Halonium and chalconium salt-catalyzed Schiff condensation: kinetics and DFT insights into organocatalyst activity parameters.

The Schiff condensation between 4-methylbenzaldehyde and 2-aminopyridine, catalyzed by chloronium, bromonium, and iodonium triflates, as well as sulfonium, selenonium, and telluronium triflates, was investigated. H NMR monitoring revealed that the catalytic activity increased significantly with heavier σ-hole-bearing heteroatoms. DFT calculations showed that the maximum electrostatic potential at the σ-hole was a more reliable predictor of the catalytic activity of these organoelement species.

Chalcogen- and Halogen-Bond-Donating Cyanoborohydrides Provide Imine Hydrogenation.

Sulfonium, selenonium, telluronium, and iodonium cyanoborohydrides have been synthesized, isolated, and fully characterized by various methods, including single-crystal X-ray diffraction (XRD) analysis. The quantum theory of atoms in molecules' analysis based on the XRD data indicated that the hydride···σ-hole short contacts observed in the crystal structures of each compound have a purely noncovalent nature. The telluronium and iodonium cyanoborohydrides provide a significantly higher rate of the model reaction of imine hydrogenation compared with sodium and tetrabutylammonium cyanoborohydrides.

Influence of Coordination to Silver(I) Centers on the Activity of Heterocyclic Iodonium Salts Serving as Halogen-Bond-Donating Catalysts.

Kinetic data based on H NMR monitoring and computational studies indicate that in solution, pyrazole-containing iodonium triflates and silver(I) triflate bind to each other, and such an interplay results in the decrease of the total catalytic activity of the mixture of these Lewis acids compared to the separate catalysis of the Schiff condensation, the imine-isocyanide coupling, or the nucleophilic attack on a triple carbon-carbon bond. Moreover, the kinetic data indicate that such a cooperation with the silver(I) triflate results in prevention of decomposition of the iodonium salts during the reaction progress. XRD study confirms that the pyrazole-containing iodonium triflate coordinates to the silver(I) center via the pyrazole N atom to produce a rare example of a pentacoordinated trigonal bipyramidal dinuclear silver(I) complex featuring cationic ligands.

Energetic Polymer Possessing Furazan, 1,2,3-Triazole, and Nitramine Subunits.

A [3 + 2] cycloaddition reaction using dialkyne and diazide comonomers, both bearing explosophoric groups, to synthesize energetic polymers containing furazan and 1,2,3-triazole ring as well as nitramine group in the polymer chain have been described. The developed solvent- and catalyst-free approach is methodologically simple and effective, the comonomers used are easily available, and the resulting polymer does not need any purification. All this makes it a promising tool for the synthesis of energetic polymers.

Sulfonium and Selenonium Salts as Noncovalent Organocatalysts for the Multicomponent Groebke-Blackburn-Bienaymé Reaction.

Sulfonium and selenonium salts, represented by -aryl dibenzothiophenium and -aryl dibenzoselenophenium triflates, were found to exhibit remarkable catalytic activity in the model Groebke-Blackburn-Bienaymé reaction. Kinetic analysis and density functional theory (DFT) calculations indicated that their catalytic effect is induced by the ligation of the reaction substrates to the σ-holes on the S or Se atom of the cations. The experimental data indicated that although 10-fold excess of the chloride totally inhibits the catalytic activity of the sulfonium salts, the selenonium salt remains catalytically active, which can be explained by the experimentally found lower binding constant of the selenonium derivative to chloride in comparison with the sulfonium analogue.