194734-10-6Relevant academic research and scientific papers
Electrochemical Generation of Hypervalent Bromine(III) Compounds
Francke, Robert,Mohebbati, Nayereh,Sokolovs, Igors,Suna, Edgars
, p. 15832 - 15837 (2021/06/14)
In sharp contrast to hypervalent iodine(III) compounds, the isoelectronic bromine(III) counterparts have been little studied to date. This knowledge gap is mainly attributed to the difficult-to-control reactivity of λ3-bromanes as well as to their challenging preparation from the highly toxic and corrosive BrF3 precursor. In this context, we present a straightforward and scalable approach to chelation-stabilized λ3-bromanes by anodic oxidation of parent aryl bromides possessing two coordinating hexafluoro-2-hydroxypropanyl substituents. A series of para-substituted λ3-bromanes with remarkably high redox potentials spanning a range from 1.86 V to 2.60 V vs. Ag/AgNO3 was synthesized by the electrochemical method. We demonstrate that the intrinsic reactivity of the bench-stable bromine(III) species can be unlocked by addition of a Lewis or a Br?nsted acid. The synthetic utility of the λ3-bromane activation is exemplified by oxidative C?C, C?N, and C?O bond forming reactions.
A highly active and selective palladium pincer catalyst for the formation of α-aryl ketones via cross-coupling
Bugarin, Alejandro,Connell, Brian T.
supporting information; scheme or table, p. 7218 - 7220 (2011/08/09)
Several air and moisture stable Pd(ii) pincer complexes were synthesized via oxidative addition of Pd(0) to novel PheBox pincer ligand precursors. Low loadings (1 mol%) of the Pd complex [t-BuPhebox-Me2]PdBr are capable of efficiently promoting the selective α-monoarylation of a variety of ketones with numerous aryl bromides in only 1 h at 70°C with 82-99% yields.
Synthesis, structure, and glutathione peroxidase-like activity of amino acid containing ebselen analogues and diaryl diselenides
Selvakumar, Karuthapandi,Shah, Poonam,Singh, Harkesh B.,Butcher, Ray J.
experimental part, p. 12741 - 12755 (2011/12/04)
The synthesis of some ebselen analogues and diaryl diselenides, which have amino acid functions as an intramolecularly coordinating group (Se O) has been achieved by the DCC coupling procedure. The reaction of 2,2′- diselanediylbis(5-tert-butylisophthalic acid) or the activated ester tetrakis(2,5-dioxopyrrolidin-1-yl) 2,2′-diselanediylbis(5-tert- butylisophthalate) with different C-protected amino acids (Gly, L-Phe, L-Ala, and L-Trp) afforded the corresponding ebselen analogues. The used precursor diselenides have been found to undergo facile intramolecular cyclization during the amide bond formation reaction. In contrast, the DCC coupling of 2,2′-diselanediyldibenzoic acid with C-protected amino acids (Gly, L/D-Ala and L-Phe) affords the corresponding amide derivatives and not the ebselen analogues. Some of the representative compounds have been structurally characterized by single-crystal X-ray crystallography. The glutathione peroxidase (GPx)-like activities of the ebselen analogues and the diaryl diselenides have been evaluated by using the coupled reductase assay method. Intramolecularly stabilized ebselen analogues show slightly higher maximal velocity (Vmax) than ebselen. However, they do not show any GPx-like activity at low GSH concentrations at which ebselen and related diselenides are active. This could be attributed to the peroxide-mediated intramolecular cyclization of the corresponding selenenyl sulfide and diaryl diselenide intermediates generated during the catalytic cycle. Interestingly, the diaryl diselenides with alanine (l,l or d,d) amide moieties showed excellent catalytic efficiency (kcat/KM) with low KM values in comparison to the other compounds. Peroxidase-like activity: Reaction of compound 1 (see figure) with glutathione (GSH) leads to the formation of the corresponding selenenyl sulfide and diaryl diselenide intermediates. The reaction of these intermediates with H2O2 leads to the formation of 1 via arylselenenic acid. This process hampers the GPx-like activity at low GSH concentrations.
Aromatic ring strain in arylselenenyl bromides: Role in facile synthesis of selenenate esters via intramolecular cyclization
Selvakumar,Singh, Harkesh B.,Butcher, Ray J.
scheme or table, p. 10576 - 10591 (2011/02/22)
The synthesis and reactivity of 2,6-disubstituted arylselenium compounds derived from 2-bromo-5-tertbutylisophthalic acid (43) are described. The syntheses of bis(5-tert-butylisophthalic acid dimethyl ester)diselenide (46) and bis(5-tert-butylisophthalic
Convenient synthesis, characterization and GPx-like catalytic activity of novel ebselen derivatives
Zade, Sanjio S.,Panda, Snigdha,Tripathi, Santosh K.,Singh, Harkesh B.,Wolmershaeuser, Gotthelf
, p. 3857 - 3864 (2007/10/03)
The synthesis and characterization of benzisochalcogenazolones (ebselen derivatives 16-21) is described. The synthesis of 16-21 was achieved by treating the bromo precursors 11-13 with an appropriate dilithium dichalcogenide. The synthesis of benzisoselenazolones 16 and 18 was also accomplished by an alternative route, that is, by treating the corresponding methoxymethyl selenides 22 and 23 with 1 equiv. of bromine. The synthesis of methoxymethyl selenides 22 and 23 was accomplished by lithiation of the bromo precursors followed by treatment with bis(methoxymethyl) diselenide. The benzisoselenazolones 16 and 17 were characterized by single-crystal X-ray techniques. The GPx-like catalytic activities of compounds 16-18 and 21 were determined by using the coupled reductase assay. Compound 16 was found to be less active than ebselen 8 whereas compounds 17 and 18 were more active than ebselen in this assay. Compound 21 showed a 1.5-fold higher activity than its selenium analogue 17. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Solution and solid state studies of some new silicon and germanium compounds stabilized by tridentate ligands
Benin, Vladimir A.,Martin, James C.,Willcott, M. Robert
, p. 10133 - 10154 (2007/10/03)
The preparation and studies of novel heterocyclic compounds, containing silicon or germanium, is described. All of them incorporate the 2,6-bis(dialkylaminomethyl)-4-(1,1-dimethylethyl)phenyl tridentate ligand (Structures 1-2, Scheme 1) as a main substruc
