Taras L. Panikorovskii

Fe(II)/Et3N-Relay-catalyzed domino reaction of isoxazoles with imidazolium salts in the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates, its ylide and betaine derivatives

Summary A simple approach was developed for the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates from easily available compounds, 5-methoxyisoxazoles and phenacylimidazolium salts under hybrid Fe(II)/Et3N relay catalysis. The products were easily transformed into the corresponding 3-(5-methoxycarbonyl-1H-imidazol-3-ium-3-yl)pyrrol-1-ides, which in turn can be hydrolyzed under basic conditions into the corresponding betaines. A carbene tautomeric form of the 4-methoxycarbonyl-substituted imidazolylpyrrolides was trapped by reaction with sulfur affording the corresponding imidazolethiones under very mild conditions.

Synthesis of natural phaeosphaeride A derivatives and an in vitro evaluation of their anti-cancer potential

Derivatives of phaeosphaeride A (PPA) were synthesised and characterised; then anti-cancer studies were carried out on the A549 cancer cell line. It was found that the acetyl derivative (compound 3) displayed comparable in vitro cytotoxicity to that of PPA (EC50=49±7 μM and EC50=46±5 μM, respectively), while chloroacetyl derivative 6 (EC50=33±7 μM) was found to have better efficacy towards the A549 cancer cell line.

Crystal structure of natural phaeosphaeride A

The asymmetric unit of the title compound, C15H23NO5, contains two independent molecules. Phaeosphaeride A contains two primary sections, an alkyl chain consisting of five C atoms and a cyclic system consisting of fused five- and six-membered rings with attached substituents. In the crystal, the molecules form layered structures. Nearly planar sheets, parallel to the (001) plane, form bilayers of two-dimensional hydrogen-bonded networks with the hydroxy groups located on the interior of the bilayer sheets. The network is constructed primarily of four O—H⋯O hydrogen bonds, which form a zigzag pattern in the (001) plane. The butyl chains interdigitate with the butyl chains on adjacent sheets. The crystal was twinned by a twofold rotation about the c axis, with refined major–minor occupancy fractions of 0.718 (6):0.282 (6).

Copper(I)-Catalyzed 1,3-Dipolar Cycloaddition of Ketonitrones to Dialkylcyanamides: A Step toward Sustainable Generation of 2,3-Dihydro-1,2,4-oxadiazoles

CuI-catalyzed cycloaddition (CA) of the ketonitrones, Ph2C=N+(R′)O– (R′ = Me, CH2Ph), to the disubstituted cyanamides, NCNR2 (R = Me2, Et2, (CH2)4, (CH2)5, (CH2)4O, C9H10, (CH2Ph)2, Ph(Me)), gives the corresponding 5-amino-substituted 2,3-dihydro-1,2,4-oxadiazoles (15 examples) in good to moderate yields. The reaction proceeds under mild conditions (CH2Cl2, RT or 45 °C) and requires 10 mol % of [Cu(NCMe)4](BF4) as the catalyst. The somewhat reduced yields are due to the individual properties of 2,3-dihydro-1,2,4-oxadiazoles, which easily undergo ring opening via N—O bond splitting. Results of density functional theory calculations reveal that the CA of ketonitrones to CuI-bound cyanamides is a concerted process, and the copper-catalyzed reaction is controlled by the predominant contribution of the HOMOdipole–LUMOdipolarophile interaction (group I by Sustmann’s classification). The metal-involving process is much more asynchronous and profitable from both kinetic and thermodynamic viewpoints than the hypothetical metal-free reaction.

Towards a revisitation of vesuvianite-group nomenclature: the crystal structure of Ti-rich vesuvianite from Alchuri, Shigar Valley, Pakistan.

Vesuvianite containing 5.85 wt% TiO2 from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, Pakistan, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement, 27Al NMR, 57Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are: a = 15.5326 (2), c = 11.8040 (2) Å, space group P4/nnc. The structure was refined to final R1 = 0.031, wR2 = 0.057 for 11247 I > 2σ(I). A general crystal-chemical formula of studied sample can be written as follows (Z = 2): [8-9](Ca17.1Na0.9) [8]Ca1.0[5](Fe2+0.44Fe3+0.34Mg0.22) [6](Al3.59Mg0.41) [6](Al4.03Ti2.20Fe3+1.37Fe2+0.40) (Si18O68) [(OH)5.84O2.83F1.33]. The octahedral site Y2 is Al-dominant and does not contain transition elements. Another octahedral site Y3 is also Al-dominant and contains Fe2+, Fe3+ and Ti. The site Y1 is split into Y1a and Y1b predominantly occupied by Fe2+ and Fe3+, respectively. The role of the Y1 site in the diversity of vesuvianite-group minerals is discussed.

A novel family of homoleptic copper(I) complexes featuring disubstituted cyanamides: a combined synthetic, structural, and theoretical study

The homoleptic copper(I) complexes [Cu(NCNRR′)4](BF4) (R/R′ = Me/Me 1, Et/Et 2, C5H103, C4H8O 4, C4H85, C3H6C6H46, CH2Ph/CH2Ph 7, Me/Ph 8) featuring disubstituted cyanamides were obtained in excellent (92–97%) yields by the reaction of [Cu(NCMe)4](BF4) and 4 equivalents of NCNRR′. Complexes 1–8 were characterized by atomic absorption spectrometry (Cu%), high resolution ESI+-MS, molar conductivities, TG/DTA, and 1H, 13C{1H} NMR, FTIR spectroscopic techniques, and also by single-crystal X-ray diffraction (1, 3, and 4). Results of DFT calculations and X-ray structure determinations reveal that equilibrium geometries of [Cu(NCMe)4]+ and [Cu(NCNMe2)4]+ in the gas phase are normal tetrahedral (Td) and significantly distorted, respectively. Effects of crystal packing influence the values of the Cu–N–C angles in [Cu(NCNRR′)4]+, which points out to the noticeable contribution of the heterocumulene mesomeric form for the dialkylcyanamide copper(I) complexes. The QTAIM and NBO analyses indicate that relatively weak Cu–N contacts (15–31 kcal mol−1) in both cases exhibit single bond character and clearly polarized toward the N atom (by 91–95%). The CDA shows that the {M} ← L σ-donation substantially prevails over the {M} → L π-back-donation in both [Cu(NCMe)4]+ and [Cu(NCNMe2)4]+. The orbital, charge, and vibrational frequency arguments as well as inspection of the FTIR data suggest that the electrophilic activation of the NC group in homoleptic nitrile and dialkylcyanamide copper(I) complexes is similar, and the different behavior of nitriles and cyanamides in the 1,3-dipolar cycloaddition of ketonitrones is mainly due to the difference in the atomic charges.

Goryainovite, Ca2PO4Cl, a new mineral from the Stora Sahavaara iron ore deposit (Norrbotten, Sweden)

Abstract Goryainovite, Ca2PO4Cl, is a new halophosphate, the chlorine analogue of ‘spodiosite’, Ca2PO4F. It is orthorhombic, Pbcm, a = 6.215(2), b = 7.011(2), c = 10.788(3) Å, V = 470.0(8) Å3, Z = 4 (from powder X-ray diffraction data). The mineral is found in a magnetite-serpentine rock of the Stora Sahavaara iron ore deposit (67.408°N 23.297°E) where it forms small (up to 20 μm in diameter) rounded inclusions in magnetite, in close association with hydroxylapatite–chlorapatite, pyrrhotite, pyrite, chalcopyrite, valleriite and thorianite. Goryainovite is a transparent, colourless mineral with a vitreous lustre and a white streak. Cleavage is not observed, and the fracture is conchoidal. The Mohs hardness is c. 4. In transmitted light, the mineral is colourless, biaxial (–), β ≈ 1.66 (for λ = 589 nm). Dcalc = 2.98 g·cm−3. The mean chemical composition specified with electron microprobe is (wt.%): P2O5 33.19, Cl 16.96, CaO 53.25, O = Cl –3.83, total 99.57. The empirical formula calculated on the basis of 3 cations per molecule is Ca2.01[P0.99O3.98]Cl1.01. The simplified formula is Ca2PO4Cl. The strongest X-ray powder diffraction lines [d in Å, (I), (hkl)] are 2.845(90)(113), 2.746(100)(211), 2.333(25)(114), 2.028(15)(132), 1.9569 (30)(115), 1.8370 (20)(025). The Raman spectrum of goryainovite includes 10 bands of -group vibrations. Goryainovite represents probably an early-formed phosphate of the magnetite-serpentine rock and crystallized together with magnetite. When chlorine fugacity decreased, almost all goryainovite was transformed into chlorapatite–hydroxylapatite, and only grains isolated in magnetite remained unaltered. The mineral is named in honour of Prof. Pavel M. Goryainov (b. 1937) for his contribution to the knowledge of the geology and petrology of banded iron formation of the north-eastern part of the Fennoscandian Shield.