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Journal of Organic Chemistry

N Perrer Tosso, Bimbisar K Desai, Eliseu De Oliveira, Juekun Wen, John Tomlin, B Frank Gupton
Ciprofloxacin is a broad-spectrum antibiotic that is recognized as one of the World Health Organization's Essential Medicines. It is particularly effective in the treatment of Gram-negative bacterial infections associated with urinary, respiratory and gastrointestinal tract infections. A streamlined and high yielding continuous synthesis of ciprofloxacin has been developed, which employs a chemoselective C-acylation step that precludes the need for intermediate isolations, extractions or purifications. The end-to end process has a residence time of 4...
February 20, 2019: Journal of Organic Chemistry
Heesun Yu, Ryangha Lee, Hyoungsu Kim, Dongjoo Lee
A Lewis acid-promoted highly regio- and diastereoselective C(sp3 )-C(sp2 ) cross-coupling reaction between unprotected aryl-substituted 1,2-diols and styryl-, aryl-, heteroaryl-, and polyarylboronic acids has been developed in a one-pot procedure. The regioselective opening of aryl-substituted cyclic boronic esters promoted by a Lewis acid, followed by subsequent intramolecular 1,4-transfer of the carbon ligand from boron to a resonance-stabilized benzylic carbenium ion minimizing the allylic 1,3-strain in a stereoselective fashion led to the corresponding α-substituted syn-phenylethyl alcohols...
February 20, 2019: Journal of Organic Chemistry
Kaitie C Cartwright, Simon B Lang, Jon A Tunge
Decarboxylative elimination of easily accessible N-acyl amino acids to provide enamide and enecarbamate building blocks has been realized through the combination of an organophotoredox catalyst and copper acetate as the terminal oxidant. This operationally simple process utilizes inexpensive and readily available reagents without preactivation of the carboxylic acid. Enamides and enecarbamates are now accessible directly from N-acyl amino acids consequently improving upon the utility of Kochi's oxidative decarboxylation of carboxylic acids...
February 20, 2019: Journal of Organic Chemistry
Henrik Hintz, Agathe Vanas, Daniel Klose, Gunnar Jeschke, Adelheid Godt
Finland trityl radical (FTR) shows very attractive EPR spectroscopical properties for a manifold of applications. For most of its applications only one chemically reactive functional group is needed. The presence of three equally reactive carboxyl groups leads to FTR modifications through reactions which give statistical mixtures of onefold, twofold and threefold modified, and unmodified FTR. To avoid the side effects of such a statistical reaction - limited yields and sepa-ration challenges - we took a route to FTR-type trityl radicals with scaffold assembly by addition of an aryllithium with one type of substituent to a diarylketone with another type of substituent...
February 20, 2019: Journal of Organic Chemistry
Mikus Puriņš, Anatoly Mishnev, Māris Turks
A general method for generation of allyl carbenium ions from propargyl silanes via 1,2-silyl shift by Brønsted acids is reported. Two possible reaction pathways are described. Deprotonation results in silyl dienes with yields from 52 % to 92 %. Intramolecular Friedel-Crafts reaction of aryl-substituted systems gives access to silyl indenes with yields 18 % to 90 % depending on substitution pattern. The obtained products have been shown to react as vinyl silanes in Hiyama coupling and electrophilic substitution, and as dienes in Diels-Alder cycloaddition...
February 20, 2019: Journal of Organic Chemistry
Deok Kyun Ahn, Young Woo Kang, Sang Kook Woo
An efficient and greener deprotection method for p-methoxybenzyl (PMB) ethers using a metal-free visible light photoredox catalyst and air and ammonium persulfate as the terminal oxidants is presented. Various functional groups and protecting groups were tolerated in the developed method to achieve good to excellent yields in short reaction times. Significantly, the developed method was compatible with PMB ethers derived from primary, secondary, and tertiary alcohols and a gram-scale reaction. Mechanistic studies support a proposed reaction mechanism that involves single electron oxidation of the PMB ether...
February 20, 2019: Journal of Organic Chemistry
Shanping Chen, Pingyu Jiang, Pu Wang, Yong Pei, Huawen Huang, Fuhong Xiao, Guo-Jun Deng
A novel method was developed for the synthesis of substituted carbazoles from commercially available starting materials under metal-free conditions. This strategy involves a [1s,6s] sigmatropic shift step and introduces an electron-withdrawing ester substituent at the C2 position of the carbazole ring. The present protocol afforded the desired carbazole derivatives with good regioselectivity and well functional group tolerance. And DFT calculations were carried out to support the reaction pathway.
February 20, 2019: Journal of Organic Chemistry
Lee C Moores, Devinder Kaur, Mathew D Smith, James S Poole
The regioselectivity of hydroxyl radical addition to arenes was studied using a novel experimental method capable of trapping radicals formed after the first elementary step of reaction, without alteration of the product distributions by secondary oxidation processes. Product analyses of these reactions indicate a preference for o- over p- substitution for electron donating groups, with both favored over m-addition. The observed distributions are qualitatively similar to those observed for the addition of other carbon-centered radicals, although the magnitude of the regioselectivity observed is greater for hydroxyl...
February 19, 2019: Journal of Organic Chemistry
Bo Qu, Renchang Tan, Madison R Herling, Nizar Haddad, Nelu Grinberg, Marisa C Kozlowski, Xumu Zhang, Chris H Senanayake
Enantioenriched aldehydes are produced through asymmetric hydroformylation of styrene derivatives using BIBOP type ligands. The featured example is enantioselective synthesis of 4-methyl-3,4-dihydroisocoumarin, which was prepared in a 95.1:4.9 enantiomeric ratio from asymmetric hydroformylation of ethyl 2-vinylbenzoate, then in situ lactonization during reduction process. The conditions are compatible with both electron-rich and electron-poor substituents.
February 19, 2019: Journal of Organic Chemistry
Song Liu, Xiaotian Qi, Ruopeng Bai, Yu Lan
A computational study was carried out to investigate the mechanism and the origin of chemoselectivity in nickel-catalyzed C-N radical-radical cross-coupling reaction. The global electrophilicity index ω° and global nucleophilicity index N° were used to quantitatively describe the electrophilic or nucleophilic character of the carbon radical, nitrogen radical, and Ni(II) complex. The calculated ω° and N° values indicate that introduction of nickel makes C-N cross-coupling to be a facile process. Detailed theoretical results show that the cross-coupling occurs through the combination of Ni(I) complex with a nitrogen-centered radical , a minimum energy crossing point to form the singlet Ni(II) complex and radical addition of the nucleophilic carbon-centered radical lead to C-N bond formation...
February 19, 2019: Journal of Organic Chemistry
Suraj K Ayer, Jennifer L Roizen
Owing to the pervasiveness of hydroxyl groups in natural isolates, alcohol derivatives are alluring directing groups. Herein, an alcohol-derived sulfamate ester guides the light initiated xanthylation of primary, secondary, or tertiary centers. This process enables formal directed deuteration, azidation, thiolation, and vinylation reactions.
February 19, 2019: Journal of Organic Chemistry
Gunnar Ehrlich, Christian B W Stark
The cytospolides are a novel group of fungal secondary metabolites first described in 2011. Although all 17 natural derivatives share the same C-14 polyketide backbone, they exhibit a fairly broad structural diversity regarding their oxygenation and acetylation pattern as well as macrolide structure, e.g. monocyclic nonanolide core or bicyclic ring systems with a bridging THF ring. In the present work, the prospects for an extension of the structural diversity of cytospolides have been investigated. Based on a previously established synthesis of cytospolide D, a modified route to a truncated analogue carrying an alkyne instead of the natural n-pentyl side chain has been developed...
February 19, 2019: Journal of Organic Chemistry
Young-Do Kwon, Jeongmin Son, Joong-Hyun Chun
Hypervalent diaryliodonium salts have been used to produce various [18 F]fluoroarenes. The iodonium salt approach as a labeling precursor has been established to equally afford complex 18 F-fluorinated molecules. Because of the inherent two-aryl ring system connected to a central iodine atom, safeguarding the chemoselectivity during radiofluorination using diaryliodonium salts is important. Herein, we introduce a superior chemoselective radiosynthesis of [18 F]fluoroarenes using an aryl(2,4,6-trimethoxyphenyl)iodonium tosylate as a precursor for 18 F-incorporation, even on electron-rich aryl rings...
February 19, 2019: Journal of Organic Chemistry
Gert-Jan Hofman, Emile Ottoy, Mark E Light, Bruno Kieffer, Jose C Martins, Ilya Kuprov, Davy Sinnaeve, Bruno Linclau
Fluorinated proline derivatives have found diverse applications in areas ranging from medicinal chemistry over structural biochemistry to organocatalysis. Depending on the stereochemistry of monofluorination at the proline 3- or 4-position, different effects on the conformational properties of proline (ring pucker, cis/trans isomerization) are introduced. Simultaneous fluorination at the 3- and 4-positions is expected to either reinforce or oppose these effects. Here we report, in full, the syntheses and conformational properties of three out of the four possible 3,4-difluoro-L-proline diastereoisomers...
February 19, 2019: Journal of Organic Chemistry
Klaus Banert, Tom Pester
Treatment of N-chlorodimethylamine with sodium azide in dichloromethane does not lead to N-azidodimethylamine, as thought for more than 50 years. Instead, surprising (azidomethyl)dimethylamine is generated with good reproducibility. A plausible reaction mechanism to explain the formation of this product is presented. The reaction of lithium dibenzylhydrazide with tosyl azide does not result in the creation of an N-azidoamine, which can be detected by IR spectroscopy at ambient temperature, as it was claimed previously...
February 19, 2019: Journal of Organic Chemistry
Patricia Fernandez, Carlos Valdés, Francisco J Fañanás, Félix Rodríguez
8-Isoquinolinones derived from a silver-catalyzed cycloisomerization of in situ formed ortho-alkynylsalicylaldimines react with one equivalent of acetylenedicarboxylate derivatives to give pyrano[2,3,4-ij]isoquinolines through a [4+2]-cycloaddition reaction. When two equivalents of the alkyne are used, structurally complex benzo[de]chromenes are obtained through an intricate cascade process comprising unusual formal [4+2]- and [2+2]-cycloadditions followed by several ring-opening and ring-closing processes.
February 19, 2019: Journal of Organic Chemistry
Cong-Shuai Wang, Tian-Zhen Li, Yu-Chun Cheng, Ji Zhou, Guang-Jian Mei, Feng Shi
A chiral guanidine-catalyzed asymmetric [4+1] cyclization of benzofuran-derived azadienes with 3-chlorooxindoles has been established, which constructed chiral spirooxindole frameworks with in situ generation of a five-membered ring in high diastereoselectivities (up to >95:5 dr) and good enantioselectivities (up to 94:6 er). This reaction represents the first catalytic asymmetric [4+1] cyclization of benzofuran-derived azadienes, which will enrich the research field of catalytic asymmetric cyclizations of such reactants...
February 19, 2019: Journal of Organic Chemistry
Xiaobao Zeng, Chulong Liu, Weiguang Yang, Yunxiang Weng, Xinyan Wang, Yuefei Hu
A new method for direct synthesis of β-ketoenamines was developed by a BF3•OEt2-catalyzed cyclization of 1-iodoalkyne and α-keto acid followed by an amine-mediated ring-opening in one-pot. Its metal-free conditions allowed the easy synthesis of those products bearing the transition metal-sensitive functional groups. Its three-component process achieved wide range of functionalized products.
February 19, 2019: Journal of Organic Chemistry
Yao-Bin Shen, Shuai-Shuai Li, Yun-Ming Sun, Xicheng Liu, Liping Yu, Qing Liu, Jian Xiao
The oxindole-embedded ortho-quinone methides, in situ generated from oxindole-embedded ortho-hydroxybenzyl alcohols, were employed as reactive intermediates in formal [4 + 2] annulation with 1,3-dicarbonyls, providing an efficient access to spiro[chromen-4,3´-oxindole] scaffolds via a cascade conjugate addition/ketalization/dehydration process. This protocol featured metal-free conditions, wide substrate scope and excellent yields.
February 19, 2019: Journal of Organic Chemistry
Bin Lu, Xiaoyu Wu, Chengyang Li, Guangni Ding, Wanfang Li, Xiaomin Xie, Zhaoguo Zhang
Dynamic kinetic resolution (DKR) of racemic aryl α-amino β-ketoesters via Ru-diphosphines catalyzed asymmetric hydrogenation was realized at 70°C under 50 atm of hydrogen, affording syn α-amido β-hydroxy esters in high yields (up to 96%) with high reactivity (TON up to 940), diastereo- and enantioselectivities (up to 99:1 dr, 98% ee). These hydrogenation products provide valuable chiral synthons in many natural products and pharmaceuticals. Gram-scale DKR asymmetric hydrogenation (DKR-AH) was also performed with retained reactivity and stereoselectivity, revealing the synthetic utility of this method...
February 19, 2019: Journal of Organic Chemistry
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