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Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/28235381/stereoselective-arylation-of-amino-aldehydes-overriding-natural-substrate-control-through-chelation
#1
Bruna Simões Martins, Angélica Venturini Moro, Diogo S Lüdtke
The chelation-controlled arylation reaction of chiral, enantiopure acyclic alpha-amino aldehydes enabled by a B/Zn exchange reaction between arylboronic acids and Et2Zn is reported. The presence of dibenzyl substituents at the nitrogen plays a key role in the stereochemical outcome of the reaction, and chelation is favored over the natural tendency of this type of substrate to undergo Felkin-Anh controlled additions with organomagnesium and organolithium reagents.
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28234479/stereoselective-copper-catalyzed-cross-coupling-of-aziridines-with-benzimidazoles-via-nucleophilic-ring-opening-and-c-sp2-h-functionalization
#2
Pinaki Bhusan De, Sourav Pradhan, Tharmalingam Punniyamurthy
A copper-catalyzed cross-coupling of 2-alkyl/2-arylaziridines with benzimidazoles is reported. The reactions involve a regiospecific ring opening of aziridines with benzimidazoles to give benzoimidazolylethylamine derivatives that lead to dehydrogenative cross-coupling between C(sp2)-H and N-H bonds to produce dihydroimidazobenzimidazoles. Optically active 2-arylaziridines can be stereo-invertivebly cross-coupled with high enantiomeric purities (77-97% ee). These aerobic catalytic systems comprise an inexpensive Cu(II) salts and PCy3 ligand at moderate temperature...
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28234004/synthesis-of-indolines-by-a-zn-mediated-mannich-reaction-pd-catalyzed-amination-sequence
#3
Marc Presset, Antoine Pignon, Jérôme Paul, Erwan Le Gall, Eric Leonel, Thierry Martens
1,2-Disubstituted indolines have been prepared in fair to good yields by a Zn-mediated organometallic Mannich reaction followed by an intramolecular Pd-catalyzed aromatic amination. The reactions are easy to set up and compatible with a large variety of simple or commercially-available reagents. The method was further extended to the preparation of a 1,2,3-trisubstituted indoline.
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28234001/iridium-catalyzed-anti-stereoselective-asymmetric-ring-opening-reactions-of-azabenzonorbornadienes-with-carboxylic-acids
#4
Meina Zhu, Jingchao Chen, Xiaobo He, Cuiping Gu, Jianbin Xu, Baomin Fan
The first anti-stereoselective asymmetric ring opening reactions of azabenzonorbornadienes with carboxylic acids had been realized with an iridium catalyst assisted by nBu4NBr. The reaction features in broad substrate scope, good functional group tolerance, allows the synthesis of chiral dihydronaphthalene derivatives with high optical purities.
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28233998/chemical-access-to-d-sarmentose-units-enables-the-total-synthesis-of-cardenolide-monoglycoside-n-1-from-nerium-oleander
#5
Jordi Mestre, M Isabel Matheu, Yolanda Díaz, Sergio Castillón, Omar Boutureira
Herein we present a chemical approach for the ready preparation of D-sarmentosyl donors enabling the first total synthesis and structure validation of cardenolide N-1, a challenging 2,6-dideoxy-3-O-methyl-β-D-xylo-hexopyranoside extracted from Nerium oleander twigs that displays anti-inflammatory properties and cell growth inhibitory activity against tumor cells. The strategy highlights the synthetic value of the sequential methodology developed in our group for the synthesis of 2-deoxyglycosides. Key steps include Wittig-Horner olefination of a D-xylofuranose precursor, [I+]-induced 6-endo cyclization, and 1,2-trans stereoselective glycosylation...
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28233495/i2-mediated-intramolecular-c-h-amidation-for-the-synthesis-of-n-substituted-benzimidazoles
#6
Zhiyuan Hu, Ting Zhao, Manman Wang, Jie Wu, Wenquan Yu, Junbiao Chang
A practical intramolecular C-H amidation methodology has been developed using molecular iodine under basic conditions. The required imine substrates were readily obtained by condensation of simple o-phenylenediamine derivatives and aldehydes. The transition metal-free cyclization reaction described here works well with crude imines, and allows for the sequential synthesis of N-protected benzimidazoles without purification of the less stable condensation intermediates. This operationally simple synthetic approach is broadly applicable to a variety of aromatic, aliphatic, and cinnamic aldehydes to produce diverse 1,2-disubstituted benzimidazole derivatives in an efficient and scalable fashion...
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28231707/enhanced-hypsochromic-shifts-quantum-yield-and-%C3%AF-%C3%AF-interactions-in-a-meso-beta-heteroaryl-fused-bodipy
#7
Ning Zhao, Sunting Xuan, Frank R Fronczek, Kevin Malcolm Smith, M Graca Henriques Vicente
We report the synthesis and investigation of an unprecedented 8-heteroaryl-fused BODIPY 4. This compound exhibits enhanced π-π stacking in the solid state, unusually large blue-shifts in the absorbance and emission spectra, and higher quantum yield than its unfused precursor; DFT calculations suggest a small energy gap for 4, and strong electronic communication between the 8-OPh and the BODIPY core.
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28219242/spiroaspertrione-a-a-bridged-spirocyclic-meroterpenoid-as-a-potent-potentiator-of-oxacillin-against-methicillin-resistant-staphylococcus-aureus-from-aspergillus-sp-tj23
#8
Yan He, Zhengxi Hu, Weiguang Sun, Qin Li, Xiao-Nian Li, Hucheng Zhu, Jinfeng Huang, Junjun Liu, Jianping Wang, Yongbo Xue, Yonghui Zhang
Bioassay-guided isolation of cultures of Aspergillus sp. TJ23 yielded a novel terpene-polyketide hybrid spiromeroterpenoid, spiroaspertrione A (1), bearing a unique spiro[bicyclo[3.2.2]nonane-2,1'-cyclohexane] carbocyclic skeleton, and a new biointermediate, andiconin B (2). Their structures and absolute configurations were elucidated by spectroscopic analyses, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Compound 1 demonstrated potent resensitization of oxacillin against methicillin-resistant Staphylococcus aureus by lowering the oxacillin minimal inhibitory concentration up to 32-fold from 32 to 1 μg/mL...
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28218535/sulfur-groups-improve-the-performance-of-triazole-and-triazolium-based-interaction-units-in-anion-binding
#9
Mónica Álvarez-Pérez, Marina Velado, Diego García-Puentes, Elena Sáez, Cristina Vicent, Roberto Fernández de la Pradilla, Alma Viso, María C de la Torre, Miguel A Sierra
An NMR comparative study of 1,2,3-triazole and triazolium anion recognition units containing sulfoxide, sulfone, and sulfoximine groups at C4 unveils an enhancement in binding ability up to ≈1 kcal/mol in acetone-d6 correlated with a theoretical increase of H5 acidity. DFT calculations provide insight into binding modes in line with experimental data for these receptors.
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28218522/one-pot-cascade-synthesis-of-substituted-carbazoles-from-indoles-ketones-and-alkenes-using-oxygen-as-the-oxidant
#10
Shanping Chen, Yuxia Li, Penghui Ni, Baichuan Yang, Huawen Huang, Guo-Jun Deng
An efficient one-pot two-step indole-to-carbazole strategy has been developed. This transition metal-free methodology uses oxygen as the sole oxidant and starts from cheap and readily available indoles, ketones, and alkenes. The present protocol efficiently enables the assembly of a diverse array of substituted carbazole products with good regioselectivity and broad tolerance of functional groups.
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28217999/total-synthesis-of-marinisporolide-c
#11
Luiz C Dias, Emilio C de Lucca
The first total synthesis of (-)-marinisporolide C is described, which establishes unequivocally the relative and absolute configuration of this oxopolyene macrolide. Key features of this synthesis include a series of highly stereoselective aldol reactions followed by directed reductions to build the polyol domain, a Stille cross-coupling reaction to assemble the polyene, and an intramolecular Horner-Wadsworth-Emmons olefination to forge the macrocyclic ring. Despite the initial approach to marinisporolide A using a Yamaguchi macrolactonization reaction that was unsuccessful due to steric hindrance of the oxygen at the C33 position, we were able to prepare a known derivative of marinisporolide A and consequently confirm its stereochemical assignment...
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28198182/synthesis-of-enantiopure-1-2-diaminobicyclo-2-2-2-octane-derivatives-c1-symmetric-chiral-1-2-diamines-with-a-rigid-bicyclic-backbone
#12
Pierre Milbeo, Laure Moulat, Claude Didierjean, Emmanuel Aubert, Jean Martinez, Monique Calmès
The synthesis of enantiopure 1,2-diaminobicyclo[2.2.2]octane (DABO, 1) and its two selectively N-Boc monoprotected derivatives 15 and 16 is described. Starting from bicyclic β-amino acid 3 or 5, strategies involving Curtius and Hofmann rearrangements were explored, demonstrating the unprecedented influence of the bicyclic backbone unsaturation for the preparation of the corresponding diamines that could be only obtained in good yield using the Hofmann rearrangement of unsaturated compound 3. The divergent outcome observed during the Hofmann rearrangement of 3 and 5 was investigated by DFT calculations...
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28186756/kinetics-of-%C3%AE-2-6-dimethylphenl-vinyllithium-how-to-control-errors-caused-by-inefficient-mixing-with-pairs-of-rapidly-competing-ketones
#13
Rudolf Knorr, Monika Knittl, Claudia Behringer, Jakob Ruhdorfer, Petra Böhrer
Kinetic studies are a suitable tool to disclose the role of tiny reagent fractions. The title compound 2 reacted in a kinetic reaction order of 0.5 (square root of its concentration) with an excess of the electrophiles ClSiMe3, 1-bromobutane (n-BuBr), or 1-iodobutane (n-BuI) at 32 °C in Et2O or in hydrocarbon solvents. This revealed that the tiny (NMR-invisible) amount of a deaggregated equilibrium component (presumably monomeric 2) was the reactive species, whereas the disolvated dimer 2 was only indirectly involved as a supply depot...
February 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230990/a-comparative-study-of-the-synthesis-structural-and-physicochemical-properties-of-diketopiperazines-vs-aza-diketopiperazines
#14
Pierre Regenass, Damien Bosc, Stéphanie Riché, Patrick Gizzi, Marcel Hibert, Lydia Brelot, A Ganesan, Dominique Bonnet
Aza-diketopiperazines (Aza-DKP) represent an underprivileged motif obtained by scaffold hopping of 2,5-diketopiperazines (2,5-DKP). Herein, we compare the synthesis but also the structural and the physicochemical properties of aza-DKP 4 vs 2,5-DKP 7. Thus, X-ray and 1H NMR studies show that aza-DKP 4 is a rigid and non-flat scaffold like the 2,5-DKP 7. Moreover, the replacement of one Calpha-stereogenic center by a nitrogen atom results in a significant improvement of both the water solubility and the microsomal stability...
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230982/synthesis-of-%C3%AE-1-2-linked-6-deoxy-l-altropyranose-oligosaccharides-via-gold-i-catalyzed-glycosylation-of-a-ortho-hexynylbenzoate-donor
#15
Zhengnan Shen, Hani Mobarak, Wei Li, Göran Widmalm, Biao Yu
The β-(1-2)-linked 6-deoxy-L-altropyranose di- to penta-saccharides 2-5, relevant to the O-antigen of the infectious Yersinia enterocolitica O:3, were synthesized for the first time. The challenging 1,2-cis-altropyranosyl linkage was assembled effectively via glycosylation with 2-O-benzyl-3,4-di-O-benzoyl-6-deoxy-L-altropyranosyl ortho-hexynylbenzoate (7) under the catalysis of PPh3AuNTf2. NMR and molecular modeling studies showed that the pentasaccharide (5) adopted a left-handed helical conformation.
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230369/synthesis-of-substituted-%C3%AE-and-%C3%AE-lactams-via-pd-catalyzed-alkene-carboamination-reactions
#16
Jordan R Boothe, Yifan Shen, John P Wolfe
The synthesis of substituted γ- and δ-lactams via palladium-catalyzed alkene carboamination reactions between aryl halides and alkenes bearing pendant amides is described. The substrates for these reactions are generated in 1-3 steps from commercially available materials, and products are obtained in good yield with up to >20:1 diastereoselectivity. The stereochemical outcome of the alkene addition is consistent with a mechanism involving anti-aminopalladation of the alkene.
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230367/copper-catalyzed-regioselective-c-h-sulfonyloxylation-of-electron-rich-arenes-with-p-toluenesulfonic-acid-and-sulfonyloxylation-of-aryl-mesityl-iodonium-sulfonates
#17
He Huang, Yang Wu, Wen Zhang, Chun Feng, Bi-Qin Wang, Wan-Fei Cai, Ping Hu, Ke-Qing Zhao, Shi-Kai Xiang
Copper catalyzed regioselective C-H sulfonyloxylation of electron-rich arenes with p-toluenesulfonic acid has been developed. Electron-rich benzene derivatives and heteroarenes can undergo this C-H sulfonyloxylation reaction to generate aryl tosylates. Furthermore, sulfonyloxylation of aryl(mesityl)iodonium sulfonates has also been investigated. Both aryl(mesityl)iodonium tosylates and triflates can react smoothly to get aryl sulfonates. The formed aryl sulfonates can be converted to phenols, as well as used as good partners of cross-coupling reactions...
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230363/inhibition-and-stabilization-cucurbituril-induced-distinct-effects-on-the-schiff-base-reaction
#18
Wanjun Gong, Jun Ma, Zhiyong Zhao, Fang Gao, Feng Liang, Haijun Zhang, Simin Liu
The different effects of cucurbit[7]uril (CB[7]) on the Schiff base reactions in aqueous solution were explored by 1H NMR spectroscopy and single X-ray crystallography. With CB[7] the condensation reaction of aldehyde and primary amine is dramatically inhibited. In contrast the presence of CB[7] does tremendously stabilize iminium cation in water through ion-dipole interactions. A single crystal structure of the complex of iminium ion 7 with CB[7] grown in water is reported.
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230362/oxidation-of-%C3%AE-ketoamides-the-synthesis-of-vicinal-tricarbonyl-amides
#19
Yueyang Liu, Zhiguo Zhang, Yameng Wan, Guisheng Zhang, Zhonglian Li, Jingjing Bi, Nana Ma, Tong-Xin Liu, Qingfeng Liu
A facile and direct oxidative reaction for the synthesis of vicinal tricarbonyl amides (VTAs) in moderate to excellent yields (53%-88%) was developed starting from readily available β-ketoamides in the presence of phenyliodine(III) bis(trifluoroacetate) (PIFA). The resulting products possess significant synthetic potential, making this approach a valuable addition to the traditional methods already available for the preparation of these molecules.
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28229592/iodine-catalyzed-cross-dehydrogenative-coupling-reaction-sulfenylation-of-enaminones-using-dimethyl-sulfoxide-as-an-oxidant
#20
Yogesh Siddaraju, Kandikere Ramaiah Prabhu
Synthesis of polyfunctionalized aminothioalkenes has been demonstrated using iodine as a catalyst (30 mol%) and dimethyl sulfoxide as an oxidant under metal-free reaction conditions. This methodology enables a facile sulfenylation of enaminones with a broad range of heterocyclic thiols and thiones under cross dehydrogenative coupling methods. Besides, this strategy is highly practical as it employs inexpensive and readily available iodine and DMSO during short reaction time. The current methodology is one of the simplest methods and provides a straightforward approach for sulfenylation of enaminones under cross dehydrogenative coupling method...
February 23, 2017: Journal of Organic Chemistry
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