Synthesis of 2-Azidomethyl-5-ethynylfuran: A New Bio-Derived Self-Clickable Building Block

Karlinskii B.Ya., Romashov L.V., Galkin K.I., Kislitsyn P.G., Ananikov V.P., Synthesis, 2019, ASAP.
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2-Azidomethyl-5-ethynylfuran, a new ambivalent compound with both azide and alkyne moieties that can be used as a self-clickable monomer, is synthesized starting directly from renewable biomass. The reactivity of the azide group linked to furfural is tested via the efficient preparation of a broad range of furfural-containing triazoles in good to excellent yields using a 'green' copper(I)-catalyzed azide–alkyne cycloaddition procedure. Access to new bio-based chemicals and oligomeric materials via a click-chemistry approach is also demonstrated using this bio-derived building block.

Switching the nature of catalytic centers in Pd/NHC systems by solvent effect driven non‐classical R‐NHC Coupling

Gordeev E. G., Ananikov V. P., J. Comput. Chem., 2019, 40, 191-199.
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A well‐established oxidative addition of organic halides (R‐X) to N‐heterocyclic carbene (NHC) complexes of palladium(0) leads to formation of (NHC)(R)Pd II(X)L species, the key intermediates in a large variety of synthetically useful cross‐coupling reactions. Typical consideration of the cross‐coupling catalytic cycle is based on the assumption of intrinsic stability of these species, where the subsequent steps involve coordination of the second reacting partner. Thus, high stability of the intermediate (NHC)(R)PdII(X)L species is usually taken for granted. In the present study it is discussed that such intermediates are prone to non‐classical R‐NHC intramolecular coupling process (R = Me, Ph, Vinyl, Ethynyl) that results in removal of NHC ligand and generation of another type of Pd catalytic system. DFT calculations (BP86, TPSS, PBE1PBE, B3LYP, M06, wB97X‐D) clearly show that outcome of R‐NHC coupling process is not only determined by chemical nature of the organic substituent R, but also strongly depends on the type of solvent. The reaction is most favorable in polar solvents, whereas the non‐polar solvents render the products less stable.

Towards Improved Biorefinery Technologies: 5‐Methylfurfural as a Versatile C6‐Platform for Biofuels Development

Galkin K. I., Ananikov V. P., ChemSusChem, 2019, ASAP.
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Low chemical stability and high oxygen content limits utilization of bio‐based platform chemical 5‐(hydroxymethyl)furfural (HMF) in biofuels development. In this work, Lewis‐acid‐catalyzed conversion of renewable 6‐deoxy sugars leading to formation of more stable 5‐methylfurfural (MF) is carried out with high selectivity. Besides its higher stability, MF is a deoxygenated analogue of HMF with increased C:O ratio. A highly selective synthesis of the innovative liquid biofuel 2,5‐dimethylfuran starting from MF under mild conditions is described. Superior synthetic utility of MF against HMF in benzoin and aldol condensation reactions leading to long‐chain alkane precursors is demonstrated.

In situ transformations of Pd/NHC complexes to colloidal Pd nanoparticles studied for N-heterocyclic carbene ligands of different nature

Kostyukovich A. Yu., Tsedilin A. M., Sushchenko E. D., Eremin D. B., Kashin A. S., Topchiy M. A., Asachenko A. F., Nechaev M. S., Ananikov V. P., Inorg. Chem. Front., 2019, ASAP.
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R–NHC coupling was previously considered as a process of degradation of M/NHC species, however recent studies have pointed out that it may be responsible for generation of catalytically active NHC-free complexes or/and metallic nanoparticles. Therefore, a detailed and systematic study of R-NHC coupling for various carbene ligands is an important topic. In the present article this process has been studied for reactive aryl iodide coupling partners by a combination of quantum chemical calculations and continuous reaction monitoring via pressurized sample infusion electrospray ionization mass spectrometry (PSI-ESI-MS). DFT calculations revealed strong tendency of (NHC)Pd(Ph)(I)DMF complexes bearing various N-heterocyclic carbene ligands (NHC) to undergo Ph–NHC coupling. Calculated energy barriers of these reactions lie in the range of 17.9 – 25.1 kcal/mol. Ph–NHC coupling is thermodynamically more favorable for the complexes containing unsaturated NHC ligands with bulky substituents. NBO analysis has suggested that the process of Ph–NHC formation is similar for different NHC ligands. In order to confirm theoretical studies, a series of ESI-MS reaction monitoring experiments was performed for (NHC)Pd(I)2(Py) and (NHC)Pd(Cl)(η3-1-Ph-C3H4) complexes interacting with iodobenzene, where Ph–NHC coupling products were observed in all cases. As a direct experimental evidence, formation of colloidal Pd-containing nanoparticles was observed in situ for different Pd/NHC complexes in the studied reaction mixtures.

Systematic Study of the Behavior of Different Metal and Metal-Containing Particles under the Microwave Irradiation and Transformation of Nanoscale and Microscale Morphology

Pentsak E.O., Cherepanova V.A., Sinayskiy M.A., Samokhin A.V., Ananikov V.P., Nanomaterials, 2019, 9, 19.
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In recent years, the application of microwave (MW) irradiation has played an increasingly important role in the synthesis and development of high performance nanoscale catalytic systems. However, the interaction of microwave irradiation with solid catalytic materials and nanosized structures remains a poorly studied topic. In this paper we carried out a systematic study of changes in morphology under the influence of microwave irradiation on nanoscale particles of various metals and composite particles, including oxides, carbides, and neat metal systems. All systems were studied in the native solid form without a solvent added. Intensive absorption of microwave radiation was observed for many samples, which in turn resulted in strong heating of the samples and changes in their chemical structure and morphology. A comparison of two very popular catalytic materials—metal particles (M) and supported metal on carbon (M/C) systems—revealed a principal difference in their behavior under microwave irradiation. The presence of carbon support influences the heating mechanism; the interaction of substances with the support during the heating is largely determined by heat transfer from the carbon. Etching of the carbon surface, involving the formation of trenches and pits on the surface of the carbon support, were observed for various types of the investigated nanoparticles.

Switchable Ni-Catalyzed Bis-Thiolation of Acetylene with Aryl Disulfides as an Access to Functionalized Alkenes and 1,3-Dienes

Degtyareva E.S., Erokhin K.S., Kashin A.S., Ananikov V. P., Appl. Catal. A Gen., 2019, 571, 170-179.
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The article provides the first example of metal-catalyzed aryl disulfide addition to unsubstituted acetylene. The use of inexpensive Ni(acac)2 precatalyst with phosphine ligands results in competitive formation of Z-1,2-bis(arylthio)ethenes and Z,Z-1,4-bis(arylthio)buta-1,3-dienes. The process with the PPhCy2 as a ligand results in selective formation of diene molecular skeletons. Replacement of PPhCy2 with the PPh3 switches the reaction toward formation of alkenes. The use of substituted phenyl disulfides does not affect the selectivity and allows obtaining alkenes or dienes in good to high yields. Mechanistic investigations reveal major differences on the catalyst activation stage depending on the nature of phosphine ligand. Key novel point is to carry out video-monitoring of catalyst evolution with electron microscopy, which revealed the dynamic nature of the catalytic system and showed that the ligand played a prominent role in formation of the catalytically active phase. For PPh3, the development of catalytically active species proceeds through nickel thiolate [Ni(SAr)2]n formation, which renders the system heterogeneous. In contrast to PPh3, the PPhCy2 ligand promotes direct activation of the catalyst in its molecular form without disturbing the homogeneous state of the system.