20:1 dr, 94% ee). Some other chiral sulfonyl derivatives, such as sulfonamide and sulfonate, were easily accessible through simple transformations with high yields, which demonstrated that the cycloaddition products could be synthetically useful in the sulfur(VI) fluoride exchange (SuFEx) chemistry.

Pt/ZrO2 catalysts promoted with MoO3 and Nb2O5 were tested for the combustion of short-chain alkanes (namely, methane, ethane, propane, and n-hexane). For short-chain alkane combustion, the inhibition of MoO3 (for the methane reaction) dramatically transformed to promotion (for the ethane, propane, and n-hexane reactions) as the carbon chain length increased, whereas the remarkable promotion of Nb2O5 gradually weakened with an increase in the carbon chain length. Based on a detailed study of the oxidation reactions of methane and propane over the catalysts, the different roles of the promoters in the reactions were ascribed to differences in the acidic properties of the surface and the oxidation or reduction states of the Pt species. The MoO3 promoter could decorate the surface of the Pt species for a Pt-Mo/ZrO2 catalyst, whereas the Nb2O5 promoter on the support could be partially covered by Pt particles for a Pt-Nb/ZrO2 catalyst. The formation of accessible Pt-MoO3 interfacial sites, a high concentration of metallic Pt species, and a high surface acidity in Pt-Mo/ZrO2 were responsible for the enhanced activity for catalytic propane combustion. The lack of enough accessible Pt-Nb2O5 interfacial sites but an enhanced surface acid sites in Pt-Nb/ZrO2 explained the slight improvement in activity for catalytic propane combustion. However, the stabilized Ptn+ species in Pt-Nb/ZrO2 were responsible for the much-improved activity for methane combustion, whereas the Ptn+ species in Pt-Mo/ZrO2 could be reduced during the oxidation reaction, and the fewer exposed surface Pt species because of MoO3 decoration accounted for the inhibited activity for methane combustion. In addition, it can be concluded that MoO3 promotion is favorable for the activation of C–C bonds, whereas Nb2O5 promotion is more beneficial for the activation of C–H bonds with high energy.

The Grubbs G-I or G-II catalyst gives the ruthenium ethoxy carbene complex, which catalyzes ring-opening cross metathesis (ROCM) of a strained cyclic alkene to give a diene where one of the two alkene moieties in the product contains an ethoxy substituent. No polymeric products are detected. Hydrocarbons such as parent norbornene or substituted cyclopropenes can proceed with the reaction smoothly. Tertiary amines, N-alkylimides, esters, and aryl or alkyl bromides remain intact under the reaction conditions. In addition to vinyl ethers, vinylic esters can also be used. The time required to reach a 50% yield of the ROCM product t50 varies from 0.01 to 140 h depending on the strain and nucleophilicity of the double bond. Anchimeric participation of an electron-rich group would result in significant enhancement of the reactivity, and the t50 could be as short as several minutes. A similar substrate without such a neighboring group shows a much slower rate. An exo-norborne derivative reacts much faster than the corresponding endo-isomer. Alkenes with poor nucleophilicity are less favored for the ROCM process, so is less strained cyclooctene.

Sulfenylation or selenylation of enaminones of l-α-amino esters requires mild reaction conditions due to the presence of a racemization-prone chiral center and reactive side chains. An N-chlorosuccinimide (NCS)-mediated methodology has been developed for rapid sulfenylation of enaminones of l-α-amino esters and aryl/alkyl amines at room temperature in open air under metal-free conditions. Enaminones of l-α-amino esters bearing aliphatic, aromatic, and heterocyclic side chains react efficiently with diverse aryl/alkyl/heteroaryl thiols (R1SH) in the presence of NCS to afford a library of biologically important sulfenyl enaminones in good-to-excellent yields (71–90%). Under similar reaction conditions, the enaminones also react with benzeneselenol to produce selenyl enaminones in good yield (73–83%). The NCS-mediated pathway generates sulfenyl chloride (R1SCl) as an intermediate which leads to rapid sulfenylation of enaminones through cross-dehydrogenative coupling (CDC) under mild reaction conditions.

A simple and practical protocol for the C3–H regioselective halogenation of 4-quinolones by the action of potassium halide salt and PIFA/PIDA in good to excellent yields was developed. The current approach provides feasible access to the diversity of C3-halgenated 4-quinolones at room temperature with high regioselectivity and good functional group tolerance, from which bioactive compounds can be easily constructed. Moreover, the current method featured eco-friendly, operational convenience and is suitable for halogenation in a gram scale of 4-quinolones in water without sacrificing yields.

A novel mononuclear ruthenium (Ru) complex bearing a PNNP-type tetradentate ligand is introduced here as a self-photosensitized catalyst for the reduction of carbon dioxide (CO2). When the pre-activation of the Ru complex by reaction with a base was carried out, an induction period of catalyst almost disappeared and the catalyst turnover numbers (TONs) over a reaction time of 144 h reached 307 and 489 for carbon monoxide (CO) and for formic acid (HCO2H), respectively. The complex has a long lifespan as a dual photosensitizer and reduction catalyst, due to the sterically bulky and structurally robust (PNNP)Ru framework. Isotope-labeling experiments under 13CO2 atmosphere indicate that CO and HCO2H were both produced from CO2.

An electron donor–acceptor (EDA) complex is an association between a Lewis base (electron donor) and a Lewis acid (electron acceptor) in the ground state. The EDA complex has received widespread at...

Lewis acids increase the catalytic activity of classical heterogeneous catalysts and molecular d0 tungsten oxo alkylidenes in a variety of olefin metathesis processes. The formation of labile adducts between the metal complex and the Lewis acid has been observed experimentally and suggested to be involved in the catalyst activity increase. In this contribution, DFT (M06) calculations have been performed to determine the role of Lewis acids on catalyst activity, Z-/E- selectivity and stability by comparing three W(E)(CHR)(2,5-dimethylpyrrolide)(O-2,6-dimesithylphenoxide) (E = oxo, imido or oxo-Lewis acid adduct) alkylidenes. Results show that the formation of the alkylidene—Lewis acid adducts influences the reactivity of tungsten oxo alkylidenes due to both steric and electronic effects. The addition of the Lewis acid on the E group increases its bulkiness and this decreases catalyst Z-selectivity. Moreover, the interaction between the oxo ligand and the Lewis acid decreases the donating ability of the former toward the metal. This is important when the oxo group has either a ligand in trans or in the same plane that is competing for the same metal d orbitals. Therefore, the weakening of oxo donating ability facilitates the cycloaddition and cycloreversion steps and it stabilizes the productive trigonal bipyramid metallacyclobutane isomer. The two factors increase the catalytic activity of the complex. The electron donating tuneability by the coordination of the Lewis acid also applies to catalyst deactivation and particularly the key β-hydride elimination step. In this process, the transition states show a ligand in pseudo trans to the oxo. Therefore, the presence of the Lewis acid decreases the Gibbs energy barrier significantly. Overall, the optimization of the E group donating ability in each step of the reaction makes tungsten oxo alkylidenes more reactive and this applies both for the catalytic activity and catalyst deactivation.

Indoloquinazolines functionalized at C-12, which are structural analogs of the natural alkaloid cephalanthrin B, are readily constructed via Ph3P/I2-mediated one-pot reactions of isatins with aromatic alcohols. In the presence of excess phenols, the C-12 aryloxy ester products are obtained in moderate to good yields under mild conditions. Moreover, fused bicyclic hydroxyaryl derivatives such as 8-hydroxyquinoline give rise to novel C-12 spiro-γ-lactone derivatives. A reactive iminium cation species derived from dehydration of the C-12 hydroxy ester precursor is proposed as the transient intermediate responsible for these transformations.

The application of a C(vinyl), C(aryl)-palladacycle from vinyl-containing substrates is challenging due to the interference of a reactive double bond in palladium catalysis. This Letter describes a [4 + 2] or [4 + 3] cyclization based on a C(vinyl), C(aryl)-palladacycle by employing α-oxocarboxylic acids as the insertion units under a palladium/air system. The reaction proceeded through the key vinyl C-H activation and dual decarboxylation sequence, forming phenanthrenes and cyclohepta[1,2,3-de]naphthalenes regioselectively in good yields. The synthetic versatility of this protocol is highlighted by the gram-scale synthesis and synthesizing functional material molecule.

New coordination compounds trans-bis(oxalato)diaquarhodiate sodium dihydrate Na[Rh(H2O)2Ox2]·2H2O (crystallizes in two polymorphic forms NaRh-1 and NaRh-2), trans-bis(oxalato)hydroxoaquarhodiate sodium tetrahydrate Na2[Rh(H2O)(OH)Ox2]·4H2O (Na2Rh) and trans-bis(oxalato)diaquarhodic acid tetrahydrate (H3O)[Rh(H2O)2Ox2]·4H2O (HRh) are synthesized. The compounds are characterized by IR spectroscopy, elemental analysis and single crystal X-ray diffraction. NaRh-1, NaRh-2 and Na2Rh crystallize in space group P 1. Trans-bis(oxalato)diaquarhodic acid exists not only in solution, but can also crystallize as a tetrahydrate (space group C2/c). The formation of various species in solution of rhodium hydroxide in oxalic acid and their redistribution were studied using 103Rh NMR spectroscopy.

A radical chain isomerization of N-sulfonyl ynamides to isolable ketenimines is developed, featuring mild reaction conditions, a high efficiency, ∼100% atom economy, a broad substrate scope, and column chromatography-free workup in most cases. Meanwhile, an unprecedented dearomatization of furans is achieved by the radical chain isomerization-triggered aza-Claisen rearrangement, providing highly chemo-, regio-, stereo-, and diastereoselective access to functionalized quaternary nitriles.

Herein we describe a phosphine-catalyzed internal redox [4 + 2] annulation of 1,4-enynoates with electron-deficient alkenes, in which the γ- and φ-C(sp3)-H of the enynoates are formally oxidized for the annulation while the alkynyl moiety is converted to an alkene. The reaction offers an efficient synthesis of highly functionalized cyclohexenes in moderate to good yields with exclusive regioselectivity and high diastereoselectivity under mild conditions.

A straightforward access to 2-unsubstituted imidazole N-oxides with subsequent deoxygenation by treatment with Raney-nickel followed by N-benzylation opens up a convenient route to lepidilines A and C. Both imidazolium salts were used to generate in situ the corresponding imidazol-2-ylidenes, which smoothly reacted with elemental sulfur, yielding imidazole-2-thiones. These reactions were performed either under classical conditions in pyridine solutions or mechanochemically using solid Cs2CO3 as a base. The structure of lepidiline C was unambiguously confirmed by X-ray analysis of its hexafluorophosphate. An analogous protocol toward lepidilines B and D and their 4,5-diphenyl analogues is less efficient due to observed instability of the key precursors, i.e., the respective 2-methylimidazole N-oxides. Comparison of cytotoxic activity against HL-60 and MCF-7 cell lines of all lepidilines, as well as their selected structural analogues (e.g., 4,5-diphenyl derivatives and PF6 salts), revealed slightly more potent activity of the 2-methylated series, irrespectively of the type of counterion present in the imidazolium salt. Remarkably, the well-known 1,3-diadamantylimidazolium bromide (the “Arduengo salt”), known as the precursor of the first, shelf-stable NHC representative, and its adamantyloxy analogue displayed the most significant cytotoxic activity in the studied series.

An enantioselective β-silylation of α,β-unsaturated phosphine oxide derivatives using a silylboronic ester as the silicon pronucleophile is reported. The reaction is catalyzed by copper salts in the presence of chiral pyridine–oxazoline (PyOx) ligands. Good to high enantioselectivities (≤95% ee) are obtained for β-aryl-substituted acceptors whereas alkyl residues in the β-position led to a lower ee value for 1° and no reaction for 2° and 3°. The new method represents another way of accessing α-chiral silanes and complements the known β-borylation.