2730-02-1Relevant academic research and scientific papers
Acrylic boronate: a multifunctional C3 building block for catalytic synthesis of rare organoborons and chemoselective heterobifunctional ligations
Lin, Shengjia,Sharma, Abhishek,Wang, Lucia
, p. 7924 - 7929 (2021)
A novel C3 acylboron building block; acrylic boronate was successfully prepared and its versatility for catalytic synthesis of several previously inaccessible organoborons is described. Cross-metathesis and Pd-catalyzed coupling of acrylic boronate enabled two complementary routes to highly functionalized α,β-unsaturated acylborons and two new types of conjugated borylated products: α,β,γ,δ-unsaturated and bis-α,β unsaturated acylborons. The synthetic application of α,β-unsaturated acylborons was demonstrated for the first time, thereby providing a general and highly regioselective route to medicinally important 3-boryl pyrazoles. Acrylic boronate also provided a unique bis-electrophilic platform for rapid and chemoselective labeling of cysteines with acylboron tags which are potentially useful for site-selective functionalization and orthogonal ligation of proteins.
Synthesis of isomeric trifluoromethyl pyrazoles and isoxazoles
Diab, Joseph,Laurent, Andre,Drean, Isabelle Le
, p. 145 - 147 (1997)
Three regioisomeric trifluoromethyl pyrazoles and four regioisomeric trifluoromethyl isoxazoles were completely selectively synthesized from three trifluoromethyl enones or acroleins (1, 2 and 3) and phenylhydrazine, azide or hydroxylamine.
Efficient Copper-Catalyzed Synthesis of Substituted Pyrazoles at Room Temperature
Wang, Haifeng,Sun, Xiangli,Zhang, Shuangling,Liu, Guanglu,Wang, Chunjie,Zhu, Lili,Zhang, Hui
, p. 2689 - 2692 (2018/12/14)
An efficient method for the synthesis of pyrazoles through a copper-catalyzed condensation reaction has been developed. The new catalytic system not only maintained a broad substrate scope but was also active under acid-free reaction conditions, overcoming the conventional requirement for an acid-catalyzed system. Furthermore, the copper catalyst enabled this reaction to be performed at room temperature and in a short reaction time.
Mild and Regioselective Synthesis of 3-CF3-Pyrazoles by the AgOTf-Catalysed Reaction of CF3-Ynones with Hydrazines
Topchiy, Maxim A.,Zharkova, Daria A.,Asachenko, Andrey F.,Muzalevskiy, Vasiliy M.,Chertkov, Vyacheslav A.,Nenajdenko, Valentine G.,Nechaev, Mikhail S.
supporting information, p. 3750 - 3755 (2018/07/31)
Gold- and silver-catalysed reactions of trifluoromethylated ynones with aryl (alkyl) hydrazines were investigated. The use of (THD-Dipp)AuOTf and AgOTf resulted in quick heterocyclization reactions to selectively give 3-CF3-pyrazoles. AgOTf was found to be the catalyst of choice, and various 3-CF3-pyrazoles were formed in up to 99 % isolated yield with high regioselectivity. The reaction has a broad scope: 3-CF3-pyrazoles with alkyl and aryl substituents as well as different functional groups can be prepared by this approach. The known pyrazole drugs Celebrex and SC-560 were efficiently prepared to demonstrate the utility of the method. Mechanistic investigations revealed that the reaction involves the formation of a hemiaminal as a key intermediate.
Selective, Metal-Free Approach to 3- or 5-CF3-Pyrazoles: Solvent Switchable Reaction of CF3-Ynones with Hydrazines
Muzalevskiy, Vasiliy M.,Rulev, Alexander Yu.,Romanov, Alexey R.,Kondrashov, Evgeniy V.,Ushakov, Igor A.,Chertkov, Vyacheslav A.,Nenajdenko, Valentine G.
, p. 7200 - 7214 (2017/07/26)
A detailed study of the reaction of trifluoroacetylated acetylenes and aryl (alkyl) hydrazines was performed, aimed to the regioselective synthesis of 3- or 5-trifluoromethylated pyrazoles. It was found that the regioselectivity of reaction depends dramatically on the solvent nature. Highly polar protic solvents (hexafluoroisopropanol) favor the formation of 3-trifluoromethylpyrazoles. In contrast, when the reaction was performed in polar aprotic solvents (DMSO), the formation of their 5-CF3-substituted isomers was preferentially observed. Alternatively, the regioselective assembly of 3-CF3-substituted pyrazoles can be performed via two-step one-pot procedure. The reaction of trifluoromethylated ynones with aryl (alkyl) hydrazines in the presence of acidic catalysts leads to formation of the corresponding hydrazones. The latter can be smoothly transformed into 3-CF3-pyrazoles by treatment with a base. This solvent-switchable procedure was used for the preparation of such important drugs as Celebrex and SC-560 as well as their isomers in gram scale. The possible reaction mechanism is discussed.
2 (Oxa) as a heterogeneous recyclable catalyst: Synthesis of pyrazoles under mild reaction conditions
Katla, Ramesh,Chowrasia, Rakhi,Manjari, Padma S.,Da Silva, Caren D. G.,Dos Santos, Beatriz F.,Domingues, Nelson L. C.
supporting information, p. 9471 - 9476 (2016/11/11)
We developed a novel and highly efficient protocol for the synthesis of important pyrazole derivatives by using some 1,3-dicarbonyl compounds and phenyl hydrazines via a one-pot protocol. As a recyclable heterogeneous catalyst, we used [Ce(l-Pro)2]2 (Oxa). In addition, the catalyst is recyclable, the proline is economically viable and readily available in both enantiomeric forms and the catalyst is insoluble in almost all solvents and may be easily filtered off from the reaction medium. Moreover, this new synthetic protocol features high conversion, short reaction times, a straightforward procedure and cleaner reaction profiles.
Solvent- and transition metal catalyst-dependent regioselectivity in the [3+2]cyclocondensation of trifluoromethyl-α,β-ynones with hydrazines: Switchable access to 3- and 5-trifluoromethylpyrazoles
Hsieh, Min-Tsang,Kuo, Sheng-Chu,Lin, Hui-Chang
, p. 683 - 689 (2015/03/18)
The regioselectivity of the [3+2]cyclocondensation of trifluoromethyl-α,β-ynones with hydrazines can be readily tuned to preferentially afford either 3- or 5-trifluoromethylpyrazoles through variation of the reaction conditions. Under catalysis with copper(II) acetate (2.0 mol%), cyclocondensation proceeded smoothly to yield 3-trifluoromethylpyrazoles with high regioselectivity. In contrast, when the reaction was conducted in dimethyl sulfoxide under catalyst-free conditions, the formation of 5-trifluoromethylpyrazoles was predominantly observed.
Cellulose sulfuric acid as a bio-supported and efficient solid acid catalyst for synthesis of pyrazoles in aqueous medium
Nasseri, Mohammad Ali,Salimi, Mehri,Esmaeili, Abbas Ali
, p. 61193 - 61199 (2015/02/19)
A convenient and practical method was described for the regioselective synthesis of pyrazoles from hydrazines/hydrazides and 1,3-dicarbonyl compounds via the Knorr synthesis in water with cellulose sulfuric acid (CSA) as a biopolymer-based solid acid catalyst. Various hydrazines and hydrazides were reacted with 1,3 diketones and the desired pyrazoles were obtained in high yields. The reaction of less reactive hydrazines with 1,3-dicarbonyl compounds stopped at the corresponding hydrazone derivatives. Hydrazides were employed with β-ketoester, and imine adducts were the only isolated product. Simple isolation of products, mild reaction conditions, reusability of solid acid catalysts and short reaction times are advantages of this green procedure. This journal is
Synthesis of 3-trifluoromethylpyrazoles via trifluoromethylation/ cyclization of α,β-alkynic hydrazones using a hypervalent iodine reagent
Ji, Guojing,Wang, Xi,Zhang, Songnan,Xu, Yan,Ye, Yuxuan,Li, Ming,Zhang, Yan,Wang, Jianbo
supporting information, p. 4361 - 4363 (2014/04/17)
A mild and efficient method for the synthesis of 3-trifluoromethylpyrazoles has been established via trifluoromethylation/cyclization of α,β-alkynic hydrazones using a hypervalent iodine reagent under transition-metal-free conditions.
New strategy for the regioselective synthesis of 1-phenyl-3- trifluoromethyl-1H-pyrazoles
Zanatta, Nilo,Amaral, Simone S.,Dos Santos, Josiane M.,Da Silva, Andréia M.P.W.,Schneider, Juliana M.F.M.,Fernandes, Liana Da S.,Bonacorso, Helio G.,Martins, Marcos A.P.
, p. 4076 - 4079 (2013/07/25)
A regioselective synthesis of 3-trifluoromethyl-1-phenyl-1H-pyrazoles (1,3-isomers) as well as their 1,5-isomers (5-trifluoromethyl-1-phenyl-1H- pyrazoles), is described. The 1,3-isomers were obtained from the reaction of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones with arylhydrazones followed by deprotective hydrolysis while the 1,5-isomer was obtained by direct cyclocondensation of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones with phenylhydrazine. An unequivocal assignment of the 1,3- and 1,5-isomers of the pyrazole products is given.
