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Organometallic Compounds as Heterogeneous Catalysts
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Garima Sachdeva, Monu Verma, Varun Rawat, Ved Prakash Verma, Manish Srivastava, Sudesh Kumar, Singh Vanshika
Nickel catalyzed cross-coupling reaction between the organometallic reagent and organic halides is one of the main ways to prepare polyfunctional molecules, and Negishi cross-coupling reaction using alkyl zinc halides has proven to give a good yield of products. It is one of the essential methodologies for synthesizing new C–C bonds between complex synthetic intermediates. Apart from synthesizing organic molecules, the Negishi coupling reaction has various optical, magnetic, electrochemical materials, and polymer chemistry applications. Knochel et al. reported an improved nickel catalyzed cross-coupling reaction to yield ortho-substituted aryl ester in excellent yields. The coupled product was synthesized by the reaction between ortho-substituted aryl iodide and alkyl zinc iodides in the solid or solution phase [48].
Metal-Catalyzed Condensation Polymerization
Published in Samir H. Chikkali, Metal-Catalyzed Polymerization, 2017
Negishi coupling is similar to Heck coupling with the difference that it uses organozinc compound of an alkene or arene. It is catalyzed by Pd complexes that give higher yields and display better functional group tolerance, although Ni complexes are also used. Organozinc reagents are more sensitive to air and moisture however they are also more reactive and afford faster reaction times. A hyperbranched polymer poly(triphenylamine) was synthesized by Negishi coupling reaction from tris(4-bromophenyl)amine with the terminal bromo group on the hyperbranched polymer bromothiophene. This functionalized hyperbranched polymer was used as a core for the synthesis of a star-structured regioregular poly(3-hexylthiophene). The star polymer had a fully conjugated system with conjugated arms of poly(3-hexylthiophene) attached to a conjugated core of poly(triphenylamine).28 A chiral binaphthalene-oligothiophene copolymer was synthesized by Negishi coupling between 2,2′-bis(2-thiophene)-1,1′-binaphthalene and 2,2′-bis(5-bromo-2-thiophene)-1,1′-binaphthalene. The monomers were prepared by Stille coupling and Negishi coupling.29 An efficient synthesis of 2,5-functionalized silole derivatives was accomplished using Negishi coupling. Bis(phenylethynyl)dimethylsilane underwent intramolecular reductive cyclization upon treatment with lithium naphthalenide to form 2,5-dilithiosilole, which was converted to dizincated silole by reaction with ZnCl2/tetramethylethylenediamine. Negishi coupling of this zincate intermediate with 2-bromothiophene gave 2,5-bis(2′-thienyl)silole in good yield.30
Understanding oxidative addition in organometallics: a closer look
Published in Journal of Coordination Chemistry, 2022
Nabakrushna Behera, Sipun Sethi
Suzuki coupling finds use in the industrial preparation of bioactive compounds as well as natural products. In addition, it has also been used for preparing many advanced materials of light emitting polymers [5]. Heck reaction is used for the synthesis of drug molecules, sunscreen agents and anti-asthma agents [5]. Negishi coupling is very little used in industry because of the moisture and air sensitivity of the organozinc substrates. However, its greater reactivity over other cross-coupling reactions gives an advantage for joining complex intermediates in the generation of natural products [40]. Sonogashira cross-coupling finds use to build the carbon backbone of each molecule for synthesizing natural products. This reaction is also applied to synthesize (Z)-enediynes, that are important substrate in Bergman cycloaromatization reactions [5]. Pharmaceutically this coupling reaction is very important as it is widely utilized in the synthesis of SIB-1508Y, commonly known as altinicline, which has shown ability in the treatment of Alzheimer’s disease, Parkinson’s disease, schizophrenia, Tourette’s syndrome, and attention deficit hyperactivity disorder (ADHD) [41, 42]. The Kumada coupling is used to construct the carbon skeleton of aliskiren (trade name Tekturna) for the treatment of hypertension [43]. It is also employed for preparation of conjugated polymers having potential applications in light-emitting diodes and organic solar cells [44]. The Stille coupling has been important for synthesizing a variety of conjugated polymers [45, 46]. Another significant use of this reaction includes the total synthesis of biologically dynamic natural products such as alkaloids, macrolides, terpenes, cyclic ethers, etc. [47]. The application of Hiyama coupling is mostly observed in generating Csp2-Csp2 (e.g. aryl–aryl) bonds as well as Csp2-Csp3 (e.g. aryl–alkyl) bonds in organic synthesis [48]. It is also utilized for synthesis of natural products [49]. Moreover, the Buchwald-Hartwig coupling reaction has gained extensive use in synthetic organic chemistry for preparation of many natural products as well as numerous pharmaceuticals [50, 51].