Benzeneselenol Research Articles

Palladium-catalyzed regioselective synthesis of mono and bis(arylthiol) alkenes from propargyl carbonate and thiophenol.

A palladium catalyzed regioselective reaction of propargylic carbonate with thiophenols and benzene selenol is described. Atom-economic addition of thiols to propargylic carbonates provides an excellent opportunity for effective processes. The reaction proceeds via hydrothiolation to produce mono(arylthiol) alkenes and hydrothiolation followed by Tsuji-Trost type substitution to form bis(arylthiol) alkenes through single and double sequential attack by soft thio nucleophiles by control of the equivalence of thiophenols. This coupling reaction with good tolerance towards functional groups in both propargylic carbonates and thiols furnished a variety of highly functionalized alkenylation products in moderate to excellent yields via the formation of new C-S and C-Se bonds.

Micellar Assembly and Disassembly of Organoselenium Block Copolymers through Alkylation and Dealkylation Processes.

The aim of this work is to demonstrate that the alkylation and dealkylation of selenium atoms is an effective tool in controlling polymer amphiphilicity and, hence, its assembly and disassembly process in water. To establish this concept, poly(ethylene glycol)-block-poly(glycidyl methacrylate) was prepared. A post-synthesis modification with phenyl selenolate through a base-catalyzed selenium-epoxy ‘click’ reaction then gave rise to the side-chain selenium-containing block copolymer with an amphiphilic character. This polymer assembled into micellar structures in water. However, silver tetrafluoroborate-promoted alkylation of the selenium atoms resulted in the formation of hydrophilic selenonium tetrafluoroborate salts. This enhancement in the chemical polarity of the second polymer block removed the amphiphilic character from the polymer chain and led to the disassembly of the micellar structures. This process could be reversed by restoring the original amphiphilic polymer character through the dealkylation of the cations.

Selenium, Benzeneselenol, and Selenophene Interaction with Cu(100)

A high-resolution synchrotron photoemission study of selenium, selenophene (Seph), and benzeneselenol (BSe) adsorption on a Cu(100) surface was performed, to investigate the film structure, chemical adsorption properties, and molecular orientation. Complementary measurements for selenophene adsorption on Au(111) were also performed. The investigation is based on determination of core level binding energies (CLBEs) by X-ray photoelectron spectroscopy (XPS) and near-edge adsorption fine structure (NEXAFS). Se chemisorption was studied as a complement to the work on molecules in order to obtain data on the CLBEs for the atomic case. Se adsorption was performed from a Na2Se solution and thereafter annealing in vacuum. Annealing leads to appearance of ordered structures in LEED. Se 3d CLBEs were determined for the different cases. Fits of Se 3d XPS spectra show existence of several components attributable to different adsorption configurations. Also coadsorption with S was studied, which leads to changes in ad...

Selenium and benzeneselenol interaction with Cu(111)

Benzeneselenol (BSe) and Selenium interaction with a Cu(111) surface was studied to investigate adsorption characteristics, molecular orientation and possibility of Se–C bond scission leading to atomic Se presence on the surface.

Efficient Ring Opening of Protected and Unprotected Aziridines Promoted by Stable Zinc Selenolate in Ionic Liquid

A highly efficient protocol is reported for the synthesis of chiral β-seleno amines via the ring-opening reaction of aziridines. Under neutral conditions, employing a stable phenyl selenolate specie (PhSeZnBr) and (BMIM)BF 4 as solvent, β-seleno amines were obtained in good to excellent yields. Reuse of the ionic liquid was also possible, and four runs were performed with no decrease in the yields.

A novel method for elimination of the gold-islands formed in the self-assembled monolayers of benzeneselenol on Au(1 1 1) surface

Molecular ordering of benzeneselenol (BSe) self-assembled monolayers (SAMs) on Au(1 1 1) substrates have been investigated by scanning tunnelling microscopy (STM) [1]. After short immersion time (10 min), elevated islands with height of 2.4 Å were found to cover the entire gold surface. On and among the islands, the STM results exhibited the formation of a highly ordered phase (α-phase) by BSe species. In the present study, a novel method is presented to completely eradicate the elevated gold-islands. The method depends on a repetitive STM scanning over the same part of the SAM at restricted tunnelling conditions. After almost 6 h of successive scanning, the surface becomes clean and free of the elevated islands. Moreover, this method was found to induce phase transformation into β-phase. The size of the ordered domains of the β-phase was found to exceed five times that of α-phase. Such a long-range ordering of the β-phase at room temperature has not been previously observed for any system on Au(1 1 1). After detailed analyses, the β-phase was found to have a 33.5% of lower packing density than that of α-phase.

ChemInform Abstract: Preparation of the First Bench‐Stable Phenyl Selenolate: An Interesting “On Water” Nucleophilic Reagent.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Preparation of the First Bench‐Stable Phenyl Selenolate: an Interesting “On Water” Nucleophilic Reagent

AbstractIn this communication we report the synthesis and the characterization of the first solid and air‐stable selenolates, starting from commercially available phenylselenenyl halides and elemental zinc. These reagents were efficiently employed in the ring opening of epoxides as well as in other nucleophilic substitution and addition reactions showing an unexpected rate acceleration in water suspension at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Selenium promoted synthesis of enantiopure pyrrolidines starting from chiral aminoalcohols

Starting from commercially available enantiomerically pure aminoalcohols and using simple conversions promoted by organoselenium reagents, several enantiomerically pure substituted pyrrolidines were prepared. After double protections (R)- or (S)-2-phenylglycinols were converted into the β-amino selenides by displacing the tosyl group with phenyl selenolate anions. The phenylseleno group was then substituted by an allyl group by treatment with allyltributyltin and AIBN. The reaction of these allylic derivatives with electrophilic phenylselenium reagents afforded selenium containing pyrrolidines as the result of a 5-exo-trig cyclization. The pyrrolidine derivatives thus obtained were reductively deselenylated with triphenyltin hydride and AIBN. Moreover, the selenides were converted into the selenones, which easily gave substitution with different nucleophiles. Enantiopure 2,5-pyrrolidines containing azido, methylthio, cyano and iodo groups were thus obtained.

Interplay of Anchoring and Ordering in Aromatic Self-Assembled Monolayers

The structure and thermal stability of differently anchored aromatic self-assembled monolayers (SAMs) of benzenethiol (BT) and benzeneselenol (BS) on Au(111) have been studied in-depth by means of thermal desorption spectroscopy, X-ray photoelectron spectroscopy, near-edge X-ray absorption spectroscopy, and scanning tunneling microscopy. In contrast to long range ordered BS-SAMs consisting of closed packed, upstanding molecules forming a structure which resembles the molecular packing of benzene in the crystalline phase, BT-SAMs are characterized by a loose packing of largely tilted molecules which are arranged in a structure appearing only in small domains. Thermal desorption spectroscopy measurements clearly show that BS is less strongly bound to the gold substrate and moreover reveal different desorption peaks for each SAM, thus indicating the presence of different adsorption states. Heating both SAMs causes initially a partial desorption and formation of a diluted phase where the remaining molecules a...

Comparative adsorption of phenyl selenolate and selenocyanate on Au nanoparticle surfaces

UV–vis absorbance spectra taken at different elapsed time for the surface plasmon band shift indicated that the self-assembly of PhSeCN on gold should be slower than that of phenyl selenolate (PhSeH). A surface-enhanced Raman scattering (SERS) study showed that a trace amount of CN species could remain on Au surfaces when aromatic selenocyanates are reduced to give CN and their selenium atoms bound to the surface. Our concentration dependent SERS spectra suggested that the CN adsorption should be more favorable at higher concentrations of PhSeCN as indicated from more prominent intensites of the CN stretching vibration at 2110–2150 cm −1.

Induction of Phase II Enzyme Activity by Various Selenium Compounds

: Twenty-seven selenium compounds and sixteen structurally related organosulfur compounds were tested for quinone reductase (QR) and glutathione-S-transferase (GST) inducing activity in murine hepatoma (Hepa 1c1c7) cells. Sixteen selenium compounds were able to double QR activity, and seven of them also doubled GST activity. The nine most potent compounds, dimethyl diselenide, 2,5-diphenyl- selenophene, dibenzyl diselenide, methylseleninic acid, diphenyl diselenide, benzeneseleninic acid, benzene selenol, triphenylselenonium chloride, and ebselen (2-phenyl- 1,2-benzisoselenazol-3(2H)-one), doubled QR-specific activity at levels lower than 7 μM. The concentration-dependence of QR induction and cell growth inhibition were linearly correlated (P < 0.001, r2 = 0.96) among the group of organoselenium compounds with putative selenol-generating potential, implying that both responses of Hepa 1c1c7 cells were based on these selenol metabolites.

A General Method for the Formation of Diaryl Selenides Using Copper(I) Catalysts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A general method for the formation of diaryl selenides using copper(I) catalysts

We report a mild, palladium-free synthetic protocol for the cross coupling reaction of aryl iodides and phenyl selenol using 10 mol% CuI/neocuproine, NaO t-Bu or K 2CO 3 as base, in toluene, at 110°C. Using this protocol, we show that a variety of diaryl selenides can be synthesized in good yields from commercially available aryl iodides.

Self-Assembled Monolayers of Organoselenium Compounds on Gold: Surface-Enhanced Raman Scattering Study

To understand the binding nature of organoselenium compounds on gold, we have examined the adsorption behavior of several representative organoselenium compounds, i.e., benzeneselenol (BSe), diphenyl diselenide, dibenzyl diselenide, dioctyl diselenide, and benzyl phenyl selenide (BPSe) on the Au surface by virtue of surface-enhanced Raman spectroscopy (SERS). BSe chemisorbs on gold as selenolate with a tilted orientation. Upon adsorption, the Se–Se bonds of diselenides are cleaved to form selenolates, analogous to the formation of thiolate monolayers from disulfides. BPSe adsorbs on gold without any C–Se bond scission. The benzyl moiety of BPSe assumes a rather vertical stance while the phenyl moiety is more tilted to the gold surface.

The First Example of a Structurally Characterized Monomeric Bismuth Selenolate

The reaction of intramolecularly coordinating 2-(4,4-dimethyloxazolino)phenyl selenolate ligand with anhydrous BiCl3 (3:1 equivalents) produces the monomeric, air stable, homoleptic bismuth(III) selenolate complex.

The First Example of a Structurally Characterized Monomeric Bismuth Selenolate

The reaction of intramolecularly coordinating 2-(4,4-dimethyloxazolino)phenyl selenolate ligand with anhydrous BiCl3 (3:1 equivalents) produces the monomeric, air stable, homoleptic bismuth(III) selenolate complex.

Nucleophilic ring cleavage of mono-activated cyclopropanes via sodium and lithium phenyl selenolate

Nucleophilic ring cleavage of mono-activated cyclopropanes via sodium and lithium phenyl selenolate

The Aminomethylation of Selenophenol

The Aminomethylation of Selenophenol