B. A. Shainyan

Bifurcate Hydrogen Bonds. Interaction of Intramolecularly H-Bonded Systems with Lewis Bases

The structure and the hydrogen bonding in the systems formed by the intramolecularly H-bonded systems, namely, maltol (3-hydroxy-2-methyl-4-pyrone), 5, 2,4,6-trinitrophenol, 6, acetylacetone enol, 7, with Lewis bases, phosgene, 8, dioxane, 9, and DMSO, 10, have been studied by density functional theory (B3LYP) and MP2 using the 6-311G* basis set. The continuum solvent effect was simulated by IEF-PCM model. The hydrogen bond analysis using the atoms in molecules (AIM) method was applied by using the MP2(full)/6-311++G** electron density to establish the nature of the bifurcate hydrogen bond (BHB) in these systems as well as contributory factors for its stabilization. The nature of interaction in the intermolecular H-complexes formed by compounds 5- 7 with the Lewis bases 8- 10 was shown to depend on the strength of the intramolecular hydrogen bond O...H and the strength of the base. The critical values of the CO...H and NO...H angles for which the formation of BHB is possible, have been determined.

Formation of a hydrogenation catalyst in the cobalt acetylacetonate-triethylaluminum system

Based on the results obtained using chemical, kinetic, and physical techniques (EPR, IR, and UV spectroscopy; transmission electron microscopy; and XRD analysis), the formation of active species in the triethylaluminum-bis(tris)(acetylacetonato)cobalt system, which is known to be a hydrogenation catalyst, has been considered. It has been found that nanosized particles are formed in this system; the core of these particles consists of Co0 atoms stabilized by a shell containing Et2Al(acac), AlEt3, and their reaction products. The extremal dependence of the hydrogenation activity of the system on the Al/Co ratio is primarily due to changes in the composition of the protective shell of nanosized particles.

Ionic liquids on the basis of 2,3,4,6,7,8,9,10-octahydropyrimido-[1,2-a]azepine (1,8-diazabicyclo[5.4.0]undec-7-ene)

New ionic liquids containing alkyl and polyfluoroalkyl substituents and various anions were synthesized from 2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepinium ion (1,8-diazabicyclo[5.4.0]undec-7-en-8-ium). Their NMR spectra and miscibility with water and organic solvents were studied.

Structure and intramolecular hydrogen bonds in bis(trifluoromethylsulfonylamino)methane and N-[(trifluoromethylsulfonyl)aminomethyl]acetamide

Bis(trifluoromethylsulfonylamino)methane in an inert medium exists as an equilibrium mixture of monomeric forms with various types of intramolecular hydrogen bonds, whose population depends on the polarity of the medium. The energetically most favorable form is a symmetrical form containing two N-H...O=S bonds. Less stable are the isomer with two N-H...F-C bonds and the unsymmetrical isomer with two different hydrogen bonds. N-[(Trifluoromethylsulfonyl)aminomethyl]acetamide contains one intramolecular intramolecular N-H...O=C hydrogen bond and preserves ability for self-association.

1,3-Dimethyl-3-silapiperidine: Synthesis, Molecular Structure, and Conformational Analysis by Gas-Phase Electron Diffraction, Low Temperature NMR, IR and Raman Spectroscopy, and Quantum Chemical Calculations

The first Si-H-containing azasilaheterocycle, 1,3-dimethyl-3-silapiperidine 1, was synthesized, and its molecular structure and conformational properties were studied by gas-phase electron diffraction (GED), low temperature NMR, IR and Raman spectroscopy and quantum chemical calculations. The compound exists as a mixture of two conformers possessing the chair conformation with the equatorial NMe group and differing by axial or equatorial position of the SiMe group. In the gas phase, the SiMe(ax) conformer predominates (GED: ax/eq = 65(7):35(7)%, ΔG = 0.36(18) kcal/mol; IR: ax/eq = 62(5):38(5)%, ΔG = 0.16(7) kcal/mol). In solution, at 143 K the SiMe(eq) conformer predominates in the frozen equilibrium (NMR: ax/eq = 31.5(1.5):68.5(1.5)%, ΔG = -0.22(2) kcal/mol). Thermodynamic parameters of the ring inversion are determined (ΔG(‡) = 8.9-9.0 kcal/mol, ΔH(‡) = 9.6 kcal/mol, ΔS(‡) = 2.1 eu). High-level quantum chemical calculations (MP2, G2, CCSD(T)) nicely reproduce the experimental geometry and the predominance of the axial conformer in the gas phase.

Reaction of trifluoromethanesulfonamide with alkenes and cycloocta-1,5-diene under oxidative conditions. Direct assembly of 9-heterobicyclo[4.2.1]nonanes

Reactions of trifluoromethanesulfonamide with α-methylstyrene, 2-methylpent-1-ene, and cycloocta-1,5-diene in the system t-BuOCl-NaI were studied. In the reaction with α-methylstyrene 1-iodo-2-phenylpropan-2-ol was the only isolated product. The reaction with 2-methylpent-1-ene gave a mixture of N,N′-(2-methylpentane-1,2-diyl)bis(trifluoromethanesulfonamide), trifluoro-N-(2-hydroxy-2-methylpentyl)-methanesulfonamide, and N,N′-[oxybis(2-methylpentan-2,1-diyl)]bis(trifluoromethanesulfonamide). Trifluoromethanesulfonamide reacted with cycloocta-1,5-diene to produce a mixture of 2,5-diiodo-9-(trifluoromethylsulfonyl)-9-azabicyclo[4.2.1]nonane and 2,5-diiodo-9-oxabicyclo[4.2.1]nonane; this reaction may be regarded as the first example of direct assembly of bicyclononane skeleton.

Synthesis and properties of N-(allyl)trifluoromethanesulfonamide

We have recently synthesized the first N-alkenylsubstituted trifluoromethanesulfonamide, N-methyl-N[(E)-2-phenylethenyl]trifluoromethanesulfonamide CF3SO2N(Me)CH=CHPh, by dehydrobromination of N-(2-bromo-2-phenylethyl)-N-(methyl)trifluoromethanesulfonamide [1]. An attempt to obtain in a similar way its NH analog, CF3SO2NHCH=CHPh was unsuccessful; instead of the dehydrobromination product, we isolated 2,5-diphenyl-1,4-(trifluoromethylsulfonyl)piperazine [2]. However, N-monosubstituted trifluoromethanesulfonamides CF3SO2NHR attract particular interest as strong NH acids which can be functionalized at the nitrogen atom. Therefore, the present communication describes the synthesis and transformations of the first unsaturated NH trifluoromethanesulfonamide, N-(allyl)trifluoromethanesulfonamide (I).

Formation of 2,6-diphenyl-1,4-bis(trifluoromethylsulfonyl)piperazine in the reaction of styrene with trifluoromethylsulfonylnitrene

The reaction of styrene with trifluoromethylsulfonylnitrene generated in the system t-BuOCl-NaI led to the formation of trifluoro-N-[2-phenyl-2-(trifluoromethylsulfonylamino)ethyl]methanesulfonamide CF3SO2NHCH(Ph)CH2NHSO2CF3, 2-iodo-1-phenylethanol, and heterocyclization product, 2,6-diphenyl-1,4-(trifluoromethylsulfonyl)piperazine. The latter is regioisomeric to 2,5-diphenyl-1,4-(trifluoromethylsulfonyl)-piperazine obtained previously by analogous reaction in the system t-BuOCl-NaI · 2 H2O.

Synthesis and relative stability of five- and six-membered S-functional derivatives of 1,3-thiasilacycloalkanes

Abstract Oxidation, imidation, and S -methylation reactions of five- and six-membered 1,3-thiasilacycloalkanes have been examined under various conditions. The S -functional derivatives of 1,3-thiasilacycloalkanes undergo solvolytic SiC(S) bond cleavage in protic media. The ease of the ring opening depends on the S -functionality and on the ring size.

N -allenyl- N -benzyltrifl uoromethanesulfonamide

First N-allenyl-substitued triflamides CF3SO2N(Bn)CH=C=CH2 were synthesized from N-allyltriflamides by sucessive reactions of bromination, N-alkylation, and dehydrobromination. Isomeric N-propargyltriflamide CF3SO2N(Bn)CH2C≡CH is present in the reaction products as a minor admixture.