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Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/28098463/absolute-configuration-of-native-oligomeric-proanthocyanidins-with-dentin-biomodification-potency
#1
Joo-Won Nam, Rasika S Phansalkar, David C Lankin, James B McAlpine, Ariene A Leme-Kraus, Cristina M P Vidal, Li-She Gan, Ana Bedran-Russo, Shao-Nong Chen, Guido F Pauli
The structurally complex oligomeric proanthocyanidins (OPACs) are promising biomimetic agents, capable of strengthening the macromolecular backbone of teeth via intermolecular and intermicrofibrillar cross-linking. This study establishes analytical methods capable of determining the absolute configuration of the catechin-type monomeric units of underivatized OPACs. This preserves the capacity of their biological evaluation, aimed at understanding the inevitably stereospecific interactions between the OPACs and dentin collagen...
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28098462/total-synthesis-of-resolvin-d5
#2
Narihito Ogawa, Takuo Sugiyama, Masao Morita, Yuta Suganuma, Yuichi Kobayashi
Resolvin D5 (RvD5) is a metabolite of docosahexanoic acid with anti-inflammatory activity that has not yet been thoroughly investigated because of its low biological availability. A synthetic route to optically active RvD5 was developed by assembling the C1-C10 aldehyde, C11-C13 phosphonium salt, and C14-C22 aldehyde building blocks. The aldehyde fragments were prepared by Sharpless asymmetric epoxidation of corresponding racemic (E)-1-TMS-1-alken-3-ols followed by reaction of the TBS ethers of the resulting epoxy alcohols with Et2AlCN, and DIBAL reduction of the (E)-1-cyano-1-alken-3-ol derivatives...
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28098461/readily-accessible-unsymmetrical-unsaturated-2-6-diisopropylphenyl-n-heterocyclic-carbene-ligands-applications-in-enantioselective-catalysis
#3
Robert Tarrieu, Adrien Dumas, Jompol Thongpaen, Thomas Vives, Thierry Roisnel, Vincent Dorcet, Christophe Crévisy, Olivier Baslé, Marc Mauduit
A new multicomponent procedure was applied to the synthesis of (a)chiral bulky unsymmetrical unsaturated 2,6-diisopropylphenyl-N-heterocyclic carbene (NHC) precursors with excellent selectivity (up to 95%) and good yields. This approach offers access to new chiral NHCs ligands, which found successful applications in both copper-catalyzed asymmetric allylic alkylation and copper-catalyzed asymmetric borylation.
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28097867/selective-aza-diels-alder-and-domino-4-2-2-2-cycloaddition-reactions-of-arynes-with-n-sulfonyl-ketimines
#4
Indukuru Naga Chaithanya Kiran, Rekula Santhosh Reddy, Chandraiah Lagishetti, Huacheng Xu, Zhen Wang, Yun He
Transition-metal-free inverse electron-demand aza Diels-Alder and tandem [4+2]/[2+2] cycloaddition reaction of arynes and N-sulfonyl ketimines has been demonstrated. This novel, mild and efficient protocol allows rapid access to isothiazole dioxide fused dihydroquinoline or dihydrocyclobutaquinoline derivatives selectively by simply varying the equivalents of aryne precursors. The application of this method has been amply illustrated in the synthesis of 2,4-diarylquinolines.
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28055212/synthesis-of-benzimidazolones-via-one-pot-reaction-of-hydroxylamines-aldehydes-and-trimethylsilyl-cyanide-promoted-by-diacetoxyiodobenzene
#5
Huaiyuan Zhang, Danfeng Huang, Ke-Hu Wang, Jun Li, Yingpeng Su, Yulai Hu
A novel and efficient PhI(OAc)2-promoted one-pot reaction of aromatic hydroxylamines, aldehydes, and TMSCN in the presence of BF3·Et2O is described. A wide variety of N-substituted benzimidazolones are obtained with satisfactory yields under mild reaction conditions. The method was proven to be efficient for the synthesis of benzimidazolone derivatives from readily available starting materials.
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28055209/diastereoselective-synthesis-of-substituted-morpholines-from-n-tethered-alkenols-total-synthesis-of-%C3%A2-chelonin-a
#6
Madhurjya Borah, Upasana Borthakur, Anil K Saikia
Intramolecular cyclization of nitrogen tethered alkenols catalyzed by palladium chloride leads to substituted morpholines in good yields. The methodology was used for the total synthesis of (±)-chelonin A.
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28029790/cu-oac-2-catalyzed-aerobic-oxidative-dehydrogenation-coupling-synthesis-of-heptacyclic-quinolizino-3-4-5-6-kla-perimidines
#7
Bin-Bin Feng, Jian-Quan Liu, Xiang-Shan Wang
A Cu(OAc)2-catalyzed domino tricyclization between naphthalene-1,8-diamine and 2-(phenylethynyl)benzaldehyde is described, enabling aerobic oxidative dehydrogenation coupling to access heptacyclic quinolizino[3,4,5,6-kla]perimidines. In this reaction, the formation of three new rings and four new bonds was achieved in a functional-group-compatible fashion, allowing a facile method toward fused aza-heterocycles containing both quinolizine and perimidine moieties.
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28094968/computational-studies-on-reaction-mechanism-and-origins-of-selectivities-in-nickel-catalyzed-2-2-2-cycloadditions-and-alkenylative-cyclizations-of-1-6-ene-allenes-and-alkenes
#8
Tao Yang, Masahiro Ehara
The reaction mechanism and origins of ligand-controlled selectivity, regioselectivity, and stereoselectivity of Ni-catalyzed (2 + 2 + 2) cycloadditions and alkenylative cyclizations of 1,6-ene-allenes and alkenes were studied by using density functional theory. The catalytic cycle involves intermolecular oxidative coupling and intramolecular concerted 1,4-addition step to afford a stable metallacycloheptane intermediate; these steps determine both the regioselectivity and stereoselectivity. Subsequent C-C reductive elimination leads to the cyclohexane product, whereas the β-hydride elimination leads to the trans-diene product...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28094947/synthesis-of-2-azulenyltetrathiafulvalenes-by-palladium-catalyzed-direct-arylation-of-2-chloroazulenes-with-tetrathiafulvalene-and-their-optical-and-electrochemical-properties
#9
Taku Shoji, Takanori Araki, Shuhei Sugiyama, Akira Ohta, Ryuta Sekiguchi, Shunji Ito, Tetsuo Okujima, Kozo Toyota
Tetrathiafulvalene (TTF) derivatives with 2-azulenyl substituents 5-11 were prepared by the palladium-catalyzed direct cross-coupling reaction of 2-chloroazulenes with TTF in good yield. Photophysical properties of these compounds were investigated by UV-vis spectra and theoretical calculations. Redox behavior of the novel azulene-substituted TTFs was examined by using cyclic voltammetry and differential pulse voltammetry, which revealed their multistep electrochemical oxidation and/or reduction properties...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28094945/pdii-agi-catalyzed-room-temperature-reaction-of-gamma-hydroxy-lactams-mechanism-scope-and-antistaphylococcal-activity
#10
Manali Dutta, Santi M Mandal, Rupa Pegu, Sanjay Pratihar
The present work reports a PdII/AgI promoted amidoalkylation reaction involving various γ-hydroxy lactam and C/O/S nucleophile at room temperature. The dual mode of activation of both the electrophile and nucleophile by in-situ generated catalytically active cationic PdII species facilitate the reaction at room temperature. Amongst the synthesized isoindoline derivatives, three compounds are found to be active against vancomycin and methicillin resistant S. aureus strain with appreciable MIC value.
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28094944/solvent-directed-switch-of-a-left-handed-10-12-helix-into-a-right-handed-12-10-helix-in-mixed-beta-peptides
#11
Prashanth Thodupunuri, Sirisha Katukuri, Kallaganti V S Ramakrishna, Gangavaram V M Sharma, Ajit C Kunwar, Akella V S Sarma, Hans-Jörg Hofmann
Present study describes the synthesis and conformational analysis of β-peptides from C-linked carbo-β-amino acids [β-Caa(l)] with a D-lyxo furanoside side chain and β-hGly in 1:1 alternation. NMR and CD investigations on peptides with an (S)-β-Caa(l) monomer at the N-terminus revealed a right-handed 10/12-mixed helix. An unprecedented solvent-directed 'switch' both in helical pattern and handedness was observed when the sequence begins with a β-hGly residue instead of a (S)-β-Caa(l) constituent. NMR studies on these peptides in chloroform indicated a left-handed 10/12-helix, while the CD spectrum in methanol inferred a right-handed secondary structure...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28094943/exploitation-of-a-multienzymatic-stereoselective-cascade-process-in-the-synthesis-of-2-methyl-3-substituted-tetrahydrofurans-precursors
#12
Elisabetta Brenna, Michele Crotti, Francesco Gilberto Gatti, Ludovico Marinoni, Daniela Monti, Sara Quaiato
Enantiopure 2-methyl-3-substituted tetrahydrofurans are key precursors of several biologically active products (drugs, flavors and agrochemicals). Thus, a stereocontrolled and efficient methodology for the obtainment of these synthons is highly desirable. We exploited a two-steps multienzymatic stereoselective cascade reduction of α-bromo-α,β-unsaturated ketones to give the corresponding bromohydrins in good yields, with high ee and de values. The cascade process is catalyzed by an ene-reductase and an alcohol dehydrogenase...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28094530/unexpected-o-h-insertion-of-rhodium-azavinylcarbenes-with-n-acylhydrazones-divergent-synthesis-of-3-6-disubstituted-and-3-5-6-trisubstituted-1-2-4-triazines
#13
Jiang Meng, Min Wen, Shiwei Zhang, Peiwen Pan, Xingxin Yu, Wei-Ping Deng
A practical and efficient method for divergent synthesis of 3,6-disubstituted- and 3,5,6-trisubstituted-1,2,4-triazines via unexpected rhodium-catalyzed O-H insertion/rearrangement/conditions-controlled intramolecular cyclization and oxidation reaction under mild conditions has been developed. Notably, it is the first example for the synthesis of 1,2,4-triazines with different substituted-patterns via a common intermediate with excellent chemoselectivities by the reaction of N-acylhydrazones as aze-[3C] or [4C] synthons with N-sulfonyl-1,2,3-triazoles as aze-[2C] synthons...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28093913/synergistic-photoredox-nickel-coupling-of-acyl-chlorides-with-secondary-alkyltrifluoroborates-dialkyl-ketone-synthesis
#14
Javad Amani, Gary A Molander
Visible light photoredox/nickel dual catalysis has been employed in the cross-coupling of acyl chlorides with potassium alkyltrifluoroborates. This protocol, based on single-electron-mediated alkyl transfer, circumvents the restriction of using reactive alkylmetallic nucleophiles in transition-metal-catalyzed acylation and achieves a mild and efficient method for the synthesis of unsymmetrical alkyl ketones. In this approach, a variety of acyl chlorides have been successfully coupled with structurally diverse potassium alkyltrifluoroborates, generating the corresponding ketones with good yields...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28093912/an-alternative-route-towards-nitrones-experimental-and-theoretical-findings
#15
Damir A Safin, Mariusz P Mitoraj, Maria G Babashkina, Piotr Kubisiak, Koen Robeyns, Yaroslav Filinchuk
Nitrones are important building blocks for natural and biologically active compounds, used as spin-trap reagents and therapeutic agents. All this makes nitrones intriguing and valuable compounds for fundamental studies and as useful chemicals in various synthetic strategies. Therefore nitrones are still of great interest and in the limelight of researches. With our initial goal to solve synthetic problems towards 5-phenyl-2,2'-bipyridine (Phbpy), we found that this reaction can proceed through the formation of 6-phenyl-3-(pyridin-2-yl)-1,2,4-triazin-4(3H)-ol (4-OH), which rapidly isomerizes to a 3,4-dihydro-1,2,4-triazine-based nitrone, namely 6-phenyl-3-pyridin-2-yl-2,3-dihydro-1,2,4-triazin-4-oxide (4'), This encouraged us to study condensation of hydrazonophenylacetaldehyde oxime (2), obtained from 2-isonitrosoacetophenone (1), with other aldehydes...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28093910/structural-and-spectral-properties-of-photochromic-diarylethenes-the-size-effect-of-the-ethene-bridge
#16
Andrey G Lvov, Alexey M Kavun, Vadim V Kachala, Yulia V Nelyubina, Anatoly V Metelitsa, Valerii Z Shirinian
The effect of the size of the ethene bridge on the structural and spectral properties of photochromic diarylethenes, which remains a poorly understood phenomenon, was studied as applied to diarylethenes containing unsymmetrical (cyclohexenone and cyclopentenone) and symmetrical (cyclohexene and cyclopentene) ethene bridges. Thiophene, oxazole, and imidazole derivatives were used as aryl moieties. An increase in the size of the ethene bridge in the cycloalkenone series was found to be accompanied by a hypsochromic shift of the absorption maximum of the photoinduced form, whereas no difference was found for cycloalkenes...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28093908/thermal-ring-contraction-reactions-of-9-aryl-5h-7h-1-2-5-thiadiazolo-3-4-h-2-3-4-benzothiadiazepine-6-6-dioxides-experimental-and-computational-studies-for-understanding-the-course-of-the-transformations
#17
Ferenc Bertha, Tamas Kegl, József Fetter, Balázs Molnár, András Dancsó, Gábor Németh, Gyula Simig, Balázs Volk
When refluxing with sodium hydrogencarbonate in acetonitrile, 7-chloro-5-(4-fluorophenyl)-1,3-dihydro-2,3,4-benzothiadiazepine 2,2-dioxide afforded, after loss of dinitrogen and subsequent ring contraction, the corresponding sulfone in 83% yield. Similar treatment of the related thiadiazolo-fused tricycles, i.e. 9-aryl-5H,7H-[1,2,5]thiadiazolo[3,4-h][2,3,4]benzothiadiazepine 6,6-dioxides, resulted in a substantially different product mixture: formation of sultines and benzocyclobutenes was observed, while only small amounts of the sulfones were formed, if any...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28054777/free-radical-bromotrifluoromethylation-of-olefin-via-single-electron-oxidation-of-naso2cf3-by-nabro3
#18
Zhong-Quan Liu, Dong Liu
A free-radical bromotrifluoromethylation of olefin by using NaSO2CF3 and NaBrO3 has been achieved. Sodium bromate acts not only as a single-electron oxidant but also as a bromine source. A radical-clock experiment and electron-spin-resonance detection support a radical process.
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28034311/total-syntheses-of-%C3%A2-rhodonoids-a-and-b-and-c12-epi-rhodonoid-b
#19
Hao Wu, Richard P Hsung, Yu Tang
Total syntheses of (±)-rhodonoids A and B and C12-epi-rhodonoid B are described here. A unified strategy employed in these syntheses is an intramolecular oxa-[3 + 3] annulation for accessing the chromene unit. A Fe(OTf)3-promoted diastereoselective cationic [2 + 2] cycloaddition and a photochemical [2 + 2] cycloaddition were featured to construct the cyclobutane core of (±)-rhodonoids A and B and C12-epi-rhodonoid B, respectively. Fe(OTf)3 also leads to an interesting bridged tetracycle, which was unambiguously confirmed by single crystal X-ray analysis...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28092703/enantioselective-three-component-amination-of-enecarbamates-enables-the-synthesis-of-structurally-complex-small-molecules
#20
Audrey Dumoulin, Guillaume Bernadat, Géraldine Masson
The control of asymmetric synthesis tools represents a major challenge, especially when it comes to the synthesis of bioactive molecules. In this context, the asymmetric synthesis of 1,2-diamines through amination of enecarbamates has appeared to us as a highly efficient and tunable approach. Indeed, reactivity of the latter species could be exploited to realize a double functionalization via an electrophilic amination followed by nucleophilic trapping. Herein, we describe a chiral phosphoric acid-catalyzed electrophilic amination of enecarbamates with dibenzylazodicarboxylate and oxygenated or thiol-containing nucleophiles affording stable precursors of α-hydrazinoimines in high yields and with almost complete enantioselectivities (up to >99%)...
January 16, 2017: Journal of Organic Chemistry
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