The Role of Potassium Cation in the Favorskii Ethynylation of Acetone: Effekt of Dibenzo-18-crown-6

Macrocyclic polyether dibenzo-18-crown-6 possessing a specific affinity for potassium cation inhibits ethynylation of acetone with acetylene in the presence of KOH according to Favorskii. The inhibition becomes stronger in the presence of the complex dibenzo-18-crown-6 ? KOH ? MeOH as catalyst (both in excess acetone and in DMSO). The effect does not originate from deactivation of acetone, for its aldol-like condensation is accelerated in the presence of both dibenzo-18-crown-6 and its complex (the selectivity of ethynylation sharply falls down). Thus, apart from the high basicity of the medium, activation of acetylene due to complex formation with potassium cation plays an important role in the Favorskii ethynylation of ketones.     

Noncatalytic Regio- and Stereoselective Addition of Secondary Phosphines to Cyanoacetylenic Alcohols

Secondary phosphines regio- and stereoselectively add to 4-hydroxy-4-methyl-2-pentynenitrile, a typical and available representative of cyanoacetylenic alcohols, without catalyst at room temperature (THF, 3 h) to form (Z)-3-[dialkyl(aryl) phosphino]-4-hydroxy-4-methyl-2-pentenenitriles in 80–85% yields. These compounds relate to a new class of functionalyzed phosphines, promising ligands for the design of metal-complex catalysts.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 552–555.Original Russian Text Copyright © 2005 by Arbuzova, Shaikhutdinova, Gusarov, Nikitin, Mal’kina, Sukhov, Bogdanova, Trofimov.     

Conservative finite-difference scheme for the problem of propagation of a femtosecond pulse in a nonlinear photonic crystal with nonreflecting boundary conditions

Conservative finite-difference schemes are constructed for the problems of self-action of a femtosecond laser pulse and of second-harmonic generation in a one-dimensional nonlinear photonic crystal with nonreflecting boundary conditions. The invariants of the governing equations are found taking into account these conditions. Nonreflecting conditions substantially improve the efficiency of conservative finite-difference schemes used in the modeling of complex nonlinear effects in photonic crystals, which require much smaller steps in space and time than those used in the case of linear propagation. The numerical experiments performed show that the boundary reflects no more than 0.01% of the transmitted energy, which corresponds to the truncation error in the boundary conditions. The amplitude of the reflected pulse is less than that of the pulse transmitted through the boundary by two (and more) orders of magnitude. The simulation is based on the approach proposed by the authors for the given class of problems.     

Synthesis of pyrrole-dihydrothiazole ensembles from 1-allenyl-1H-pyrrole,isothiocyanates, and propargyl bromide

Russian Journal of Organic Chemistry - N-Alkylidene-1-(propargylsulfanyl)-2-(1H-pyrrol-1-yl)buta-1,3-dien-1-amines at treatment by a superbasic system t-BuONa–THF–DMSO under standard...     

Formation of 1-aminophenazine from 3,4-dihydrophenazin-1(2H)-one oxime in the system acetylene–KOH–DMSO

Russian Journal of Organic Chemistry - The reaction of 3,4-dihydrophenazin-1(2H)-one oxime with acetylene in the superbasic system KOH–DMSO afforded 1-aminophenazine in 32% yield instead of...     

Formation of 2-methyl-3,5-diphenylfuran from chalcone and acetylene in the system KOH–DMSO

Russian Journal of Organic Chemistry - Chalcone reacted with acetylene in a suspension of KOH in DMSO at 90°C (30 min) to give 36% of 2-methyl-3,5-diphenylfuran.     

15-[(Z)-Phenylmethylidene]-7,14-dioxadispiro[5.1.5.2]pentadecanes: stereoselective one-pot assembly from cyclohexanones and phenylacetylene in a KOH/DMSO suspension

Cyclohexanones react with phenylacetylene in a KOH/DMSO suspension (80 °C, 1 h) to give unexpectedly phenylmethylidene dispirocyclic ketals, 15-[(Z)-phenylmethylidene]-7,14-dioxadispiro[5.1.5.2]pentadecanes, in 16-22% yields (along with the anticipated β,γ- and α,β-ethylenic ketones).     

New approaches to processing and fabrication of oxide nuclear fuels

It was shown that, in contrast to the Purex process using aggressive and environmentally hazardous 8M HNO₃ solutions for dissolving spent oxide nuclear fuel (SNF), this fuel can be easily dissolved in aqueous subacid ([H⁺] ∼0.1 M) solutions of Fe(III) nitrate (chloride) with partial separation of uranium and plutonium from fission products (FP). The low acidity of the solutions obtained (pH ∼1) allows direct application of modern technologies of finishing processing of nuclear fuel by fluoride, carbonate, oxalate, or peroxide precipitation of uranium and plutonium. It was established that U(VI) is isolated from nearly neutral nitric acid solutions as a poorly soluble uranyl hydroxylaminate complex after adding hydroxylamine. It was shown that on thermal decomposition at 200–300°C under ambient atmosphere this compound converts into uranium dioxide. A similar approach was applied to obtain mixed oxide uranium-plutonium fuel (MOX fuel).