50476-17-0Relevant articles and documents
Unsubstituted quinoidal pyrrole and its reaction with oxygen, charge transfer and palladium(ii) complexes via DDQ oxidation
Ghorai, Debasish,Mani, Ganesan
, p. 45603 - 45611 (2014)
The dehydrogenation reaction of 2,5-bis(3,5-dimethylpyrazolylmethyl)pyrrole with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) followed by treatment with sodium bicarbonate afforded two new products containing oxygen atoms, 2,5-bis(3,5-dimethylpyrazolylcarbonyl)pyrrole (2) and 5-{bis-(3,5-dimethylpyrazolyl)methyl}pyrrole-2-carbaldehyde (3). Interestingly, the products are different, when the reaction mixture is not treated with base; they are 2,2-tri(3,5-dimethylpyrazolylmethyl)-5-(3,5-dimethylpyrazolylcarbonyl)pyrrole (4) and the adduct 5, the 2,3-dichloro-5,6-dicyanohydroquinone (DDQH2) adduct of 2,5-bis{di(3,5-dimethylpyrazolyl)methene}-2,5-dihydropyrrole (6) isolated in 22% yield, in which 6 acts as an electron acceptor and DDQH2as an electron donor. The treatment of 5 with NaBH4or basic alumina afforded the free base 6 in good yield, representing a discrete unsubstituted quinoidal structure of pyrrole. 6 is fluorescent, reactive and could have a biradical resonance structure, which is demonstrated by its reaction with dioxygen only under the irradiation of sunlight, not reacting in darkness, giving the oxygen containing products: 2, bis-(3,5-dimethylpyrazolyl)methanone (7) and 2-(3,5-dimethylpyrazolylcarbonyl)-5-(3,5-dimethylpyrazolyl)pyrrole (8). Moreover, the quinoidal molecule loses its fluorescence property on coordinating with palladium metal atom and gives a binuclear complex, [Pd2Cl4{μ-C4H3N-2,5-(C(Me2pz)2)2-N,N,N,N}], in good yield. The structures of most of the compounds, including this palladium complex, were determined by single crystal X-ray diffraction studies.
Metal-free, Mild, and Selective Synthesis of Bis(pyrazolyl)alkanes by Nucleophile-Catalyzed Condensation
Tansky, Maxym,Gu, Zipeng,Comito, Robert J.
, p. 1601 - 1611 (2021/01/14)
Bis(pyrazolyl)alkanes are a prolific class of ligands for catalysis, accessible by the condensation between bis(pyrazolyl)methanones and carbonyls. In this report, we describe a nucleophile-catalyzed innovation on this condensation that avoids the transition metals, high temperatures, reagent excess, and air-sensitive reagents common among the existing protocols. Significantly, this method accommodates sterically hindered and electronically diverse pyrazoles and aldehydes, applicable for systematic ligand optimization. Furthermore, our scope includes azoles and bridging functional groups previously unreported for this reaction, promising for new heteroscorpionate catalysts. We provide the first direct evidence for an elusive reaction intermediate and characterize the most complete mechanism for this condensation.
NNNO-Heteroscorpionate nickel (II) and cobalt (II) complexes for ethylene oligomerization: the unprecedented formation of odd carbon number olefins
Zubkevich, Sergey V.,Tuskaev, Vladislav A.,Gagieva, Svetlana Ch.,Kayda, Anatoliy S.,Khrustalev, Victor N.,Pavlov, Alexander A.,Zarubin, Dmitry N.,Bulychev, Boris M.
, (2020/07/04)
The unprecedented observation of odd carbon number olefins is reported during nickel- catalyzed ethylene oligomerization. Two complexes based on Co (II) and Ni (II) with novel tetradentate heteroscorpionate ligand have been synthesized and fully characterized. These complexes showed the ability to oligomerize ethylene upon activation with various organoaluminum compounds (Et2AlCl, Et3Al2Cl3, EtAlCl2, MMAO). Ni (II) based catalytic systems were sufficiently more active (up to 1900 kg·mol (Ni)?1·h?1·atm?1) than Co (II) analogs and have been found to be strongly dependent on the activator composition. The use of PPh3 as an additive to catalytic systems resulted in the increase of activity up to 4,150 kg·mol (Ni)?1·h?1·atm?1 and in the alteration of selectivity. All Ni (II) based systems activated with EtAlCl2 produce up to 5 mol. percent of odd carbon number olefins; two probable mechanisms for their formation are suggested – metathesis and β-alkyl elimination.
Synthesis and reactivity in ethylene oligomerization by heteroscorpionate dibromonickel(II) complexes
Zubkevich, Sergei V.,Gagieva, Svetlana Ch.,Tuskaev, Vladislav A.,Dorovatovskii, Pavel V.,Khrustalev, Victor N.,Sizov, Alexandr I.,Bulychev, Boris M.
, p. 58 - 67 (2017/01/06)
Novel heteroscorpionate ligands were synthesized by a Peterson rearrangement during the reaction of 2-pyridinecarboxaldehyde (or 2-quinolinecarboxaldehyde) and 1,1-carbonyl-bis(pyrazoles). Nickel(II) dibromide reacts with these ligands in THF to give the heteroscorpionate dibromo complexes of general formula LNiBr2. Crystal structures of two full-sandwich heteroscorpionate Ni(II) complexes were determined. Preliminary studies of catalytic activity in ethylene oligomerization using different organoaluminum cocatalysts were performed. The addition of one equivalent of triphenylphosphine resulted in increased catalytic activity for most examples. The catalyst system of (2-[bis(3,5-dimethylpyrazol-1-yl)methyl]pyridine nickel(II) dibromide/Et2AlCl/PPh3dimerized ethylene with an activity of 650?g oligomer mol?1?Ni?h?1while the share of 1-butene in the mixture has reached 75%. Tris(3,5-dimethylpyrazol-1-yl)methyl nickel(II) dibromide, activated by Et2AlCl/PPh3produced isobutylene (75% of the butene fraction).
Titanium and zirconium compounds stabilized by coordination of heteroscorpionate [N,N,O]-donor ligands. Synthesis, characterization and polymerization activity
Alesso, Giuseppe,Tabernero, Vanessa,Cuenca, Tomás
, p. 202 - 210 (2012/11/06)
The bis(pyrazol-1-yl)methane compounds [(2-hydroxyphenyl)bis(pyrazol-1-yl) methane (4) bpzmpH, (3,5-di-tert-butyl-2-hydroxyphenyl)bis(pyrazol-1-yl)methane (5) bpzmtBu2pH, (2-hydroxyphenyl)bis(3,5-dimethyl-pyrazol-1-yl) methane (6) Me2bpzmpH, (3,5-di-tert-butyl-2-hydroxyphenyl)bis(3,5- dimethyl-pyrazolyl)methane (7) Me2bpzmtBu2pH, (2-hydroxyphenyl)bis(4-methyl-pyrazolyl)methane (8) MebpzmpH and (3,5-di-tert-butyl-2-hydroxyphenyl)bis(4-methyl-pyrazolyl)methane (9) MebpzmtBu2pH] as heteroscorpionate precursor ligands have been prepared by reaction of the corresponding bis(pyrazol-1-yl)ketone (1), bis(3,5-dimethylpyrazol-1-yl)ketone (2) and bis(4-methylpyrazol-1-yl)ketone (3) with the appropriate salicylaldehyde derivative. The coordination of these molecules to titanium and zirconium compounds containing a cyclopentadienyl ligand has been studied. TiCpRCl3 (CpR = η5-C5H5 (Cp); η5-C 5H4SiMe3 (Cp′); η5-C 5Me5 (Cp*)) reacts with 4-9 in the presence of 2.5 equiv of NEt3, in toluene at room temperature, through an alcoholysis process to give the monocyclopentadienyl heteroscorpionate dichloro complexes TiCpRLCl2 [CpR = Cp, L = bpzmp (10), Me2bpzmtBu2p (11), MebpzmtBu2p (12); CpR = Cp′, L = Me2bpzmtBu2p (13); CpR = Cp*, L = bpzmp (14), Me2bpzmtBu2p (15)] (Scheme 2). Treatment of TiCp*Me3 with 4, 6 and 8 affords the dimethyl complexes TiCp*LMe2 [L = bpzmp (16), Me2bpzmp (17), Mebpzmp (18)]. Analogous dichloro ZrCpLCl2 [L = bpzmp (19), bpzmtBu2p (20), Me2bpzmp (21), MebpztBu2p (22)] and dibenzyl ZrCpLBz2 [L = bpzmp (23), bpzmtBu2p (24), Me2bpzmp (25), MebpzmtBu2p (26)] zirconium complexes have also been prepared by reaction of ZrCpCl3 in THF or ZrCpBz3 in toluene with 4, 5, 6 and 8 at room temperature. From spectroscopic data tetrahedral structures in solution with a κ1-O coordination mode are suggested for the titanium complexes, while distorted octahedral geometries with a κ3-N,N, O coordination are proposed for the zirconium derivatives. Fluxional exchange between coordinated and non-coordinated pyrazolate rings is concluded in some zirconium compounds, depending on the electronic and steric effects imposed by the substituents of the heteroscorpionate ligands. Preliminary studies of catalytic activity for ethylene polymerization using sMAO as cocatalyst were performed. The complexes proved to be moderate catalysts due to loss of the scorpionate ligand.
(Arene)ruthenium(II) complexes containing substituted bis(pyrazolyl)methane ligands - Catalytic behaviour in transfer hydrogenation of ketones
Carrion, M. Carmen,Jalon, Felix A.,Manzano, Blanca R.,Rodriguez, Ana M.,Sepulveda, Francisco,Maestro, Miguel
, p. 3961 - 3973 (2008/03/12)
A new and safer methodology has been developed for the synthesis of bis(pyrazol-1-yl)methane ligands (NN). Several ligands containing different phenyl groups on the central carbon atom have been obtained. Ruthenium derivatives of the type [Ru(arene)Cl(NN)]BPh4 (arene = benzene, p-cymene) have been synthesised using these ligands. One or two isomers that differ regarding the axial or equatorial disposition of the phenyl group on the metallacycle have been obtained. Their formation is rationalised by considering steric effects. The structures of five derivatives were determined by X-ray diffraction. In four complexes the phenyl substituent is in the axial disposition of the metallacycle and in one case in the equatorial orientation. The dihedral angle formed by the planes of the two pyrazole rings is always bigger for the complexes containing unsubstituted pyrazolyl heterocycles. The behaviour of the new derivatives in the transfer hydrogenation of benzophenone in the presence of KOH was studied. The benzene derivatives showed higher activity than the p-cymene complexes. A marked and positive effect of the methyl groups on the pyrazolyl rings was observed. The effect of the substituents on the benzyl carbon atom was also important. It has been observed that the benzophenone hydrogenation was possible without the addition of complexes. The effect of the KOH concentration was evaluated and a concentration that leads to negligible conversion in a base-only process was chosen. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Antidiabetic activity of some 1-substituted 3,5-dimethylpyrazoles
Soliman,Darwish
, p. 1659 - 1663 (2007/10/02)
Several new 1-substituted 3,5-dimethylpyrazoles were prepared for testing as hypoglycemic agents. A number of these containing para-substituted 1-carbonylphenylurea and para-substituted 1-carbamoylbenzenesulfonylurea derivatives were found to possess potent hypoglycemic activity.
