Center for Magnetic Resonance

G. Werner, K.S. Rodygin, A.A. Kostin, E.G. Gordeev, A.S. Kashin, V.P. Ananikov

“A solid acetylene reagent with enhanced reactivity: fluoride-mediated functionalization of alcohols and phenols”

Green Chemistry, 2017, 19, 3032–3041
DOI: 10.1039/C7GC00724H

The direct vinylation of an OH group in alcohols and phenols was carried out utilizing a novel CaC₂/KF solid acetylene reagent in a simple K₂CO₃/KOH/DMSO system. The functionalization of a series of hydroxyl-group-containing substrates and the post-modification of biologically active molecules were successfully performed using standard laboratory equipment, providing straightforward access to the corresponding vinyl ethers. The overall process developed involves an atom-economical addition reaction employing only inorganic reagents, which significantly simplifies the reaction set-up and the isolation of products. A mechanistic study revealed a dual role of the F⁻ additive, which both mediates the surface etching/renewal of the calcium carbide particles and activates the C[triple bond, length as m-dash]C bond towards the addition reaction. The development of the fluoride-mediated nucleophilic addition of alcohols eliminates the need for strong bases and may substantially extend the areas of application of this attractive synthetic methodology due to increasing functional group tolerance. As a replacement for dangerous and difficult to handle high-pressure acetylene, we propose the solid reagent CaC₂/KF, which is easy to handle, does not require dedicated laboratory equipment and demonstrates enhanced reactivity of the acetylenic triple bond. Theoretical calculations have shown that fluoride-mediated activation of the hydroxyl group towards nucleophilic addition significantly reduces the activation barrier and facilitates the reaction.

S. Miltsov, V. Karavan, A. Misharev, G. Starova, J. Alonso-Chamarro, M. Puyol

“Unprecedented acid-catalyzed Wurtz-type coupling of meso-bromoindodicarbocyanine dyes”

Tetrahedron Letters, 2017,58, 3353–3357
DOI: 10.1016/j.tetlet.2017.07.043

meso-Bromosubstituted indodicarbocyanine dyes produce dimeric molecules, together with the debrominated species, under acid catalysis. The relationship between the dimerization and hydrodebromination routes depends on the aryl substitution of the dyes. A possible reaction mechanism is also proposed.

E. Abakumov

“Characterisation of humic acids, isolated from selected subantarctic soils by 13C-NMR spectroscopy”

Czech Polar Reports, 2017, 7(1), 1-10
DOI: 10.5817/CPR2017-1-1

Soils of Antarctic considered as underestimated in terms of soils organic matter polls, organic remnants humification/mineralization rates and biogenic-abiogenic interactions. Humic acids of selected Sub Antarctic soils were investigated in terms of elemental and structural composition with special reference to evaluation of organic matter stabilisation degree and assessment of carbon species distributions in the molecules with use of solid state 13C-NMR spectroscopy. It was shown, that the prevailing of aliphatic compounds on the aromatic one is more pronounced in Antarctic soils than in Arctic ones. Average portion of the aromatic compounds is about 20% in humic acids, extracted from soils with evident ornitogenic effect from Fildes Peninsula (Norh-West Antarctic peninsula). This indicates that the role of humification precursors composition is the leading in the humification process. The stabilisation rate of the Antarctic HAs can be assessed as low and the potential risk of biodegradation of their molecules are high.