Polycyclic aromatic sulfur-containing compounds are widely distributed in oil, especially in its low-volatile and heavy fractions (resins, asphaltenes), and this dictates the need for their determination when reliable methods for sulfur removing, cleaning and processing oil are developed. In these cases, “soft” ionization mass spectrometry methods, based on electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI), are particularly effective. However, aromatic sulfur-containing compounds have low polarity and cannot be readily ionized by these methods. To overcome the problem, their preliminary conversion into sulfonium salts by the action of alkyl iodides and a silver-containing agent is widely used. In the process of developing more economical derivatization methods, we found a rather unexpected possibility of implementing S-alkylation of organic sulfides with commercial polydialkylsiloxanes (alkyl = CH₃ or C₂H₅) in the presence of triflic acid (CF₃SO₃H) as a superacid co-alkylating agent. For homologous dibenzothiophenes as a typical model representative of petroleum sulfur-containing aromatic compounds, ESI and MALDI mass spectra exhibited the signals of corresponding S-alkylsulfonium salts with a high signal-to-noise ratio. A rational mechanism for the described chemical transformation is proposed, including the indispensable activation by triflic acid and the cleavage of the Si-C bond. Specific collision-induced dissociation of corresponding S-alkylated sulfonium cations is considered. The applicability of the derivatization approach to the analysis of petroleum products by high-resolution mass spectrometry is demonstrated.

A concise preparative IMDAV strategy for the synthesis of pyrrolo[3,4-c]pyridines, which exhibit anti-inflammatory activity, starting from readily available materials was proposed.

Many practically relevant inorganic solution systems have complex compositions with tens or hundreds of distinct species. Here, we present an approach to analyzing ESI-MS spectra combining a set of scripts for peak assignment and a quantum chemical methodology for the determination of the structure of selected ions. We selected solutions of CuCl, PdCl₂, and the CuCl–PdCl₂ mixture as models of popular precatalysts in cross-coupling reactions and the Wacker process that can form “cocktail”-type systems. The spectra exhibited a great number of signals of mono- and bimetallic oligomeric chloride subnanoclusters. Few oligometallic ions had core–shell structures, according to the computations; the structure of most ions was completely unsymmetric, with bridging Cl⁻ ligands supporting the oligomeric structures. Born-Oppenheimer molecular dynamics showed that some ions were structurally flexible under the selected conditions. Many considered ions exhibited rich configurational and conformational isomerism. The activation (polarization) of the N₂ molecule (from the drying gas used during electrospray ionization) by some ions was determined by the analysis of electron density distributions. For the first time, we describe a flexible approach for semiautomatic analysis of highly complex mass-spectra of organometallic systems in solution with the possibility of revealing molecular structures.

The conditions for recording electrospray ionization mass spectra of dicarboxylic acids are selected to ensure the generation of doubly-charged negative ions of compounds containing more than 14 carbon atoms in the chain. The fragmentation of such ions under the conditions of collision-induced activation is described. It is shown that the main decomposition route is associated with the break of C–C bonds in the hydrocarbon skeleton of molecules. Thus, in contrast to the fragmentation of singly charged negative ions, the forced decomposition of bis-deprotonation products of decarboxylic acids makes it possible to obtain information about the structure of the molecular skeleton.