A methodology is reported for visible‐light‐promoted synthesis of unsymmetrical chalcogenides enabled by dimsyl anion in the absence of transition‐metals or photoredox catalysts. The cross‐coupling ...reaction between aryl halides and diaryl dichalcogenides proceeds with electron‐rich, electron‐poor, and heteroaromatic moieties. Mechanistic investigations using UV‐Vis spectroscopy, time‐dependent density functional theory (TD‐DFT) calculations, and control reactions suggest that dimsyl anion forms an electron‐donor‐acceptor (EDA) complex capable of absorbing blue light, leading to a charge transfer responsible for generation of aryl radicals from aryl halides. This previously unreported mechanistic pathway may be applied to other light‐induced transformations performed in DMSO in the presence of bases and aryl halides.
Radical Fluoroalkylation Reactions Barata-Vallejo, Sebastián; Cooke, Maria Victoria; Postigo, Al
ACS catalysis,
08/2018, Volume:
8, Issue:
8
Journal Article
Peer reviewed
Open access
Recent protocols and reactions for catalytic radical perfluoroalkylations will be described. The production of perfluoroalkyl radicals (RF = C n F2n+1, n ≥ 2), which effect both addition and ...substitution reactions on organic substrates, can be realized through a range of diverse methods such as the well-established visible-light transition-metal-mediated photocatalysis, organic-dye-photocatalyzed reactions, electron donor–acceptor complexes, and more recently frustrated Lewis pairs. Thus, perfluoroalkylation reactions of carbon–carbon multiple bonds, isocyanides, nitrones, hydrazones, β-keto esters, α-cyano arylacetates, sulfides, and (hetero)arenes will be described. Special emphasis will be placed on examples published after 2015, where higher fluorinated series of fluoroalkylating reagents are studied.
ZEB1 is a master regulator of the Epithelial-to-Mesenchymal Transition (EMT) program. While extensive evidence confirmed the importance of ZEB1 as an EMT transcription factor that promotes tumor ...invasiveness and metastasis, little is known about its regulation. In this work, we screened for potential regulatory links between ZEB1 and multiple cellular kinases. Exploratory
analysis aided by phospho-substrate antibodies and ZEB1 deletion mutants led us to identify several potential phospho-sites for the family of PKC kinases in the N-terminus of ZEB1. The analysis of breast cancer cell lines panels with different degrees of aggressiveness, together with the evaluation of a battery of kinase inhibitors, allowed us to expose a robust correlation between ZEB1 and PKCα both at mRNA and protein levels. Subsequent validation experiments using siRNAs against PKCα revealed that its knockdown leads to a concomitant decrease in ZEB1 levels, while ZEB1 knockdown had no impact on PKCα levels. Remarkably, PKCα-mediated downregulation of ZEB1 recapitulates the inhibition of mesenchymal phenotypes, including inhibition in cell migration and invasiveness. These findings were extended to an
model, by demonstrating that the stable knockdown of PKCα using lentiviral shRNAs markedly impaired the metastatic potential of MDA-MB-231 breast cancer cells. Taken together, our findings unveil an unforeseen regulatory pathway comprising PKCα and ZEB1 that promotes the activation of the EMT in breast cancer cells.
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•Static Gas Phase Pyrolysis of fungicide Chlorothalonil and its derivatives yield mainly dehalogenated compounds and coke.•Homogeneous and Heterogeneous reactions (over Fe or Cu ...wires, H-ZSM-11 and (H/Fe/Cu)-Y Zeolites) have been explored.•Pyrolysis products at temperatures higher than 300 °C were identified through NMR, IR and GC–MS.•H–Y zeolite as well as Cu wires proved to be Reusable Catalysts for thermal decomposition of chlorothalonil.
Homogeneous and heterogeneous gas-phase static thermolysis of chlorothalonil (CT, 1) and four derivatives are presented. After thermal decomposition, many interesting products are formed. Chlorothalonil yielded principally carbonaceous residues and dehalogenated compounds, while all the derivatives also afforded a condensed dihydrophenazine (17). Relevant information from pyrolysis states that: CT is quantitatively decomposed when compared to its aromatic derivatives; in all cases some potential toxic compounds (which were detected with the help of NMR, GC–MS and IR) are produced; the best catalysts to perform the decomposition are the acidic zeolite H–Y and metallic Cu; the two zeolites used, (H-ZSM-11 and H–Y) are able to adsorb the substrates, but only H–Y is capable of decomposing CT in carbonaceous residues.
A metal-free regioselective C(sp3)–H amination of amides using N-haloimides in the presence of lithium tert-butoxide and visible light is presented herein. This photoexcited approach is ...straightforward, and it aminates a wide variety of amides under mild conditions without the use of photocatalysts, external radical initiators, or oxidants. A halogen-bonded intermediate between the tert-butoxide base and the N-haloimide is proposed to be responsible for the increased photoreactivity. Calculations show that the formation of this electron donor–acceptor complex presents an exergonic energy profile.
A photoinduced, iron(III) chloride-catalyzed C–H activation of N-methyl amides and ethers leads to the formation of C–S and C–Se bonds via a ligand-to-metal charge transfer (LMCT) process. This ...methodology converts secondary and tertiary amides, sulfonamides, and carbamates into the corresponding amido-N,S-acetal derivatives in good yields. Mechanistic work revealed that this transformation proceeds through a hydrogen atom transfer (HAT) involving chlorine radical intermediates.
Presented is a light-promoted C–C bond forming reaction yielding sulfone and phosphate derivatives at room temperature in the absence of metals or photoredox catalyst. This transformation proceeds in ...neat conditions through an auto-oxidation mechanism which is maintained through the leaching of trace amounts of O2 as sole green oxidant.
Presented is a light-promoted C-C bond forming reaction yielding sulfone and phosphate derivatives at room temperature in the absence of metals or photoredox catalyst. This transformation proceeds in ...neat conditions through an auto-oxidation mechanism which is maintained through the leaching of trace amounts of O
as sole green oxidant.
Polyfluoroarene moieties are of interest in medicinal chemistry, agrochemicals, and material sciences. Herein, we present the first polyfluoroarylation of unactivated alkyl halides via a halogen atom ...transfer process. This method converts primary, secondary, and tertiary alkyl halides into the respective polyfluoroaryl compounds in good yields in the presence of amide, carbamate, ester, aromatic, and sulfonamide moieties, including derivatives of complex bioactive molecules. Mechanistic work revealed that this transformation proceeds through an alkyl radical generated after the halogen atom transfer.
We report the synthesis of aryl boronic esters and aryl phosphonate esters promoted by visible-light in the absence of transition-metals or photoredox catalysts. The transformation proceeds at room ...temperature using sodium hydride, as a non-nucleophilic base, and exhibits functional group tolerance for anilines, amides, and esters. UV–vis spectroscopy, radical trapping experiments, and computational (TD-DFT) calculations suggest an electron-donor–acceptor (EDA) complex between solvent anions and aryl halides as the species responsible for this reactivity.
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