Center for Magnetic Resonance

N.A. Danilkina, A.G. Lyapunova, A.F. Khlebnikov, G.L. Starova, S. Brase, I.A. Balova

“Ring-Closing Metathesis of Co₂(CO)₆–Alkyne Complexes for the Synthesis of 11-Membered Dienediynes: Overcoming Thermodynamic Barriers”

J. Org. Chem., 2015, 80, 5546-5555
DOI:10.1021/acs.joc.5b00409

The feasibility of ring-closing metathesis (RCM) as a synthetic entry to 10- and 11-membered dienediynes fused to a benzothiophene core was explored by experimental and theoretical investigations. An established sequence of iodocyclization of o-(buta-1,3-diynyl)thioanisoles followed by Sonogashira coupling to form diethynylbenzothiophenes was used to synthesize terminal benzothiophene-fused enediyne diolefins as substrates for RCM. Encountering an unexpected lack of reactivity of these substrates under standard RCM conditions, we applied DFT calculations to reveal that the underlying cause was a positive change in Gibbs free energy. The change in Gibbs free energy was also found to be positive for RCM of indole- and benzannulated terminal diolefins when affording smaller than 12-membered rings. We found that modification of the enediyne–diolefin substrate as the Co₂(CO)₆–alkyne complex allowed the target benzothiophene-fused 11-membered dienediyne to be obtained via RCM; the alkyne complexation strategy therefore provides one valid technique for overcoming challenges to macrocyclization of this kind.

O.A. Tomashenko, A.F. Khlebnikov, I.P Mosiagin, M.S. Novikov, E.V. Grachova, J.R. Shakirova, S.P. Tunik

“A new heterocyclic skeleton with highly tunable absorbtion/emission wavelength via H-bonding”

RSC Adv., 2015, accepted
DOI:10.1039/C5RA17755C

A new heterocyclic system, pyrido[2,1-a]pyrrolo[3,2-c]isoquinoline, was synthesized via Pd-catalyzed intramolecular cyclization of 1-[1-benzyl-2-(2-bromophenyl)-1H-pyrrol-3-yl]pyridin-1-ium bromides. The heterocycles obtained display stimuli responsive fluorescence in solution depending on the nature of the solvent. The strongest blue shift of the emission maxima and growth in luminescence intensity was observed in protic solvents and upon addition of proton donors to solutions of compounds in aprotic solvents. The effect of proton donors on emission characteristics was explained by DFT calculations in terms of H-complex formation with the nucleophilic centres of the molecular skeleton

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.