56119-90-5Relevant articles and documents
One-pot construction of pyrazoles and isoxazoles with palladium-catalyzed four-component coupling
Mohamed Ahmed, Mohamed S.,Kobayashi, Kei,Mori, Atsunori
, p. 4487 - 4489 (2005)
(Chemical Equation Presented) Four-component coupling of a terminal alkyne, hydrazine (hydroxylamine), carbon monoxide, and an aryl iodide furnishes pyrazole or isoxazole derivatives in the presence of a palladium catalyst. The reaction proceeds at room temperature and an ambient pressure of carbon monoxide in an aqueous solvent system.
Preparation method for pyrazole
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Paragraph 0011; 0012; 0013; 0014; 0015; 0016; 0061; 0062, (2017/08/26)
The invention relates to a preparation method for pyrazole, belonging to the field of organic chemistry. The preparation method disclosed in the invention realizes preparation of pyrazole through a cyclization reaction of N-alkylated phenylsulfonylhydrazone with terminal alkyne. The reaction has good function group tolerance and high yield and is applicable to a wide range of substrates.
One-Pot Coupling-Coupling-Cyclocondensation Synthesis of Fluorescent Pyrazoles
G?tzinger, Alissa C.,The?eling, Florian A.,Hoppe, Corinna,Müller, Thomas J. J.
, p. 10328 - 10338 (2016/11/17)
Consecutive four-component coupling-coupling-cyclocondensation syntheses of pyrazoles and pyrimidines were developed by taking advantage of the provisional, sequentially Pd-catalyzed one-pot generation of alkynones from aryl iodides, ethynylmagnesium bromide, and acid chlorides. This one-pot methodology allows the concise, diversity-oriented generation of a set of donor-, acceptor-, and donor-acceptor-substituted pyrazoles, which are interesting fluorophores. Most distinctly, donor-acceptor pyrazoles display remarkably red-shifted emission maxima and pronounced positive solvochromicity, spanning an overall range from 363 nm (cyclohexane) to 595 nm (acetonitrile). DFT and TD-DFT calculations elucidate the electronic structure and the photophysical behavior. Upon photonic excitation, considerable charge-transfer character becomes apparent, which rationalizes the origin of huge Stokes shifts and solvochromic behavior.
Visible-light photocatalytic aerobic annulation for the green synthesis of pyrazoles
Ding, Ya,Zhang, Te,Chen, Qiu-Yun,Zhu, Chunyin
supporting information, p. 4206 - 4209 (2016/09/09)
A selective and high yielding synthesis of polysubstituted pyrazoles through a VLPC (visible light photoredox catalysis)-promoted reaction of hydrazine with Michael acceptors is reported. The method employs very mild reaction conditions and uses air as the terminal oxidant, which makes the process environmentally benign. Different types of Michael acceptors with various substituents can undergo the reaction to afford corresponding pyrazoles in good to excellent yields. The reaction is proposed to go through VLPC-promoted oxidation of hydrazine to diazene followed by its addition to Michael acceptors, other than the conventional condensation of hydrazine with a carbonyl.
Regioselective synthesis of 1,3,5-Trisubstituted Pyrazoles from N-Alkylated Tosylhydrazones and terminal Alkynes
Kong, Yuanfang,Tang, Meng,Wang, Yun
, p. 576 - 579 (2014/04/03)
An efficient synthesis of 1,3,5-trisubstituted pyrazoles from Nalkylated tosylhydrazones and terminal alkynes was developed. The protocol was applied to a wide range of substrates and demonstrated excellent tolerance to a variety of substituents, includin
Preparation of 3,5-disubstituted pyrazoles and isoxazoles from terminal alkynes, aldehydes, hydrazines, and hydroxylamine
Harigae, Ryo,Moriyama, Katsuhiko,Togo, Hideo
, p. 2049 - 2058 (2014/04/03)
The reaction of terminal alkynes with n-BuLi, and then with aldehydes, followed by the treatment with molecular iodine, and subsequently hydrazines or hydroxylamine provided the corresponding 3,5-disubstituted pyrazoles or isoxazoles in good yields with high regioselectivity, through the formations of propargyl secondary alkoxides and α-alkynyl ketones. The present reactions are one-pot preparation of 3,5-disubstituted pyrazoles from terminal alkynes, aldehydes, molecular iodine, and hydrazines, and 3,5-disubstituted isoxazoles from terminal alkynes, aldehydes, molecular iodine, and hydroxylamine.
1,3-Diketones from acid chlorides and ketones: A rapid and general one-pot synthesis of pyrazoles
Heller, Stephen T.,Natarajan, Swaminathan R.
, p. 2675 - 2678 (2007/10/03)
1,3-Diketones were synthesized directly from ketones and acid chlorides and were then converted in situ into pyrazoles by the addition of hydrazine. This method is extremely fast, general, and chemoselective, allowing for the synthesis of previously inaccessible pyrazoles and synthetically demanding pyrazole-containing fused rings.
Regioselective Synthesis of 1,3,5-Substituted Pyrazoles from Acetylenic Ketones and Hydrazines
Bishop, Brian C.,Brands, Karel M. J.,Gibb, Andrew D.,Kennedy, Derek J.
, p. 43 - 52 (2007/10/03)
The synthesis of diversely substituted 1,3,5-substituted pyrazoles from the reaction of acetylenic ketones with substituted hydrazines is reported. The reactions were shown to be highly regioselective regardless of the nature of the substituents in the su
Regiospecific synthesis of pyrazoles from 1-azabutadiene derivatives.
a Jose,Gotor, Vicente
, p. 1478 - 1492 (2007/10/02)
Reaction of 4-amino-1-azabutadienes with different hydrazines leads to pyrazoles.On the other hand, when 4-alkylidene-1-hydrazino-1-azabutadiene derivatives are treated with trifluoroacetic acid, N-alkenylpyrazoles are obtained.
