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Abstract: An efficient one-pot multicomponent synthesis of 3,4- dihydropyrimidin-2(1H)-ones has been developed from aldehyde bisulfite adducts, ethyl acetoacetate and urea using recyclable polymer- supported sulfonic acid catalyst. This new method provides several advantages over the previous synthesis, including high product yields, commercially viable, minimal workup operations and sustainable chemical practices.

The Beckmann rearrangement has been predominantly studied for the synthesis of amide and lactam. By strategically using the in situ generated Appel's salt or Mitsunobu's zwitterionic adduct as the dehydrating agent, a series of Beckmann rearrangement and following cascade reactions have been developed herein. The protocol allows the conversion of various ketoximes into amide, thioamide, tetrazole and imide products in modular procedures. The generality and tolerance of functionalities of this method have been demonstrated.

Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/ O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation.

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.

Thiolate adducts of dirhodium(II) tetraacetate have proven difficult to prepare. We isolated a stable, paramagnetic Ni4Rh2 adduct containing Ni-based metallothiolates bound in axial positions of the Rh24+ core. The adduct formation is accompanied by a change of the magnetic exchange interaction in the dinuclear Ni2 subunits.

Mononuclear high-valent iron(IV)-oxo intermediates are excellent oxidants towards oxygenation reactions by heme and nonheme metalloenzymes and their model systems. One of the most important functions of these intermediates in nature is to detoxify various environmental pollutants. Organic substrates such as halogenated phenols are known to be water pollutants which can be degraded to their less hazardous forms through an oxidation reaction by iron(IV)-oxo complexes. Metalloproteins in the Nature utilize various types of second-coordination sphere interactions to anchor the substrate in the vicinity of the active site. This concept of substrate-binding is well-known for natural enzymes, but quite elusive for the relevant biomimetic model systems. Herein, we report the oxidative reactivity patterns of an iron(IV)-oxo intermediate, [FeIV(O)(2PyN2Q)]2+, (2PyN2Q = 1,1-di(pyridin-2yl)-N, N-bis(quinolin-2-ylmethyl)methanamine) with a series of mono-, di- and tri-halophenols. A detailed experimental study shows that the dehalogenation reactions of the halophenols by such iron(IV)-oxo intermediates proceed via an initial hydrogen atom abstraction from the phenolic O-H group. Further, based on the size and nucleophilicity of the halophenol, an intermediate substrate-bound species forms , that is a phenolate adduct to the ferric species - which thereafter leads to the formation of the corresponding products.

The installation of (benzo)thiophene-containing biaryls via coupling reactions has become a staple in designing photoelectric materials. Undeniably, C-H/C-H cross-coupling reactions between two (hetero)aromatics would be a shortcut toward these structural fragments. While more reliable cross-coupling technologies are well-established to provide C2-arylated (benzo)thiophenes, efficient methods that arylate the C3-position remain underdeveloped. Herein we provide insight into the factors that determine regioselectivity switching for these cross-coupling reactions. X-ray crystallographic analysis gives solid evidence for the key roles of triflate in regioselective dearomatization and acetate in base-assisted anti-β-deprotonated rearomatization. The first isolation and X-ray characterization of a medium-sized dearomatized cyclometalated adduct involving both substrates provide extra insight into aerobic oxidative Ar-H/Ar-H cross-coupling reactions. The mechanistic breakthrough incubates the first example, enabling C-H/C-H-type C3-arylation of benzothiophenes. Finally, this chemistry is used to design blue-emitting thermally activated delayed fluorescence (TADF) materials with a helicene conformation that exhibit a high maximum external quantum efficiency of 25.4% in OLED.

Two pairs of enantiomeric diarylheptanoid-phenylpropanoid adducts bearing a cyclohexenone core, (±)-saccardianones A and B (1 and 2), an alkaloidal diarylheptanoid-phenylpropanoid adduct bearing a 4-piperidone core, (±)-saccardianine A (3), a pair of enantiomeric dimeric diarylheptanoid alkaloids bearing a tetrahydropyridine core, (±)-saccardianine B (4), and a suspected degradation product, saccardianine C (5), in addition to a known diarylheptanoid, platyphyllenone (6), were isolated from the leaves of Pellacalyx saccardianus. Their chemical structures were elucidated based on detailed analyses of the NMR and MS data. The structure of (±)-(1) was also confirmed by X-ray diffraction analysis. Compounds (±)-2 and 6 exhibited selective cytotoxicity towards the AsPC-1 and PANC-1 pancreatic cancer cell lines, respectively.

Mycobacterium tuberculosis (Mtb) cells are known to synthesize very long chain (C60-90) structurally complex mycolic acids with various functional groups. In this study, we applied linear ion-trap (LIT) multiple-stage mass spectrometry (MSn), combined with high-resolution mass spectrometry to study the mechanisms underlying the fragmentation processes of mycolic acid standards desorbed as lithiated adduct ions by ESI. This is followed by structural characterization of a Mtb mycolic acid family (Bovine strain). Using the insight fragmentation processes gained from the study, we are able to achieve a near complete characterization of the whole mycolic acid family, revealing the identity of the α-alkyl chain, the location of the functional groups including methyl, methoxy, and keto groups along the meroaldehyde chain in each lipid species. This study showcased the power of LIT MSn toward structural determination of complex lipids in a mixture, which would be otherwise very difficult to define using other analytical techniques.

Mutagenic agents such as aromatic amines undergo metabolic activation and produce DNA adducts at C8 position of guanine bases. N-2-acetylaminofluorene (AAF) generates different mutational outcomes when placed at G1, G2, and G3 of a NarI sequence (-G1G2CG3CC/T-). These outcomes are dictated by the conformations adopted by these adducts. Detection of such lesions is of considerable interest owing to their hazardous effects. Here, we report the synthesis of three cyclometalated [Ir(L)2dppz]+ complexes (L = 2-phenylpyridine (ppy) 1; benzo[h]quinoline (bhq) 2; 2-phenylquinoline (pq) 3; dppz = dipyrido[3,2-a:2',3'-c]phenazine) and their interaction with AAF adducted NarI DNA. Remarkably, complexes 1 and 2 displayed dominant 3LC transition characteristic of polar environment despite binding to the adducted sites. On the other hand, complex 3 binds to NarI sequences and behaves as a luminescent reporter for AAF-modified DNA. The results reported here emphasize that molecular light switching phenomenon can be stimulated by switching ancillary ligands and might act as potential probes for covalent-DNA defects.

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.

A mononuclear manganese(V) oxo complex of a bis(amidate)bis(alkoxide) ligand, (NMe4)[MnV(HMPAB)(O)] [2; H4HMPAB = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene], was synthesized and structurally characterized. A Mn-Oterm distance of 1.566(4) A was observed in the solid-state structure of 2, consistent with the Mn≡O formulation. The reaction of redox-inactive metal ions (Mn+ = Li+, Ca2+, Mg2+, Y3+, and Sc3+) with 2 resulted in the formation of 2-Mn+ species, which were characterized by UV-vis, 1H NMR, cyclic voltammetry, and in situ IR spectroscopy. Theoretical calculations suggested that the alkoxide oxygen atoms of the ligand scaffold are energetically most favorable for coordinating the Mn+ ions in 2. Complex 2 revealed one-electron-reduction potential at -0.01 V versus ferrocenium/ferrocene, which shifted anodically upon coordination of Mn+ ions to 2, and such a shift became more prominent with stronger Lewis acids. The oxygen-atom transfer (OAT) reactivities of 2 and 2-Mn+ species with triphenylphosphine were compared, which exhibited a systematic increase of the reaction rate with increasing Lewis acidity of Mn+ ions, and a plot of log k2 versus Lewis acidity of Mn+ ions (ΔE) followed a linear relationship. It was observed that 2-Sc3+ was ca. 3200 times more reactive toward the OAT reaction compared to 2. Hammett analysis of 2 exhibited a V-shaped plot, indicating a change of the reaction mechanism upon going from electron-rich to electron-deficient Ar3P substrates. In contrast, 2-Ca2+ and 2-Sc3+ showed an electrophilic nature toward the OAT reaction, thus demonstrating the role of the Lewis acid in controlling the OAT mechanism. The hydrogen-atom abstraction reaction of 2 and 2-Mn+ adducts with 1-benzyl-1,4-dihydronicotinamide was investigated, and it was observed that the rate of reaction did not vary considerably with the Lewis acidity of Mn+ ions. On the basis of Eyring analysis of 2 and 2-Mn+ adducts, we hypothesized an entropy-controlled hydrogen-atom-transfer reaction for 2-Sc3+, which is different from the reaction mechanism of 2 and 2-Ca2+.

A direct general method for the preparation of α-oxyacylated vinyl ketones using Koser's hypervalent iodine reagent is reported. A variety of acyloxy groups from long-chain aliphatic, aromatic, α,β-unsaturated carboxylic acids have been installed efficiently for the first time. The oxyacylated adducts were used for the preparation of densely functionalized chiral δ-lactones and cyclopentenes using carbene organocatalysis.

Quinones are potent genotoxic agents through generating reactive oxygen species or undergo covalent bonding to modify the nucleobases of DNA. The formation of DNA adducts is an early indication of cancer, as it may lead to gene mutation, thereby initiating tumor development. The present review aims to summarize different types of quinone-induced DNA damages and the corresponding DNA adducts. In addition to the considerably stable naphthoquinone and halobenzoquinones in the environment, quinones are also metabolically activated from estrogen, bisphenol A, ochratoxin A, polychlorinated biphenyls, benzo[a]pyrene and polybrominated diphenyl ethers, in which the inducement from these pollutants to produce DNA adducts were systematically discussed. Liquid chromatography-mass spectrometry (LC-MS)-based method with high accuracy and sensitivity for the detection of DNA adducts in mononucleotides, DNA duplexes, and biological samples was methodically summarized. It is believed that the presence of dione moiety in quinones is an imperative element that induce the formation of DNA adducts. The investigation on DNA adducts is helpful for understanding the generation, transformation, and repair of DNA damages, and for elucidating the underlying mechanism of carcinogenesis. This review provides a new perspective to assess the toxicological potential of quinones, and intends to put forward strategies of analyzing DNA adducts, which act as biomarkers, for indicating the potential health risks of multiDNA damages.

The first title compound, [Au(C7H11BrN2)2]I, crystallizes in the space group P\overline{1} without imposed symmetry. The cations and anions are linked to form chains by Br...I...Br halogen-bond linkages. The second title compound, [Au(C7H11BrN2)2][AuI2(C7H11BrN2)2]I2, is an adduct of the first and its formally I2-oxidized AuIII analogue. It also crystallizes in space group P\overline{1}, whereby both gold atoms occupy inversion centres. The extended structure is a reticular layer involving Br...I...Br and I...I...Au linkages.

New silicone based adducts were synthesized by reacting equimolar ratio of carbinol polydimethylsiloxane (CPDMS), 2,4-toluene diisocyanate (TDI) and polyethylene glycol (PEG, having a molecular weight of 300, 600, 1000, 2000 or 6000 Da) at 100 °C for 90 min. Only the PEG 600, 1000, and 2000 based adducts are self-water dispersible. The chemical structure of the CPDMS/TDI/PEG1000 adduct was confirmed via FTIR analysis while TEM analysis assured that the particles size of its emulsion ranges from 8 to 22 nm. The higher the PEG molecular weight of adduct, the higher is the adduct emulsion particles size. Incorporation of the aforementioned adducts emulsions as textile softeners in easy care finishing formulation of cotton fabric gives rise to an enhancement in functional properties of treated fabric namely softness and anti-crease, an improvement in percent nitrogen, tear strength, and flexibility as well as a reduction in whiteness index and wettability of treated fabric. The CPDMS/TDI/PEG1000 adduct emulsion treated fabric was characterized via SEM and EDX analysis. Combining of that adduct emulsion with triclosan, as bio-active additives, in the soft/resin finishing formulation of cotton fabric results in durable antibacterial properties of treated fabric.

The bicyclic amido-substituted silicon(I) ring compound Si4 {N(SiMe3 )Mes}4 2 (Mes=Mesityl=2,4,6-Me3 C6 H2 ) features enhanced zwitterionic character and different reactivity from the analogous compound Si4 {N(SiMe3 )Dipp}4 1 (Dipp=2,6-i Pr2 C6 H3 ) due to the smaller mesityl substituents. In a reaction with the N-heterocyclic carbene NHC Me4 (1,3,4,5-tetramethyl-imidazol-2-ylidene), we observe adduct formation to give Si4 {N(SiMe3 )Mes}4 ⋅ NHC Me4 (3). This adduct reacts further with the Lewis acid BH3 to yield the Lewis acid-base complex Si4 {N(SiMe3 )Mes}4 ⋅ NHC Me4 ⋅ BH3 (4). Coordination of AlBr3 to 2 leads to the adduct 5. Calculated proton affinities and fluoride ion affinities reveal highly Lewis basic and very weak Lewis acidic character of the low-valent silicon atoms in 1 and 2. This is confirmed by protonation of 1 and 2 with Brookharts acid yielding 6 and 7. Reaction with diphenylacetylene only occurs at 111 °C with 2 in toluene and is accompanied by fragmentation of 2 to afford the silacyclopropene 8 and the trisilanorbornadiene species 9.

This work describes that a sterically bulky o-carboranylsilylene can significantly enhance the stability of the resultant carboranylsilylene-borane adducts. Removal of one halide from the boron cen...

The reaction of manganese(II) acetate hydrate with cymantrenecarboxylic acid under inert atmosphere gave the complex [Mn(Thf)2(OH2)4][OOCC5H4Mn(CO)3]2 (I), which was highly unstable to air oxygen and temperature of the adduct, in which the anions occupy the outer-sphere positions. The oxidation of the mother liquor after isolation of the single crystals of I afforded the complex Mn6(µ4-O)2[µ,η2-OOCC5H4Mn(CO)3]2[µ-OOCC5H4Mn(CO)3]8(OH2)4·5C6H6·THF·3H2O (II). According to X-ray diffraction data, the metal core of II was a hexanuclear cluster $${\text{Mn}}_{4}^{{{\text{II}}}}{\text{Mn}}_{2}^{{{\text{III}}}}$$ containing mixed-valence metal atoms. Apart from X-ray diffraction, the obtained unstable complexes were characterized by elemental analysis and IR spectroscopy (powders).

Cyclophosphamide is one of the nitrogen mustard agents that is frequently used in cancer chemotherapy. Nevertheless, long-term use of high dosage cyclophosphamide has been proven to increase the risk of secondary cancer. This can be traced by the mutagenic DNA adduct formation, for instance, N5-nitrogen mustard formamidopyrimidine (NM-Fapy-G). Therefore, it may serve as one of the secondary cancer biomarkers in patients receiving cyclophosphamide. Several NM-Fapy-G analysis methods employ Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) developed by experts. However, it was discovered not applicative for patients because cells and tissues were utilized as the biospecimens. Therefore, this summary is presented to emphasize the idea of adopting Dried Blood Spot (DBS) as the blood bio sampling method, DNA extraction and hydrolysis method that is suitable for enriching NM-Fapy-G adduct; and method that is proper for NM-Fapy-G analysis. Based on the literature study, DBS has been proven beneficial for this analysis; DNA can be extracted from the DBS cards using the QIAamp DNA Mini Kit. Therefore, research with a little bit of adjustment can be applied for NM-Fapy-G analysis.

Acrolein (ACR) derives from the external environment and the endogenous metabolism of organisms. It has super-reactivity and can induce various diseases. We investigated the capacity of cyanidin-3-O-glucoside (C3G) and its degradants/metabolites to capture ACR during thermal processing or in vivo. Our results indicated that both C3G and its degradants, including phloroglucinaldehyde (PGA) and protocatechuic acid (PCA), could efficiently trap ACR to form adducts, such as C3G-ACR, C3G-2ACR, PGA-ACR, PGA-2ACR, PCA-ACR, and PCA-2ACR. Additionally, these adducts were detected in commercial canned red bayberry products. The adducts of C3G and its metabolites conjugated with ACR, such as C3G-ACR, C3G-2ACR, PGA-ACR, and 4-hydroxybenzoic-acid-ACR (4-HBA-ACR), were also detected in mice feces treated with C3G by oral gavage, where the adduct level was dose-dependent. A similar pattern was observed in tests on human consumption of red bayberry. In human urine, only PGA-2ACR and 4-HBA-ACR, were found, whereas C3G-ACR, C3G-2ACR, myricetin-3-O-rhamnoside-ACR (M3R-ACR), PGA-2ACR, 4-HBA-ACR and ferulic acid-ACR (FA-ACR) were detected in human feces following administration of red bayberry. Our results are the first demonstration that C3G and its metabolites can capture ACR in vitro and in vivo (mice and humans) and present a novel strategy, the development of C3G as a promising ACR inhibitor.

We report that exposing the dipyrrin complex ((EMind)L)Cu(N(2)) to air affords rapid, quantitative uptake of O(2) in either solution or the solid-state to yield ((EMind)L)Cu(O(2)). The air and thermal stability of ((EMind)L)Cu(O(2)) is unparalleled in molecular copper-dioxygen coordination chemistry, attributable to the ligand flanking groups which preclude the [Cu(O(2))](1+) core from degradation. Despite the apparent stability of ((EMind)L)Cu(O(2)), dioxygen binding is reversible over multiple cycles with competitive solvent exchange, thermal cycling, and redox manipulations. Additionally, rapid, catalytic oxidation of 1,2-diphenylhydrazine to azoarene with generation of hydrogen peroxide is observed, through the intermittency of an observable ((EMind)L)Cu(H(2)O(2)) adduct. The design principles gleaned from this study can provide insight for the formation of new materials competent capable of reversible scavenging of O(2) from air under ambient conditions with low-coordinate Cu(I) sorbents.

Understanding binding site preferences in biological systems as well as affinities to binding partners is a crucial aspect in metallodrug development. We here present a mass spectrometry-based method to compare relative stabilities of metal-peptide adducts in the gas phase. Angiotensin 1 and substance P were used as model peptides. Incubation with isostructural N-heterocyclic carbene (NHC) complexes of RuII , OsII , RhIII , and IrIII led to the formation of various adducts, which were subsequently studied by energy-resolved fragmentation experiments. The gas-phase stability of the metal-peptide bonds depended on the metal and the binding partner. Of the four complexes used, the OsII derivative bound strongest to Met, while RuII formed the most stable coordination bond with His. RhIII was identified as the weakest peptide binder and IrIII formed peptide adducts with intermediate stability. Probing these intrinsic gas-phase properties can help in the interpretation of biological activities and the design of site-specific protein binding metal complexes.

The mechanism as well the stereochemistry of cascade cycloisomerization of 15–membered triazatriacetylenic macrocycle was investigated theoretically by using M062X/6–31+G(d,p) and M062X/LANL2DZ calculations. The results showed that the mechanism and outcome of the reaction depended on the absence and presence of a transition metal catalyst. So that, in thermal-induced condition, the reaction had to experience several suprafacial concerted reactions including Ene-reaction (DG#=35.38 kcal/mol), Diels–Alder cycloaddition (DG# = 17.16 kcal/mol), and sigmatropic H-shift rearrangement (DG# = 56.21 kcal/mol) to produce diastereoselective fused cis–tetracyclic aromatic bearing a pyrrole moiety by following kinetic considerations. Also, the [2+2+2] cycloaddition mechanism was neglected in thermal–induced conditions because of high activation free Gibbs energy (DG# = 63.90 kcal/mol). In the presence of palladium catalyst, Pd(0) formed an adduct by coordinating to C = C bonds and decreased the DG# of the process to 29.58 kcal/mol, and consequently provided a facilitated media for the reaction to follow the [2+2+2] to produce more stable fused tetracyclic benzenoid aromatic by passing through the lower energy barrier.

The isocitrate lyase paralogs of Mycobacterium tuberculosis (ICL1 and 2) are essential for mycobacterial persistence and constitute targets for the development of antituberculosis agents. We report that (2R,3S)-2-hydroxy-3-(nitromethyl)succinic acid (5-NIC) undergoes apparent retro-aldol cleavage as catalyzed by ICL1 to produce glyoxylate and 3-nitropropionic acid (3-NP), the latter of which is a covalent-inactivating agent of ICL1. Kinetic analysis of this reaction identified that 5-NIC serves as a robust and efficient mechanism-based inactivator of ICL1 (kinact/KI = (1.3 ± 0.1) × 103 M-1 s-1) with a partition ratio

The properties of metal/dioxygen species, which are key intermediates in oxidation catalysis, can be modulated by interaction with redox-inactive Lewis acids, but structural information about these adducts is scarce. Here we demonstrate that even mildly Lewis acidic alkali metal ions, which are typically viewed as innocent "spectators", bind strongly to a reactive cis-peroxo dicopper(II) intermediate. Unprecedented structural insight has now been obtained from X-ray crystallographic characterization of the "bare" CuII2(μ-η1:η1-O2) motif and its Li+, Na+, and K+ complexes. UV-vis, Raman, and electrochemical studies show that the binding persists in MeCN solution, growing stronger in proportion to the cation's Lewis acidity. The affinity for Li+ is surprisingly high (∼70 × 104 M-1), leading to Li+ extraction from its crown ether complex. Computational analysis indicates that the alkali ions influence the entire Cu-OO-Cu core, modulating the degree of charge transfer from copper to dioxygen. This induces significant changes in the electronic, magnetic, and electrochemical signatures of the Cu2O2 species. These findings have far-reaching implications for analyses of transient metal/dioxygen intermediates, which are often studied in situ, and they may be relevant to many (bio)chemical oxidation processes when considering the widespread presence of alkali cations in synthetic and natural environments.

International audience; Due to the omnipresence of chiral organofluorine compounds in pharmaceutical, agrochemical, and material chemistry, the development of enantioselective methods for their preparation is highly desirable. In the present study, the enantioselective organocatalyzed acylation of a,a-difluorohydrins using a commercially available chiral isothiourea is reported through a kinetic resolution (KR) process. It reveals that the difluoromethylene moiety (C(sp 3)F 2) can serve as a directing group through electrostatic fluorine-cation interactions, greatly improving the enantioselectivity of the KR. In this context, a broad range of fluorinated alcohols such as valuable 4,4-difluoro-1,3-diols could be synthesized with exquisite enantiocontrol (typically > 99:1 er). Turning to 2,2difluoro-1,3-diols, we also demonstrated that aromatic and fluorinated groups were mutually compatible to provide the expected enantioenriched adducts with > 99:1 er.

Лекарственная устойчивость к антибиотикам вызвала необходимость поиска новых лекарственных средств и лекарственных форм. Известно, что семиорганические аддукты иода обладают широким спектром антимикробного действия. Эти же соединения, содержащие в своем составе молекулу галогена - иода, могут выступать в качестве галогенирующего агента в отношении антибиотиков. Изучено взаимодействие антибиотиков тетрациклина, гентамицина, хлорамфеникола, относящихся к классам поликетидов, аминогликозидов и амфениколов, соответственно, с аддуктом иода методами рефрактометрии, УФ-спектроскопии и ИК-спектроскопии. Показано, что антибиотик хлорамфеникол не взаимодействует с семиорганическим аддуктом иода ди2-аминопропионовой кислоты дитрииодоводород моногидратом (субстанция D1). Antibiotic drug resistance has necessitated the search for new drugs and dosage forms. It is known that semiorganic iodine adducts have a wide spectrum of antimicrobial effects. The same compounds containing a halogen-iodine molecule may act as a antibiotics halogenating agent. The interaction of antibiotics tetracycline, gentamicin, chloramphenicol belonging to the classes of polyketides, aminoglycosides and amphenicols, respectively, with iodine adduct by refractometry, UV spectroscopy and IR spectroscopy was studied. It has been shown that the antibiotic chloramphenicol does not interact with the semiorganic adduct of di-2-aminopropionic acid ditriiodinehydride monohydrate (D1 substance).

Here, we report an unprecedented catalytic enantioselective cyanation of ketonitrones enabled by the bifunctional cyanating reagent Me2(CH2Cl)SiCN. This approach allows facile access to optically active N-hydroxyl-α-amino nitriles that are of high synthetic value but difficult to acquire by other methods. The use of bifunctional cyanating reagent Me2(CH2Cl)SiCN not only achieves an enantioselectivity higher than that with TMSCN but also enables various diversification reactions of the resulting silylated adducts. This represents the first enantioselective catalytic nucleophilic addition reaction of unactivated ketone-derived nitrones, exhibiting the potential of such tetrasubstituted C═N bonds for asymmetric synthesis of N-hydroxy α-amino acids and other N-hydroxy tertiary amines.

Oxidative addition represents a critical elementary step in myriad catalytic transformations. Here, the importance of thoughtful ligand design cannot be overstated. In this work, we report the intermolecular activation of iodobenzene (PhI) at a coordinatively saturated 18-electron [Ni 0(diphosphine) 2] complex bearing a Lewis acidic secondary coordination sphere. Whereas alkyl-substituted diphosphine complexes of Group 10 are known to be unreactive in such reactions, we show that [Ni 0(P 2B Cy 4) 2] (P 2B Cy 4=1,2-bis(di(3-dicyclohexylboraneyl)-propylphosphino)ethane) is competent for room-temperature PhI cleavage to give [Ni II(P 2B Cy 4)(Ph)(I)]. This difference in oxidative addition reactivity has been scrutinized computationally – an outcome that is borne out in ring-opening to provide the reactive precursor – for [Ni 0(P 2B Cy 4) 2], a “boron-trapped” 16-electron κ 1-diphosphine Ni(0) complex. Moreover, formation of [Ni II(P 2B Cy 4)(Ph)(I)] is inherent to the P 2B Cy 4 secondary coordination sphere: treatment of the Lewis adduct, [Ni 0(P 2B Cy 4) 2(DMAP) 8] with PhI provides [Ni II(P 2B Cy 4) 2(DMAP) 8(I)]I via iodine-atom abstraction and not a [Ni II(Ph)(I)(diphosphine)] compound – an unusual secondary sphere effect. Finally, the reactivity of [Ni 0(P 2B Cy 4) 2] with 4-iodopyridine was surveyed, which resulted in a pyridyl-borane linked oligomer. The implications of these outcomes are discussed in the context of designing strongly donating, and yet labile diphosphine ligands for use in a critical bond activation step relevant to catalysis.

Upon addition of 5-15% PhNMe2H+X- (X = B(3,5-(CF3)2C6H3)4 or B(C6F5)4) to Mo(NAr)(styrene)(OSiPh3)2 (Ar = N-2,6-i-Pr2C6H3) in C6D6 an equilibrium mixture of Mo(NAr)(styrene)(OSiPh3)2 and Mo(NAr)(CMePh)(OSiPh3)2 is formed over 36 h at 45 °C (Keq = 0.36). A plausible intermediate in the interconversion of the styrene and 1-phenethylidene complexes is the 1-phenethyl cation, [Mo(NAr)(CHMePh)(OSiPh3)2]+, which can be generated using [(Et2O)2H][B(C6F5)4] as the acid. The interconversion can be modeled as two equilibria involving protonation of Mo(NAr)(styrene)(OSiPh3)2 or Mo(NAr)(CMePh)(OSiPh3)2 and deprotonation of the α or β phenethyl carbon atom in [Mo(NAr)(CHMePh)(OSiPh3)2]+. The ratio of the rate of deprotonation of [Mo(NAr)(CHMePh)(OSiPh3)2]+ by PhNMe2 in the α position versus the β position is ∼10, or ∼30 per Hβ. The slow step is protonation of Mo(NAr)(styrene)(OSiPh3)2 (k1 = 0.158(4) L/(mol·min)). Proton sources such as (CF3)3COH or Ph3SiOH do not catalyze the interconversion of Mo(NAr)(styrene)(OSiPh3)2 and Mo(NAr)(CMePh)(OSiPh3)2, while the reaction of Mo(NAr)(styrene)(OSiPh3)2 with pyridinium salts generates only a trace (∼2%) of Mo(NAr)(CMePh)(OSiPh3)2 and forms a monopyridine adduct, [Mo(NAr)(CHMePh)(OSiPh3)2(py)]+ (two diastereomers). The structure of [Mo(NAr)(CHMePh)(OSiPh3)2]+ has been confirmed in an X-ray study; there is no structural indication that a β proton is activated through a CHβ interaction with the metal. W(NAr)(CMePh)(OSiPh3)2 is also converted into a mixture of W(NAr)(CMePh)(OSiPh3)2 and W(NAr)(styrene)(OSiPh3)2 (Keq = 0.47 at 45 °C in favor of the styrene complex) with 10% [PhNMe2H][B(C6F5)4] as the catalyst; the time required to reach equilibrium is approximately the same as in the Mo system.

A chiral Ir-catalyzed reaction of α-aryl-α,β-unsaturated amides with β-substituted acrylates proceeded to give formal conjugate adducts in high yield and ee (up to 99% yield and up to 95% ee). This is the first example of the enantioselective cross-coupling of two different electron-deficient alkenes via vinylic sp2 C-H activation, and polyfunctionalized chiral compounds were obtained.

An efficient kinetic resolution of sulfinamides via an asymmetric N-allylic alkylation reaction was realized using hydroquinine as a catalyst under mild conditions. The kinetic resolution of a range of Morita-Baylis-Hillman adducts and N-aryl tert-butylsulfinamides was highly effective. In addition, the synthetic utility of the protocol was demonstrated by a scaled-up reaction. Density functional theory calculations provide convincing evidence for the interpretation of stereoselection.

The scarcity of reliable methods for synthesizing chiral gem-diarylmethine borons limits their applications. Herein, we report a method for highly enantioselective dirhodium-catalyzed B-H bond insertion reactions with diaryl diazomethanes as carbene precursors. These reactions afforded chiral gem-diarylmethine borane compounds in high yield (up to 99 % yield), high activity (turnover numbers up to 14 300), high enantioselectivity (up to 99 % ee) and showed unprecedented broad functional group tolerance. The borane compounds synthesized by this method could be efficiently transformed into diaryl methanol, diaryl methyl amine, and triaryl methane derivatives with good stereospecificity. Mechanistic studies suggested that the borane adduct coordinated to the rhodium catalyst and thus interfered with decomposition of the diazomethane, and that insertion of a rhodium carbene (generated from the diaryl diazomethane) into the B-H bond was most likely the rate-determining step.

Acrolein (ACR), the simplest α,β-unsaturated aldehyde, possesses high reactivity and toxicity both in vitro and in vivo and results in various chronic diseases. This has attracted increasing interest from researchers to screen various bioactive compounds to control it. In this article, we attempted to discover a new attribute of cyanidin-3-O-glucoside (C3G), including its ACR-scavenging capacity, reaction pathway, and possible application. Our findings revealed that C3G could capture ACR to form mono- and diadducts at room temperature by using liquid chromatography-mass spectrometry, and we further synthesized and elucidated the structures of C3G-ACR and C3G-2ACR using HRMS and 2D NMR. The structural data validated that there were two active sites of C3G for trapping ACR: at C-6 in the A-ring and C-5' in the B-ring. In addition, we found that C3G-ACR exhibited a more remarkable clearing ability than C3G within a short time. More than 65.9% of ACR was eliminated by C3G-ACR within 5 min via further formation of C3G-2ACR, but there was no obvious effect of C3G on ACR. When the incubation time was extended to 120 min, C3G could remove up to 83.2% of ACR. Subsequently, we also observed that mynica red (>5% C3G), as a pigmented food additive, could efficiently eliminate ACR generated in the Chinese liquor model and real red bayberry wine products to form C3G-ACR and C3G-2ACR. Both adducts increased significantly, by 10 times to a 100 times, after adding mynica red to red bayberry wine products for 24 h; they also increased rapidly with prolonged incubation time in the liquor-mynica red model system. Therefore, our findings suggest that C3G or mynica red may be developed as a promising novel ACR inhibitor in fruit wine and assembled alcoholic drinks or as a health food.

The Lewis acid-base adducts MoF5(NC5H5)n and MoOF4(NC5H5)n (n = 1, 2) were synthesized from the reactions of MoF5 and MoOF4 with C5H5N and structurally characterized by X-ray crystallography. Whereas the crystal structures of MoF5(NC5H5)2 and MoOF4(NC5H5)2 are isomorphous containing pentagonal-bipyramidal molecules, the fluorido-bridged, heptacoordinate [MoF5(NC5H5)]2 dimer differs starkly from monomeric, hexacoordinate MoOF4(NC5H5). For the weaker Lewis base CH3CN, only the 1:1 adduct, MoF5(NCCH3), could be isolated. All adducts were characterized by Raman spectroscopy in conjunction with vibrational frequency calculations. Multinuclear NMR spectroscopy revealed an unprecedented isomerism of MoOF4(NC5H5)2 in solution, with the pyridyl ligands occupying adjacent or nonadjacent positions in the equatorial plane of the pentagonal bipyramid. Paramagnetic MoF5(NC5H5)2 was characterized by electron paramagnetic resonance (EPR) spectroscopy as a dispersion in solid adamantane as well as in a diamagnetic host lattice of MoOF4(NC5H5)2; EPR parameters were computed using ZORA with the BPW91 functional using relativistic all-electron wave functions for Mo and simulated using EasySpin. Density functional theory calculations (B3LYP) and natural bond orbital analyses were conducted to elucidate the distinctive bonding and structural properties of all adducts reported herein and explore fundamental differences observed in the Lewis acid behavior of MoF5 and MoOF4.

An efficient copper-catalyzed cyclization of N-propargyl ynamides with borane adducts through B-H bond insertion has been developed. A series of valuable organoboron compounds are constructed in generally good yields with a wide substrate scope and good functional group tolerance under mild reaction conditions. Importantly, this protocol via vinyl cation intermediates constitutes a novel way of B-H bond insertion.

Glutathione (GSH), due to the ability to capture the reactive electrophiles of exoand endogenous origins, is expected to prevent cross-linking induced by these compounds. However, it may instead become cross-linked itself. We subjected glutathione to reactions with model α,β-unsaturated carbonyl systems resulting from the interactions of adenosine with bifunctional aldehyde products of lipid peroxidation, and identified a range of adducts and cross-linked products. We found that the S-conjugated adducts, initially formed in the typical GSH Michael addition to α,β-unsaturated carbonyl system, unexpectedly undergo gradual degradation giving rise to the final N-conjugated products, in which formation of peptide amino group is involved instead of sulfhydryl functionality. This finding shows that the role of the GSH amino group in the non-enzymatic detoxification is underestimated, and that reactions between cellular α,β-unsaturated carbonyl compounds and GSH may be more complex than are presently perceived.

The development of efficient synthetic methods for accessing enantioenriched α-chiral amines is of great importance in the disciplines of medicinal and synthetic organic chemistry. Enantioselective Rh-catalyzed 1,2-addition reactions to activated imine derivatives are regarded as useful protocols for forming α-chiral amines. This personal account outlines our efforts to develop chiral bicyclo[2.2.1]heptadiene ligands for Rh-catalyzed asymmetric additions of various organoboron reagents to a wide range of imine derivatives. Transformations of the thus-obtained adducts into known natural products or molecules of pharmaceutical importance serve to confirm their synthetic usefulness.

A systematic study on Lewis-acid/base adducts of N-heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene cAAC\(^{Me}\) (1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) with antimony(III) chlorides of the general formula SbCl\(_{2}\)R (R=Cl, Ph, Mes) is presented. The reaction of the NHCs Me\(_{2}\)Im\(^{Me}\) (1,3,4,5-tetra-methyl-imidazolin-2-ylidene), iPr\(_{2}\)Im\(^{Me}\) (1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene), Mes\(_{2}\)Im, Dipp\(_{2}\)Im (R\(_{2}\)Im=1,3-di-organyl-imidazolin-2-ylidene; Mes=2,4,6-trimethylphenyl, Dipp=2,6-di-isopropylphenyl) and cAAC\(^{Me}\) with antimony(III) compounds SbCl\(_{2}\)R (R=Cl (1), Ph (2) and Mes (3)) yields the adducts NHC ⋅ SbCl\(_{2}\)R (R=Cl (4), Ph (5) and Mes (6); NHC=Me\(_{2}\)Im\(^{Me}\) (a), iPr\(_{2}\)Im\(^{Me}\) (b), Dipp\(_{2}\)Im (c) and Mes\(_{2}\)Im (d)) and cAAC\(^{Me}\) ⋅ SbCl\(_{2}\)R (R=Cl (4 e) and Ph (5 e)). Thermal treatment of (Dipp\(_{2}\)Im) ⋅ SbCl\(_{2}\)Ar (Ar=Ph (5 c) and Mes (6 c)) in benzene leads to isomerization to the backbone coordinated \(^{a}\)NHC-adduct \(^{a}\)Dipp\(_{2}\)Im ⋅ SbCl\(_{2}\)Ar (Ar=Mes (7) and Ph (8)) (\(^{"a"}\) denotes “abnormal” coordination mode of the NHC) in high yields. One of the chloride substituents at antimony of 7 can be abstracted by GaCl3 or Ag[BF\(_{4}\)] to obtain the imidazolium salts [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][BF\(_{4}\)] (9) and [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][GaCl\(_{4}\)] (10).

Metal-organic frameworks (MOFs) provide a platform to design new heterogeneous catalysts for catalytic CO2 reduction, but selective formation of C2 valuable liquid fuel products remains a challenge. Herein, we propose a strategy to synthesize composites by integrating MoS2 nanosheets into hierarchically porous defective UiO-66 (d-UiO-66) to form Mo-O-Zr bimetallic sites on the interfaces between UiO-66 and MoS2 . The active interfaces are favorable for the efficient transfer of photo-generated charge carriers and for promoting the activity, whereas, the synergy of the components at the interfaces achieves selectivity for C2 production. The d-UiO-66/MoS2 composite facilitates the photo-catalytic conversion of gas phase CO2 and H2 O to CH3 COOH under visible light irradiation without any other adducts. The evolution rate and selectivity of CH3 COOH reached 39.0 μmol g-1 h-1 and 94 %, respectively, without any C1 products, suggesting a new approach for the design of highly efficient photocatalysts of CO2 for C2 production. Theoretical calculations demonstrate the charge-polarized Zr-O-Mo aided the C-C coupling process with the largely reduced energy barrier.

A mixed-valent high spin (μ-hydroxo)dicobalt(II/III) complex bearing N, N′-bis(5-tertbutylsalicylidene)-1,2-diaminobenzene (SalophentBu) ligand was synthesized by reacting (SalophentBu)Co(II)(Py) with O2 at low temperature. This complex was isolated and structurally characterized by single crystal X-ray diffraction and infrared spectrum. Magnetic measurement showed a quartet ground state for this complex at room temperature, which was also supported by electron paramagnetic resonance (EPR) characterization. Computational investigations indicated the deviation of the equatorial N2O2 coordination geometry around the Co(II) center from plane stabilized the quartet state. The end-on type O2 adduct of this (μ-hydroxo)dicobalt(II/III) complex was isolated as dark-brown crystals and structurally and spectroscopically characterized. EPR measurement of this compound in solid state at room temperature presented an isotropic singlet at g ∼2, revealing the superoxide-like electronic feature of the coordinated O2 and was in line with the calculation results. The reactivity of the Co(III)-O2 complex with N-hydroxyphthalimide, which can act as hydrogen atom donor, was also examined.

N-Heterocyclic carbene (NHC) ligands are widely investigated in medicinal inorganic chemistry. Here, we report the preparation and characterization of a series of half-sandwich [M(L)(NHC)Cl2] (M = Ru, Os, Rh, Ir; L = cym/Cp*) complexes with a N-flanking anthracenyl moiety attached to imidazole- and benzimidazole-derived NHC ligands. The anticancer activity of the complexes was investigated in cell culture studies where, in comparison to a Rh derivative with an all-carbon-donor-atom-based ligand (5a), they were found to be cytotoxic with IC50 values in the low micromolar range. The Ru derivative 1a was chosen as a representative for stability studies as well as for biomolecule interaction experiments. It underwent partial chlorido/aqua ligand exchange in DMSO-d6/D2O to rapidly form an equilibrium in aqueous media. The reactions of 1a with biomolecules proceeded quickly and resulted in the formation of adducts with amino acids, DNA, and protein. Hen egg white lysozyme crystals were soaked with 1a, and the crystallographic analysis revealed an interaction with an l-aspartic acid residue (Asp119), resulting in the cleavage of the p-cymene ligand but the retention of the NHC moiety. Cell morphology studies for the Rh analog 3a suggested that the cytotoxicity is exerted via mechanisms different from that of cisplatin.