19933-24-5Relevant articles and documents
Tsuchiya et al.
, p. 568 (1978)
Tris(pyrazolyl)methanides of the alkaline earth metals: Influence of the substitution pattern on stability and degradation
Müller, Christoph,Koch, Alexander,G?rls, Helmar,Krieck, Sven,Westerhausen, Matthias
, p. 635 - 645 (2015)
Trispyrazolylmethanides commonly act as strong tridentate bases toward metal ions. This expected coordination behavior has been observed for tris(3,4,5-trimethylpyrazolyl)methane (1a), which yields the alkaline-earth-metal bis[tris(3,4,5-trimethylpyrazolyl)methanides] of magnesium (1b), calcium (1c), strontium (1d), and barium (1e) via deprotonation of 1a with dibutylmagnesium and [Ae{N(SiMe3)2}2] (Ae = Mg, Ca, Sr, and Ba, respectively). Barium complex 1e degrades during recrystallization that was attempted from aromatic hydrocarbons and ethers. In these scorpionate complexes, the metal ions are embedded in distorted octahedral coordination spheres. Contrarily, tris(3-thienylpyrazolyl)methane (2a) exhibits a strikingly different reactivity. Dibutylmagnesium is unable to deprotonate 2a, whereas [Ae{N(SiMe3)2}2] (Ae = Ca, Sr, and Ba) smoothly metalates 2a. However, the primary alkaline-earth-metal bis[tris(3-thienylpyrazolyl)methanides] of Ca (2c), Sr (2d), and Ba (2e) represent intermediates and degrade under the formation of the alkaline-earth-metal bis(3-thienylpyrazolates) of calcium (3c), strontium (3d), and barium (3e) and the elimination of tetrakis(3-thienylpyrazolyl)ethene (4). To isolate crystalline compounds, 3-thienylpyrazole has been metalated, and the corresponding derivatives [(HPzTp)4Mg(PzTp)2] (3b), dinuclear [(tmeda)Ca(PzTp)2]2 (3c), mononuclear [(pmdeta)Sr(PzTp)2] (3d), and [(hmteta)Ba(PzTp)2] (3e) have been structurally characterized. Regardless of the applied stoichiometry, magnesiation of thienylpyrazole 3a with dibutylmagnesium yields [(HPzTp)4Mg(PzTp)2] (3b), which is stabilized in the solid state by intramolecular N-H···N···H-N hydrogen bridges. The degradation of [Ae{C(PzR)3}2] (R = Ph and Tp) has been studied by quantum chemical methods, the results of which propose an intermediate complex of the nature [{(PzR)2C}2Ca{PzR}2]; thereafter, the singlet carbenes ([:C(PzR)2]) dimerize in the vicinity of the alkaline earth metal to tetrapyrazolylethene, which is liberated from the coordination sphere as a result of it being a very poor ligand for an s-block metal ion.
Molybdenum-silver co-catalyzed cycloaddition of alkynes with: N -isocyanoiminotriphenylphosphorane (NIITP): An efficient strategy for the synthesis of monosubstituted pyrazoles
Mi, Pengbing,Lang, Jiajia,Lin, Shaojian
supporting information, p. 7986 - 7989 (2019/07/10)
A new molybdenum-silver co-catalyzed [3+2] cycloaddition of alkynes with N-isocyanoiminotriphenylphosphorane (NIITP) has been described. The NIITP serves as a non-toxic, facile "CNN" source. Over 30 substrates were successfully converted to the desired compounds in good to excellent yields.
Consecutive three-component synthesis of 3-(hetero)aryl-1H-pyrazoles with propynal diethylacetal as a three-carbon building block
Levi, Lucilla,Boersch, Christina,Gers, Charlotte F.,Merkul, Eugen,Mueller, Thomas J. J.
scheme or table, p. 9340 - 9356 (2012/01/04)
A novel consecutive three-component synthesis of 3-(hetero)aryl-1H- pyrazoles via room temperature Sonogashira arylation of propynal diethylacetal used as a propargyl aldehyde synthetic equivalent has been disclosed. The final acetal cleavage-cyclocondensation with hydrazine hydrochloride at 80 °C rapidly furnishes the title compounds in a one-pot fashion.
