- Substrate or Solvent-Controlled PdII-Catalyzed Regioselective Arylation of Quinolin-4(1H)-ones Using Diaryliodonium Salts: Facile Access to Benzoxocine and Aaptamine Analogues
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Regioselective C3, C5, and C8 arylation of quinolin-4(1H)-ones have been accomplished either by substrate-control or by tuning the reaction solvent. A variety of aryl(mesityl)iodonium triflates could smoothly deliver arylated products in good to excellent yields. Additionally, it offers great flexibility by arylating medicinally potent quinolone related heterocycles such as acridin-9(10H)-one, and phenanthridin-6(5H)-one under standard reaction conditions. This strategy was further extended with diphenyleneiodonium triflate to access oxacine fused quinolines. The post-modifications of synthesized products enhance the further utility of this protocol in organic synthesis. To the best of our knowledge, this is the first report on C5 arylation of quinolin-4(1H)-ones using iodine(III) reagents.
- Mehra, Manish K.,Sharma, Shivani,Rangan, Krishnan,Kumar, Dalip
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supporting information
p. 2409 - 2413
(2020/03/16)
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- Efficient construction of 3-arylquinolin-4(1H)-ones via in situ Meinwald rearrangement/intramolecular reductive cyclization of 2′-nitrochalcone epoxides
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An efficient method for construction of 3-arylquinolin-4(1H)-ones via in situ Meinwald rearrangement/intramolecular reductive cyclization of 2′-nitrochalcone epoxides has been developed. The practical approach is of excellent functional groups compatibili
- Wang, Sheng,Zhao, Chao,Liu, Ting,Yu, Lifang,Yang, Fan,Tang, Jie
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p. 7025 - 7031
(2016/10/14)
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- Unraveling innate substrate control in site-selective palladium-catalyzed C-H heterocycle functionalization
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Understanding the regioselectivity of C-H activation in the absence of directing groups is an important step towards the design of site-selective C-H functionalizations. The Pd(ii)-catalyzed direct arylation of chromones and enaminones provides an intriguing example where a simple substitution leads to a divergence in substrate-controlled site-selectivity. We describe computational and experimental studies which reveal this results from a switch in mechanism and therefore the selectivity-determining step. We present computational results and experimentally measured kinetic isotope effects and labelling studies consistent with this proposal. The C-H activation of these substrates proceeds via a CMD mechanism, which favors more electron rich positions and therefore displays a pronounced kinetic selectivity for the C3-position. However, C2-selective carbopalladation is also a competitive pathway for chromones so that the overall regiochemical outcome depends on which substrate undergoes activation first. Our studies provide insight into the site-selectivity based on the favorability of two competing CMD and carbopalladation processes of the substrates undergoing coupling. This model can be utilized to predict the regioselectivity of coumarins which are proficient substrates for carbopalladation. Furthermore, our model is able to account for the opposite selectivities observed for enaminone and chromone, and explains how a less reactive coupling partner leads to a switch in selectivity.
- Choi, Hwanho,Min, Minsik,Peng, Qian,Kang, Dahye,Paton, Robert S.,Hong, Sungwoo
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p. 3900 - 3909
(2016/06/09)
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- Ohmic Heating-Assisted Synthesis of 3-Arylquinolin-4(1H)-ones by a Reusable and Ligand-Free Suzuki-Miyaura Reaction in Water
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Potential bioactive 3-arylquinolin-4(1H)-ones were synthesized under ohmic heating using an efficient, reusable, and ligand-free protocol developed for the Suzuki-Miyaura coupling of 1-substituted-3-iodoquinolin-4(1H)-ones with several boronic acids in water using Pd(OAc)2 as a catalyst and tetrabutylammonium bromide (TBAB) as the phase transfer catalyst. Good substrate generality, ease of execution, short reaction time, and practicability make this method exploitable for the generation of libraries of B ring-substituted 3-arylquinolin-4(1H)-ones. After a simple workup, the Pd/catalyst-H2O-TBAB system could be reused for at least seven cycles without significant loss of activity.
- Pinto, Joana,Silva, Vera L. M.,Silva, Ana M. G.,Santos, Luís M. N. B. F.,Silva, Artur M. S.
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p. 6649 - 6659
(2015/10/06)
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- Ohmic heating-assisted synthesis of 3-arylquinolin-4(1h)-ones by a reusable and ligand-free Suzuki-Miyaura reaction in water
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Potential bioactive 3-arylquinolin-4(lH)-ones were synthesized under ohmic heating using an efficient, reusable, and ligand-free protocol developed for the Suzuki-Miyaura coupling of l-substituted-3-iodoquinolin-4(lH)-ones with several boronic acids in water using Pd(OAc)2 as a catalyst and tetrabutylammonium bromide (TBAB) as the phase transfer catalyst. Good substrate generality, ease of execution, short reaction time, and practicability make this method exploitable for the generation of libraries of B ring-substituted 3-arylquinolin-4(lH)-ones. After a simple workup, the Pd/catalyst-H2O-TBAB system could be reused for at least seven cycles without significant loss of activity.
- Pinto, Joana,Silva, Vera L. M.,Silva, Ana M. G.,Santos, Luis M. N. B. F.,Silva, Artur M. S.
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p. 6649 - 6659
(2015/11/09)
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- Azaisoflavones: Synthesis, antimicrobial evaluation and binding affinity with DNA gyrase
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Antimicrobial potency of azaisoflavones has been evaluated in vitro against nine bacterial and two fungal strains, respectively. The requisite azaisoflavones are conveniently synthesized in three steps, with the key step being the super acid catalyzed tandem reaction. The biological results reveal that out of twelve compounds screened, 3 compounds (5a, 5j and 5l) exhibited comparable activities against the standard drugs and demonstrated activities at μM concentration. In addition, molecular docking revealed that compound 5a as the most potent by showing a least binding energy of -5.99 kcal/mol with DNA gyrase receptor compared to other compounds.
- Praveen,Parthasarathy,Kumar, P. Senthil,Perumal
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p. 373 - 382
(2015/03/31)
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- Synthesis of bridged benzazocines and benzoxocines by a titanium-catalyzed double-reductive umpolung strategy
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A sequence of two titanium(III)-catalyzed reductive umpolung reactions is reported that allows the rapid construction of benzazo- and benzoxozine building blocks. The first step is a reductive cross-coupling of quinolones or chromones with Michael acceptors. This reaction proceeds with complete syn-selectivity for the quinolone functionalization while the anti-diastereomers are obtained as the major products from chromones. With different reaction conditions, the stereochemical outcome can be altered to afford the syn-chromanone products as well. A subsequent reductive ketyl radical cyclization forges the tricyclic title compounds in good yields. A stereochemical model explaining the observed stereoselectivities is provided and the product configurations were unambiguously verified by X-ray analyses and 2D NMR spectroscopic experiments.
- Bichovski, Plamen,Haas, Thomas M.,Kratzert, Daniel,Streuff, Jan
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p. 2339 - 2342
(2015/02/05)
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- Palladium-catalyzed dehydrogenation/oxidative cross-coupling sequence of β-heteroatom-substituted ketones
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Concise and selective: The title one-pot sequence allows formation of the enone functionality and subsequent cross-coupling. The process provides access to highly functionalized cyclic enolones and enaminones from readily accessible β-heteroatom-substitut
- Moon, Youngtaek,Kwon, Daeil,Hong, Sungwoo
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supporting information
p. 11333 - 11336,4
(2012/12/12)
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- Palladium-catalyzed decarboxylative coupling of quinolinone-3-carboxylic acids and related heterocyclic carboxylic acids with (Hetero)aryl halides
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An efficient and practical decarboxylative cross-coupling reaction of quinolin-4(1H)-one 3-carboxylic acids with (hetero)aryl halides has been established. Under a bimetallic system of PdBr2 and silver carbonate, the protocol proved to be general, and a variety of 3-(hetero)aryl 4-quinolinones and related heterocycles, such as 3-aryl-1,8-naphthyridin-4(1H)- ones, 3-arylcoumarins, 3-arylquinolin-2(1H)-ones, and 2-arylchromones, can be prepared in good to excellent yields.
- Messaoudi, Samir,Brion, Jean-Daniel,Alami, Mouad
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supporting information; experimental part
p. 1496 - 1499
(2012/05/20)
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- Pd-catalyzed dehydrogenative cross-coupling of polyfluoroarenes with heteroatom-substituted enones
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The first example of intermolecular regioselective α-arylation of heteroatom-substituted enones with polyfluoroarenes via twofold C-H bond functionalization using a palladium catalyst is reported. This approach provides rapid access to a wide range of α-fluoroarylated enones of interest in life science.
- Chen, Fei,Feng, Zhang,He, Chun-Yang,Wang, Hao-Yang,Guo, Yin-Long,Zhang, Xingang
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supporting information; experimental part
p. 1176 - 1179
(2012/04/04)
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