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Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/29141145/homochiral-versus-heterochiral-trifluoromethylated-pseudoproline-containing-dipeptides-a-powerful-tool-to-switch-the-prolyl-amide-bond-conformation
#1
Grégory Chaume, Julien Simon, Nathalie Lensen, Julien Pytkowicz, Thierry Brigaud, Emeric Miclet
The design of constrained peptides is of prime importance in the development of bioactive compounds and for applications in supramolecular chemistry. Due to its nature, the peptide bond undergoes a spontaneous cis-trans isomerism and the cis isomers are much more difficult to stabilize than the trans forms. By using oxazolidine-based pseudoprolines (ΨPro) substituted by a trifluoromethyl group, we show that the cis peptide bond can be readily switched from 0% to 100% in Xaa-ΨPro dipeptides. Our results prove that changing the configuration of the Cα in Xaa or in ΨPro is sufficient to invert the cis:trans populations while changing the nature of the Xaa side chain finely tuned the conformers ratio...
November 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29141143/michael-michael-addition-reactions-promoted-by-secondary-amine-thiourea-stereocontrolled-construction-of-barbiturate-fused-tetrahydropyrano-scaffolds-and-pyranocoumarins
#2
Jing Zhang, Guohui Yin, Yuchao Du, Ziqi Yang, Yang Li, Ligong Chen
Bifunctional secondary amine-thiourea organocatalysts were successfully applied in the stereocontrolled synthesis of barbiturate fused tetrahydropyrano scaffold. As compared with the generally used tertiary amine-thiourea organocatalysts, they exhibited Bifunctional secondary amine-thiourea organocatalysts were successfully applied in the stereocontrolled synthesis of barbiturate-fused tetrahydropyrano scaffolds. Compared with typically used tertiary amine-thiourea organocatalysts, the developed catalysts exhibited excellent catalytic performance in the domino Michael-Michael reaction between N,N'-dimethylbarbituric acid and Morita-Baylis-Hillman acetates of nitroalkenes to yield pharmaceutically important heterocycles in good yields with excellent enantioselectivities...
November 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29141141/electronic-and-torsional-effects-on-hydrogen-atom-transfer-from-aliphatic-c-h-bonds-a-kinetic-evaluation-via-reaction-with-the-cumyloxyl-radical
#3
Michela Salamone, Teo Martin, Michela Milan, Miquel Costas, Massimo Bietti
A kinetic study on the HAT reactions from the aliphatic C-H bonds of a series of 1-Z-pentyl, 1-Z-propyl and Z-cyclohexyl derivatives, and of a series of N-alkylamides and N-alkylphthalimides to the electrophilic cumyloxyl radical (CumO•) has been carried out. With 1-pentyl and 1-propyl derivatives, α-CH2 activation towards CumO• is observed for Z = Ph, OH, NH2, NHAc, evidenced by an increase in kH as compared to the unsubstituted alkane substrate. A decrease in kH has been instead measured for Z = OAc, NPhth, CO2Me, Cl, Br, CN, indicative of α-CH2 deactivation with HAT that predominantly occurs from the most remote methylenic site...
November 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29140703/synthesis-of-2s-2-chloro-2-fluoro-ribolactone-via-stereoselective-electrophilic-fluorination
#4
Coralie De Schutter, Ozkan Sari, Steven J Coats, Franck Amblard, Raymond Felix Schinazi
A novel and efficient route for the preparation of (2S)-2-chloro-2-fluoro lactone 29 is described. This approach takes advantage of a highly efficient diastereoselective electrophilic fluorination reaction (94% yield; >50:1 dr).
November 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29139295/synthesis-of-aminobenzopyranoxanthenes-with-nitrogen-containing-fused-rings
#5
Natsumi Fukino, Shinichiro Kamino, Minami Takahashi, Daisuke Sawada
An efficient and practical method for the synthesis of a variety of aminobenzopyranoxanthenes (ABPXs) with different nitrogen-containing fused rings was developed. Based on mechanistic studies of the formation of the xanthene framework, the presented methodology was developed and facilitates access to previously inaccessible asymmetric ABPXs.
November 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29139289/tetraaza-14-and-octaaza-18-paracyclophane-synthesis-and-characterization-of-their-neutral-and-cationic-states
#6
Daisuke Sakamaki, Akihiro Ito, Yusuke Tsutsui, Shu Seki
Two kinds of aza[1n]paracyclophanes, tetraaza[14]paracyclophane (P4) and octaaza[18]paracyclophane (P8), were synthesized as the smallest and the largest monodisperse macrocyclic oligomers of polyaniline ever made. Herein we reports the electronic nature of the cationic species of these two macrocycles with different ring-size. By combining ESR spectroscopy and DFT calculations, it was suggested that P4·+ was classified into delocalized class III or poised on the class II/III borderline, while P8·+ was regarded as localized class II mixed-valence system...
November 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29087195/ruthenium-catalyzed-c-h-benzoxylation-of-tert-benzamides-with-aromatic-acids-by-weak-coordination
#7
Nagnath Yadav More, Kishor Padala, Masilamani Jeganmohan
A highly regioselective C-H benzoxylation of tertiary benzamides with aromatic acids by weak O-amide coordination in the presence of [{RuCl2(p-cymene)}2], AgSbF6, and (NH4)2S2O8 in 1,2-dichloroethane at 100 °C for 24 h to afford ortho-benzoxylated tertiary benzamides is described. Selectively, ortho-benzoxylated cyclic benzamides were converted into ortho-benzoxylated benzaldehydes by using Cp2ZrHCl at room temperature. Subsequently, substituted salicylic acids were prepared by deprotection of the ester and amide groups of ortho-benzoxylated cyclic benzamides...
November 15, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29136463/benzo-b-thiophene-fusion-enhances-local-borepin-aromaticity-in-polycyclic-heteroaromatic-compounds
#8
Reid E Messersmith, Sangeeta Yadav, Maxime A Siegler, Henrik Ottosson, John D Tovar
This report documents the synthesis, characterization and computational evaluation of two isomeric borepin-containing polycyclic aromatics. The syntheses of these two isomers involved symmetrical disubstituted alkynes that were reduced to Z-olefins followed by borepin formation either through an isolable stannocycle intermediate or directly from the alkene via the trapping of a transient dilithio intermediate. Comparisons of their magnetic, crystallographic and computational characterization to literature compounds gave valuable insights about the aromaticity of these symmetrically fused [b,f]borepins...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29136376/mn-oac-3-promoted-oxidative-csp3-p-bond-formation-through-csp2-csp2-and-p-h-bond-cleavage-access-to-%C3%AE-ketophosphonates
#9
Pan Zhou, Biao Hu, Lingdan Li, Kairui Rao, Jiao Yang, Fuchao Yu
The Mn(OAc)3-promoted oxidative phosphonylation of N,N-dimethylenaminones with H-phosphonates, involving a chemo- and regioselective Csp2-Csp2 bond cleavage and Csp3-P bond formation in one step, provid successfully functionalized β-ketophosphonates under mild reaction conditions. Oxidative Csp3-H/P-H cross-coupling reactions via Csp3-C(C=O) bond cleavage and mechanistic studies are conducted preliminarily, and a possible mechanism is proposed. This novel method proceeds in good to excellent yields, shows operational simplicity, broad substrate scope and large-scale preparation...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29135249/photoreductive-removal-of-o-benzyl-groups-from-oxyarene-n-heterocycles-assisted-by-o-pyridine-pyridone-tautomerism
#10
Aleksandar R Todorov, Tom Wirtanen, Juho Helaja
Facile photoreductive protocols have been developed to remove benzyl O-protective groups from oxyarene N-heterocycles at positions capable for 2-/4-O-pyridine - 2-/4-pyridone tautomerism. Blue light irradiation, a [Ru] or [Ir] photocatalyst and ascorbic acid in a water-acetonitrile solution debenzylates a variety of aryl N-heterocycles cleanly and selectively. Ascorbic acid has two functions in the reaction. On the one hand, it protonates the N-heterocycles that reduces their reduction potentials notably and on the hand it acts as a sacrificial reductant...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29135247/divergent-synthesis-of-porous-tetraphenylmethane-dendrimers
#11
Julio Ignacio Urzúa, Mercedes Torneiro
Tetraphenylmethane-ethynylene-based shape-persistent dendrimers are new class of nanoobjects with an intriguing 3D architecture. We report an efficient divergent strategy for their synthesis based on the Sonogashira Pd-catalyzed coupling of terminal alkynes with aryl iodides. As repeat unit, we prepared a tetraphenylmethane derivative bearing a terminal alkyne and three triazene moieties. Coupling of this building block to tetrakis(p-iodophenyl)methane afforded, after triazene activation, a dodecaiodo-terminated first generation dendrimer, which was transformed by another Sonogashira coupling into a methoxy-terminated second generation dendrimer with persistent globular shape and well-defined cavities...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29135242/computational-study-on-%C3%AE-c-h-functionalization-of-%C3%AE-%C3%AE-unsaturated-ester-catalyzed-by-n-heterocyclic-carbene-mechanisms-origin-of-stereoselectivity-and-role-of-catalyst
#12
Yang Wang, Donghui Wei, Mingsheng Tang
The N-heterocyclic carbene (NHC)-catalyzed γ-C-H deprotonation/functionalization of α,β-unsaturated esters with hydrazones leading to the δ-lactams has been theoretically investigated by using the density functional theory. Three possible reaction mechanisms including Mechanism A, for which the NHC catalyst serves as a nucleophilic catalyst to attack on the carbonyl carbon atom to initiate the reaction, for Mechanism B, in which NHC triggers the reaction through the hydrogen bond, and Mechanism C is the direct deprotonation/functionalization process without the presence of NHC have been suggested and studied in detail...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29134811/synthetic-utility-of-arylmethylsulfones-annulative-%C3%AF-extension-of-aromatics-and-hetero-aromatics-involving-pd-0-catalyzed-heck-coupling-reactions
#13
Elumalai Sankar, Potharaju Raju, Jayachandran Karunakaran, Arasambattu Kannan Mohanakrishnan
A straightforward and general method for synthesis of annulated thiophene, dibenzothiophene and carbazoles analogues have been achieved involving alkylation of 2-bromo-1-(phenylsulfonylmethyl)arene/heteroarene with arylmethylbromides/heteroarylmethylbromides using t-BuOK as a base in DMF followed by Pd(0)-mediated intramolecular Heck coupling in the presence of K2CO3 in DMF at 80-140 degrees C. The attractive feature of this protocol is that a wide variety of π-conjugated heterocycles could be readily accessed by an appropriate choice of arylmethyl sulfones and benzylic bromides...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29134810/c-h-bond-functionalization-of-tetrahydropyridopyrimidines-and-other-related-hetereocycles
#14
Zhanling Cheng, Zhiliang Yu, Song Yang, Hong C Shen, Weili Zhao, Sheng Zhong
A novel and efficient 2-step method for the functionalization of the C-H bond adjacent to the amino group as well as the heteroaryl group of tetrahydropyridopyrimidine (THPP) was reported herein. The reaction features mild conditions and excellent tolerance of a wide range of functional groups. Moreover, this method is applicable to tetrahydroisoquinolone (THIQ) which provides a useful supplement to literature method. This method gives chemist a new tool to functionalize a C-H bond at late stage and may find applications in both synthetic organic and medicinal chemistry...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29134809/ru-ii-catalyzed-c-h-amidation-of-indoline-at-the-c7-position-using-dioxazolone-as-an-amidating-agent-synthesis-of-7-amino-indoline-scaffold
#15
Akshay Ekanath Hande, Kandikere Ramaiah Prabhu
Ru(II)-Catalyzed C-H amidation of indoline at the C-7 position en route for synthesizing 7-amino indole scaffold has been achieved using dioxazolone, which is an environmentally benign amidating reagent. This protocol paves the way for synthesizing a variety of 7-amino indole derivatives in excellent yields at ambient reaction conditions. The readily cleavable amide group has been utilized as a directing group for the amidation. The derivatives of 7-amino indole are synthetically useful for accessing a variety of natural products, drug molecules, and biologically active compounds...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29134806/acid-catalyzed-skeletal-rearrangements-in-arenes-aryl-vs-alkyl-ring-pirouettes-in-anthracene-and-phenanthrene
#16
Sarah L Skraba-Joiner, Jeffrey W Brulet, Min K Song, Richard P Johnson
In 1 M triflic acid/dichloroethane, anthracene is completely protonated at C9 and the resulting 9-anthracenium ion is easily observed at ambient temperature. When heated at > 84 °C as a dilute (10-3 M) solution in 1 M triflic acid/dichloroethane (DCE), anthracene undergoes conversion to phenanthrene as the major volatile product. Minor dihydro and tetrahydro products are also observed. MALDI analysis supports the simultaneous formation of oligomers, primarily dimeric, which represent 10 - 60% of the product mixture...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29132210/organocatalytic-visible-light-enabled-snar-of-heterocyclic-thiols-a-metal-free-approach-to-2-aminobenzoxazoles-and-4-aminoquinazolines
#17
Eakkaphon Rattanangkool, Mongkol Sukwattanasinitt, Sumrit Wacharasindhu
The direct amination reaction of heterocyclic thiols has been developed in the presence of the nonhazardous photocatalyst Rose Bengal under irradiation of visible light. The reaction provides a straightforward approach to pharmaceutically and synthetically useful to 2-aminobenzoxazole and 4-aminoquinazoline derivatives from the corresponding heterocyclic thiols with amines in good to excellent yields. Our photochemical reaction can be successfully adapted into continuous flow reactor which is applicable for large scale chemical industry...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29096432/asymmetric-net-cycloaddition-for-access-to-diverse-substituted-1-5-benzothiazepines
#18
Yukihiro Fukata, Koichi Yao, Ryota Miyaji, Keisuke Asano, Seijiro Matsubara
In this study, the isothiourea-catalyzed enantioselective formal [4+3] cycloaddition of various α,β-unsaturated carboxylic acid derivatives with 2-aminothiophenols was developed. Mechanistic studies suggested that the reaction proceeds via a reversible sulfa-Michael addition to α,β-unsaturated acylammonium intermediates, followed by the enantioselective formation of a seven-membered ring, enabling the facile and divergent synthesis of optically active 2- and 3-substituted 1,5-benzothiazepines. This process was demonstrated to be highly versatile, affording the corresponding products in excellent regioselectivities and high enantioselectivities...
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29094946/bimetallic-cobalt-rhodium-nanoparticle-catalyzed-reductive-amination-of-aldehydes-with-nitroarenes-under-atmospheric-hydrogen
#19
Isaac Choi, Supill Chun, Young Keun Chung
A cobalt-rhodium heterobimetallic nanoparticle (Co2Rh2/C)-catalyzed tandem reductive amination of aldehydes with nitroaromatics to sec-amines has been developed. The tandem reaction proceeds without any additives under mild conditions (1 atm H2 and 25 °C). This procedure can be scaled up to the gram scale, and the catalyst can be reused more than six times without loss of activity.
November 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29092395/metal-free-blue-dye-synthesis-oxidative-coupling-of-benzylamines-and-n-n-dimethylanilines-to-yield-4-4-diaminotriarylmethanes-in-the-presence-of-salicylic-acid-as-a-co-oxidant
#20
Chun-Ping Dong, Shintaro Kodama, Akinori Uematsu, Akihiro Nomoto, Michio Ueshima, Akiya Ogawa
A convenient, novel, and metal-free method for the synthesis of 4,4'-diaminotriarylmethanes (DTMs) is described. This process is based on a one-pot condensation of benzylamines with N,N-dimethylaniline derivatives using 4,6-dihydroxysalicylic acid as a co-oxidant and N-iodosuccinimide as an oxidant. To the best of our knowledge, the present method provides the first reported synthesis of DTMs from benzylamines via oxidative C-N bond cleavage and subsequent double C-C bond formations. The obtained DTMs were then easily converted into a series of blue dyes upon treatment with tetrachloro-1,4-benzoquinone (chloranil)...
November 14, 2017: Journal of Organic Chemistry
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