Center for Magnetic Resonance

A.D. Lisakova, D.S. Ryabukhin, R.E. Trifonov, V.A. Ostrovskii, A.V. Vasilyev

“Alkylation of 5-substituted NH-tetrazoles by alcohols in the superacid CF₃SO₃H”

Tetrahedron Lett., 2015, 56, 7020-7023
DOI:10.1016/j.tetlet.2015.11.005

Reactions of 5-substituted NH-tetrazoles with alcohols in the superacid CF3SO3H have been studied. Both the structure of the tetrazole and the nature of alcohol were found to dramatically influence the selectivity of the reaction and yields of products. Tetrazoles bearing phenyl, electron-donating aryl, or benzyl groups at the 5-position, have been alkylated using various alcohols (including MeOH and EtOH) in CF₃SO₃H upon heating at 60 °C for 0.3–12 h to afford 2-alkyl-2H-tetrazoles in 30–98% yields.

K.S. Rodygin, V.P. Ananikov

“An efficient metal-free pathway to vinyl thioesters with calcium carbide as the acetylene source”

Green Chemistry, 2015, accepted
DOI:10.1039/c5gc01552a

Chemical reactions involving high-pressure acetylene are not easily performed in a standard laboratory setup. The risk of explosion and technical difficulties drastically complicate the equipment and greatly increase the cost. In this study, we propose the replacement of acetylene with calcium carbide, which was successfully utilized to synthesize practically useful vinyl thioesters in accordance with a simple and environmentally benign procedure. The reaction proceeded under mild conditions using a standard laboratory setup. The optimized reaction conditions allowed the selective synthesis of the vinyl thioesters in high yields, and the reaction conditions can be scaled up to synthesize grams of sulfides from inexpensive starting materials.

A.P. Molchanov, E.V. Sirotkina, M.M. Efremova, R.R. Kostikov, A.V. Ivanov, V.S. Shcherbakova

“Regio- and Stereoive Cycloaddition of Nitrones to 1-Vinyl-4,5-dihydro-1Н-benzo[g]indole”

Russ. J. Org. Chem., 2015, 51, 640-643
DOI:10.1134/S1070428015050097

Nitrones cycloaddition to 1-vinyl-4,5-dihydro-1Н-benzo[g]indole proceeds regio- and steroselectively affording a single diastereomer of 5-(hetaryl-substituted)isoxazolidine.

I.S. Ignatyev, T.A. Kochina, V.V. Avrorin, V.V. Gurzha, I.M. Fundamensky

“Molecular and crystal structure of 2-phenyl-2-hydro-6-methyl-1,3-dioxa-6-aza-2-silacyclooctane”

J. Molec. Struct., 2015, 1094, 169-173
DOI:10.1016/j.molstruc.2015.03.061

The crystal structure of 2-phenyl-2-hydro-6-methyl-1,3-dioxa-6-aza-2-silacyclooctane [HPhSi(OCH₂CH₂)₂NMe – phenylhydrosilocane (I)] is determined by single-crystal X-ray diffraction at 100 K. The unit cell consists of four molecules connected only by Van-der-Waals interactions. Each molecule has an eight-membered heterocycle with a phenyl group in the axial position. The Si⋯N transannular bond has a short (2.206 Å) interatomic distance which exceeds only this distance in ocanes with highly electronegative fluorine substituents at Si. Since there exist experimental data on the occurrence of different conformers of I in the liquid phase, the PES of the molecule was analyzed by DFT B3LYP and MP2 methods with the aug-cc-pVDZ basis set. The energy minimum belongs to the boat–chair conformation with the axial position of the phenyl group. Rotation of the phenyl ring around the SiC bond has a barrier ca. 1 kcal/mol. The conformer with the equatorial position of this group lies 6 kcal/mol higher. Interconversion of this conformers which was observed in experiment proceeds through the chair–chair configuration in which the Si⋯N transannular bond is absent and coordination at silicon is tetrahedral, rather than trigonal bipyramidal one observed in other conformers.

D.V. Kurandina, E.V. Eliseenkov, T.S. Khaibulova, A.A. Petrov, V.P. Boyarskiy

“Copper-catalyzed C-N bond cross-coupling of aryl halides and amines in water in the presence of ligand derived oxalyl dihydrazide: scope and limitation”

Tetrahedron, 2015, 71, 7931-7937
DOI:10.1016/j.tet.2015.07.071

An efficient and convenient method has been developed for the copper-catalyzed C–N bond cross-coupling of aryl bromides with electron-donor substituents and aliphatic amines in water. The new ligand system N-phenyloxalyl bishydrazide/hexane-2,5-dione has been shown to be considerably more efficient in the copper-catalyzed C–N bond cross-coupling reaction as compared to the ligands described in the literature and allowed decreasing of the catalyst amount (up to 2 mol %) to achieve acceptable yields of isolated products (46–84%). Acceptor substituted aryl bromides, aryl bromides with substituents in the ortho-position, and some aryl dichlorides can undergo the C–N cross-coupling under the developed conditions, but their reactivity is lower.

Yu.B. Koptelov, D.O. Antuganov, A.P. Molchanov, R.R. Kostikov

“Steric Hindrances to the Cycloaddition of (Z)-1-Arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides to N-Arylmaleimides”

Russ. J. Org. Chem., 2015, 7, 972-981
DOI:10.1134/S1070428015070143

Sterically hindered cycloaddition of (Z)-1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides to 4-mono- and 2,6-disubstituted N-arylmaleimides requires prolonged heating (40–60 h) at ~150–155°C and yields mixtures of diastereoisomeric cycloadducts. The observed diastereoselectivity is determined by both electronic and steric interactions, depending on the nature and position of substituents in the azomethine imine and maleimide. The reactions of (Z)-1-(2,6-dichlorobenzylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide with 4-substituted N-arylmaleimides give mainly the corresponding cis adducts as a result of preferential exo attack by the dipolarophile, whereas trans adducts predominate in the cycloaddition of (Z)-1-(4-X-benzylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide and (Z)-1-(2,6-dichlorobenzylidene) -5,5-dimethyl-3-oxopyrazolidin- 1-ium-2-ide to 2,6-disubstituted N-arylmaleimides.