- Borylative Heterocyclization without Air-Free Techniques
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In contrast to previously reported borylative heterocyclization methods, a reaction here proceeds without air-free techniques to access synthetically useful borylated thiophenes, benzothiophenes, and isocoumarins. A comparison of stability/decomposition rates in air of several catecholboronic ester (Bcat) compounds derived from different heterocycle cores showed a strong dependence on the heterocycle structure. Lessons learned from this comparison were then harnessed for the development of borylative heterocyclization reactions under ambient-atmosphere conditions and with wet solvent. In contrast to literature reports suggesting general moisture sensitivity, a subset of Bcat products resulting from this technique were chromatography-stable and directly isolable, obviating the requirement for an extra synthetic transformation into more stable boron species, such as pinacolboronic esters (Bpin), for isolation. The isolated Bcat products were amenable to various downstream functionalization reactions, including reactions that were not accessible with their better-known Bpin counterparts, showing the complementarity of Bcat reaction partners and expanding their known chemistry. These results suggest the value of conceptual revisitation of substitution and solvent influence on stability and isolability of organo-Bcat compound classes and lay the groundwork for development of additional practical borylative methods in air.
- Blum, Suzanne A.,Gao, Chao,Nakao, Shuichi
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- Facile syntheses of 3-trifluoromethylthio substituted thioflavones and benzothiophenes via the radical cyclization
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3-CF3S substituted thioflavones and benzothiophenes were achieved via the reactions of AgSCF3 with methylthiolated alkynones and alkynylthioanisoles, respectively, promoted by persulfate. This protocol possesses good functional group tolerance and high yields. Mechanistic studies suggested that a classic two-step radical process was involved, which includes addition of CF3S radical to triple bond and cyclization with SMe moiety.
- Wang, Lu,Wang, Huaiyu,Meng, Weidong,Xu, Xiu-Hua,Huang, Yangen
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p. 389 - 392
(2020/03/04)
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- B(C6F5)3-Catalyzed cyclization of alkynes: direct synthesis of 3-silyl heterocyclic compounds
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An efficient one-pot strategy for easy access to 3-silyl heterocyclic compounds was developedviaa B(C6F5)3-catalyzed cycloaddition reaction ofo-(1-alkynyl)(thio)anisoles oro-(1-alkynyl)-N-methylaniline. In this reaction, benzenethiophene, benzofuran or indole skeletons could be constructed by an intermolecular cyclization with diphenylsilane. This protocol elicited moderate-to-good yields with metal-free reaction systems.
- Li, Mengxing,Wang, Ting,An, Zhenyu,Yan, Rulong
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p. 11953 - 11956
(2020/10/15)
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- Synthesis of 2-substituted benzo[: B] thiophenes via gold(i)-NHC-catalyzed cyclization of 2-alkynyl thioanisoles
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Benzo[b]thiophene heterocycles are important components of many important small molecule pharmaceuticals and drug candidates as well as organic semiconducting materials. Many methods have been developed for the construction of a benzo[b]thiophene core via cyclization reaction of alkynes. Although few catalytic reactions were disclosed, most methods rely on stoichiometric activation of alkynes. Here we report an efficient method for the synthesis of 2-substituted benzo[b]thiophenes from 2-alkynyl thioanisoles catalyzed by a gold(i)-IPr hydroxide that is applicable to a wide range of substrates with diverse electronic and steric properties. Additionally, we demonstrate experimentally that the acid additive and its conjugate base are essential to catalyst turnover.
- Dillon, Christopher C.,Keophimphone, Bagieng,Sanchez, Melissa,Kaur, Parveen,Muchalski, Hubert
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supporting information
p. 9279 - 9284
(2019/01/03)
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- Heterotetracenes: Flexible Synthesis and in Silico Assessment of the Hole-Transport Properties
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Thienoacenes and furoacenes are among the most frequent molecular units found in organic materials. The efficient synthesis of morphologically different heteroacenes and the rapid determination of their solid-state and electronic properties are still challenging tasks, which slow down progress in the development of new materials. Here, we report a flexible and efficient synthesis of unprecedented heterotetracenes based on a platinum- and gold-catalyzed cyclization–alkynylation domino process using EthynylBenziodoXole (EBX) hypervalent iodine reagents in the key step. The proof-of-principle in silico estimation of the synthesized tetracenes’ charge transport properties reveals their strong dependence on both the position and nature of the heteroatoms in the ring system. A broad range of mobility is predicted, with some compounds displaying performance potentially comparable to that of state-of-the-art electronic organic materials.
- Li, Yifan,Gryn'ova, Ganna,Saenz, Felipe,Jeanbourquin, Xavier,Sivula, Kevin,Corminboeuf, Clémence,Waser, Jér?me
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supporting information
p. 8058 - 8065
(2017/06/19)
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- Catalyst-Free Formal Thioboration to Synthesize Borylated Benzothiophenes and Dihydrothiophenes
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The first ring-forming thioboration reaction of C?C π bonds is reported. This catalyst-free method proceeds in the presence of a commercially available external electrophilic boron source (B-chlorocatecholborane) in good to high yields. The method is scalable and tolerates a variety of functional groups that are intolerant of other major borylation methods. The resulting borylated benzothiophenes participate in a variety of in situ derivatization reactions, showcasing that these borylated intermediates do not need to be isolated prior to downstream functionalization. This methodology has been extended to the synthesis of borylated dihydrothiophenes. Mechanistic experiments suggest that the operative mechanistic pathway is through boron-induced activation of the alkyne followed by electrophilic cyclization, as opposed to S?B σ bond formation, providing a mechanistically distinct pathway to the thioboration of C?C π bonds.
- Faizi, Darius J.,Davis, Ashlee J.,Meany, Fiach B.,Blum, Suzanne A.
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supporting information
p. 14286 - 14290
(2016/11/11)
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- Mercury(II)-catalyzed cyclization of 2-alkynylphenyl alkyl sulfoxides provides 3-acylbenzo[b]thiophenes
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Ring cyclization: A mercury-catalyzed cyclization reaction to provide 3-benzoylbenzo[b]thiophenes was achieved in good yields by treatment of 2-alkynylphenyl alkyl sulfoxides with mercury chloride and 2,3-dichloro-5,6- dicyano-1,4-benzoquinone (DDQ) in be
- Lin, Cheng-Han,Chen, Chin-Chau,Wu, Ming-Jung
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supporting information
p. 2578 - 2581
(2013/03/14)
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- Diverse methyl sulfone-containing benzo[b] thiophene library via iodocyclization and palladium-catalyzed coupling
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Parallel solution-phase methods for the synthesis of a 72-membered benzo[b]thiophene library are reported. Medicinally interesting, drug-like, methyl sulfone-substituted benzo[b]thiophenes have been prepared by the palladium-catalyzed substitution of 3-iodobenzo[b]thiophenes by Suzuki-Miyaura, Sonogashira, Heck, carboalkoxylation, and aminocarbonylation chemistry. The key intermediates for library generation, methyl sulfone-containing 3-iodobenzo[b]thiophenes, are readily prepared by iodocyclization and oxidation methodologies from readily available alkynes.
- Cho, Chul-Hee,Neuenswander, Benjamin,Larock, Richard C.
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supporting information; experimental part
p. 278 - 285
(2010/08/06)
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