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Aurelia Pascariu Gheorghe Ilia Alina Bora Alina Bora Smaranda Iliescu Adriana Popa Gheorghe Dehelean Liliana Pacureanu 《Central European Journal of Chemistry》2003,1(4):491-534
Wittig and Wittig-Horner reactions are favorite tools in preparative organic chemistry. These olefination methods enjoy widespread
and recognition because of their simplicity, convenience, and effciency. Phase transfer catalysis (PTC) is a very important
method in synthetic organic chemistry having many advantages over conventional, homogenous reaction procedures. In this paper,
we attempt to summarize the aspects concerning Wittig and Wittig-Horner reactions that take place under phase transfer catalysis
conditions. 相似文献
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phase transfer catalysis has been used for the first time in a reaction of hydrogen deuterium exchange in heterocyclic chemistry. The method provide a good synthetic path for the synthesis of D - 2 thiazoles by direct exchange. Moreover, even with substituents such as t-butyl, hydrogen exchange on positions adjacent to the alkyl group occured. 相似文献
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Henri J. M. Dou Parina Hassanaly Jacky Kister Gaston Vernin Jacques Metzger 《Helvetica chimica acta》1978,61(8):3143-3148
S-Alkylation in heterocyclic serie by phase transfer catalysis: 2-alkylthiothiazoles, 2-alkylthio-Δ-4-thiazolines and 2-alkylthiobenzothiazoles Some Δ-4-thiazoline-, thiazolidine-, and benzothiazoline-2-thiones have been S-alkylated by phase transfer catalysis; yields averaged 80 to 90%. With halogenated heterocyclic compounds of poor reactivity, the main reaction consisted in a dequaternization of the catalyst by the thiones acting as nucleophiles. 相似文献
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For a long time multi-component syntheses of heterocycles have undeniably been a domain of classical carbonyl condensation chemistry. However, the advent of transition-metal catalysis not only has fertilized strategies in heterocyclic synthesis by uni- and bimolecular transformations but the past decade has also witnessed a rapid development of transition-metal catalysis in new multi-component reactions (MCR). Expectedly, palladium catalyzed processes have received a dominant position, yet, other transition-metal complexes are catching up implying organometallic elementary steps that reach even further than cross-coupling and carbometallation. Besides domino MCRs that are purely based upon organometallic catalysis the sequential and consecutive combination with condensation, addition and cycloaddition steps opens a vast playground for the invention of new sequences in heterocyclic synthesis. This tutorial review outlines the underlying reaction based principles of transition-metal catalysis in multi-component syntheses of heterocycles, summarizes recent developments of palladium catalyzed MCR, and highlights the more recent contributions to MCR based heterocyclic synthesis by virtue of rhodium, ruthenium, and copper catalysis. 相似文献
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Radical reactions have been a fascinating arena in organic chemistry for decades and the rapid progress in this field is the topic of this review. Generation of radicals through sustainable catalysis using photoredox catalysts and iron based catalysts have significantly expanded the scope of radical reactions for carbon–carbon and carbon-heteroatom bond formations in recent years. Selective transformations using silver salts and other single electron transfer oxidants have also played significant roles. Cascade reactions based on radical intermediates have even widened the potential of radical reactions for carbocyclic and heterocyclic constructions. The recent advances (2014–2017) in radical based methods for CC bond formations are discussed in this digest review. 相似文献
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The Reaction of 1‐Phenylpyrazolidine‐3,5‐dione with Active Nitriles Using Phase Transfer Catalysis Conditions Technique 下载免费PDF全文
Heterocyclization reaction of 1‐phenylpyrazolidine‐3,5‐dione with some active nitriles and acrylonitriles is described. These cyclization reactions afforded novel heterocyclic derivatives such as pyrano[2,3‐c]pyrazoles, pyrazolyl‐thiazole, pyrazolyl‐1,3‐thiazines, and pyrazolyl‐1,3‐oxathiino[6,5‐c]pyrazoles. Heating 1‐phenylpyrazolidine‐3,5‐dione alone under phase transfer catalysis conditions afforded the tricyclic dipyrazolofurandione. The structure of the new products has been characterized by IR, NMR, mass spectra, and their elemental analyses. 相似文献
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The synthetic utility of alkyl‐onium salt compounds is widely recognized in the field of organic chemistry. Among the wide variety of onium salts, quaternary ammonium, phosphonium, and tertiary sulfonium salts have been the most useful compounds in organic syntheses. These compounds have been very useful reagents in the construction of organic building blocks. In addition, onium salts are known as reliable catalysts, which are used to promote important organic transformations by serving as phase‐transfer and ion‐pair catalysts through the activation of nucleophiles. Although phase‐transfer catalysis is a major direction for onium salt catalysis, hydrogen‐bonding catalysis of alkyl‐onium salts, which is promoted via the activation of electrophiles, has recently become a relevant topic in the field of onium salt chemistry. This Minireview introduces new possibilities and future directions for alkyl‐onium salt chemistry based on its use in hydrogen‐bonding catalysis and on its overall utility. 相似文献
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Henri J.-M. Dou Maria Ludwikow Parina Hassanaly Jacky Kister Jacques Metzger 《Journal of heterocyclic chemistry》1980,17(2):393-395
A general study of the chemical behavior of heterocyclic anions, dianions and dianionic reagents under phase transfer catalysis conditions allowed us to synthesize various heterocyclic compounds such as imidazo[2,1-b]thiazole and derivatives; imidazo[2,1-b]thiazine and imidazo[2,1-b]benzothiazepine. Reaction conditions e.g., catalyst, solvent, temperature, etc., are indicated. 相似文献
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Cycloaddition reactions are an integral and weighty part of organic chemistry in pedagogy and research as well. The wealthy literature on cycloaddition reactions from their birth up to now, unequivocally witnesses to their leading chemistry. The so-called “conventional solvents” are organic solvents that have indubitably promoted their success. Yet, the toxicity facet of these solvents impedes their use freely and with no fear. Not only is the operating chemist uncomfortable while experimenting, but also the environment is equally threatened. Working out the cycloaddition reactions and other organic ones in aqueous systems would certainly bring some relief to the chemist and to the environment as well. Unusual outcomes in terms of yield, reactivity and selectivity compared to those performed in organic solvents were commonly observed, and have overwhelmed the chemists with surprise indeed. In this review, homo Diels–Alder reactions in aqueous media include those involving the following dienophiles: maleimides, α,β-unsaturated esters, p-benzoquinones, vinyl ketones, phenyl-1-(2-pyridyl)-2-propen-1-one, α,β-unsaturated esters. A special case is the organocatalysis of Diels–Alder cycloaddition of α,β-unsaturated ketones (aldehydes). Of no less importance, some hetero Diels–Alder cycloaddition reactions in water systems are delineated. The impact of additives (salts, organic and inorganic chemicals), micellar catalysis and Lewis/Brønstëd acid catalysis on outcomes of such cycloaddition reactions is discussed. The 1,3-dipolar cycloaddition methodology applied to aqueous media has brought forth a number of heterocyclic compounds, usually with a regio- and stereoselectivity pecularity. These heterocycles include triazoles, tetrazoles, pyrazoles, isoxazoles, isoxazolidines, pyrroles and pyrrolidines. The superiority of copper(I) catalysis in the azide-alkyne cycloaddition (Huisgen cycloaddition) in water is endorsed by a number of examples. 相似文献
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Navjeet Kaur Yamini Verma Pooja Grewal Neha Ahlawat Pranshu Bhardwaj Nirmala Kumari Jangid 《合成通讯》2020,50(9):1286-1334
AbstractFew conversions cannot take place with ground-state reactions even with the help of a catalyst, therefore they are made to occur under photochemical conditions. The transfer of electrons took place even with the photochemical excitement of one molecule where redox reaction cannot occur at the ground state. The ground-state reactions resulted in the formation of side products. The substrates did not require any sort of chemical activation for C–N bond construction in the course of photochemical reactions. The source of energy; light has always been the interest of researchers in order to induce chemical reactions ever since the starting of scientific chemistry. The present review encloses the chemistry of photochemical transformations with a focus on their synthetic uses. The organic photochemical reactions prevent the polluting or harmful reagents thus, provides a possibility for sustainable procedures as well as green chemistry. This review article displays the formation of numerous of five-membered fused nitrogen-heterocyclic compounds. 相似文献
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H. K. Hall Anne Buyle Padias 《Journal of polymer science. Part A, Polymer chemistry》2004,42(12):2845-2858
A survey of the spontaneous reactions of electrophilic olefins and nucleophilic olefins is presented as an area in which organic chemistry merges with polymer chemistry. The products include both small molecules and polymers, arising via tetramethylene biradical zwitterions that can cyclize or initiate polymerizations. Electrophilic tri‐ and tetrasubstituted olefins are particularly useful in delineating the transition from radical chemistry to ionic chemistry. A periodic table embodying these results enables predictions. Charge‐transfer complexes, although observed in many of these reactions, play no significant role. Various aspects arising from these investigations include new cationic initiators, Lewis acid catalysis, quinodimethane chemistry, and photochemistry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2845–2858, 2004 相似文献
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The modern state of the chemistry of heterocyclic cation radicals is examined, Methods for the preparation (generation) of these particles, as well as their stabilities and the factors that determine them, are described, The mechanisms of the reactions of heterocyclic cation radicals with nucleophiles and specific examples of such reactions are discussed. Special attention is directed to the role of cation radicals as intermediate particles in dehydrogenation, nitration, and radical substitution reactions and in processes involving the cleavage of C-C bonds and dehydrodimerization in the heterocyclic series. The cation radicals of some natural heterocyclic compounds and their possible role in the functioning of biochemical systems are also examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1029, August, 1980 相似文献
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G. I. Koldobskii 《Russian Chemical Bulletin》1995,44(11):2019-2025
The methods for synthesis and reactions of five-membered nitrogen-containing heterocycles under the conditions of phase transfer catalysis as well as the application of quaternized heterocycles as phase transfer catalysts are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2115–2121, November, 1995. 相似文献