Fluorinated 2-arylchroman-4-ones and their derivatives: synthesis, structure and antiviral activity

A number of new biologically interesting fluorinated 2-arylchroman-4-ones and their 3-arylidene derivatives were synthesized based on the p-toluenesulfonic acid-catalyzed one-pot reaction of 2-hydroxyacetophenones with benzaldehydes. It was found that obtained (E)-3-arylidene-2-aryl-chroman-4-ones reacted with malononitrile under base conditions to form 4,5-diaryl-4H,5H-pyrano[3,2-c]chromenes. The structures of the synthesized fluorinated compounds were confirmed by 1H, 19F, and 13C NMR spectral data, and for some representatives of heterocycles also using NOESY spectra and X-ray diffraction analysis. A large series of obtained flavanone derivatives as well as products of their modification (35 examples) containing from 1 to 12 fluorine atoms in the structure was tested in vitro for cytotoxicity in MDCK cell line and for antiviral activity against influenza A virus. Among the studied heterocycles 6,8-difluoro-2-(4-(trifluoromethyl)phenyl)chroman-4-one (IC50 = 6 μM, SI = 150) exhibited the greatest activity against influenza A/Puerto Rico/8/34 (H1N1) virus. Moreover, this compound appeared active against phylogenetically distinct influenza viruses, A(H5N2) and influenza B (SI's of 53 and 42, correspondingly). The data obtained suggest that the fluorinated derivatives of 2-arylchroman-4-ones are prospective scaffolds for further development of potent anti-influenza antivirals.

Fulleride-metal η5 sandwich and multi-decker sandwich complexes: A DFT prediction

The (C₆₀ CN)^- formed by the reaction of CN^- with fullerene shows high electron rich character, very similar to C₆₀ ˙^- , and it behaves as a large anion. Similar to Cp^- , the bulky anion, (C₆₀ CN)^- , acts as a strong η⁵ ligand towards transition metal centers. Previous studies on η⁵ coordination of fullerene cage are reported for pseudo fullerenes whereas the present study deals with sandwich complexes of (C₆₀ CN)^- with Fe(II), Ru(II), Cr(II), Mo(II), and Ni(II) and multi-decker sandwich complexes of CN-fullerides with Fe(II). The structural parameters of these complexes and the corresponding Cp^- complexes showed very close resemblance. Analysis of the metal-to-carbon bonding molecular orbitals showed that sandwich complex [Fe(η⁵ -(C₆₀ CN)^- )₂ ] exhibit bonding features very similar to that of ferrocene. Also, a 6-fold decrease in the band gap energy is observed for [Fe(η⁵ -(C₆₀ CN)^- )₂ ] compared to ferrocene. The energy of dissociation (ΔE) of the ligand (C₆₀ CN)^- from [Fe(η⁵ -(C₆₀ CN)^- )₂ ] is slightly lower than the ΔE of a Cp* ligand from a ferrocene derivative wherein each cyclopentadienyl unit is substituted with four tertiary butyl groups. The (C₆₀ CN)^- ligand behaved as one of the bulkiest ligands in the chemistry of sandwich complexes. Further, the coordinating ability of the dianion, (C₆₀ (CN)₂ )^2- is evaluated which showed strong coordination ability simultaneously with two metal centers leading to the formation of multi-decker sandwich and pearl-necklace type polymeric structures.

Diazepinium perchlorate: a neutral catalyst for mild, solvent-free acetylation of carbohydrates and other substances

Diazepinium perchlorate-promoted acetylation of free as well as partially protected sugars, phenols, thiophenols, thiols, other alcohols and amines is described.

Facile solvolysis of a surprisingly twisted tertiary amide

A twisted 3° amide is cleaved at the same rate as a methyl ester under alkaline conditions at 22 °C.