In the current ecological context, use of insect sex pheromones as an alternative to conventional pesticides is in constant growth. In this report, we discuss the recent contributions brought by our ...groups in the field of iron-catalyzed cross-couplings applied to the synthesis of insect pheromones. The pivotal question of the development of sustainable synthetic procedures involving cheap, non-toxic and efficient additives is also discussed, as well as the mechanistic features guiding the reactivity of such catalytic systems.
Research into environmentally friendly strategies for hydrogen transfer reduction is increasing, along with the need for more elaborate heterocyclic platforms. Within this context, we develop a new ...approach for substituted dihydrobenzoccarbazoles and indoles. These compounds were synthesized through an iron-catalyzed hydrogen transfer reduction of nitroarenes, followed by intramolecular cyclization. This transformation involves using a Knölker-type catalyst, Cs2CO3 as the base, and benzyl alcohol as the non-expensive and low volatile hydrogen donor. We synthesize 30 examples of aza-heterocycles with moderate to excellent yields by applying this strategy. Additionally, DFT calculations demonstrated that the pathway reaction could follow an anionic mechanism.
In pursuing more eco-compatible strategies in hydrogen transfer reduction, we developed a novel robust strategy for synthesizing dihydrobenzoccarbazoles and indoles, based on an iron-catalyzed reductive cyclization of nitroraryls. In addition, DFT modelings demonstrated a new pathway reaction with the Knölker complex. Display omitted
•A low-valent non-innocent iron complex supported by phen-type ligands efficiently promotes reductive coupling of heteroaryl halides;•High efficiency of this complex in alkyne 2+2+2 cycloaddition is ...enhanced by assistance of main-group salts;•Analysis of the non-innocent electronic structure of this complex by means of DFT calculations allows a thorough analysis of its temperature-variable 1H NMR spectral properties.
We report in this work the spectroscopic and reactivity properties of a non-innocent paramagnetic iron complex (bcp•–)2FeII featuring formally a Fe° center stabilized by two bathocuproine (bcp) ligands. The origin of the paramagnetic 1H NMR behavior is analyzed by means of DFT calculations, and shows that two electronic states of the complex contribute to its spectroscopic properties. The dynamics of the coordination sphere in (bcp•–)2FeII is governed by the duality between the two electronic descriptions (bcp•–)2FeII, and (bcp)2Fe0. The strong antiferromagnetic coupling between the reduced bcp scaffolds and the ferrous ion in (bcp•–)2FeII makes substitution of the bcp•– ligand difficult; however, the reduced (bcp)2Fe° character allows substitution of bcp by π-accepting ligands, such as alkynes, which can be activated in catalytic cycloadditions with the assistance of main-group salts. (bcp•–)2FeII also shows reductive activity towards a variety of organic electrophiles, and preliminary results using this complex as a catalyst for the reductive coupling of heteroaryl chlorides are discussed.
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An iron(II) borohydride complex ((η1-H3BH)FeCl(NCCH3)4) is employed as the precatalyst in iron-catalyzed radical cyclizations of unsaturated organic halides in the presence of NaBH4. Mechanistic ...investigations have established that the ligand bound to the metal center (acetonitrile versus ethylenebis(diphenylphosphine) (dppe)) plays a crucial role in the structure and reactivity of the active anionic iron(I) hydride (HFeCl(dppe)2−) and borohydride ((η1-H3BH)FeCl(NCCH3)4−) with unsaturated haloacetals. This work provides new insights into iron(I) hydride and borohydride species and their potential implication in single-electron processes.
Objective
Studies assessing the prevalence of anti–RNA polymerase III (anti–RNAP III) antibodies in systemic sclerosis (SSc) have yielded a wide range of results. The aim of the present study was to ...describe a new SSc cohort tested for presence of anti–RNAP III and perform a systematic review and meta‐analysis to assess the prevalence of anti–RNAP III in patients worldwide and the potential factors of variability.
Methods
Seropositivity for anti–RNAP III was evaluated in a French cohort of SSc patients. A systematic review of the literature was carried out in PubMed and EMBase. Meta‐analysis was performed using available data on prevalence, clinical characteristics of SSc patients, and the types of assays used for anti–RNAP III testing.
Results
One hundred thirty‐three French SSc patients were tested for anti–RNAP III, and a prevalence of 6–9% was found in these patients. Thirty studies representing a total population of 8,437 SSc patients were included in the meta‐analysis. Prevalence of anti–RNAP III in this population was highly variable (range 0–41%). The overall pooled prevalence of anti–RNAP III was 11% (95% confidence interval 8–14), but heterogeneity was high among studies (I2 = 93%, P < 0.0001). Geographic factors such as continent or country of study origin partially explained this heterogeneity and correlated with the prevalence. No other baseline SSc characteristics were significantly correlated with the prevalence of anti–RNAP III.
Conclusion
Data on our new cohort and our meta‐analysis of the literature confirmed that anti–RNAP III prevalence in SSc varies among centers. Geographic factors were significantly associated with prevalence, which underscores the probable implication that genetic background and environmental factors play a role. Heterogeneity among studies remained largely unexplained.
The mechanism of cross-coupling reactions of aryl halides PhX (X = I, Br, Cl) with cyclohexylamine catalyzed by CuI associated with a diketonate ligand (ket = 2-acetylcyclohexanoate) has been ...investigated via DFT. Phenyl halides which can be involved in halogen-bond formation (X = I, Br) with the anionic nitrogen of the intermediate (ket)Cu-NHCy− can undergo intramolecular oxidative addition, which is in competition with the classical oxidative addition three-centered pathway, whereas those which cannot (X = Cl) undergo a classical oxidative addition, leading to the common complex (ket)CuIIIPh(NHCy). The latter is involved in a faster reductive elimination, leading to PhNHCy. C6F5I, which involves the strongest C6F5I- - -N halogen bond, generates the anion C6F5 – and consequently not the expected C–N cross-coupling product by substitution at the C–I bond, as evidenced experimentally.
A one‐step conversion of CO2 into heteroaromatic esters is presented under metal‐free conditions. Using fluoride anions as promoters for the C−Si bond activation, pyridyl, furanyl, and thienyl ...organosilanes are successfully carboxylated with CO2 in the presence of an electrophile. The mechanism of this unprecedented reaction has been elucidated based on experimental and computational results, which show a unique catalytic influence of CO2 in the C−Si bond activation of pyridylsilanes. The methodology is applied to 18 different esters, and it has enabled the incorporation of CO2 into a polyester material for the first time.
Metal free! A novel methodology is described to convert CO2 into heteroaromatic esters in the presence of organosilanes and organic halides using fluoride anions as promoters for the C−Si bond activation (see scheme). CO2 exhibits a unique catalytic influence in the C−Si bond cleavage of pyridylsilanes, serving as a traceless activator.
Eosinophils are multifunctional leukocytes that are involved in innate and adaptive immune responses through the expression of various receptors and mediators. Previously, we showed that human ...eosinophils and T cells shared cytotoxic activities against tumor cells that involved the γ-δ TCR and cell-cell contact. In this study, we investigated the molecules involved in eosinophil-tumor cell interactions. Given the role of IL-18 in cell adhesion and in protecting against colon cancer, we evaluated its role in eosinophil-mediated cytotoxicity against Colo-205, a human colon carcinoma cell line. We found that human eosinophils exerted dose- and time-dependent tumoricidal activity against Colo-205 cells. Neutralization of IL-18 significantly reduced eosinophil-mediated Colo-205 apoptosis and inhibited cell-cell adhesion. Moreover, addition of rIL-18 led to upregulation of CD11a and ICAM-1 adhesion molecules, which were involved in the contact between eosinophils and Colo-205 cells. Our results indicated that IL-18 was involved in the eosinophil-mediated death of Colo-205 by facilitating contact between effector and target cells. These data underscored the involvement of an additional mediator in eosinophil-mediated antitumor cytotoxicity. Our findings support existing evidence that eosinophils could play a beneficial role in the context of colon cancer.
A Pd-catalyzed Hiyama cross-coupling reaction using SO
2
is described. The use of silicon-based nucleophiles leads to the formation of allyl sulfones under mild conditions with a broad functional ...group tolerance. Control experiments coupled with DFT calculations shed light on the key steps of the reaction mechanism, revealing the crucial role of a transient sulfinate anion.
The kinetics of the oxidative additions of haloheteroarenes HetX (X=I, Br, Cl) to Pd0(PPh3)2 (generated from Pd0(PPh3)4) have been investigated in THF and DMF and the rate constants have been ...determined. In contrast to the generally accepted concerted mechanism, Hammett plots obtained for substituted 2‐halopyridines and solvent effects reveal a reaction mechanism dependent on the halide X of HetX: an unprecedented SNAr‐type mechanism for X=Br or Cl and a classical concerted mechanism for X=I. These results are supported by DFT studies.
X changes everything: Kinetics of the oxidative additions of HetX (X=I, Br, Cl) to Pd0(PPh3)2 generated from Pd0(PPh3)4 and DFT calculations reveal a mechanism that, contrary to the generally accepted concerted mechanism, depends on the nature of X. The data point to an unprecedented SNAr‐type mechanism for X=Br or Cl, whereas a classical concerted mechanism is at play for X=I (see scheme).
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