- Mixing with microwaves: Solvent-free and catalyst-free synthesis of pyrazoles and diazepines
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A simple and facile condensation of hydrazines/hydrazides and diamines with 1,3-diketones/β-ketoester leads to the preparation of pyrazoles and diazepines in high yields. This eco-friendly protocol is accelerated by microwave heating and efficiently carried out without any reaction solvent or catalyst in as little as 5 min.
- Vaddula, Buchi Reddy,Varma, Rajender S.,Leazer, John
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- Greener and rapid access to bio-active heterocycles: room temperature synthesis of pyrazoles and diazepines in aqueous medium
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An expeditious room temperature synthesis of pyrazoles and diazepines by condensation of hydrazines/hydrazides and diamines with various 1,3-diketones is described. This greener protocol was catalyzed by polystyrene supported sulfonic acid (PSSA) and proceeded efficiently in water in the absence of any organic solvent within 1-2 min.
- Polshettiwar, Vivek,Varma, Rajender S.
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- HBF4/ACN: A simple and efficient protocol for the synthesis of pyrazoles under ambient reaction conditions
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An efficient and novel protocol for pyrazole synthesis has been developed by using fluoroboric acid as the acid catalyst. Simple and easily available 1,3-diketone and hydrazine derivatives are taken as the substrates for this purpose. The reaction entails
- Hazarika, Roktopol,Konwar, Manashjyoti,Damarla, Krishnaiah,Kumar, Arvind,Sarma, Diganta
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p. 329 - 337
(2020/01/08)
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- Transition metal containing ionic liquid-assisted one-pot synthesis of pyrazoles at room temperature
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Abstract: The feasible and one of the green ways to synthesize organic compounds especially pyrazole and its derivatives are systematically presented. The one-pot synthesis of pyrazole was achieved by condensation of various hydrazines and 1,3-diketone derivatives at room temperature using transition metal-based ionic liquids. Herein, the unique combination of Fe(III) with ionic liquid is explored and utilized as an efficient homogeneous catalyst for the synthesis of pyrazole and its derivatives. The homogenous catalyst thus synthesised was re-used up to the fourth cycle (with 90%, 88%, 84%, 78% yields respectively). Graphic abstract: Pyrazoles are synthesized in the presence of transition metal-based ionic liquids at room temperature. From the green chemistry perspective, ionic liquids are considered as green solvents which have gained remarkable attention because of its non-toxic, non-corrosive and non-flammable nature while the presence of transition metal as a part of counter anion gives it more catalytic activity. [Figure not available: see fulltext.].
- Konwar, Manashjyoti,Elnagdy, Hanan M F,Gehlot, Praveen Singh,Khupse, Nageshwar D,Kumar, Arvind,Sarma, Diganta
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- Cellulose sulfuric acid as a bio-supported and efficient solid acid catalyst for synthesis of pyrazoles in aqueous medium
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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
- Nasseri, Mohammad Ali,Salimi, Mehri,Esmaeili, Abbas Ali
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p. 61193 - 61199
(2015/02/19)
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- A facile one-pot synthesis of sulfur-Linked thieno[1,2,4]- Triazolo[4,3-c]pyrimidine derivatives containing phenylpyrazole or thienopyrimidinylpyrazole moiety
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A facile synthesis of sulfur-linked thieno[1,2,4]triazolo[4,3-c]pyrimidine derivatives containing phenylpyrazole or thienopyrimidinylpyrazole moiety via a one-pot reaction of thieno[1,2,4]triazolo[4,3-c]pyrimidine-3(2H)-thiones, 3-chloropentane-2,4-dione
- Whang, Jina,Song, Yang-Heon
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experimental part
p. 155 - 164
(2012/02/04)
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- Magnetic Nanoparticle-Supported Glutathione as a Sustainable Organocatalyst
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This invention relates to the use of nano-organocatalysts, and, more specifically, to the use of magnetic nanomaterial-supported organocatalysts. It is an object of the present invention to provide “green” catalysts and protocols. According to one embodiment of the invention, a nano-organocatalyst in the form of a magnetic nanomaterial-supported organocatalyst is provided. According to other embodiments of the invention, glutathione and cysteine are provided as organocatalysts and magnetic nanomaterial-supported glutathione and magnetic nanomaterial-supported cysteine are provided for use as nano-organocatalysts. According to another embodiment of the invention, a method of using a recyclable magnetic nanomaterial-supported organocatalyst using a totally benign aqueous protocol, without using any organic solvent in the reaction or during the workup, is provided. According to a further embodiment of the invention, a recyclable magnetic nanomaterial-supported organocatalyst for various organocatalytic reactions, including but not limited to Paal-Knorr reactions, aza-Michael addition and pyrazole synthesis, is provided.
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Page/Page column 9-10
(2011/04/14)
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- Nano-organocatalyst: magnetically retrievable ferrite-anchored glutathione for microwave-assisted Paal-Knorr reaction, aza-Michael addition, and pyrazole synthesis
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Postsynthetic surface modification of magnetic nanoparticles by glutathione imparts desirable chemical functionality and enables the generation of catalytic sites on the surfaces of ensuing organocatalysts. In this article, we discuss the developments, unique activity, and high selectivity of nano-organocatalysts for microwave-assisted Paal-Knorr reaction, aza-Michael addition, and pyrazole synthesis. Their insoluble character coupled with paramagnetic nature enables easy separation of these nano-catalysts from the reaction mixture using external magnet, which eliminates the requirement of catalyst filtration.
- Polshettiwar, Vivek,Varma, Rajender S.
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experimental part
p. 1091 - 1097
(2010/03/25)
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