Center for Magnetic Resonance

D.A. Markelov, V.V. Matveev, P. Ingman, M.N. Nikolaeva, A.V. Penkova, E. Lahderanta, N.I. Boiko, V.I. Chizhik

“Unexpected Temperature Behavior of Polyethylene Glycol Spacers in Copolymer Dendrimers in Chloroform”

Sci. Rep., 2016, 6, 24270
DOI:10.1038/srep24270

We have studied copolymer dendrimer structure: carbosilane dendrimers with terminal phenylbenzoate mesogenic groups attached by poly(ethylene) glycol (PEG) spacers. In this system PEG spacers are additional tuning to usual copolymer structure: dendrimer with terminal mesogenic groups. The dendrimer macromolecules were investigated in a dilute chloroform solution by 1H NMR methods (spectra and relaxations). It was found that the PEG layer in G = 5 generations dendrimer is “frozen” at high temperatures (above 260 K), but it unexpectedly becomes “unfrozen” at temperatures below 250 K (i.e., melting when cooling). The transition between these two states occurs within a small temperature range (~10 K). Such a behavior is not observed for smaller dendrimer generations (G = 1 and 3). This effect is likely related to the low critical solution temperature (LCST) of PEG and is caused by dendrimer conformations, in which the PEG group concentration in the layer increases with growing G. We suppose that the unusual behavior of PEG fragments in dendrimers will be interesting for practical applications such as nanocontainers or nanoreactors.

N.A. Danilkina, P.S. Vlasov, S.M. Vodianik, A.A. Kruchinin, Y.G. Vlasov, I.A. Balova

“Synthesis and chemosensing properties of cinnoline-containing poly(arylene ethynylene)s”

Beilstein J. Org. Chem., 2015, 11, 373-384
DOI:10.3762/bjoc.11.43

Novel poly(arylene ethynylene)s comprising a cinnoline core were prepared in high yields via a three-step methodology. A Richter-type cyclization of 2-ethynyl- and 2-(buta-1,3-diynyl)aryltriazenes was used for cinnoline ring formation, followed by a Sonogashira coupling for the introduction of trimethylsilylethynyl moieties and a sila-Sonogashira coupling as the polycondensation technique. The fluorescence of the cinnoline-containing polymers in THF was highly sensitive to quenching by Pd²⁺ ions.

M.V. Sorokina, A.S. Pankova, M.A. Kuznetsov

“Oxidative Aminoaziridination of 2-Vinylfuran Derivatives as an Approach to Hexa-2,5-diene-1,4-dione Monohydrazones”

Asian J. Org. Chem., 2016, 5, 389-398
DOI:10.1002/ajoc.201500460

The oxidative addition of N-aminophthalimide to substituted 2-vinylfurans provides monophthaloylhydrazones of (2Z)-hexa-2,5-diene-1,4-dione derivatives instead of 2-furylaziridines by proceeding through an aziridination of the endocyclic furan C=C bond followed by a regio- and stereoselective rearrangement of the bicyclic intermediate. The formation of stable aziridines can then occur through the aziridination of the (E)-C=C bond of these phthaloylhydrazones. Detailed structure elucidations and mechanistic considerations are provided.

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

“Boron trifluoride–methanol complex. Mild and powerful reagent for deprotection of acetylated amines. Scope and selectivity”

Tetrahedron Lett., 2016, 57, 641-644
DOI:10.1016/j.tetlet.2015.12.087

A boron trifluoride–methanol complex demonstrated remarkable deprotection selectivity against commonly used amino-protecting groups in the deacetylation of acetanilides and high sensitivity to the steric hindrance of substrates. The scope and limitations of the reaction were explored.