Alexander S. Goloveshkin

Ridges and valleys on charged 1T-MoS2 sheets guiding the packing of organic cations

Using a novel powder X-ray pattern refinement technique, DFT calculations and TEM, we reveal for the first time the three-dimensional structure of hybrid (R4N)xMoS2 layered compounds. Both the precise coordinates of Mo and S atoms in the inorganic layer and the preferred positions of the organic cations relative to them are reported. The distorted geometry of the MoS2 sheet is found to be the driving force behind the arrangement of cations within the organic layers. The refined atomic coordinates, confirmed by periodic DFT modeling, show octahedral Mo atoms arranged in zigzag chains and the S atoms following the Mo ones, forming “ridges” and “valleys” on the sheet surface. The size of alkylammonium cations is compatible with these valleys, leading to a strong preferred arrangement: the cations exclusively occupy the space between the ridges. This result allows predicting the layer structure and ultimately the composition of the hybrid compound depending on the cation structure. The reported features of the MoS2 surface are important for understanding of MoS2-based sensors and hybrid flexible conductors, both relying on charged sheets of MoS2.

Synthesis of thiazolo[3,2-a]pyridines via an unusual Mannich-type cyclization

ABSTRACT The Mannich-type reaction of N-methylmorpholinium 4-aryl-3-cyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates with 3-(1,3-benzodioxol-5-yl)-2-methylpropanal (ocean propanal) and p-toluidine afforded 7-aryl-2-(1,3-benzodioxol-5-ylmethyl)-2-methyl-3-[(4-methylphenyl)amino]-5-oxo-2,3,6,7-tetrahydro-5H-thiazolo[3,2-a]pyridine-8-carbonitriles in modest (25–46%) yields. The structure of the key compound was confirmed by X-ray crystal structure analysis. GRAPHICAL ABSTRACT

Efficient and facile ‘on-solvent’ multicomponent synthesis of medicinally privileged pyrano[3,2-c]pyridine scaffold

The new type of ‘on-solvent’ multicomponent reaction was found: transformation of benzaldehydes, malononitrile and 4–hydroxy-6-methylpyridin-2(1H)-one in the presence of sodium acetate as catalyst in a small amount of ethanol results in formation of substituted 2-amino-7-methyl-5-oxo-4-phenyl-5,6-dihydro-4H-pyrano[3,2-c]pyridine-3-carbonitriles in excellent 92–99% yields. This novel ‘one-pot’ process opens an efficient and convenient way to functionalize pyrano[3,2-c]pyridine systems, which are promising compounds for different biomedical applications.

Stereoselective one-pot synthesis of polycyanosubstituted piperidines

An effective and facile multicomponent method for the synthesis of polysubstituted piperidines is described. The Michael–Mannich type cascade of benzylidenemalononitriles with aromatic aldehydes and ammonium acetate or aqueous ammonia provides convenient access to the stereoselective synthesis of 3,3,5,5-tetracyano-2,4,6-triarylpiperidines in good to excellent yields in one-pot manner. Ammonium acetate or aqueous ammonia plays a role both as a catalyst and as a nitrogen source. It is established that the reaction proceeds via sequence of equilibriums and a competitive mechanisms are implemented.Graphical abstract

High diastereoselective amine-catalyzed Knoevenagel–Michael-cyclization–ring-opening cascade between aldehydes, 3-arylisoxazol-5(4 H )-ones and 3-aminocyclohex-2-en-1-ones

A highly diastereoselective three-component cascade reaction among aromatic aldehydes, 3-arylisoxazol-5(4H)-ones and 3-aminocyclohex-2-en-1-ones takes place under the catalysis of triethylamine, providing (3SR,4SR)-4-aryl-3-[(E)-(hydroxyimino)(aryl)methyl]-4,6,7,8-tetrahydroquinoline-2,5(1H,3H)-diones in 45–85% yields. The transformation presumably proceeds through a sequential cascade of Knoevenagel/Michael-addition/cyclization/ring-opening reactions. This process was carried out in green media (EtOH/water, 1:1–1:3) at reflux. Products are crystallized directly from the reaction mixture and their isolation includes only filtration. The structure of (3SR,4SR)-3-[(E)-(hydroxyimino)(phenyl)methyl]-7,7-dimethyl-4-phenyl-4,6,7,8-tetrahydroquinoline-2,5(1H,3H)-dione was confirmed by X-ray diffraction analysis.Graphical Abstract

Mechanochemistry – a new powerful green approach to the direct synthesis of alkoxysilanes

The present work shows a new one-stage mechanochemical method for the direct synthesis of alkoxysilanes by silicon mechanoactivation followed by a reaction with an alcohol. Alkoxysilanes were obtained with nearly complete silicon and alcohol conversion. This method allows for a considerable simplification of the traditional multistage process by eliminating three stages that include silicon and catalyst preparation, and adapts it to green chemistry requirements. Vibration milling removed the oxide film, and the mechanoactivation of the large silicon fraction (1000–2000 μm) occurs in the reactor working space. Abrasion of the reactor walls and grinding bodies made of brass results in a developed catalytic surface on silicon, as it has been proven by a set of physical analytical methods such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS).

Comparable study of the structure of 1,2-bis(2-acetamidoethyl) diaziridine and 3,3-diethyldiaziridine with structures of related compounds by X-ray diffraction analysis and quantum chemical calculations

The crystal structures of 1,2-bis(2-acetamidoethyl)diaziridine and 3,3-diethyldiaziridine have been determined by single-crystal X-ray diffraction study. The studied diaziridine molecules have C2 total group symmetry. The conformation of the studied molecules is similar to those of other diaziridines. A topological study within the framework of Bader’s atoms in molecule (AIM) theory was performed for these molecules, their analogs and related compounds. From AIM and natural bond orbital (NBO) analysis data, an influence of the intramolecular interaction on chemical bonds was described and quantified. It was found that the N-N bond length increases on going from acyclic to cyclic molecules in accordance with increasing p-character of σN-N bonding orbitals. The lengthening of N-N bond lengths in diaziridine molecules in most cases is accompanied with increasing of the bond ellipticities demonstrating the π-component contribution to these bonds.

Mannich-type reaction of tetrahydropyridine-2-thiolates with primary amines and α-substituted propanals

The Mannich-type reaction of N-methylmorpholinium 4-aryl-3-cyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates with 2-R-propanals (ocean propanal, isobutyraldehyde) and primary aromatic amines afforded 7-aryl-2-R-2-methyl-3-arylamino-5-oxo-2,3,6,7-tetrahydro-5Н-thiazolo[3,2-a]pyridine-8-carbonitriles in modest yields; the structure of a key compound was confirmed by X-ray crystal structure analysis. The mechanism of the reaction is discussed.