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1.
Vieira Renata Leia Demario Gaglieri Caroline de Oliveira Cristina Soltovski Ferreira Laura Teófilo Schnitzler Egon Bannach Gilbert 《Journal of Thermal Analysis and Calorimetry》2021,144(3):689-697
Journal of Thermal Analysis and Calorimetry - Buckwheat starch is an alternative source to supply the high global demand for starch. The properties of starch can be modified through chemical and... 相似文献
2.
Structures of New SeII and TeII Complexes Containing 2,2-Dicyanethylene-1,1-dithiolate, 2,2-Dicyanethylene-1,1-thioselenolate, and 2,2-Dicyanethylene-1,1-diselenolate (NBu4)2{Se[S2C?C(CN)2]2} ( I ), (AsPh4)2 · {Te[SSeC?C(CN)2]2} ( II ), and (NBu4)2{Te[Se2C?C(CN)2]2} ( III ) containing the bidentate chelate ligands 2,2-dicyanethylene-1,1-dithiolate i-mnt , 2,2-dicyanethylene-1,1-thioselenolate i-mnts , and 2,2-dicyanethylene-1,1-diselenolate i-mns have been prepared and characterized by X-ray structure analysis. The central units consist of [M(X? X)2E2]2? (M = Se, Te; X? X = ligand; E = lone-pair) with fourfold coordinated SeII and TeII, respectively. The complex anions [Se(i-mnt)2E2]2? as well as [Te(i-mnts)2E2]2? show a trapezoide distortion with d(Se? S) = 2.276(5); 2.287(5); 2.803(5); 2.789(5) Å and d(Te? Se) = 2.611(2); 2.617(3); d(Te? S) = 2.889(5); 2.935(4) Å. In III there are centrosymmetric complex anions [Te(i-mns)2E2]2? with nearly identical Te? Se-bond-lengths: 2.674(3) and 2.692(2) Å. These Te? Se bonds are elongated compared to usual Te? Se bonds. 相似文献
3.
The characterization of the compounds CF3SeX (X = H, Cl, Br, CN, CF3, SeCF3) is completed by the report of melting points, boiling points, enthalpies of vaporization and entropies of vaporization. Ultraviolet and mass spectra are presented and discussed. An improved synthesis for CF3SeH is reported. 相似文献
4.
Werner Bihlmaier Rolf Huisgen Hans-Ulrich Reissig Sabine Vass 《Tetrahedron letters》1979,20(28):2621-2624
Whereas diazomethane cycloadditions are only accelerated by electron-attracting substituents in the olefinic or acetylenic dipolarophile, the cycloadditions of diazoacetic, diazomalonic and diazo(phenylsulfonyl)acetic ester show in accordance with the PMO treatment U-shaped activity functions when log k2 is plotted versus the lowest IP of the dipolarophiles. 相似文献
5.
6.
Flögel O Dash J Brüdgam I Hartl H Reissig HU 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(17):4283-4290
Addition of lithiated methoxyallene to pivalonitrile afforded after aqueous workup the expected iminoallene 1 in excellent yield. Treatment of this intermediate with silver nitrate accomplished the desired cyclization to the electron-rich pyrrole derivative 2 in moderate yield. Surprisingly, trifluoroacetic acid converted iminoallene 1 to a mixture of enamide 3 and trifluoromethyl-substituted pyridinol 4 (together with its tautomer 5). A plausible mechanism proposed for this intriguing transformation involves addition of trifluoroacetate to the central allene carbon atom of an allenyl iminium intermediate as crucial step. Enamide 3 is converted to pyridinol 4 by an intramolecular aldol-type process. A practical direct synthesis of trifluoromethyl-substituted pyridinols 4, 10, 11, and 12 starting from typical nitriles and methoxyallene was established. Pyridinol 10 shows an interesting crystal packing with three molecules in the elementary cell and a remarkable helical supramolecular arrangement. Trifluoromethyl-substituted pyridinol 4 was converted to the corresponding pyridyl nonaflate 13, which is an excellent precursor for palladium-catalyzed reactions leading to pyridine derivatives 14-16 in good to excellent yields. The new synthesis of trifluoromethyl-substituted pyridines disclosed here demonstrates a novel reactivity pattern of lithiated methoxyallene which is incorporated into the products as the unusual tripolar synthon B. 相似文献
7.
[reaction: see text] Diastereoselective hydroborations of enantiopure 3,6-dihydro-2H-1,2-oxazines led to dihydroxy-substituted 1,2-oxazines. Samarium diiodide-induced N-O bond cleavage generated 1,4-amino alcohols which were recyclized to polyhydroxylated pyrrolidines which are potential glycosidase inhibitors. 相似文献
8.
9.
G Bannach E Schnitzler O Treu
Filho V H S Utuni M Ionashiro 《Journal of Thermal Analysis and Calorimetry》2006,83(1):233-240
Solid-state
compounds of general formula LnL3⋅nH2O,
where Ln represents heavier lanthanides
and yttrium and L is 2-chlorobenzylidenepyruvate,
have been synthesized. Chemical analysis, simultaneous thermogravimetry-differential
analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry,
elemental analysis and infrared spectroscopy have been employed to characterize
and to study the thermal behaviour of these compounds in dynamic air atmosphere.
On heating these compounds
decompose in four (Gd, Tb, Ho to Lu, Y) or five (Eu, Dy) steps. They lose
the hydration water in the first step and the thermal decomposition of the
anhydrous compounds up to 1200°C occurs with the formation of the respective
oxide, Tb4O7 and Ln2O3
(Ln=Eu, Gd, Dy to Lu and Y) as final residue.
The dehydration enthalpies found for these compounds (Eu, to Lu and Y) were:
65.77, 55.63, 86.89, 121.65, 99.80, 109.59, 131.02, 119.78, 205.46 and 83.11
kJ mol-1, respectively. 相似文献
10.
The reaction of the silyl complex Cp(CO)2FeSiH3 (1) with various donors under photochemical conditions leads to the formation of Cp(CO)(L)FeSiH3 (2a-2c) and Cp(L)2FeSiH3 (3a, 3b) (L = MeNC, t-BuNC, Me3P) via stepwise CO-substitution. 2a,2b are transformed by Co2(CO)8 to the complexes μ2-[Cp(CO)-(RNC)FeSiH] [μ2-(CO)] Co2(CO)6 (3a,3b), the first complexes with a hydrogen substituted ferrio-silanediyl unit bridging two cobalt atoms. 相似文献