- Iron(0)-Catalyzed Transfer Hydrogenative Condensation of Nitroarenes with Alcohols: A Straightforward Approach to Benzoxazoles, Benzothiazoles, and Benzimidazoles
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The iron-catalyzed hydrogen transfer strategy has been applied to the redox condensation of o-hydroxynitrobenzene with alcohol, leading to the formation of benzoxazole derivatives. A wide range of 2-substituted benzoxazoles were synthesized in good to excellent yields without the addition of an external redox agent. A series of control experiments provided a plausible mechanism. Furthermore, the reaction system was successfully extended to the synthesis of benzothiazoles and benzimidazoles.
- Putta, Ramachandra Reddy,Chun, Simin,Choi, Seung Hyun,Lee, Seok Beom,Oh, Dong-Chan,Hong, Suckchang
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p. 15396 - 15405
(2020/12/02)
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- Continuous flow/waste-minimized synthesis of benzoxazoles catalysed by heterogeneous manganese systems
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Herein, we present our results on the development of a waste minimized protocol for the synthesis of 2-arylbenzoxazoles in continuous flow. Manganese-based heterogeneous catalysts were used in combination with cyclopentylmethyl ether as an environmentally friendly and safe reaction medium. The use of oxygen promotes the oxidative process ensuring at the same time a complete regeneration of the catalyst adopting a flow configuration which does not include the use of an additional mechanical pump. These features allowed for a faster synthesis compared to batch procedures with minimal metal leaching.
- Ferlin, Francesco,Van Der Hulst, Mitchell K.,Santoro, Stefano,Lanari, Daniela,Vaccaro, Luigi
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supporting information
p. 5298 - 5305
(2019/10/11)
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- Base-Free Selective O-Arylation and Sequential [3,3]-Rearrangement of Amidoximes with Diaryliodonium Salts: Synthesis of 2-Substituted Benzoxazoles
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A variety of functionalized 2-substituted benzoxazoles can be prepared in good yields from amidoximes and diaryliodonium salts by selective O-arylation and sequential [3,3]-rearrangement under metal-free conditions. O-arylation of amidoximes was promoted by 3 ? molecule sieves in the absence of a base and a sequential TFA-mediated [3,3]-rearrangement was used to synthesize 2-substituted benzoxazoles. Both of the O-aryl products and rearrangement products were compatible with a broad range of sensitive functional groups such as ester, aldehyde, nitro, vinyl, amine, and amide groups in addition to halides. A bidentate N-ligand with double benzoxazoles was prepared at gram-scale in two steps. (Figure presented.).
- Shi, Wei-Min,Li, Xiao-Hua,Liang, Cui,Mo, Dong-Liang
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supporting information
p. 4129 - 4135
(2017/12/15)
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- A Polystyrene-Cross-Linking Bisphosphine: Controlled Metal Monochelation and Ligand-Enabled First-Row Transition Metal Catalysis
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A polystyrene-cross-linking bisphosphine PS-DPPBz was synthesized through radical emulsion copolymerization between 4-t-butylstyrene as a monomer and tetravinylated 1,2-bis(diphenylphosphino)benzene (DPPBz) as a 4-fold cross-linker. The location of the DPPBz bisphosphine moiety at the branching points of the cross-linked network organic polymer allowed controlled bisphosphine monochelation to transition metals under conditions where homogeneous ligands may form bischelated single metal complexes or multinuclear complexes. PS-DPPBz showed high ligand performance in first-row transition metal catalysis, enabling challenging molecular transformations that were not possible through the screening of existing homogeneous ligands. In the Ni-catalyzed amination of aryl chlorides with N-alkyl-substituted primary amines, the substrate scope has been expanded to include 2,6-disubstituted aryl chlorides and N-tertiary-alkyl-substituted primary amines. PS-DPPBz was effective for the Ni-catalyzed C-H/C-O coupling between 1,3-azoles and monocyclic aryl pivalates, which showed poor reactivity in the reported homogeneous catalytic system based on 1,2-bis(dicyclohexylphosphino)ethane (DCYPE). The usefulness of the polymer-cross-linking strategy was also demonstrated in alkene hydroboration reactions catalyzed by Cu or Co.
- Iwai, Tomohiro,Harada, Tomoya,Shimada, Hajime,Asano, Kiichi,Sawamura, Masaya
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p. 1681 - 1692
(2017/08/15)
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- Palladium-catalyzed intra-and intermolecular C-H arylation using mesylates: Synthetic scope and mechanistic studies
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This paper describes the development of Pd-catalyzed inter-and intramolecular direct arylation using mesylates. Furthermore, a sequential mesylation/arylation protocol using phenols as substrates is described. These transformations are general with respect to the electronics of the C-H substrates and allow for the synthesis of diverse heterocyclic motifs in good yields. Both arenes and heteroarenes efficiently participate in these reactions. Preliminary mechanistic studies are presented for both inter-and intramolecular arylations.
- Ferguson, Devin M.,Rudolph, Stacey R.,Kalyani, Dipannita
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p. 2395 - 2401
(2014/07/21)
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- One-pot synthesis of 2-substituted benzoxazoles promoted by copper acetate monohydrate
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An efficient synthesis of 2-substituted benzoxazoles via copper acetate monohydrate oxidative coupling of aldehydes with o-aminophenol is described. This synthetic strategy has some advantages as simple procedure, inexpensive and easily available catalyst, and facile isolation of the products in moderate to good yields.
- Chen, Guo-Feng,Shen, Hai-Dong,Zhang, Li-Yan,Li, Hong-Yang,Lan, Rui-Jia,Chen, Bao-Hua,Li, Ji-Tai,Hu, Qing-Hui
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p. 180 - 187
(2014/05/20)
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- Palladium-catalyzed direct arylation of heteroarenes with aryl mesylates
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Not so challenging after all! The first general examples of the direct arylation of heteroarenes by using challenging aryl mesylates as electrophiles are disclosed. These easy reaction conditions also allow the functionalization of other heterocycles, such as caffeine, triazole and benzathiazole (see scheme). Copyright
- So, Chau Ming,Lau, Chak Po,Kwong, Fuk Yee
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supporting information; experimental part
p. 761 - 765
(2011/03/20)
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- Cu-Nanoparticles: efficient catalysts for the oxidative cyclization of Schiffs' bases
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Cu-Nanoparticles provide an efficient catalysis for the synthesis of 2-arylbenzoxazoles by the coupling of aromatic or heteroaromatic aldehydes with 2-aminophenol though the oxidative cyclization of the Schiffs' bases using 10 mol % of the Cu-nanoparticles in the presence of K2CO3 in MeOH. This method avoids the use of metal oxide or organic oxidizing agents, namely, DDQ or strong acids such as polyphosphoric acid or boric acid.
- Kidwai, Mazaahir,Bansal, Vikas,Saxena, Amit,Aerry, Swati,Mozumdar, Subho
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p. 8049 - 8053
(2007/10/03)
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- SYNTHESIS OF HETEROCYCLES: PART I. N-IODOSUCCINIMIDE, A CONVENIENT OXITATIVE CYCLISING AGENT IN THE SYNTHESIS OF OXAZOLE, ISOXAZOLE, BENZOFURAN, FUROXAN AND 1,2,3-TRIAZOLE-1-OXIDE DERIVATIVES
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N-Iodosuccinimide has been successfully employed as an oxidative cyclising agent for the synthesis of oxazole, isoxazole, benzofuran, furoxan and 1,2,3-triazole-1-oxide derivatives.Synthesis of compounds (II), (IV), (VI), (VIII) and (X) having these basic skeletons respectively are reported.
- Talapatra, Sunil K.,Chaudhuri, Prabir,Talapatra, Bani
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p. 1279 - 1282
(2007/10/02)
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