- Highly Efficient Synthesis of 2-Substituted Benzo[ b ]furan Derivatives from the Cross-Coupling Reactions of 2-Halobenzo[ b ]furans with Organoalane Reagents
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A highly efficient and simple route for the synthesis of 2-substituted benzo[ b ]furans has been developed by palladium-catalyzed cross-coupling reaction of 2-halobenzo[ b ]furans with aryl, alkynyl, and alkylaluminum reagents. Various 2-aryl-, 2-alkynyl-, and 2-alkyl-substituted benzo[ b ]furan derivatives can be obtained in 23-97% isolated yields using 2-3 mol% PdCl 2/4-6 mol% XantPhos as the catalyst under mild reaction conditions. The aryls bearing electron-donating or electron-withdrawing groups in 2-halobenzo[ b ]furans gave products in 40-97% isolated yields. In addition, aluminum reagents containing thienyl, furanyl, trimethylsilanyl, and benzyl groups worked efficiently with 2-halobenzo[ b ]furans as well, and three bioactive molecules with 2-substituted benzo[ b ]furan skeleton were synthesized. Furthermore, the broad substrates scope and the typical maintenance of vigorous efficiency on gram scale make this protocol a potentially practical method to synthesize 2-substituted benzo[ b ]furan derivatives. On the basis of the experimental results, a possible catalytic cycle has been proposed.
- Wen, Chang,Wu, Chuan,Luo, Ruiqiang,Li, Qinghan,Chen, Feng
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p. 3847 - 3861
(2021/07/02)
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- Regio- and Stereoselective Synthesis of 1,2-Dihaloalkenes Using In-Situ-Generated ICl, IBr, BrCl, I2, and Br2
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We describe a catalyst-free 1,2-trans-dihalogenation of alkynes with an unprecedented substrate scope and exclusive regio- and stereoselectivity. This versatile dihalogenation system—a combination of NX1S electrophile and alkali metal halide (MX2) in acetic acid—is applicable for diverse categories of alkynes (electron-rich or poor alkynes, internal and terminal alkynes, or heteroatoms such as O-, N-, S-substituted alkynes). The hydrogen bonding donor solvent acetic acid is essential for the in-situ generation of X1X2 electrophile, including ICl, IBr, BrCl, I2, and Br2. Haloalkenes are not only commonly found in biologically active natural products but also have been used extensively in cross-coupling reactions. More specifically, 1,2-dihaloalkenes are especially important synthons because of the presence of two synthetic handles that open a broad avenue to expeditiously generate multisubstituted alkenes. Dihalogenation of alkynes is a straightforward way to prepare 1,2-dihaloalkenes. However, existing alkyne dihalogenation methods either rely on the use of toxic reagents, such as IBr and ICl, lack regio- and stereoselectivity or have limited substrate scope. Thus, the development of a widely applicable and yet efficient alkyne dihalogenation method is still highly desired. Here, we have addressed the aforementioned issues based on an in-situ-generated dihalogenation of reagents, such as ICl and Ibr, by using the readily available N-halosuccinimide (NXS) and alkali metal halides as halogen sources. Our method offers an unprecedented substrate scope, the regio- and stereoselectivity for the synthesis of 1,2-dihaloalkenes. Our simple and mild conditions might find wild applications in the preparation of high-value building blocks for medicines and materials. Dihaloalkenes are important raw materials for pharmaceutical and chemical industries. However, existing preparation methods suffer from a limited substrate scope as well as poor regio- and stereoselectivity. Furthermore, these methods often necessitate highly toxic reagents, such as Cl2, ICl, and BrCl. Our environmentally friendly 1,2-trans-dihalogenation is based on easy-handling halide sources, such as alkali metal halides. What is more, our method offers an unprecedented substrate scope, the regio- and stereoselectivity for the synthesis of 1,2-dihaloalkenes.
- Hammond, Gerald B.,Liu, Shiwen,Xu, Bo,Yang, Yi,Yang, Yuhao,Zeng, Xiaojun
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supporting information
p. 1018 - 1031
(2020/04/08)
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- Palladium/copper-cocatalyzed decarbonylative alkynylation of acyl fluorides with alkynylsilanes: Synthesis of unsymmetrical diarylethynes
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Palladium/copper-cocatalyzed decarbonylative alkynylation of acyl fluorides with alkynylsilanes is described. This reaction not only effectively inhibits the formation of undesired homocoupled products by avoiding the addition of a base, but also exhibits a wide substrate scope to provide a general access to diverse unsymmetrical diarylethynes.
- Chen, Qiang,Fu, Liyan,Nishihara, Yasushi
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supporting information
p. 7977 - 7980
(2020/09/09)
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- DBU-Mediated Efficient Synthesis of Diaryl Ethynes and Enynes from 1,1-Dibromoalkenes at Room Temperature
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The reaction of 1,1-dibromoalkenes and aryl iodides in the presence of DBU and a PdII/CuI catalytic system afforded diaryl alkynes and enynes at ambient temperature. Control experiments demonstrated the essential ligand role of DBU i
- Thummala, Yadagiri,Morri, Ashok K.,Karunakar, Galla V.,Doddi, Venkata Ramana
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supporting information
p. 6280 - 6285
(2018/11/23)
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- Palladium-Catalyzed Decarbonylative Alkynylation of Amides
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A palladium-catalyzed decarbonylative alkynylation of amides via C-N bond activation is developed. Compared with the reported Ni/Cu catalyzed reaction, which only proceeded well with silylacetylenes, this transformation was also applicable to both aromatic and aliphatic terminal alkynes, including those bearing functional groups, and thus provided a general and straightforward access to diverse internal alkynes.
- Liu, Long,Zhou, Dan,Liu, Min,Zhou, Yongbo,Chen, Tieqiao
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supporting information
p. 2741 - 2744
(2018/05/22)
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- Single electron transfer-induced coupling of alkynylzinc reagents with aryl and alkenyl iodides
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Alkynylzinc reagents were found to undergo coupling with aryl and alkenyl iodides to give arylalkynes and alkenylalkynes without the aid of transition metals. The coupling reaction proceeds through a single electron transfer mechanism, where a substoichiometric amount of a phosphine works as an indispensable activator.
- Okura, Keisho,Kawashima, Hitomi,Tamakuni, Fumiko,Nishida, Naoya,Shirakawa, Eiji
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supporting information
p. 14019 - 14022
(2016/12/09)
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- Synthesis of internal alkynes through the Pd-catalyzed coupling of heteroaryl halides with terminal alkynes
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Sonogashira-type cross-couplings of functionalized heterocyclic halides with terminal alkynes were performed efficiently at room temperature. The heteroaryl halides were easily prepared from the corresponding heterocyclic compounds. The catalytic system tolerated a very broad scope of substrates; oxazoles, thiazoles, and furans participate in this type of reaction for the first time. This reaction provides an efficient method for the direct functionalization of heterocycles. Sonogashira-type cross-coupling of functionalized heterocyclic halides with terminal alkynes are performed efficiently at room temperature. The catalytic system tolerates a very broad scope of substrates; oxazoles, thiazoles, and furans participate in this type of reaction for the first time. The reaction provides an efficient method for the direct functionalization of heterocycles. Copyright
- Lu, Linhua,Yan, Hong,Sun, Peng,Zhu, Yan,Yang, Hailong,Liu, Defu,Rong, Guangwei,Mao, Jincheng
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supporting information
p. 1644 - 1648
(2013/04/10)
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- A simple and efficient approach to 2-alkynylbenzofurans under mild copper(i)-catalyzed conditions
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The copper(i)-catalyzed synthetic method for the preparation of 2-alkynylbenzofurans from gem-dihaloolefins has been established using DABCO and TBAF·3H2O as a cocatalyst. This methodology relies on a simple reaction system and inexpensive Cu s
- Liu, Jianming,Zhang, Ningfei,Yue, Yuanyuan,Wang, Dong,Zhang, Yuanli,Zhang, Xin,Zhuo, Kelei
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p. 3865 - 3868
(2013/04/24)
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- A highly efficient TBAF-promoted intramolecular cyclization of gem-dibromoolefins for the synthesis of 2-bromobenzofurans(thiophenes)
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A highly efficient tetra-(n-butyl)ammonium fluoride (TBAF)-promoted intramolecular cyclization of gem-dibromoolefins has been developed for the synthesis of 2-bromobenzofused heterocycles. The reaction provides a convenient approach to 2-bromobenzofurans(
- Chen, Wei,Zhang, Yicheng,Zhang, Lei,Wang, Min,Wang, Lei
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supporting information; experimental part
p. 10476 - 10478
(2011/10/31)
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- 2-substituted benzo[b]furans from (E)-1,2-dichlorovinyl ethers and organoboron reagents: Scope and mechanistic investigations into the one-pot Suzuki coupling/direct arylation
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2-Substituted benzo[b]furans can easily be assembled from simple phenols, boronic acids or other organoboron reagents, and trichloroethylene. The overall process requires only two synthetic steps, with the key step being a one-pot sequential Suzuki cross-coupling/direct arylation reaction. The method tolerates many useful functional groups and does not require the installation of any other activating functionality. The modular nature of the process permits the rapid synthesis of many analogues using essentially the same chemistry, of particular value in drug development. Results of kinetic isotope effect studies and investigations into the regioselectivity of the process indicate that the direct arylation step most likely does not involve an electrophilic palladation. The most likely mechanism lies somewhere on the continuum between a C-H bond metathesis and an assisted palladation or concerted metallation-deprotonation pathway. A very efficient modular approach to the construction of benzo[b]furans using trichloroethylene as a scaffold is described. This method gives easy access to highlysubstituted heterocycles in only two synthetic operations, and is especially suitable for rapid construction of compound libraries.
- Geary, Laina M.,Hultin, Philip G.
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supporting information; experimental part
p. 5563 - 5573
(2010/12/29)
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- Palladium-catalyzed modular assembly of electron-rich alkenes, dienes, trienes, and enynes from (E)-1,2-dichlorovinyl phenyl ether
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We have devised a modular construction of electron-rich alkene derivatives from trichloroethylene (TCE). The three C-l bonds of TCE have sufficiently different reactivities that they can be sequentially and selectively functionalized. Following the substitution of one chlorine by phenol to generate (E)-1,2-dichlorovinyl ether, the C1-Cl group next participates in palladium-catalyzed cross-coupling reactions with a variety of organometallic reagents. Subsequently, the C2-Cl group can engage in cross-couplings, while the C2-H may be deprotonated and quenched with an electrophile. Thus, isomerically pure tri- and tetrasubstituted electron-rich alkenes may be accessed in as few as two steps from simple and inexpensive starting materials. This method is ideally suited for diversity-oriented synthesis of highly conjugated molecules of interest as chromophores or as potential molecular electronics. It also gives access to diverse building blocks for further synthetic elaboration into high-value compounds.
- Geary, Laina M.,Hultin, Philip G.
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experimental part
p. 6354 - 6371
(2010/12/19)
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- Modular construction of 2-substituted benzo[b]furans from 1,2-Dichlorovinyl ethers
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"Chemical Equation Presented" (E)-1,2-Dichlorovinyl ethers and amides are easily accessible from trichloroethylene via nucleophilic addition across in situ synthesized dlchloroacetylene. A one-pot, sequential Suzukl-Miyaura coupling/intramolecular direct
- Geary, Laina M.,Hultin, Philip G.
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supporting information; experimental part
p. 5478 - 5481
(2010/02/27)
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- Palladium-catalyzed cross-coupling reactions of 1,2-diiodoalkenes with terminal alkynes: Selective synthesis of unsymmetrical buta-1,3-diynes and 2-ethynylbenzofurans
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(E)-1,2-Diiodoalkenes were found to be effective building blocks for the preparation of unsymmetrical buta-1,3-diynes and 2-ethynylbenzofurans. In the presence of palladium(II) acetate and copper(I) iodide, unsymmetrical buta-1,3-diynes were selectively o
- Liang, Yun,Tao, Li-Ming,Zhang, Yue-Hua,Li, Jin-Heng
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experimental part
p. 3988 - 3994
(2009/05/27)
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- A rapid synthesis of 2-alkynylindoles and 2-alkynylbenzofurans
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An expeditious synthesis of 2-alkynylindoles and 2-alkynylbenzofuran derivatives has been devised starting from easily available ortho-substituted aryl diynes.
- Fiandanese, Vito,Bottalico, Daniela,Marchese, Giuseppe,Punzi, Angela
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p. 7301 - 7306
(2008/12/20)
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- A general and practical method of alkynyl indole and benzofuran synthesis via tandem Cu- And Pd-catalyzed cross-couplings
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A new tandem coupling approach to synthesize 2-alkynyl indoles and benzofurans is described. This reaction utilizes easily accessible gemdibromovinyl substrates and terminal alkynes and proceeds via Pd/C- and Cul-catalyzed tandem Ullman/Sonogashira coupli
- Nagamochi, Masatoshi,Fang, Yuan-Qing,Lautens, Mark
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p. 2955 - 2958
(2008/02/11)
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- 2-VINYL INDOLES, PYRIDO AND AZEPINO INDOLE DERIVATIVES, 2-ALKYNYL INDOLES, 2-ALKYNYL BENZO[b]FURANS, THEIR PRECURSORS AND NOVEL PROCESSES FOR THE PREPARATION THEREOF
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The present invention relates to the preparation of 2-vinyl indoles from ortho-gem-dibromovinylaniline compounds and alkene reagents using a palladium pre-catalyst, a base, and, in some instances, a ligand or additive. The present invention also relates t
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Page/Page column 82; 84; 136-137
(2008/06/13)
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- A novel access to disubstituted acetylenes
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Reactions of organometallic reagents with 1-(substituted ethynyl)-1H-1,2,3-benzotriazoles 5 derived from a variety of benzotriazolylmethyl ketones 3 afforded disubstituted acetylenes in synthetically useful yields.
- Katritzky, Alan R.,Abdel-Fattah, Ashraf A. A.,Wang, Mingyi
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p. 7526 - 7529
(2007/10/03)
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- INTRAMOLECULAR ANIONIC CYCLIZATIONS OF o-CINNAMYLOXY- AND o-PHENYLPROPARGYLOXYBENZYLIDENEAMINES
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The intramolecular anionic cyclization of o-cinnamyloxybenzylideneamines proceeded via an allyl anion and/or an azaallyl anion to give a mixture of 2,3-dihydrobenzofurans and/or a perhydropyrrobenzopyrane.In a similar reaction o-phenylpropargyloxyb
- Tsuge, Otohiko,Ueno, Kazunori,Oe, Koji
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p. 135 - 138
(2007/10/02)
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