Heavy-alkali selenate and sulfate complexes with periodic acid and periodates

The complexing features of heavy-alkali selenates and sulfates with periodic acid and periodates are studied. Adducts CsHSeO₄ · 2CsH₄IO₆, CsHSeO₄ · H₅IO₆ and MHSO₄ · H₅IO₆ with M = Cs, Rb, or K are isolated for the first time, and conditions are found for preparing adduct CsHSO₄ · 2CsH₄IO₆ in an individual state. The adducts are characterized by IR spectroscopy, X-ray powder diffraction, thermal analysis, and chemical analysis. They do not contain hydrosulfate or hydroseleante anions as shown by their IR spectra. All protons are bound to iodine-oxygen octahedra to form hydrogen biperiodate anion [H(H₄IO₆)₂]^? or hexahydroxoiodonium cation [H₆IO₆]⁺.     

A versatile strategy for the synthesis of functionalized 2,2'-bi- and 2,2':6',2' '-terpyridines via their 1,2,4-triazine analogues

A general synthetic route for the synthesis of functionalized bi- and terpyridines is reported. Functionalized 1,2,4-triazene 4-oxides 7 and 8-obtained from the reaction of hydrazones 1 with pyridine aldehydes and followed by oxidation-are functionalized by introduction of a cyano group via nucleophilic aromatic substitution. The thus-obtained 5-cyano-1,2,4-triazines 9 and 10 undergo facile inverse-electron-demand Diels-Alder reactions with enamines and alkenes to yield functionalized bi- and terpyridines, respectively. The substituent at position 6 of the 1,2,4-triazene 4-oxides must be aromatic or heteroaromatic in order to allow their facile synthesis, but other substituents and reagents may vary. Each step of the synthetic route allows diversification, which makes the approach particularly useful for the facile synthesis of a large variety of functionalized bi- and terpyridines.     

Vinyl Ethers Containing an Epoxy Group: XXII. Synthesis and Base-Catalyzed Transformations of 1-(Allyloxy)- and 1-[2-(Vinyloxy)ethoxy]-3-(2-propynyloxy)propan-2-ols

Reactions of 2-(allyloxymethyl)- and 2-[2-(vinyloxy)ethoxy]methyloxiranes with 2-propynol (～3 wt % of t-BuOK, 75–85°C, 5–10 h) lead to formation of new 1-organyloxy-3-(2-propynyloxy)propan-2-ols (yield 65–95%). On heating to 45–100°C in the presence of bases (KOH, t-BuOK), 1-allyloxy- and 1-[2-(vinyloxy)ethoxy]-3-(2-propynyloxy)propan-2-ols are transformed into the corresponding 2-vinyl-1,3-dioxolane, 6-methyl-2,3-dihydro-1,4-dioxine, 6-methylene-1,4-dioxane, and 2,3-dihydro-5H-1,4-dioxepine derivatives, whose yield and ratio strongly depend on the solvent nature, catalyst, and substituent at the hydroxy group. 2-Vinyl-1,3-dioxolane and 6-methyl-2,3-dihydro-1,4-dioxine derivatives are formed as the major products (yield 70–99%) in the presence of t-BuOK in aprotic media (toluene, THF, DMSO) or in the absence of a solvent as a result of prototropic isomerization followed by intramolecular heterocyclization. Intramolecular nucleophilic cyclization of 3-(2-propynyloxy)propan-2-ols to 6-methylene-1,4-dioxane is the predominant process in water in the presence of KOH. In all cases, the fraction of 2,3-dihydro-5H-1,4-dioxepine derivatives among the cyclization products ranges from 0 to 5% (KOH) or to 14% (t-BuOK).     

Synthesis of amino derivatives of caranol by the addition of cyclic amines to 3-carene oxides

Addition reactions of cyclic amines (morpholine, piperidine) to oxides of 3-carene in the presence of water have been studied. The reactions take place regio- and stereoselectively with the formation of amino derivatives of the carane series.S. V. Kurashov Kazan' State Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 203–208, March–April, 1992.     

From Molecules to Particles: Quantum-chemical View Applied to Fumed Silica

An extended quantum-chemical study has been performed to examine the flame-generated silica formation at the atomic level. Starting from a set of free molecules, condensation was shown to be a non-barrier and energetically favorable. The coalescence of the formed bare-surface protoparticles can be prevented by particle surface passivation in the course of the hydroxylation reaction. The protoparticle size is determined by a balance of the fusion and hydroxylation/dehydroxylation processes. The main factors responsible for the inherent amorphicity of the fumed silica have been determined.     

Bifurcations of a limit cycle in nonlinear dynamic systems

A skew-symmetry principle that governs the formation of closed and quasiperiodic trajectories is formulated. Bifurcations of a limit cycle in nonlinear dynamic systems are analyzed. The phenomenon of drift is explained. An approximate solution of the limit cycle equations is found through a qualitative analysis