Chemistry
Coupling Reactions
Coupling reactions in chemistry refer to the process of joining two molecular entities to form a new compound. This is typically achieved by the formation of a chemical bond between the two entities, often facilitated by a catalyst or reagent. Coupling reactions are widely used in organic synthesis to create complex molecules and are important in the production of pharmaceuticals, agrochemicals, and materials.
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eBook - PDFMicrowave-Assisted Organic Synthesis
A Green Chemical Approach
- Suresh C. Ameta, Pinki B. Punjabi, Rakshit Ameta, Chetna Ameta, Suresh C. Ameta, Pinki B. Punjabi, Rakshit Ameta, Chetna Ameta(Authors)
- 2014(Publication Date)
- Apple Academic Press(Publisher)
CHAPTER 12 COUPLING SURBHI BENJAMIN, NEELAM KUNWAR, KUMUDINI BHANAT, and SURESH C. AMETA CONTENTS 12.1 Heck Reaction ................................................................................ 231 12.2 Hiyama Reaction ............................................................................ 233 12.3 Liebeskind-Srogl Coupling ............................................................ 234 12.4 Negishi Coupling ........................................................................... 235 12.5 Sonogashira Coupling .................................................................... 238 12.6 Stille Cross-Coupling ..................................................................... 240 12.7 Suzuki Coupling ............................................................................. 243 12.8 Suzuki-Miyaura Cross-Coupling ................................................... 245 Keywords .................................................................................................. 249 References ................................................................................................. 249 230 Microwave-Assisted Organic Synthesis: A Green Chemical Approach Coupling reaction in organic chemistry is a term for a variety of reactions, where two hydrocarbon fragments are coupled with the aid of a metal, it salts or complexes as a catalyst. Two types of Coupling Reactions have been recognized: • Homo couplings couple two identical partners, for example, the conversion of iodobenzene (PhI) to biphenyl (Ph-Ph) and • Cross couplings involving reactions between two different partners, for ex-ample, bromobenzene (PhBr) and vinyl chloride (CH 2 =CH-Cl) to give sty -rene (PhCH=CH 2 ).
eBook - PDF- François Diederich, Peter J. Stang, François Diederich, Peter J. Stang(Authors)
- 2008(Publication Date)
- Wiley-VCH(Publisher)
In other words, carbon-carbon bond formation between sp and sp2C-atom centers was often difficult and tedious. In the intervening 25 years, a wide variety of cross-coupling methodologies have been developed and cross-Coupling Reactions have emerged among the most powerful and useful synthetic tools in chemistry. Metal-catalyzed cross-Coupling Reactions are extensively employed in a wide range of areas of preparative organic chemistry, from the synthesis of complex natural products to supramolecular chemistry and materials science. For example, the formation of new carbon- rich polymers and networks by acetylenic molecular scaffolding, the development of many abiotic receptors, and the preparation of many dendrimers depends heavily on modern cross-coupling methodologies. In fact, in the 1990s one can hardly open a chemical journal in the broad area of organic chemistry or materials science that does not contain several examples of cross-Coupling Reactions. Many of the metal-mediated cross-Coupling Reactions discussed in this book follow a similar mechanistic scheme. The general features of the catalytic cycles are currently quite well understood and involve an oxidative addition-transmetallation-reductive elimination sequence. The reaction is initiated by the oxidative addition of the electrophile to the zero- valent metal. The most widely used active catalysts are diverse Ni(0) and Pd(0) complexes with organic triflates or halides (mostly iodides or bromides; rarely chlorides) as the electrophilic partners. A wide variety of organometallic reagents (organo-boron-aluminum, -copper, -zirconium, -silicon, -tin, etc.) serve as nucleophiles. However, the details of the individual steps, and in particular the transmetallation process, are less well understood and the reaction pathways are highly dependent upon the specific organometallic nucleophiles as well as reaction conditions.
- T.F. Jamison, G. Koch(Authors)
- 2018(Publication Date)
- Thieme(Publisher)
10 Intermolecular Transition-Metal-Catalyzed C — C Coupling Reactions in Continuous Flow C. Bottecchia and T. Noël General Introduction Since their introduction in the 1970s, cross-coupling methods have become one of the most relevant strategies for C — C and C — heteroatom bond formation. [1–3] Moreover, cross-coupling strategies have been successfully applied to the synthesis of (hetero)biaryl motifs, which are of high importance in the synthesis of active pharmaceutical ingredi-ents for the pharmaceutical industry. [4] In most cross-Coupling Reactions, the formation of a C — C or C — heteroatom bond is achieved by the combination of an organometallic (or organoboron) nucleophile with an organic halide electrophile and is catalyzed by a transition-metal catalyst (most often Pd or Ni). The success of cross-Coupling Reactions can be explained by taking into account that they allow a precise control of the regiose-lectivity of the products formed. The newly formed C — C bonds are created exclusively be-tween the halide-or pseudohalide-bearing carbon of one substrate and the metal-bearing carbon of the other substrate. However, despite being the key to the regioselectivity, the necessity to prefunctionalize substrates with either halides or metallic groups inevitably results in poor atom economy and in the formation of stoichiometric amounts of chemi-cal waste. Therefore, traditional cross-coupling methods fail to satisfy some of the 12 green chemistry principles, which are currently considered as major guidelines for an en-vironmentally friendly chemical production process. [5] Over the years, efforts toward the development of greener cross-coupling methods have resulted in a plethora of methodologies, relying on the use of milder reaction condi-tions, tailor-made ligands, and lower catalyst loadings.
eBook - PDF- Metin Balcı(Author)
- 2021(Publication Date)
- Wiley-VCH(Publisher)
537 11 Carbon–Carbon Coupling Reactions 11.1 History The Coupling Reactions of organometallic reagents with organic electrophiles are widely used in the industry for the syn- thesis of agrochemicals, pharmaceuticals, and polymers. Among these tools, Pd-catalyzed Coupling Reactions are of great interest because of the favorable working conditions, excellent functional group tolerance, and chemoselectivity as well as their wide applicability. These cross-coupling processes have a rich and intriguing history commencing in the nineteenth century. The history of acetylenic coupling began in 1869 with the observation by Carl Glaser that copper(I) phenylacetylide when exposed to air underwent smooth oxidative dimerization to diphenyldiacetylene [1]. Later, the Glaser coupling was extended to various organic compounds possessing a terminal ethynyl group. H 2 CuCl NH 4 OH, EtOH Cu O 2 NH 4 OH, EtOH In 1905, Straus observed that heating copper(I) phenylacetylide in acetic acid under inert gas (CO 2 ) gave enynes instead of the expected diphenyldiacetylene. This Straus coupling has even found industrial application in the production of viny- lacetylene and divinyl-acetylene [2]. HC CH CuCl/NH 4 OH 60 °C C CH CH H 2 C C C CH H 2 C CH CH 2 + An important modification was reported in 1956 by Eglinton and Galbraith, who performed oxidative acetylenic cou- plings with a copper(II) salt in methanolic pyridine to construct macrocyclic compounds [3] including the pioneering annulene syntheses by Sondheimer [4]. + Cu(OAc) 2 MeOH, pyridine high dilution 20–40% The advantages of this new sp—sp bond forming reaction were successfully used for the construction of various acetylenic compounds. An impressive example of the use of the Glaser coupling was the synthesis of indigo by Baeyer in 1882 [5]. Reaction Mechanisms in Organic Chemistry, First Edition. Metin Balcı. © 2022 WILEY-VCH GmbH. Published 2022 by WILEY-VCH GmbH. 538 11 Carbon–Carbon Coupling Reactions COOH 1. H 2 O, heat 2.
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