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Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/29350934/a-molecular-electron-density-theory-study-of-the-reactivity-and-selectivities-in-3-2-cycloaddition-reactions-of-c-n-dialkyl-nitrones-with-ethylene-derivatives
#1
Luis R Domingo, Mar Ríos-Gutiérrez, Patricia Pérez
The zw-type [3+2] cycloaddition (32CA) reactions of C,N-dialkyl nitrones with a series of ethylenes of increased electrophilic character have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. Both, reactivity and selectivities are rationalised depending on the polar character of the reaction. Due to the strong nucleophilic character of C,N-dialkyl nitrones, the corresponding zw-type 32CA reactions are accelerated with the increased electrophilic character of the ethylene, which also plays a crucial role in the reaction mechanism, thus determining the regio- and stereoselectivities experimentally observed...
January 19, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29350930/curtin-hammett-driven-intramolecular-cyclization-of-heteroenyne-allenes-to-phenanthridine-fused-quinazoliniminiums
#2
Pamela S Filby, Sundeep Rayat
Intramolecular cyclization of the heteroenyne-allene, 2-((biphenyl-2-ylimino)methyleneamino)benzonitrile 1 to phenanthridine-fused quinazoliniminium salt PQ in the presence of a Lewis acid at room temperature involves formation of two new bonds: a C-C bond and a C-N bond. In this article, density functional theory (B3LYP and M06-2X) was employed in conjunction with 6-311G* basis set to gain insights into the mechanism of this cyclization reaction. The solvent effects were considered using Polarizable Continuum Model with nitromethane as the solvent...
January 19, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29350923/casscf-calculations-reveal-competitive-chair-pericyclic-and-boat-pseudopericyclic-transition-states-for-the-3-3-sigmatropic-rearrangement-of-allyl-esters
#3
Henry W Kreiman, Mackenzie E Batali, Cooper Jamieson, Molly A Lyon, James Alan Duncan
(10,8)CASPT2/6-31G**//(10,8)CASSCF/6-31G** calculations have been performed on the potential surface for the [3,3] sigmatropic allyl ester rearrangements of cis-3-penten-2-yl acetate (16) to trans-3-penten-2-yl acetate (17) and 3-buten-2-yl acetate (21) to trans-2-buten-1-yl acetate (22). The results are compared to DFT (B3LYP/6-31G**) calculations on the known 16→17 rearrangement that reported it to be concerted and pseudopericyclic through a boat-shaped transition structure (Birney, D. M. et al. J. Am. Chem...
January 19, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29350915/dichloroimidazolidinedione-activated-beckmann-rearrangement-of-ketoximes-for-accessing-amides-and-lactams
#4
Yu Gao, Jingjing Liu, Zhenjiang Li, Tianfo Guo, Songquan Xu, Hui Zhu, Fulan Wei, Siming Chen, Hailemariam Gebru, Kai Guo
A novel protocol for the activation of Beckmann rearrangement utilizing the readily available and economical geminal dichloroimidazolidinediones (DCIDs) on a substoichiometric scale (10 mol%) has been developed. A unique self-propagating mechanism for substoichiometric dichloroimidazolidinedione-activated transformation was proposed and validated. The substrate scope of the developed protocol has been demonstrated by 23 examples with good to excellent yields (mostly 90-98%) in a short time (mostly 10-30 min), including a substrate for synthesizing monomer of nylon-12 and a complicated steroidal substrate on a preparative scale...
January 19, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29345936/copper-catalyzed-one-pot-cross-dehydrogenative-thienannulation-chemoselective-access-to-naphtho-2-1-b-thiophene-4-5-diones-and-subsequent-transformation-to-benzo-a-thieno-3-2-c-phenazines
#5
Gaurav Shukla, Abhijeet Srivastava, Dhananjay Yadav, Maya Shankar Singh
A facile, cost-effective and highly efficient copper-catalyzed, TEMPO-mediated straightforward synthesis of 2,3-disubstituted naphtho[2,1-b]thiophene-4,5-diones has been achieved via Cross-Dehydrogenative Thienannulation (CDT). The reaction proceeded via in situ generated naphthalene-1,2-diones by dearomatization of β-naphthols, followed by oxidative heteroannulation with α-enolic dithioesters chemoselectively in an open-flask. Further, the naphtho[2,1-b]thiophene-4,5-diones undergo L-Proline-catalyzed cross-dehydrative coupling with ortho-phenylenediamine enabling pentacyclic benzo[a]thieno[3,2-c]phenazines in good yields under solvent-free conditions...
January 18, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29345935/rhodium-catalyzed-asymmetric-2-2-2-cycloaddition-of-unsymmetrical-%C3%AE-%C3%AF-diynes-with-acenaphthylene
#6
Yukimasa Aida, Yu Shibata, Ken Tanaka
It has been established that a cationic rhodium(I)/(R)-BINAP complex catalyzes the asymmetric [2+2+2] cycloaddition of unsymmetrical α,ω-diynes with acenaphthylene at room temperature to give the corresponding chiral multicyclic compounds with high yields and ee values. Interestingly, enantioselectivity highly depended on the structures of α,ω-diynes used. The structural requirements of α,ω-diynes for high enantioselectivity were opposite to those in our previously reported cationic rhodium(I)/(R)-Difluorphos complex-catalyzed asymmetric [2+2+2] cycloaddition of α,ω-diynes with indene...
January 18, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29345932/synthesis-of-polysubstituted-quinolines-from-%C3%AE-2-aminoaryl-alcohols-via-nickel-catalyzed-dehydrogenative-coupling
#7
Sanju Das, Debabrata Maiti, Suman De Sarkar
This study reports a nickel catalyzed sustainable synthesis of polysubstituted quinolines from α-2-aminoaryl alcohols by a sequential dehydrogenation and condensation process that offers the advantages of low catalyst loading and wide sub-strate scope. In contrast to earlier reported methods, this strategy allows the use of both primary as well as secondary α-2-aminoaryl alcohols in combination with either ketones or secondary alcohols for desired product formation. Using this methodology, thirty substituted quinoline derivatives were synthesized with up to 93% isolated yield...
January 18, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29345463/-%C3%A2-sativamides-a-and-b-two-pairs-of-racemic-nor-lignanamide-enantiomers-from-the-fruits-of-cannabis-sativa-hemp-seed
#8
Guo-Yuan Zhu, Ji Yang, Xiao-Jun Yao, Xing Yang, Jing Fu, Xin Liu, Li-Ping Bai, Liang Liu, Zhi-Hong Jiang
(±)-Sativamides A (1) and B (2), two pairs of nor-lignanamide enantiomers featuring a unique benzo-angular triquinane skeleton, were isolated from the fruits of Cannabis sativa (hemp seed). Their structures were elucidated by detailed spectroscopic analysis and ECD calculations. The resolution of (+)- and (-)-sativamides A and B were achieved by chiral HPLC. Pretreatment of neuroblastoma cells with 1 and 2 significantly reduced the endoplasmic reticulum (ER) stress-induced cytotoxicity.
January 18, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29345136/regioselective-reaction-of-heterocyclic-n-oxides-an-acyl-chloride-and-cyclic-thioethers
#9
Przemyslaw Frei, D Heulyn Jones, Steven T Kay, Jayde A McLellan, Blair F Johnston, Alan R Kennedy, Nicholas C O Tomkinson
Treatment of electron deficient pyridine N-oxides with 4-nitrobenzoyl chloride and a cyclic thioether in the presence of triethylamine leads to the corresponding 2-functionalized product in up to a 74% isolated yield. The transformation can also be accomplished with alternative nitrogen containing heterocycles, including quinolines, pyrimidines, and pyrazines. To expand the scope of the transformation, diisopropyl ether can be used as the reaction medium to allow for the use of solid thioether substrates.
January 18, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29345126/enantioselective-synthesis-of-boryl-tetrahydroquinolines-via-cu-catalyzed-hydroboration
#10
Duanyang Kong, Suna Han, Guofu Zi, Guohua Hou, Jiaxin Zhang
A Cu-catalyzed regio- and enantioselective hydroboration of 1,2-dihydroquinolines with high yields and excellent enantioselectivities (up to 98% ee) was presented. This method could be applied in the asymmetric synthesis of the important intermediates used in the enantioselective synthesis of the potential agent Sumanirole for the treatment of Parkinson's disease and potentially interesting positive inotropic agent (S)-903.
January 18, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29342362/stereospecific-syntheses-of-enaminonitriles-and-%C3%AE-enaminoesters-via-domino-ring-opening-cyclization-droc-of-activated-cyclopropanes-with-pronucleophilic-malononitriles
#11
Amrita Saha, Aditya Bhattacharyya, Ranadeep Talukdar, Manas K Ghorai
Two novel synthetic protocols for the syntheses of highly functionalized five-membered carbocyclic enaminonitriles and β-enaminoesters have been developed via domino ring-opening cyclization (DROC) and DROC/decarboxylative tautomerization of activated cyclopropanes with malononitrile pronucleophiles, respectively. Both of the efficient strategies (yield up to 93%) have been generalized with various donor-acceptor and acceptor cyclopropanes as well as with malononitrile derivatives. The stereospecific variants of the two SN2-type DROC strategies have also been developed by employing enantiopure donor-acceptor (DA) cyclopropanes to synthesize the corresponding nonracemic products with excellent stereoselectivities (dr up to >99:1, ee up to >99%)...
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29342353/synthesis-and-computational-studies-demonstrate-the-utility-of-an-intramolecular-styryl-diels-alder-reaction-and-bht-assisted-1-3-shift-to-construct-anticancer-dl-deoxypodophyllotoxin
#12
Diana I Saavedra, Benjamin D Rencher, Doo-Hyun Kwon, Stacey J Smith, Daniel H Ess, Merritt B Andrus
Deoxypodophyllotoxin is a secondary metabolite lignan possessing potent anticancer activity with potential as a precursor for known anticancer drugs, but its use is limited by scarcity from natural sources. We here report the total synthesis of racemic deoxypodophyllotoxin (DPT) in seven steps using an intramolecular styryl Diels-Alder reaction (ISDA) strategy uniquely suited to assemble the deoxypodophyllotoxin core. Computational studies are also reported for this reaction that demonstrate the ability to overcome the limitations of slow reactivity and electronic mismatch of the diene and dieneophile...
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29341614/synthesis-of-quinazolines-via-an-iron-catalyzed-oxidative-amination-of-n-h-ketimines
#13
Cheng-Yi Chen, Fengxian He, Guangrong Tang, Huiqing Yuan, Ning Li, Jinmin Wang, Roger Faessler
An efficient synthesis of quinazolines based on an iron-catalyzed C(sp3)-H oxidation and intramolecular C-N bond formation using tert-BuOOH as the terminal oxidant is described. The reaction of readily available 2-alkylamino benzonitriles with various organometallic reagents led to 2-alkylamino N-H ketimine species. The FeCl2-catalyzed C(sp3)-H oxidation of the alkyl group employing tert-BuOOH followed by intramolecular C-N bond formation and aromatization afforded a wide variety of 2,4-disubstituted quinazolines in good to excellent yields...
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29341612/stabilization-of-nabh4-in-methanol-using-a-catalytic-amount-of-naome-reduction-of-esters-and-lactones-at-room-temperature-without-solvent-induced-loss-of-hydride
#14
Prasanth C P, Ebbin Joseph, Abhijith A, Nair D S, Ibrahim Ibnusaud, Jevgenij Raskatov, Bakthan Singaram
Rapid reaction of NaBH4 with MeOH precludes its use as a solvent for large-scale ester reductions. We have now learned that a catalytic amount of NaOMe (5 mol %) stabilizes NaBH4 solutions in methanol at 25 °C and permits the use of these solutions for the reduction of esters to alcohols. The generality of this reduction method was demonstrated using 22 esters including esters of naturally occurring chiral γ-butyrolactone containing dicarboxylic acids. This method permits the chemoselective reductions of esters in the presence of cyano and nitro groups and the reductive cyclization of a pyrrolidinedione ester to a fused five-membered furo[2,3-b]pyrrole and a (-)-crispine A analogue in high optical and chemical yields...
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29341610/visible-light-mediated-ipso-carboacylation-of-alkynes-synthesis-of-3-acylspiro-4-5-trienones-from-n-p-methoxyaryl-propiolamides-and-acyl-chlorides
#15
Yu Liu, Qiao-Lin Wang, Cong-Shan Zhou, Biquan Xiong, Pan-Liang Zhang, Chang-An Yang, Ke-Wen Tang
A novel visible-light-mediated ipso-carboacylation of N-(p-methoxyaryl)propiolamides with acyl chloride has been established for the synthesis of diverse 3-acylspiro[4,5]trienones with high selectivity and efficiency. This method represents a new difunctionalization of alkynes through cross coupling of the acyl chloride C-Cl bonds with an ipso-aromatic carbon by simultaneously forming two new carbon-carbon bonds and one carbon-oxygen double bond.
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29338230/organosilicon-reducing-reagents-for-stereoselective-formations-of-silyl-enol-ethers-from-%C3%AE-halo-carbonyl-compounds
#16
Suman Pramanik, Supriya Rej, Shun Kando, Hayato Tsurugi, Kazushi Mashima
Salt-free stereoselective synthesis of silyl enol ethers was achieved by treating α-halo carbonyl compounds with 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine. In this reaction, easily removable trimethylsilyl halides and 2,3,5,6-tetramethylpyrazine were generated as the reaction byproducts. Due to the inertness of the reaction byproducts, we found a one-pot transformation of the in situ-generated silyl enol ethers into various α-functionalized carbonyls by the reaction with Togni-II reagent or aldehydes...
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29338225/stereoselective-photodimerization-of-3-arylindenones-in-solution-and-in-the-solid-state
#17
Naohiro Uemura, Hiroki Ishikawa, Naoki Tamura, Yasushi Yoshida, Takashi Mino, Yoshio Kasashima, Masami Sakamoto
Photodimerization of 3-arylindenones in solution and in the solid-state was examined. Irradiation of 3-arylindenones in benzene exclusively gave C2-symmetric anti-HH cyclobutane dimers in good yields. In contrast, photolysis in the solid-state afforded syn-HH cyclobutane dimers efficiently, which was considerably influenced by the molecular arrangement in the crystal lattice.
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29338239/vinyl-grignard-mediated-stereoselective-carbocyclization-of-lactone-acetals
#18
Christinne Hedberg, Morten Estrup, Espen Z Eikeland, Henrik Helligsø Jensen
A novel Ferrier-type carbocyclization is reported. It involves a carbohydrate-derived lactone acetal synthesized from methyl α-D-glucopyranoside, which upon treatment with excess vinylmagnesium bromide provides a highly substituted carbocyclic product as a single stereoisomer. The yield is greatly increased when N,N,N',N'-tetramethylethylenediamine is added to the reaction mixture. Optimized reaction conditions have been applied to lactone acetals derived from other carbohydrates. Based on the obtained results, a possible reaction mechanism has been proposed...
January 16, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29338235/enantioselective-dearomatization-of-alkyl-pyridiniums-by-n-heterocyclic-carbene-catalyzed-nucleophilic-acylation
#19
Graziano Di Carmine, Daniele Ragno, Olga Bortolini, Pier Paolo Giovannini, Andrea Mazzanti, Alessandro Massi, Marco Fogagnolo
A chiral-NHC-catalyzed dearomatizing reaction of activated N-alkylpyridinium salts with aliphatic aldehydes is described. The resulting acylated 1,4-dihydropyridines have been obtained with complete C4 regioselectivity and enantioselectivities in the range of 52-78% ee. The (4R) absolute configuration of the synthesized compounds has been determined by TD-DFT simulation of the electronic circular dichroism spectra.
January 16, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29338231/a-fluorous-phase-approach-to-%C3%AE-hydroxytropolone-synthesis
#20
Michael P D'Erasmo, Ryan Patrick Murelli
α-Hydroxytropolones (αHTs) are troponoids that demonstrate inhibition against an array of therapeutically significant targets, making them potential drug leads for several human diseases. We have utilized a recently discovered one-pot three-component oxidopyrylium cycloaddition in a solid-supported synthesis of αHTs. Though the procedure is time efficient and generates assay-ready molecules, the system suffers from low yields and an inability to perform reaction modifications on resin-bound intermediates...
January 16, 2018: Journal of Organic Chemistry
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