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Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/30005575/uva-and-visible-light-mediated-generation-of-carbon-radicals-from-organochlorides-using-non-metal-photocatalyst
#1
Ryosuke Matsubara, Tatsushi Yabuta, Ubaidah Md Idros, Masahiko Hayashi, Fumitoshi Ema, Yasuhiro Kobori, Ken Sakata
Carbon radicals are reactive species useful in various organic transformations. The C-X bond cleavage of organohalides by photo-irradiation is a common method to generate carbon radicals in a controlled fashion. The use of organochloride substrates is still a formidable challenge due to the low reduction potential and the high dissociation energy of the C-Cl bond. In this report, we address these issues by using a non-metal organic molecule with a relatively simple structure as a photocatalyst. In this catalyst (bis(dimethylamino)carbazole), the amino groups increase both the HOMO and LUMO energy levels, especially in the former...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30005572/cooperation-of-the-neutral-and-the-cationic-leaving-group-pathways-in-acid-catalyzed-o-benzylation-of-tribot
#2
Hikaru Fujita, Naoko Hayakawa, Munetaka Kunishima
The reaction profile of acid-catalyzed O-benzylation with 2,4,6-tris(benzyloxy)-1,3,5-triazine (TriBOT) was analyzed to study the reaction kinetics. The first-order kinetic constant for the formation of benzyl cation species from N-protonated TriBOT (neutral leaving group pathway) was estimated and compared with that of the model compound for TriBOT. Since rapid consumption of TriBOT in the late stage could not be explained solely by this pathway, cooperation of another reaction mechanism, the cationic leaving group pathway, was proposed to rationalize the rate acceleration...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30005167/mechanistical-insights-into-the-bioconjugation-reaction-of-triazolinediones-with-tyrosine
#3
Dustin Kaiser, Johan M Winne, Maria Elena Ortiz-Soto, Juergen Seibel, Thien Anh Le, Bernd Engels
The bioconjugation at tyrosine residues using cyclic diazodicarboxamides, especially 4-substituted-3H-1,2,4-triazole-3,5(4H)-dione (PTAD), is a highly enabling synthetic reaction because it can be employed for orthogonal and site-selective (multi)functionalizations of native peptides and proteins. Despite its importance, the underlying mechanisms have not been thoroughly investigated. The reaction can proceed along four distinctive pathways: (i) the SEAr path, (ii) along a pericyclic group transfer pathway (a classical ene-reaction), (iii) along a step-wise reaction path, or (iv) along an unusual higher order concerted pericyclic mechanism...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30005155/diversity-oriented-approach-towards-the-syntheses-of-amaryllidaceae-alkaloids-via-a-common-chiral-synthon
#4
Prachi Verma, Atish Chandra, Ganesh Pandey
Functionalized hydroindole (1), a common chiral synthon, for versatile transformations to synthesize broad range of amaryllidaceae alkaloids (AA) including (-)-crinine, (-)-crinane, (-)-amabiline, (+)-mesembrine, (-)-maritidine, (-)-oxomaritidine and (+)-mesembrane is reported. Scaffold 1 is found as a prime structural motif in a wide variety of the AA's and is a novel synthon towards designing a divergent route for the synthesis of these natural products. This is established in a few steps, starting from a chiral aza-bicyclo-heptene sulfone scaffold (2) via conjugate addition and concomitant stereoselective ring opening with allyl magnesium bromide, a key step that generates a crucial quaternary stereocentre, fixing the stereochemistry of the rest of the molecule at an early stage...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004702/reactions-of-n-heterocyclic-carbene-boranes-with-5-diazo-2-2-dimethyl-1-3-dioxane-4-6-dione-synthesis-of-mono-and-bis-hydrazonyl-nhc-boranes
#5
Wen Dai, Steven J Geib, Dennis P Curran
N-Heterocyclic carbene boranes (NHC-boranes) react with 5-diazo-2,2-dimethyl-1,3-dioxane-4,6-dione at 40 degrees C in dichloromethane to provide NHC-boryl hydrazone derivatives of 2,2-dimethyl-1,3-dioxane-4,6-dione. These hydrazones disproportionate to bis-hydrazones on treatment with diiodine in dichloromethane at room temperature. The mono- and bis-hydrazones are yellow solids that are stable to chromatography and storage.
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004701/correction-to-synthesis-of-2-acylindoles-via-ag-and-cu-catalyzed-anti-michael-hydroamination-of-%C3%AE-2-aminophenyl-%C3%AE-%C3%AE-ynones-experimental-results-and-dft-calculations
#6
Navnath D Rode, Issam Abdalghani, Antonio Arcadi, Massimiliano Aschi, Marco Chiarini, Fabio Marinelli
No abstract text is available yet for this article.
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004700/degradation-of-sulfur-mustard-hd-on-kf-al2o3-the-role-of-organic-solvents-and-active-species
#7
Gil Fridkin, Ishay Columbus, Lea Yehezkel, Yossi Zafrani
Solvent effects on the ability of KF/Al2O3 supports to degrade the warfare agent sulfur mustard (HD) were explored. RP-KF/Al2O3 possessing hydroxide ions and ECUF/KF/Al2O3 holding fluoride ions, were examined. Reactions on RP-KF/Al2O3 containing 10 wt % of organic solvents were faster than those on ECUF/KF/Al2O3. Additionally, RP-KF/Al2O3 led to elimination products while ECUF/KF/Al2O3 mainly to substitution derivatives. Enlarging the solvent amounts to 90 wt % resulted in decreased reaction rates. The significance of solvent identity/amount and active species are discussed...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004232/reactions-of-3-3-3-trihalogeno-1-nitropropenes-with-arenes-in-the-superacid-cf3so3h-synthesis-of-z-3-3-3-trihalogeno-1-2-diarylpropan-1-one-oximes-and-study-on-the-reaction-mechanism
#8
Andrei A Golushko, Maria A Sandzhieva, Alexander Yu Ivanov, Irina A Boyarskaya, Olesya V Khoroshilova, Alexey Yu Barkov, Aleksander Viktorovich Vasilyev
3,3,3-Trihalogeno-1-nitropropenes C(Hal3)CH=CH(NO2) (Hal = F, Cl, Br) in reaction with arenes in the superacid CF3SO3H (TfOH) at room temperature in 1 h afford 3,3,3-trihalogeno-1,2-diarylpropan-1-one oximes C(Hal3)CH(Ar)-C(Ar)=NOH (CHal3-oximes) in yields of 23-99%. Such CHal3-oximes having one ortho-substituent in aryl ring exist as atropoisomers in solutions at room temperature. Several cationic intermediates of this reaction were studied by means of NMR and DFT calculations, that proves the detailed reaction mechanism of the formation of CHal3-oximes in TfOH...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004231/enantioselective-synthesis-of-2-aminomethyl-and-3-amino-pyrrolidines-and-piperidines-through-1-2-diamination-of-aldehydes
#9
Anas Ansari, Ramesh Ramapanicker
An efficient method for the synthesis of 1,2-diamines from aldehydes through proline-catalyzed asymmetric α-amination followed by reductive amination is reported. The products resemble those obtained through direct asymmetric diamination of terminal alkenes. The methodology is used to synthesize 2-aminomethyl and 3-amino pyrrolidines and piperidines in high yields and with good enantioselectivity. The usefulness of the method is demonstrated through the synthesis of a 2-aminomethyl iminocyclitol.
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004228/access-to-highly-enantioenriched-donepezil-like-1-4-dihydropyridines-as-promising-anti-alzheimer-prodrug-candidates-via-enantioselective-tsuji-allylation-and-organocatalytic-aza-ene-type-domino-reactions
#10
Mihaela-Liliana Tintas, Rabah Azzouz, Ludovic Peauger, Vincent Gembus, Emilie Petit, Laetitia Bailly, Cyril Papamicaël, Vincent Levacher
This work aims at exploiting both the enantioselective Tsuji allylation of allyl carbonate 6 and an organocatalytic aza-ene-type domino reaction between enal 3a and β-enaminone 4a to develop a straightforward access to all of the four possible stereoisomers of a donepezil-like 1,4-dihydropyridine 1a (er up to 99.5:0.5; overall yield up 64%); an anti-Alzheimer prodrug candidate. This strategy was extended to the preparation of other enantioenriched 1,4-dihydropyridines 1b-i (8 examples), highlighting its potential in the development of these chiral AChE inhibitors...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004225/chemical-resolution-of-c-n-unprotected-%C3%AE-substituted-%C3%AE-amino-acids-using-stable-and-recyclable-proline-derived-chiral-ligands
#11
Shuni Wang, Yong Nian, Shengbin Zhou, Jiang Wang, Hong Liu
We report the first purely chemical method for the resolution of C,N-unprotected racemic α-substituted-β-amino acids (β2-AAs) using thermodynamically stable and recyclable chiral proline-derived ligands. The ligands and racemic β2-AAs along with Ni(II) could form a pair of Ni(II) complex diastereoisomers with desirable diastereoselectivity (dr up to 91:9). Enantiomerically pure C,N-unprotected β2-AAs could be obtained by simple hydrolysis of isolated favored-Ni(II) complex. The method featured unique versatility compared with enzymatic approaches, and characterized by its broad synthetic generality, good stereochemical outcome and mild reaction conditions, thus making it a powerful supplement in the field of chemical resolution of β2-AAs...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30004223/synthesis-of-chiral-cis-cyclopropane-bearing-indole-and-chromone-as-potential-tnf%C3%AE-inhibitors
#12
Ryutaro Kanada, Makoto Tanabe, Ryuta Muromoto, Yukina Sato, Tomoki Kuwahara, Hayato Fukuda, Mitsuhiro Arisawa, Tadashi Matsuda, Mizuki Watanabe, Satoshi Shuto
Conformationally-restricted analogues of SPD-304, the first small-molecule TNFα inhibitor, in which two heteroaryl groups, indole and chromone, are connected by chiral methyl- or ethyl-cis-cyclopropane, were designed. Synthesis of these molecules was achieved via Suzuki-Miyaura or Stille coupling reactions with chiral bromomethylenecyclopropane or iodovinyl-cis-cyclopropane as the substrate, both of which were prepared from chiral methylenecyclopropane as a common intermediate, constructing the heteroaryl-methyl or -ethyl-cis- cyclopropane structures as key steps...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30003784/attractive-nonbonded-interactions-help-stabilize-the-z-form-of-alkenyl-anions
#13
Benjamin G Janesko, Hector Villegas
Alkenyl anions ((-)H2C-CH=CH-Y, Y=aliphatic, aromatic, amine, ether) are often thermodynamically stable in the sterically congested Z form. This preference for Z structures is used to control regiochemistry in organometallic and Grignard reactions, allyl amine rearrangements to enamines, and allyl ether rearrangements to enol ethers. Explanations for Z stability in alkenes (Y=CH2R) typically invoke through-space attraction (Coulomb or charge transfer) between the formally anionic carbon C1 and the Y=CH2R hydrogens...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30003773/strategies-setbacks-and-successes-in-the-synthesis-of-spiroleucettadine
#14
Richard A Lamb, Nigel T Lucas, Guillaume Lessene, Bill Corey Hawkins
Various strategies toward the synthesis of the marine natural product (-)-spiroleucettadine are described. In the original strategy, a biomimetic inspired oxidation of a 2-imidazoline scaffold uncovered unexpected reactivity, where benzylic oxidation followed by a Baeyer-Villiger was observed. The second generation approach examined oxidative dearomatization of the phenol ring system first, where a competing spirocyclization process was uncovered. Efforts to forge the scaffold via a carbocation mediated benzyl migration were unsuccessful...
July 13, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30001484/oxidopyrylium-alkene-5-2-cycloaddition-conjugate-addition-cascade-c-3-sequences-scope-limitation-and-computational-investigations
#15
Riley H Kaufman, Chunyin Marshall Law, Justin A Simanis, Erica L Woodall, Christian R Zwick, Henry B Wedler, Paul Wendelboe, Christopher G Hamaker, John R Goodell, Dean J Tantillo, T Andrew Mitchell
Oxidopyrylium-alkene [5 + 2] cycloaddition conjugate addition cascade (C3 ) sequences are described. Intramolecular cycloadditions involving terminal alkenes, enals, and enones were investigated. Substrates with tethers of varying lengths delivered five- and six-membered carbocycles and heterocycles thus demonstrating the scope and limitation of the cycloaddition-conjugate addition cascade. Several experiments and theoretical calculations provide evidence for the proposed mechanistic pathway.
July 12, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29999313/copper-catalyzed-cascade-synthesis-of-2-aryl-3-cyanobenzofuran-and-dibenzo-b-f-oxepine-10-carbonitrile-derivatives
#16
Bharath Kumar Villuri, Sachin S Ichake, Sabbasani Rajasekhara Reddy, Veerababurao Kavala, Vijayalakshmi Bandi, Chun-Wei Kuo, Ching-Fa Yao
The copper catalyzed reaction of aryl aldehydes with 2-iodobenzylcyanides afforded 2-aryl-3-cyanobenzofurans in isolated yields of up to 74% in a cascade manner, which involves Knoevenagel condensation, aryl hydroxylation, oxa-Michael addition and aromatization reactions. Conversely, 2-halo benzaldehydes as reacting partners with 2-iodobenzylcyanide furnished regi-oselectively dibenzo[b,f]oxepine-10-carbonitrile derivatives up to 85% isolated yields via tandem Knoevenagel condensation, aryl hydroxylation and Ullmann coupling reactions...
July 12, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29998734/a-synthesis-of-cytisine-using-a-6-endo-aza-michael-addition
#17
Viktor Barat, Daniel Csokas, Roderick Wayland Bates
An asymmetric synthesis of (-)-cytisine has been achieved. The piperidine C-ring was formed using a stereodivergent intramolecular 6-endo aza-Michael addition. The B-ring was established by intramolecular pyridine N-alkylation. The absolute stereochemistry was established by an Evans acyl oxazolidinone enolate alkylation reaction that proceeded with an unexpected stereochemical outcome due to participation of the pyridine nitrogen lone pair.
July 12, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29995406/carbene-catalyzed-tandem-1-2-phospha-brook-1-4-phosphate-rearrangement-access-to-%C3%AE-ketophosphates-via-controlled-cross-acyloin-condensation
#18
Ram Subhawan Verma, Chandra Bhan Pandey, Shailesh Kumar, Bhoopendra Tiwari
The first N-Heterocyclic Carbene (NHC)-organocatalytic tandem [1,2]-phospha-Brook/[1,4]-phosphate rearrangement is reported. Acyl phosphonates, unlike acyl silanes that are well exploited, make entry as the acyl anion precursors under NHC-catalysis. The reactions proceed with absolute chemoselectivity via cross-acyloin condensation between acyl phos-phonates and aldehydes giving the products α-ketophosphates in good to excellent yield. The challenging (enolizable) ali-phatic-aliphatic substrates coupling also furnished the desired product in good yield...
July 11, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29993248/organocatalytic-asymmetric-synthesis-of-3-3-pyrrolidinyl-bispirooxindoles-via-michael-n-hemiketalization-cascade-reaction-between-3-aminooxindoles-and-isatin-derived-%C3%AE-%C3%AE-unsaturated-%C3%AE-keto-esters
#19
Ye Lin, Bo-Liang Zhao, Da-Ming Du
A novel strategy for construction of 3,3'-pyrrolidinyl-bispirooxindoles through Michael/N-hemiketalization cascade reaction of 3-aminooxindoles and isatin-derived β,γ-unsaturated α-keto esters was developed. Under mild conditions, a series of 3,3'-pyrrolidinyl-bispirooxindoles were obtained in moderate to good yields with high diastereo- and enantioselectivities by using cinchona-derived bifunctional squaramide organocatalyst. This work represents the first example using the 3-aminooxindoles for the construction of 3,3'-pyrrolidinyl-bispirooxindoles...
July 11, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29993245/agsbf6-mediated-selective-thiolation-and-selenylation-at-c-4-position-of-isoquinolin-1-2h-ones
#20
You-Quan Zhu, Jing-Li He, Yun-Xia Niu, Hui-Ying Kang, Ting-Feng Han, Hao-Yu Li
A new and facile AgSbF6-mediated protocol for the construction of C-4 thiolated or selenylated isoquinolin-1(2H)-ones via a radical pathway was established. This reaction proceeded efficiently with excellent regioselectivity, a broad range substrate scope and good functional group tolerance. A radical reaction mechanism involving thiyl radicals as key intermediates is proposed for the present transformation.
July 11, 2018: Journal of Organic Chemistry
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