- Dehydration Polymerization for Poly(hetero)arene Conjugated Polymers
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The lack of scalable and sustainable methods to prepare conjugated polymers belies their importance in many enabling technologies. Accessing high-performance poly(hetero)arene conjugated polymers by dehydration has remained an unsolved problem in syntheti
- Mirabal, Rafael A.,Vanderzwet, Luke,Abuadas, Sara,Emmett, Michael R.,Schipper, Derek
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supporting information
p. 12231 - 12235
(2018/04/19)
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- Photo-oxidative Cross-Dehydrogenative Coupling-Type Reaction of Thiophenes with α-Position of Carbonyls Using a Catalytic Amount of Molecular Iodine
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A metal-free photo-oxidative intermolecular C-H/C-H coupling reaction of thiophenes is demonstrated with carbonyls using a catalytic amount of molecular iodine. In this system, molecular oxygen in the air acted as a terminal oxidant to regenerate molecular iodine. A mechanistic study was also performed.
- Sudo, Yusuke,Yamaguchi, Eiji,Itoh, Akichika
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supporting information
p. 1610 - 1613
(2017/04/13)
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- Visible-light-induced regioselective synthesis of polyheteroaromatic compounds
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A method for visible-light-induced synthesis of polyheteroaromatics from 2-heteroaryl-substituted anilines and heteroarylalkynes was developed. The process, which uses fac-Ir(ppy)3 as the photocatalyst and tBuONO as the diazotization reagent, is highly regioselective.
- Chatterjee, Tanmay,Choi, Myung Gil,Kim, Jun,Chang, Suk-Kyu,Cho, Eun Jin
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p. 4203 - 4206
(2016/03/19)
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- Programmed synthesis of arylthiazoles through sequential C-H couplings
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A programmed synthesis of privileged arylthiazoles via sequential C-H couplings catalyzed by palladium or nickel catalysts has been accomplished. This versatile protocol can supply all possible arylthiazole substitution patterns (2-aryl, 4-aryl, 5-aryl, 2
- Tani, Satoshi,Uehara, Takahiro N.,Yamaguchi, Junichiro,Itami, Kenichiro
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p. 123 - 135
(2014/01/06)
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- Reigoselective arylation of thiazole derivatives at 5-position via Pd catalysis under ligand-free conditions
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An efficient regioselective arylation of thiazole derivatives via Pd-catalyzed C-H activation is reported. The transformation was hypothesized through a Pd(0/II) catalytic cycle in the absence of special ligand sets. This method provided an efficient proc
- Liu, Xiang-Wei,Shi, Jiang-Ling,Yan, Jia-Xuan,Wei, Jiang-Bo,Peng, Kun,Dai, Le,Li, Chen-Guang,Wang, Bi-Qin,Shi, Zhang-Jie
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supporting information
p. 5774 - 5777
(2013/12/04)
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- Direct arylation of simple azoles catalyzed by 1,10-phenanthroline containing palladium complexes: An investigation of C4 arylation of azoles and the synthesis of triarylated azoles by sequential arylation
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Direct triarylation and sequential triarylation reactions of simple azoles catalyzed by [Pd(phen)2]PF6 are described. Simple azoles, such as N-methylimidazole, thiazole, and oxazole, were observed to undergo triaryaltion reactions even at their C4 positions when treated with aryl iodides in the presence of [Pd(phen)2]PF6 as a catalyst and a stoichiometric amount of Cs2CO3 in DMA at 150 °C. Using excess amounts of azoles, selective C5 monoarylation was achieved by using the same catalytic system. Subsequent efforts demonstrated that C5 arylated azoles undergo exclusive C2 arylation using [Pd(phen)2]PF6 as the catalyst with galvinoxyl as an additive. Finally, unprecedented C4 arylation reactions of 2,5-diaryl-azoles occur by using the new catalytic system to give the corresponding triarylated products in good to excellent yields. The results of mechanistic studies suggest that the C2 arylation process takes place by way of an electrophilic aromatic substitution (SEAr) palladation pathway, while arylation reactions at the C4 position occur via a SEAr palladation and/or radical mechanism. Finally, a concise, three-step synthesis of the Tie-2 Tyrosine Kinase Inhibitor has been executed starting with commercially available N-methylimidazole by a route that employs the new sequential arylation process.
- Shibahara, Fumitoshi,Yamaguchi, Eiji,Murai, Toshiaki
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experimental part
p. 2680 - 2693
(2011/06/20)
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- Palladium-catalyzed decarboxylative cross-coupling reaction between heteroaromatic Carboxylic acids and Aryl halides
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"Chemical Equation Presented" A full overview of the decarboxylative cross-coupling reaction between heteroaromatic carboxylic acids and aryl halides is described. This transformation employs palladium catalysts with short reaction times providing facile synthesis of aryl-substituted heteroaromatics. The effect of each reaction parameter including solvent, base, and additive employed as well as the full substrate scope of this transformation are reported. Mechanistic evidence is also disclosed that sheds light on possible reaction pathways.
- Bilodeau, Francois,Brochu, Marie-Christine,Guimond, Nicolas,Thesen, Kris H.,Forgione, Pat
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experimental part
p. 1550 - 1560
(2010/06/12)
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- Synthesis of 5-arylthiazoles. Comparative study between Suzuki cross-coupling reaction and direct arylation
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A facile synthetic route to the new thiazol-5-ylboronic acid pinacol ester was described herein. Its reactivity toward Suzuki cross-coupling reaction was studied to provide various 5-arylthiazoles. A comparative study between Suzuki cross-coupling reactio
- Primas, Nicolas,Bouillon, Alexandre,Lancelot, Jean-Charles,El-Kashef, Hussein,Rault, Sylvain
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experimental part
p. 5739 - 5746
(2009/12/03)
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- Efficient access to 5-substituted thiazoles by a novel metallotropic rearrangement
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A novel rearrangement process involving the migration of trimethylstannanyl or trimethylsilanyl groups around the thiazole ring provides access to either 2- or 5-metallated thiazoles by tuning the reaction conditions. The proposed mechanism, based on expe
- Zambon, Alfonso,Borsato, Giuseppe,Brussolo, Stefania,Frascella, Pietrogiulio,Lucchini, Vittorio
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- Facile generation of a library of 5-aryl-2-arylsulfonyl-1,3-thiazoles
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Treatment of N,N-diformylaminomethyl aryl ketones with phosphorus pentasulfide/triethylamine in chloroform gives 5-arylthiazoles directly in good yield. The 5-aryl-1,3-thiazole core has been successfully functionalised at the 2-position to yield, over two
- Sheldrake, Peter W.,Matteucci, Mizio,McDonald, Edward
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p. 460 - 462
(2007/10/03)
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- Unexpected intermolecular Pd-catalyzed cross-coupling reaction employing heteroaromatic carboxylic acids as coupling partners
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Aryl-substituted five-membered heteroaromatics have attracted great interest over the past years due to their presence in a large number of pharmaceuticals and natural products. Recently, an advance in the preparation of these scaffolds was achieved by employing a C-H functionalization strategy. This method allows easy access to these biaryl motifs by precluding the necessity of preparing specific coupling partners, although poor regioselectivity is sometimes observed when more than one reactive C-H is present on the substrate. In an effort to circumvent this liability, we envisioned the use of a carboxylic acid moiety as a blocking group that could be later functionalized or removed. Remarkably, the coupling was found to occur exclusively at the position previously occupied by the acid, even in the presence of a reactive C-H group. This selective transformation was also found to proceed with other heteroaromatic carboxylic acids, allowing for the preparation of a variety of aryl-substituted heteroaromatics that would be difficult to obtain via other methods. Copyright
- Forgione, Pat,Brochu, Marie-Christine,St.-Onge, Miguel,Thesen, Kris H.,Bailey, Murray D.,Bilodeau, Francois
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p. 11350 - 11351
(2007/10/03)
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- Direct arylation reactions catalyzed by Pd(OH)2/C: Evidence for a soluble palladium catalyst
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Palladium hydroxide on carbon (Pearlman's catalyst) effectively catalyzes direct arylation reactions of aryl iodides and bromides, providing excellent arylation-to-hydrodehalogenation ratios (>30:1) with broad scope for both intra- and intermolecular arylation processes. Studies aimed at determining the nature of the active catalyst indicate that an active homogeneous palladium species is produced under the reaction conditions.
- Parisien, Mathieu,Valette, Damien,Fagnou, Keith
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p. 7578 - 7584
(2007/10/03)
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- Cobalt-catalyzed arylation of azole heteroarenes via direct C-H bond functionalization
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(Equation presented) We herein report a new cobalt-catalyzed method for arylation of azole heteroarenes, including thiazole, oxazole, imidazole, benzothiazole, benzoxazole, and benzimidazole. The direct arylation of thiazole and oxazole was achieved both with iodo- and bromoarenes as the aryl donors in the presence of cobalt catalyst [Co(OAc)2/IMes] and cesium carbonate, while imidazole required the use of zinc oxide as the base. A complete reversal of arylation from C-5 to C-2 was accomplished using the bimetallic Co/Cu/IMes system. A direct comparison of the new cobalt method and the previously developed palladium protocol revealed significant differences, in terms of both chemical yield and selectivity.
- Sezen, Bengue,Sames, Dalibor
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p. 3607 - 3610
(2007/10/03)
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- Photochemistry of 3- and 5-phenylisothiazoles. Competing phototransposition pathways
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5-Phenylisothiazole undergoes phototransposition via the electrocyclic ring closure-heteroatom migration pathway and by the N2-C3 interchange reaction pathway. The latter route is enhanced by the addition of triethylamine (TEA) to the reaction medium and by increasing the polarity of the solvent. In addition to phototransposition, 5-phenylisothiazole also undergoes photocleavage to 2-cyano-1-phenylethenethiol which was trapped by reaction with benzyl bromide to yield 2-cyano-1-phenylethen-1-ylbenzyl thioether. 3-Phenylisothiazole also phototransposes by both reaction pathways, but the product distribution is not affected by the addition of TEA or by changing the solvent polarity.
- Pavlik, James W.,Tongcharoensirikul, Pakamas
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p. 3626 - 3631
(2007/10/03)
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- Palladium-Catalyzed Arylation of Azole Compounds with Aryl Halides in the Presence of Alkali Metal Carbonates and the Use of Copper Iodide in the Reaction
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The reactions of iodobenzene with azole compounds, 1,2-disubstituted imidazoles and 2-substituted oxazoles and thiazoles, were examined in the presence of catalytic amounts of Pd(OAc)2 and PPh3 in DMF using alkali metal carbonates as bases. It was found that the coupling products, 5-arylazoles, could be selectively produced in good yields by using CS2CO3. In the case that their 2-position is unsubstituted, the site could also be arylated. In reactions using bromobenzene in place of iodobenzene, K2CO3 was also as effective as Cs2CO3- The addition of a stoichiometric amount of Cul appeared to specifically promote the reactions of thiazoles as well as those of thiophene derivatives. The reactions of 2-unsubstituted azole compounds with aryl iodides could be mediated by Cul to some extent without using the palladium species to give 2-arylazoles.
- Pivsa-Art, Sommai,Satoh, Tetsuya,Kawamura, Yoshiki,Miura, Masahiro,Nomura, Masakatsu
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p. 467 - 473
(2007/10/03)
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- Phototransposition chemistry of phenylisothiazoles and phenylthiazoles. 1. Interconversions in benzene solution
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Phenylthiazoles 1-3 and phenylisothiazoles 4-6 undergo phototransposition in benzene solvent mainly by P5, P6, and P7 permutation pathways. Phenylisothiazoles 5 and 6 also transpose via a P4 permutation process to yield phenylthiazoles 2 and 3 in less than 1% yield. In benzene saturated with D2O, 2-phenylthiazole (1) and 5-phenylisothiazole (6) each phototranspose to yield 4-deuterio-3-phenylisothiazole (4-D-4) and 4-phenylthiazole (2) without deuterium incorporation. Irradiation of 4-phenylthiazole (2) under these conditions results in rapid photodeuteration to yield 2-deuterio-4-phenylthiazole (2-D-2), which subsequently phototransposes to 5-deuterio-3-phenylisothiazole (5-D-3). These experimental results can be rationalized by a mechanism involving initial electrocyclic ring closure and sigmatropic shift of sulfur around the four sides of the azetine ring. Rearomatization of each bicyclic intermediate thus allows sulfur to insert into each position in the carbon-nitrogen sequence. As a consequence, these compounds divide into a tetrad in which isomers 1, 2,4, and 6 interconvert mainly via P5, P6, and P7 pathways and a dyad of two compounds in which 3 phototransposes to 5 via P5 and P7 pathways. Within the tetrad, BC-6, the bicyclic intermediate derived from 5-phenylisothiazoles (6), is postulated to undergo deuteration with simultaneous sigmatropic shift of sulfur when the reaction is carried out in benzene-D2O. This mechanistic view provides one coherent interpretation for the observed phototransposition and photodeuteration reactions.
- Pavlik, James W.,Tongcharoensirikul, Pakamas,Bird, Nigel P.,Day, A. Colin,Barltrop, John A.
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p. 2292 - 2300
(2007/10/02)
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