32251-84-6Relevant academic research and scientific papers
Synthesis, structures, and reactivities of six-membered C[sbnd]N chelate protic pyrazole complexes of iridium
Kashiwame, Yohei,Ikariya, Takao,Kuwata, Shigeki
, (2021)
The reaction of the bis(acetato)iridium complex [Cp*Ir(OAc)2] with an equimolar amount of 3-benzyl-5-alkylpyrazoles followed by addition of an excess of potassium chloride afforded the six-membered, C–N chelate protic pyrazole complexes [Cp*IrCl(R-LH)] (2a, R = Me; 2b, R = tBu; R-LH = C6H4CH2-C3N2H2R-5-κC,κN). The reaction of 2a with carbon monoxide led to the formation of the carbonyl complex [Cp*Ir(CO)(Me-LH)]Cl (3a) featuring a CO stretching wavenumber comparable with that of the five-membered chelate complex. Meanwhile, dehydrochlorination of the methylpyrazole complex 2a with potassium tert-butoxide in toluene resulted in uptake of adventitious water to give the hydroxido-bridged dinuclear complex [(Cp*Ir)2{μ-Me-LH···(Me-L)}(μ-OH)] (4a). In 2-propanol, the reaction caused hydrogen transfer from the solvent to yield the hydrido-bridged dinuclear complex [(Cp*Ir)2{μ-Me-LH···(Me-L)}(μ-H)] (6a). These dinuclear products could not be obtained from the more sterically-demanding complex 2b, but the intermediary coordinatively unsaturated pyrazolato species can be trapped from both 2a and 2b by triphenylphosphine to give the pyrazolato–phosphine complexes [Cp*Ir(PPh3)(R-L)] (5a and 5b) The detailed structures of 2a, 2b, 3a, 4a, and 5b bearing a folded six-membered C–N chelate pyrazole ligand have been determined by X-ray analysis. The chlorido complexes 2a and 2b also catalyzed transfer hydrogenation of acetophenone with 2-propanol at 50 °C.
β-Tosylhydrazono phosphonates in organic synthesis. An unambiguous entry to polysubstituted pyrazoles
Almirante,Benicchio,Cerri,Fedrizzi,Marazzi,Santagostino
, p. 299 - 302 (2007/10/03)
β-Tosylhydrazono phosphonates are novel, bifunctional reagents which were used for a concise approach to a wide range of polysubstituted pyrazoles in a single operation from aromatic and aliphatic aldehydes.
A NEW SYNTHESIS OF 3,5-DISUBSTITUTED PYRAZOLES BY REACTION OF α,γ-DIPYROLIDINYLGLUTARONITRILES (MASKED α,γ-DIKETONE EQUIVALENTS) WITH HYDRAZINES
Takahashi, Kazumasa,Suzuki, Akira,Ogura, Katsuyuki,Iida, Hirotada
, p. 1075 - 1078 (2007/10/02)
An efficient sequence proposed for a new synthetic method of 3,5-disubstituted pyrazoles involves the reaction of α,γ-dipyrolidinylglutaronitriles (masked α,γ-diketone equivalents) with hydrazines.
REGIOSELECTIVE ADDITION OF HYDRAZINES TO ALLENYLACETYLENES - CONVENIENT ROUTE TO 3(5)-METHYL-5(3)-SUBSTITUTED PYRAZOLES
Khrimyan, A. P.,Karapetyan, A. V.,Badanyan, Sh. O.
, p. 189 - 196 (2007/10/02)
It is shown that hydrazine hydrate, methylhydrazine, and phenylhydrazine add smoothly and regioselectively to allenylacetylenes to give 3(5)-methyl-5(3)-substituted pyrazoles.In addition to the principal process, isomerization of allenylacetylenes to methyldiacetylenes, and the degree of which depends on the structure of the substrate, is observed in the reaction of methylhydrazine in an aqueous alcohol medium.
