- Ultrasound assisted synthesis of 1,5-disubstituted pyrazole using Cu(I) catalyst
-
A new efficient and convenient approach towards the synthesis of pyrazole is described. The α,β-unsaturated cyanoesters were obtained from substituted benzaldehyde and ethyl cyanoacetate by reported methods. 1,5-Disubstituted pyrazoles were synthesized fr
- Pise, Ashok S.,Burungale, Arvind S.,Devkate, Santosh S.
-
p. 575 - 579
(2020/02/06)
-
- Molybdenum-Mediated One-Pot Synthesis of Pyrazoles from Isoxazoles
-
A one-pot approach for the direct synthesis of substituted pyrazoles from isoxazoles is reported. The process involves isoxazole N-O bond cleavage mediated by a molybdenum complex, in situ hydrolysis of the resulting β-amino enone to the corresponding 1,3-diketone, followed by pyrazole formation in the presence of hydrazine or substituted hydrazine. Good to excellent yields and regioselectivities are obtained with nonsymmetric isoxazoles. By using readily available starting materials, a wide range of substituted pyrazoles may be synthesized by this method.
- Beaumont, Stéphane,Rey, Marine
-
p. 3796 - 3804
(2019/10/11)
-
- Heterocyclic Allylsulfones as Latent Heteroaryl Nucleophiles in Palladium-Catalyzed Cross-Coupling Reactions
-
Heterocyclic sulfinates are effective reagents in palladium-catalyzed coupling reactions with aryl and heteroaryl halides, often providing high yields of the targeted biaryl. However, the preparation and purification of complex heterocylic sulfinates can be problematic. In addition, sulfinate functionality is not tolerant of the majority of synthetic transformations, making these reagents unsuitable for multistep elaboration. Herein, we show that heterocyclic allylsulfones can function as latent sulfinate reagents and, when treated with a Pd(0) catalyst and an aryl halide, undergo deallylation, followed by efficient desulfinylative cross-coupling. A broad range of allyl heteroarylsulfones are conveniently prepared, using several complementary routes, and are shown to be effective coupling partners with a variety of aryl and heteroaryl halides. We demonstrate that the allylsulfone functional group can tolerate a range of standard synthetic transformations, including orthogonal C- and N-coupling reactions, allowing multistep elaboration. The allylsulfones are successfully coupled with a variety of medicinally relevant substrates, demonstrating their applicability in demanding cross-coupling transformations. In addition, pharmaceutical agents crizotinib and etoricoxib were prepared using allyl heteroaryl sulfone coupling partners, further demonstrating the utility of these new reagents.
- Markovic, Tim,Murray, Philip R.D.,Rocke, Benjamin N.,Shavnya, Andre,Blakemore, David C.,Willis, Michael C.
-
p. 15916 - 15923
(2018/11/23)
-
- Cycloisomerization of acetylenic oximes and hydrazones under gold catalysis: Synthesis and cytotoxic evaluation of isoxazoles and pyrazoles
-
The synthesis of substituted isoxazoles and pyrazoles through a general cycloisomerization methodology has been reported. The capability of gold(III) chloride to promote cycloisomerization of both α, β-acetylenic oximes and α, β-acetylenic hydrazones is t
- Jeyaveeran,Praveen, Chandrasekar,Arun,M Prince,Perumal
-
-
- Oxone-mediated facile access to substituted pyrazoles
-
An Oxone-mediated transition-metal-free oxidative C-N bond formation has been achieved for the regioselective synthesis of substituted pyrazoles. The reactions accompany the chelation-controlled ortho-oxidation of N-substituted aromatic ring to provide ph
- Kashiwa, Mitsuhiro,Kuwata, Yoshiyuki,Sonoda, Motohiro,Tanimori, Shinji
-
p. 304 - 311
(2015/12/30)
-
- Novel crown ether functionalized imidazolium-based acidic ionic liquid catalyzed synthesis of pyrazole derivatives under solvent-free conditions
-
Abstract An innovatively designed novel crown ether functionalized imidazolium-based reusable acidic ionic liquid [crown ether MIm] [HSO4] has been efficiently implemented for the synthesis of pyrazole derivatives using various substituted enaminones, hydrazine hydrate and phenyl hydrazine under solvent-free conditions. Structural novelty and task efficiency of the catalyst, high yields of desired products, greener approach attributing high atom economy and solvent-free conditions render this protocol suitable to cope with the current demand in contemporary organic chemistry. The inventive idea of utilizing crown ether functionalized ionic liquid as a catalyst was for the first time demonstrated in this protocol.
- Patil, Dayanand,Chandam, Dattatraya,Mulik, Abhijeet,Jagdale, Suryabala,Patil, Prasad,Deshmukh, Madhukar
-
p. 6843 - 6858
(2015/08/18)
-
- Synthesis of pyrazoles via CuI-mediated electrophilic cyclizations of α,β-alkynic hydrazones
-
Synthesis of pyrazoles via electrophilic cyclization of α,β-alkynic hydrazones by copper(I) iodide is described. When treated with copper(I) iodide in the presence of triethylamine in refluxing acetonitrile, α,β-alkynic hydrazones, prepared readily from hydrazines and propargyl aldehydes and ketones, undergo electrophilic cyclization to afford pyrazole derivatives in good to excellent yields. The reaction appears to be general for a variety of α,β-alkynic hydrazones and tolerates the presence of aliphatic, aromatic, and ferrocenyl moieties with electron-withdrawing and electron-donating substituents.
- Zora, Metin,Kivrak, Arif
-
experimental part
p. 9379 - 9390
(2012/01/06)
-
- Evaluation of electron-deficient phosphine ligands for direct arylation of heterocycles
-
New electron-deficient biarylphosphine ligands were studied and proved to be efficient for the direct arylation of heteroarenes with aryl iodides. The ability of a more electron-deficient palladium centre to accelerate the arylation of heterocycles that remained unreactive with aryl iodides in the past has been validated and these heteroarenes can now be smoothly reacted in the presence of a new electrophilic catalyst. Experimental evidence suggests a viable concerted metalation-deprotonation pathway for the C-H bond cleavage step with an electron-deficient palladium centre.
- Rene, Olivier,Fagnou, Keith
-
supporting information; experimental part
p. 2116 - 2120
(2010/11/04)
-
- Regioselective microwave-assisted synthesis of substituted pyrazoles from ethynyl ketones
-
Reaction of α,β-ethynyl ketones and hydrazine derivatives gives 1,3- and 1,5-disubstituted pyrazoles in good yield. Microwave irradiation in concentrated hydrochloric acid-methanol (1.5% v/v), with concurrent cooling at sub-ambient temperatures or at 120°
- Bagley, Mark C.,Lubinu, M. Caterina,Mason, Christopher
-
p. 704 - 708
(2007/12/27)
-
- New Synthesis of Pyrazole and Isoxazole Derivatives
-
A convenient synthesis of 5-aryl-1-phenylpyrazoles and 5-arylisoxazoles, from readily available ketimine 1 dimethylformamide dimethylacetal and phenylhydrazine or hydroxylamine, is described.
- Molina, P.,Fresneda, P. M.
-
p. 461 - 464
(2007/10/02)
-