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The nucleophilic addition of imidazole derivatives to trifluoromethylated acetylenes was studied. Unpredictable regioselectivity of the reaction was observed to yield both β- and α-addition products. The reaction is 100% stereoselective to give the corresponding adducts as a Z -isomers only. The observed regioselectivity is discussed in terms of polarization of triple bond using experimental and calculated data.

The rapid development of organic chemistry and catalysis has provided outstanding chemical tools to build complex molecular architectures that were never possible before. In spite of amazing progress in studying individual molecules and reactions, practical applications are limited due to the high cost of newly developed technologies and the difficulty in understanding the processes at the molecular level. Herein, we summarize our first steps and experiences carrying out an ongoing project on organic and hybrid molecular systems that highlights new fascinating opportunities and identifies future challenges.

The formation of the corresponding benzyl cations [ArHC+–CH(X)CF3] takes place under protonation of E-/Z-2-halogeno-2-CF3 styrenes [ArCH═C(X)CF3, X = F, Cl, Br] in superacids. The structures of these new electrophiles were studied by means of NMR and theoretical DFT calculations. According to these data, in the case of bromo derivatives, the formed cations, most probably, exist as cyclic bromonium ions; however, in the cases of chloro and fluoro derivatives, open forms are more preferable. Subsequent reaction of these benzyl cations with arenes proceeds as Friedel–Crafts alkylation to afford 1,1-diaryl-2-halo-3,3,3-trifluoropropanes [Ar(Ar′)CH–CH(X)CF3] in high yields (up to 96%) as a mixture of two diastereomers. The prepared halogenopropanes were easily converted into the corresponding mixtures of E-/Z-trifluoromethylated diarylethenes [Ar(Ar′)C═CCF3] (in yields up to 96%) by dehydrohalogenation with base (KOH or t-BuOK). The mechanism of elimination (E2 and Ecb) depends on the nature of the leaving gro...

We have evaluated a range of functionalized isocyanides in the aziridine aldehyde-driven multicomponent synthesis of piperazinones. High diasteroselectivity for each isocyanide was observed. A theoretical evaluation of the reaction course corroborates the experimental data. Moreover, the reactivity of cis- and trans-configured aziridine aldehyde dimers has been compared. This study further probes the dimer-driven mechanism of cyclization and enables an efficient access to a wide range of chiral piperazinones bearing functionalized side chains.

Environmental profiles for the selected metals were compiled on the basis of available data on their biological activities. Analysis of the profiles suggests that the concept of toxic heavy metals and safe nontoxic alternatives based on lighter metals should be re-evaluated. Comparison of the toxicological data indicates that palladium, platinum, and gold compounds, often considered heavy and toxic, may in fact be not so dangerous, whereas complexes of nickel and copper, typically assumed to be green and sustainable alternatives, may possess significant toxicities, which is also greatly affected by the solubility in water and biological fluids. It appears that the development of new catalysts and novel applications should not rely on the existing assumptions concerning toxicity/nontoxicity. Overall, the available experimental data seem insufficient for accurate evaluation of biological activity of these metals and its modulation by the ligands. Without dedicated experimental measurements for particular metal/ligand frameworks, toxicity should not be used as a "selling point" when describing new catalysts.

The reaction of 2-halogeno-2-CF3 substituted styrenes [ArCH C(X)CF3, X = F, Cl, Br] with the superacid TfOH resulted in 100% regioselective formation of the corresponding benzyl cations [ArHC+ CH(X)CF3]. Subsequent reaction of these electrophilic species with arenes [Ar′H] afforded diastereomeric 1,1-diaryl-2-halogeno-3,3,3-trifluoro propanes [Ar(Ar′)CH–CH(X)CF3] in high yields (up to 96%). The obtained halogenopropanes were easily transformed to the corresponding trifluoromethylated diarylethenes [Ar(Ar′)C CCF3] in yields of up to 95% by dehydrohalogenation using base. The elimination of chlorides and bromides using the KOH–ethanol system proceeds via an E2 elimination, whereas in the case of fluorides an E1cb elimination most probably takes place as the major reaction path.

The new 2-amino-3-R-4-aryl-6-ethyl-4,6-dihydropyrano[3,2-c][2,1]benzothiazine 5,5-dioxides were synthesized via three-component interaction of 1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide with arylcarbaldehydes and active methylene nitriles. Depending on the nature of an active methylene nitrile and an arylcarbaldehyde this interaction can lead either to the target 2-amino-4H-pyrans or to the stable triethylammonium salts of bis(1H-2,1-benzothiazin-4(3H)-one 2,2-dioxides) (bis-adducts). The latter is a completely new product of such interaction. The structure of the bis-adduct was confirmed by single crystal X-ray diffraction. Actually, the formation of stable triethylammonium salts (as the process competitive with the 2-amino-4H-pyrans formation) appeared to be reversible and their interaction with active methylene nitriles led to the formation of 2-amino-4H-pyrans. The extended and adjusted mechanism of the three-component interaction, that includes the bis-adducts formation stage, was proposed. Taking into account the peculiarities of the mechanism, we were capable to control the reaction selectivity.

3-Bromomethyl-2,8-dioxaspiro[4.4]nonane-1,6-diones were efficiently prepared from 3-ethoxycarbonyltetrahydrofuran-2-ones. Subsequent conversion of the bromomethyl group into azidomethyl one followed by click reaction with alkynes afforded the multifunctional triazole-containing spiro dilactones in almost quantitative yields.

Acetylene, HC≡CH, is one of the primary building blocks in synthetic organic and industrial chemistry. Several highly valuable processes have been developed based on this simplest alkyne and the development of acetylene chemistry has had a paramount impact on chemical science over the last few decades. However, in spite of numerous useful possible reactions, the application of gaseous acetylene in everyday research practice is rather limited. Moreover, the practical implementation of high-pressure acetylene chemistry can be very challenging, owing to the risk of explosion and the requirement for complex equipment; special safety precautions need to be taken to store and handle acetylene under high pressure, which limit its routine use in a standard laboratory setup. Amazingly, recent studies have revealed that calcium carbide, CaC2 , can be used as an easy-to-handle and efficient source of acetylene for in situ chemical transformations. Thus, calcium carbide is a stable and inexpensive acetylene precursor that is available on the ton scale and it can be handled with standard laboratory equipment. The application of calcium carbide in organic synthesis will bring a new dimension to the powerful acetylene chemistry.

Various aliphatic and aromatic vinyl thioethers are efficiently synthesized involving the in situ generation of acetylene from CaC2.

Calcium carbide was studied as a useful solid-state reagent to incorporate acetylene unit into synthetic procedures. Atom-economic thiol-yne click reaction was successfully performed with single and double additions. Heterocyclic thiols and aliphatic dithiols reacted with acetylene generated in situ from calcium carbide to afford corresponding vinyl sulfides and bis(thiovinyl)ethers in good to high yields.

CF3-Substituted ketimines synthesized from trifluoroacetone, hexafluoroacetone, and trifluoroacetophenones were studied in aza-Henry reactions with nitroalkanes. We found that nitromethane and nitropropane react with CF3-substituted ketimines to form the target β-nitroamines in high yield. The aza-Henry reaction proceeded under mild conditions in the presence of an appropriate base. A new simple method for the synthesis of β-nitroamines bearing CF3 group was developed. α-CF3-β-nitroamines can easily be converted into trifluoromethylated 1,2-diamines, α-aminooximes, and imidazolidinones.

Reaction of 4-aryl-1,1,1-trifluorobut-3-en-2-ols [CF3-allyl alcohols, ArCH═CHCH(OH)CF3] with arenes under activation with anhydrous FeCl3 or FSO3H was studied. We found that the transformation led to trifluoromethylated alkenes [Ar(Ar′)CHCH═CHCF3] or 1-trifluoromethylated indanes (CF3-indanes). The formation of these two types of reaction products strongly depends on the nucleophilicity of the starting arene and the electrophilicity of cationic intermediates generated from CF3-allyl alcohols under reaction conditions. Benzene, anisole, veratrole, and ortho-xylene lead exclusively to CF3-alkenes with an E-configuration. More π-donating polymethylated arenes (pseudocumene, mesitylene) afford only CF3-indanes with a predominantly cis-orientation of substituents at positions 1 and 3 of the indane ring. Meta- and para-xylenes show an intermediate behavior; they may form both CF3-alkenes and/or CF3-indanes. The mechanisms of the investigated transformations are discussed.

The reaction of 2-perfluoroalkyl-substituted cyclic imines with arylhydrazines was investigated. We found that 2-perfluoroalkylated cyclic imines are highly reactive electrophiles that form, through ring opening, the corresponding hydrazones bearing an amine group at the end of the alkyl chain. Subsequent acidic treatment resulted in a Fischer rearrangement. Thus, a new synthesis of 2-perfluoroalkylated tryptamines and their homologues through a Fischer reaction was developed. The possibility of modification of the indole core of the 2-CF3-substituted tryptamine products was demonstrated, and various 2-trifluoromethylated tryptamines substituted at the 5-position were prepared.

The regioselective base-catalyzed addition of nitromethane to 2-oxo-4-trifluoromethyl-1,2-dihydropyrimidine-5-carboxylates is reported. It was found that the Michael-like pathway is highly reversible and substantially dominating under conditions of kinetic control (0–5 °C, 10 h) whereas the aza-Henry reaction leads to thermodynamically stable adducts after 8–24 h exposure at room temperature. The adjacent nitro and alkoxycarbonyl groups were exploited to demonstrate the synthetic potential of the obtained products by converting to the isomeric trifluoromethylated pyrrolo[3,4-d]pyrimidine-2,5-diones. With this aim an efficient protocol for selective reduction of nitro-derivatives to the corresponding 4- or 6-aminomethyl-2-oxo-4-trifluoromethyl-1,2,3,4-tetrahydropyrimidine-5-carboxylates and their subsequent thermal cyclocondensations was applied.

A unique Ni-catalyzed transformation is reported for the one-pot highly selective synthesis of previously unknown monoseleno-substituted 1,3-dienes starting from easily available terminal alkynes and benzeneselenol. The combination of a readily available catalyst precursor, Ni(acac)2, and an appropriately tuned phosphine ligand, PPh2Cy, resulted in the exclusive assembly of the s-gauche diene skeleton via the selective formation of C–C and C–Se bonds. The unusual diene products were stable under regular experimental conditions, and the products maintained the s-gauche geometry both in the solid state and in solution, as confirmed by X-ray analysis and NMR spectroscopy. Thorough mechanistic studies using ESI-MS revealed the key Ni-containing species involved in the reaction.

In the presence of FeCl3 trifluoromethylated allyl alcohols undergo an electrophilic dimerization to indane derivatives.

The target heterocycles are formed under mild conditions in good yields and with high selectivity.

Experimental and theoretical investigation of the regiodivergent palladium-catalyzed dimerization of terminal alkynes is presented. Employment of N-heterocyclic carbene-based palladium catalyst in the presence of phosphine ligand allows for highly regio- and stereoselective head-to-head dimerization reaction. Alternatively, addition of carboxylate anion to the reaction mixture triggers selective head-to-tail coupling. Computational studies suggest that reaction proceeds via the hydropalladation pathway favoring head-to-head dimerization under neutral reaction conditions. The origin of the regioselectivity switch can be explained by the dual role of carboxylate anion. Thus, the removal of hydrogen atom by the carboxylate directs reaction from the hydropalladation to the carbopalladation pathway. Additionally, in the presence of the carboxylate anion intermediate, palladium complexes involved in the head-to-tail dimerization display higher stability compared to their analogues for the head-to-head reaction.

Utilization of NMR spectroscopy and mass spectrometry for joint mechanistic and structural studies is a well-known practice. Several opportunities have appeared in recent years because of new hardware development and design of novel experimental procedures. Recent progress in this area and leading examples of new development, as well as already distinguished techniques, are discussed.

In the present review we describe the emerging tendency for creating target-oriented analytical approaches designed to solve important chemical tasks by using a combination of analytical tools. The concept is illustrated by selected examples of advances of NMR spectroscopy, mass spectrometry and electron microscopy in the analysis and study of gas-phase, liquid-state and solid-state chemical systems. Comparative description of chemical applications of these analytical methods is presented and discussed. The bibliography includes 359 references.

The hydrophosphorylation of internal alkynes (I) can be controlled by the catalyst loading to give mono- and bis-phosphonates selectively.

The synthetic capabilities of chiral α,β-azidoisocyanides were systematically reviewed. The potential of using them as bifunctional building blocks for multicomponent Passerini and Ugi reactions and also for Cu(I)-catalyzed [3+2]-cycloaddition to form 1,2,3-triazoles was demonstrated. The bifunctional nature of these compounds enabled the development of a methodology for preparing peptides containing an azide group and conjugating them subsequently with various biologically active compounds containing an ethynyl group for targeted modification of biomolecules.

The catalytic olefination of hydrazines of terephthalic (I) and isoterephthalic (XI) aldehydes with several polyhaloalkanes is studied.

Rapid progress in the field of ionic liquids in recent decades led to the development of many outstanding energy-conversion processes, catalytic systems, synthetic procedures, and important practical applications. Task-specific optimization emerged as a sharpening stone for the fine-tuning of structure of ionic liquids, which resulted in unprecedented efficiency at the molecular level. Ionic-liquid systems showed promising opportunities in the development of green and sustainable technologies; however, the chemical nature of ionic liquids is not intrinsically green. Many ionic liquids were found to be toxic or even highly toxic towards cells and living organisms. In this Review, we show that biological activity and cytotoxicity of ionic liquids dramatically depend on the nature of a biological system. An ionic liquid may be not toxic for particular cells or organisms, but may demonstrate high toxicity towards another target present in the environment. Thus, a careful selection of biological activity data is a must for the correct assessment of chemical technologies involving ionic liquids. In addition to the direct biological activity (immediate response), several indirect effects and aftereffects are of primary importance. The following principal factors were revealed to modulate toxicity of ionic liquids: i) length of an alkyl chain in the cation; ii) degree of functionalization in the side chain of the cation; iii) anion nature; iv) cation nature; and v) mutual influence of anion and cation.

An efficient catalytic system based on easily available palladium acetate was developed for the selective addition of aliphatic thiols to the triple bond of internal alkynes. Formed in situ [M(SR)2]n nanostructured particles were found to be an active form of the catalyst. It was experimentally confirmed for the first time that the most active form of the catalyst for thiol addition to internal alkynes is formed only in the reaction mixture containing the both reactants, namely, alkyne and thiol.

Reaction of binucleophiles with 1,4- and 1,3-bis(2-chloro-2-cyanovinyl)benzenes, synthesized using a catalytic olefination of terephthalic and isophthalic aldehydes, gave high yields of aminopyrazoles, 3-amino-5-arylthiophene-2-carboxylic acid esters, and 2,4-diamino-6-arylpyrimidines.

Self-assembled monolayers (SAMs) of selenium have emerged into a rapidly developing field of nanotechnology with several promising opportunities in materials chemistry and catalysis. Comparison between sulfur-based self-assembled monolayers and newly developed selenium-based monolayers reveal outstanding complimentary features on surface chemistry and highlighted the key role of the headgroup element. Diverse structural properties and reactivity of organosulfur and organoselenium groups on the surface provide flexible frameworks to create new generations of materials and adaptive catalysts with unprecedented selectivity. Important practical utility of adaptive catalytic systems deals with development of sustainable technologies and industrial processes based on natural resources. Independent development of nanotechnology, materials science and catalysis has led to the discovery of common fundamental principles of the surface chemistry of chalcogen compounds.

In situ generated catalysts and preformed catalysts are two practical strategies widely used in cross-coupling methodology that have long been considered to involve the same active species in the catalytic cycle. Recent mechanistic studies have revealed two fundamentally different pictures of catalytic reactions in solution. Preformed catalysts with strongly bound ligands initiate transformations mainly involving single type of metal species. In contrast, in situ generated catalysts give rise to cocktail-type systems with different metal species presented in solution. The role of catalyst precursor, interconversions of catalytic species during reaction, stability and recycling of catalyst, catalysis by autocatalyst exhaust and plausible sources of metal-containing contaminants are the key points discussed in this review.

Efficient algorithm was developed for the analysis of products of the catalytic reaction of diynes multiphosphorylation based on combined application of 31P NMR DOSY spectra and HPLC-MS method. Using this analytical approach the reaction of H-phosphonates addition to diynes was investigated and a simple synthetic procedure got alkyl tetraphosphonates preparation was developed.

Template condensation of CCl 3 CN and ammonia on zinc(II) (used as acetate) afforded, in one step, bis(2,4-bis(trichloromethyl)-1,3,5-triazapentadienato)-zinc(II) 1 , which was characterized by elemental analysis, ESI-MS, IR and X-ray single-crystal analysis. The complex 1 was shown to be an effective catalyst in the nitroaldol (Henry) reaction, providing high yields (up to 99%) and good diastereoselectivities ( threo/erythro up to 3:1) at ambient conditions.

All living systems are comprised of four fundamental classes of macromolecules – nucleic acids, proteins, lipids, and carbohydrates (glycans). Glycans play a unique role of joining three principal hierarchical levels of the living world: (1) the molecular level (pathogenic agents and vaccine recognition by the immune system, metabolic pathways involving saccharides that provide cells with energy, and energy accumulation via photosynthesis); (2) the nanoscale level (cell membrane mechanics, structural support of biomolecules, and the glycosylation of macromolecules); (3) the microscale and macroscale levels (polymeric materials, such as cellulose, starch, glycogen, and biomass). NMR spectroscopy is the most powerful research approach for getting insight into the solution structure and function of carbohydrates at all hierarchical levels, from monosaccharides to oligo- and polysaccharides. Recent progress in computational procedures has opened up novel opportunities to reveal the structural information available in the NMR spectra of saccharides and to advance our understanding of the corresponding biochemical processes. The ability to predict the molecular geometry and NMR parameters is crucial for the elucidation of carbohydrate structures. In the present paper, we review the major NMR spectrum simulation techniques with regard to chemical shifts, coupling constants, relaxation rates and nuclear Overhauser effect prediction applied to the three levels of glycomics. Outstanding development in the related fields of genomics and proteomics has clearly shown that it is the advancement of research tools (automated spectrum analysis, structure elucidation, synthesis, sequencing and amplification) that drives the large challenges in modern science. Combining NMR spectroscopy and the computational analysis of structural information encoded in the NMR spectra reveals a way to the automated elucidation of the structure of carbohydrates.