Specific features of the interaction of components in the DMSO−HBr−Pd0 system

The products of interaction of components in the donor-acceptor electron-transport (DAET) DMSO−HBr system and their complex formation with the metallic palladium surface were studied. H₂O and Me₂S (main reaction products) and CO, CS₂, C₂H₆, MeBr, H, and CH₄ (minor reaction products) were found in the gas phase by mass spectrometry (MS). The samples of metallic palladium treated with the DAET system with a components ratio corresponding to the minimum and maximum rates of metal dissolution were studied by the methods of thermoprogrammed desorption with MS detection (TPD-MS) and XPS. According to the TPD-MS data, two forms of Me₂S are present on the metal surface, whereas the XPS method detected two complexes with the molecular compositions Pd^IIBr₄S_1.26 and Pd^IIBr_3.86S_1.42. The addition of an aqueous solution of NaOH to the system results in the formation of HCOONa, which indicates that compounds (CH₂O, HCOOH) capable of reducing the palladium complexes are present in the DAET system. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1740–1743, October, 2000.     

Reactivity of lithium 2,3-dihydro-1-benzothiophene-1-oxide toward aldehydes and imines and DFT calculations

The sulfinyl carbanion derived from 2,3-dihydro-1-benzothiophene-1-oxide and its lithium salt has been investigated by DFT calculations. The lithium carbanion was treated with aldehydes and imines to give chiral hydroxy and amino derivatives, with high stereoselectivity at the carbon α to the sulfoxide group (trans diastereoisomers), but with low diastereoselectivity at the hydroxyl or amine group. DFT calculations were used to rationalize the different stereochemical behavior of cyclic and acyclic lithiated sulfoxides in the reaction with aldehydes and azomethines.     

Synthesis of highly functionalized indeno[1,2-b]furans

Some novel functionalized indeno[1,2-b]furans were synthesized from the reaction of indandione/indanone and aldehydes at room temperature followed by the reaction of the Knoevenagel condendensed intermediate with 4-hydroxycoumarins in the presence of iodine as catalyst in dimethyl sulfoxide (DMSO) under thermal conditions. The reaction involved in a condensation and Michael addition followed by lactone ring opening and intramolecular cyclization process to afford the product in high yield in easy work-up procedure.     

Separation of post-translational modifications in monoclonal antibodies by exploiting subtle conformational changes under mildly acidic conditions

Chromatographic separation plays a key role in the identification, quantification, and characterization of protein variants. Here we describe separation of species containing two post-translational modifications (glycosylation and methionine oxidation) in the Fc fragment of a monoclonal antibody. The method is based on cation-exchange chromatography under mildly acidic conditions that destabilize mainly the CH2 domain. Our data suggest that the separation is not mediated by the chemical modification itself, but rather by subtle structural changes induced by the chemical modification in the domain-decoupled conformation that monoclonal antibodies adopt around pH 4. Compared to other procedures already described in the literature, this method demonstrates an improved separation and allows purification of species in the native fold for additional functional characterization. This approach of separation under conditions where the protein assumes an alternative conformation could find a more general utility for the separation of chemical modifications in proteins.     

Non-selectivity in the reaction of levoglucosenone with the sulfinyl allyl carbanion

Condensation of levoglucosenone with the carbanion ofrac-allyl phenyl sulfoxide, in contrast with reactions of this anion with the majority of other unsaturated ketones, proceeds without regio- or enantioselectivity to give a (1.0–1.8): 1 mixture of products of both 1,2- and 1,4-γ-addition of the allylic residue. Each product is a (1.2–1.6): 1 mixture of epimers at the asymmetric sulfur atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 157–159, January, 1999.     

Optically Active Sulfoxides and Low-Valent Titanium in Asymmetric Synthesis of Natural Products

The total synthesis of lasiodiplodin via optically active sulfoxides and the preparation of polyenes through low valent titanium reagents are described.     

Functionalization of Graphene Oxide with 3‐Mercaptopropyltrimethoxysilane and Its Electrocatalytic Activity in Aqueous Medium

In this work, a highly dispersed graphene oxide (GO) was successfully functionalized with 3‐mercaptopropyltrimethoxysilane (MPTS) molecule by silanization method. The chemically generated GO and MPTS functionalized GO (MPTS‐GO) were structurally characterized by thermogravimetric analysis (TGA), X‐ray diffraction analysis (XRD), scanning electron microscope (SEM), energy dispersive X‐ray (EDAX), fourier transform infrared spectroscopy (FT‐IR) and ultraviolet visible spectroscopy (UV‐Vis) techniques. The MPTS‐GO is highly suspensable in water. The thermal and conductivity results for MPTS‐GO are significantly increased compared to GO. Moreover, glassy carbon electrode modified with MPTS‐GO hybrid (MPTS‐GO/GCE) was prepared by casting of the MPTS‐GO solution on GCE. The MPTS‐GO/GCE showed an excellent electrocatalytic activity towards methionine (Met). This was understood from the observed less positive oxidation potential and higher oxidation current when compared to bare GC electrode. The MPTS‐GO has excellent electrocatalytic activity, making it an ideal candidate for sensor applications.     

Visible‐Light‐Accelerated C−H Sulfinylation of Heteroarenes

Heteroaromatic sulfoxides are a frequent structural motif in natural products, drugs, catalysts, and materials. We report a metal‐free visible‐light‐accelerated synthesis of heteroaromatic sulfoxides from sulfinamides and peroxodisulfate. The reaction proceeds at room temperature with blue‐light irradiation and allows the C−H sulfinylation of electron‐rich heteroarenes, such as pyrroles and indoles. An electrophilic aromatic substitution mechanism is proposed based on the substrate scope, substitution selectivity, and competition experiments with different nucleophiles.     

Cascades of Interrupted Pummerer Reaction‐Sigmatropic Rearrangement

A new class of Pummerer chemistry has emerged as a powerful tool in organic synthesis. The new technology consists of a beautiful cascade of an interrupted Pummerer reaction and the subsequent [3,3] sigmatropic rearrangement. The interrupted Pummerer reactions of alkenyl or aryl sulfoxides with unsaturated nucleophiles such as allylic silanes, ketones, and phenols provide sulfonium intermediates, which are ready to undergo smooth charge‐accelerated [3,3] sigmatropic rearrangement with excellent to exclusive regioselectivity. Some of the transformations proceed with transient loss of aromaticity. The reactions afforded five‐membered heterocycles, benzofurans, and biaryls of importance, depending on the sulfoxides and nucleophiles used. The reactions are unique and game‐changing because they are efficient, robust, redox‐neutral, regioselective, and metal‐free, which perfectly fits the need of modern organic synthesis. This chemistry also underscores the synthetic potential of organosulfur chemistry.     

Nonideality in diffusion of ionic and neutral solutes and hydrogen bond dynamics in dimethyl sulfoxide-chloroform mixtures of varying composition

Molecular dynamics simulations of charged and neutral solutes in dimethyl sulfoxide (DMSO)-chloroform mixtures reveal pronounced nonideality in the solute diffusion with changes of composition of the mixtures. The diffusion coefficient of the anionic solute first decreases, passes through a minimum at DMSO mole fraction of about 0.50, and then increases to reach its value for pure DMSO. The diffusion coefficients of the cationic and neutral solutes are found to decrease with increase in DMSO content of the solvent mixture. The extent of nonideality in the diffusion and orientational relaxation of solvent molecules is found to be somewhat stronger than that in diffusion of the anionic solute in these mixtures. We have also calculated the relaxation of hydrogen bonds formed between DMSO and chloroform molecules. The lifetimes of DMSO-chloroform hydrogen bonds are found to increase monotonically with increase in DMSO concentration. The average number of hydrogen bonds and their average energies are also computed. It is found that an increase in DMSO concentration causes a decrease in the number of DMSO-chloroform hydrogen bonds per DMSO or chloroform molecules but increases the strength of these hydrogen bonds.