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Organic & Biomolecular Chemistry

Pravat Mondal, Narshinha P Argade
Correction for 'Stereoselective synthesis of (-)-desethyleburnamonine, (-)-vindeburnol and (-)-3-epitacamonine: observation of a substrate dependent diastereoselectivity reversal of an aldol reaction' by Pravat Mondal et al., Org. Biomol. Chem., 2016, DOI: 10.1039/c6ob01438k.
October 24, 2016: Organic & Biomolecular Chemistry
Yongjian Chi, Lihua Qiu, Xinfang Xu
A chiral dirhodium(ii) carboxylate complex catalyzed enantioselective cyclopropanation reaction of N-Boc diazooxindoles with olefins, including aryl, alkyl, cyclic, and disubstituted olefins, under mild conditions is described. This reaction provides complementary access to the corresponding chiral spirocyclopropyloxindole products in good to high yields with good to excellent enantioselectivities.
October 24, 2016: Organic & Biomolecular Chemistry
Marie Vayer, Weizhen Fang, Régis Guillot, Sophie Bezzenine-Lafollée, Christophe Bour, Vincent Gandon
1,3-Dienyl β-keto esters are cyclised into bicyclolactones using the Bi(OTf)3/TfOH catalytic system. This reaction represents a rare case of simultaneous C-C and C-O bond formation at positions 1 and 3 of a 1,3-diene. Application to the synthesis of ramulosin is presented.
October 24, 2016: Organic & Biomolecular Chemistry
Venkata A K Adiraju, Gregory M Ferrence, Timothy D Lash
Azuliporphyrins are intriguing porphyrin analogues that incorporate an azulene ring in place of a pyrrolic unit. This system undergoes regioselective oxidation reactions and favors the formation of stable organometallic derivatives. Reaction of meso-unsubstituted azuliporphyrins with Co2(CO)8 or CoCl2·6H2O gave 21-oxyazuliporphyrins, while Cu(OAc)2 produced the corresponding copper(ii) complexes. Treatment of an oxyazuliporphyrin with Ni(OAc)2 or Pd(OAc)2 afforded analogous nickel(ii) and palladium(ii) derivatives...
October 24, 2016: Organic & Biomolecular Chemistry
Jérémie Grolleau, Frédéric Gohier, Clément Cabanetos, Magali Allain, Stéphanie Legoupy, Pierre Frère
Synthetic access to new push-pull molecules based on 3-cyano-4-hexyloxythiophene and triphenylamine moieties is presented herein using a clean methodology. The key step involves a direct heteroarylation coupling reaction in the presence of a homogeneous or heterogeneous [Pd] catalyst followed by Knoevenagel condensation performed in ethanol as a solvent. Structure-electronic property relationships of the new molecular materials are discussed and then their use as donors in bilayer planar heterojunction solar cells is investigated...
October 21, 2016: Organic & Biomolecular Chemistry
Noriaki Sugita, Satoshi Hayashi, Masashi Shibata, Taiga Endo, Masahiro Noji, Kazuhiko Takatori, Toshikatsu Takanami
An efficient approach to meso-unsubstituted β-silylporphyrins was developed through highly regioselective Ir-catalyzed C-H activation, in the presence of HSiMe(OSiMe3)2 as the Si source, from meso-unsubstituted porphyrins. Further transformations of the silyl group, such as oxidation, halogenation, and cross-coupling reactions, could be achieved under mild conditions, demonstrating the synthetic utility of β-silylporphyrins as a multipurpose synthon for fabricating porphyrin derivatives.
October 21, 2016: Organic & Biomolecular Chemistry
Kosuke Murai, Keiichiro Tateishi, Akio Saito
Barluenga's reagent (IPy2BF4, Py = pyridine) treated with HBF4 efficiently catalyzes the inter- and intramolecular alkyne-carbonyl metathesis of unactivated alkynes with aldehydes or ketones, most of which proceed at room temperature. This work represents the first catalytic application of the Barluenga's reagent.
October 21, 2016: Organic & Biomolecular Chemistry
Ho Cheol Jeong, Suk Hyun Lim, Dae Won Cho, Sung Hong Kim, Patrick S Mariano
Single electron transfer (SET) promoted photoaddition reactions of secondary N-α-trimethylsilyl-N-alkylamines to C60 were explored to gain a deeper understanding of the mechanistic pathways followed and to expand the library of novel types of organofullerenes that can be generated using this approach. The results show that photoreactions of 10% EtOH-toluene solutions containing C60 and N-α-trimethylsilyl-N-alkylamines produce either aminomethyl-1,2-dihydrofullerenes or symmetric fulleropyrrolidines as major products depending on the nature of alkyl substituents...
October 21, 2016: Organic & Biomolecular Chemistry
Song-Lin Zhang, Ze-Long Yu
Divergent synthesis of indoles, oxindoles, isocoumarins and isoquinolinones is described in this report by using a general Pd-catalyzed tandem reaction of β-hydroxy carbonyl compounds with aryl halides bearing an ortho-nitro, -ester or -cyano substituent. A key retro-aldol/α-arylation reaction is involved that merges classic Pd cross-coupling chemistry with novel Pd-promoted retro-aldol C-C activation to produce α-arylated ketones or esters. Subsequent intramolecular condensation of the carbonyl with the ortho-synthon gives target heterocycles...
October 21, 2016: Organic & Biomolecular Chemistry
Nicolás Grimblat, Ariel M Sarotti, Teodoro S Kaufman, Sebastian O Simonetti
The Duff reaction is one of the most employed methods for the ortho-formylation of phenols; however, not much is truly known about its mechanism. Using DFT calculations, we disclose the first theoretical study regarding the selectivity-determining step of the reaction. We have found that this stage is governed by a hydrogen bond, that gives rise to a cyclohexa-2,4-dienone intermediate and establishes the position where the formylation will take place. These findings were evaluated by analysis of the reaction outcome of several non-symmetrically substituted phenols...
October 20, 2016: Organic & Biomolecular Chemistry
Junki Tanabe, Daisuke Taura, Naoki Ousaka, Eiji Yashima
The photoirradiation of 9-phenylethynylanthracene in degassed chloroform and benzene afforded not only a [4 + 2]-anti Diels-Alder addition dimer, but also a [4 + 4]-anti-dimer as a minor product for the first time as revealed by single-crystal X-ray analysis, while the anthracene residue was quantitatively oxidised in undegassed dilute chloroform, giving the corresponding endoperoxides. The photochemical reactions of carboxylic acid monomers bearing a 9-phenylethynylanthracene unit at one and both ends were further investigated in the presence and absence of the complementary amidine dimer as the template...
October 20, 2016: Organic & Biomolecular Chemistry
Arun K Ghosh, Luke A Kassekert, Joseph D Bungard
We have elucidated the complete absolute configuration of callyspongiolide and unambiguously assigned its stereochemistry at the C-21 center through synthesis. Four stereoisomers of callyspongiolide were synthesized in a convergent and enantioselective manner. A late-stage Sonogashira coupling forges the diene-ynic side chain. Other notable reactions are Yonemitsu's variation of Yamaguchi macrolactonization to cyclize an alkynic seco acid, highly trans-selective Julia-Kocienski olefination, CBS reduction to set the C-21 stereocenter, and methyl cuprate addition to an unsaturated pyranone to install the C-5 methyl center...
October 20, 2016: Organic & Biomolecular Chemistry
Anil K Saikia, Manash J Deka, Upasana Borthakur
A one-pot, metal-free procedure has been developed for the synthesis of 4-tosylthiomorpholine from N-tethered thioalkenols via bromination, cyclization and subsequent elimination reaction in good yields. The reaction is found to be highly regioselective.
October 20, 2016: Organic & Biomolecular Chemistry
Han-Xiao Wang, Shu-Zhen Hu, Qiang Shi, Chuan-Feng Chen
With an expanded electron-rich cavity and a fixed conformation, macrocycle H was found to encapsulate π-extended viologens G1-G4 to form the first case of pseudo[3]rotaxanes based on oxacalixarenes. The complexation was investigated in detail both in solution and in the solid state using NMR spectroscopy and X-ray crystallography. Due to the three-dimensional nonsymmetric structure of H, three orientational isomers of the pseudorotaxanes could be expected theoretically. However, as the crystal structure analysis revealed, only one of the three isomers was obtained with either G1 or G3...
October 20, 2016: Organic & Biomolecular Chemistry
Ming Wang, Zhijian Huang
By using a diaryliodonium salt as a benzyne precursor, a transition metal-free approach for N-arylation of secondary amides is developed. This novel benzyne precursor, which can be prepared easily by a one step process from an aryl iodide, shows different reactivities with previous benzyne precursors in the N-arylation reaction. Mechanistic studies confirm the involvement of benzyne species (generated in situ from the diaryliodonium salts) as key intermediates.
October 19, 2016: Organic & Biomolecular Chemistry
Yujing Zhou, Yan Zhang, Jianbo Wang
A general approach towards diverse fluorinated phosphonates via geminal difunctionalization reactions of α-diazo arylmethylphosphonates is described. The diazo functionality (RR'C[double bond, length as m-dash]N2) is successfully converted to RR'CF2, RR'CHF, RR'CFBr or RR'CFNR''2 groups by employing different fluorination reagents. A variety of fluorinated organophosphorus compounds were readily accessed in good to excellent yields from a common type of precursor.
October 19, 2016: Organic & Biomolecular Chemistry
Youngeun Jung, Ikyon Kim
An efficient synthetic approach to polysubstituted benzofurans is described, using 2-methoxyquinone as a benzofuran backbone. Nucleophilic addition of terminal alkynes to 2-methoxy-1,4-benzoquinone afforded the corresponding quinols containing an alkyne unit, which were converted to phenols via mild Zn-mediated reduction. After proper protection of the free phenolic OH, 5-endo-dig iodocyclization allowed facile access to a number of 3-iodobenzofurans. In addition, it was demonstrated for the first time that o-methoxyarylalkynes underwent intramolecular hydroalkoxylation under the influence of AgOTf furnishing the corresponding benzofurans...
October 19, 2016: Organic & Biomolecular Chemistry
Sylvain Daunay, Remi Lebel, Laurence Farescour, Jean-Claude Yadan, Irene Erdelmeier
The discovery of a non-enzymatic oxidative introduction of sulfur to the 5-position of histidine is reported, by activation with bromine or NBS followed by reaction with thioacetic acid forming novel 5-acetylsulfanyl-histidine. Complementing the previously developed regioselective oxidative S-introduction to the 2-position of histidine by reaction with cysteine, this surprising finding provides straightforward access in multi-gram quantities to naturally occurring 5-sulfanyl-histidine and its N-methylated analogues, including a hitherto unknown regioisomer of l-ergothioneine...
October 19, 2016: Organic & Biomolecular Chemistry
L Brulikova, Y Okorochenkova, J Hlavac
An efficient methodology using the Fukuyama-Mitsunobu reaction was successfully applied to prepare various Rhodamine B-based amides with the locked possibility to form a lactam ring. The procedure was developed for solid-phase synthesis, which can be advantageously applied to the synthesis of chemical libraries in a combinatorial fashion. A series of derivatives including aliphatic as well as aromatic rhodamine amides alkylated via a reaction with various alcohols were synthesized, and their spectral properties were investigated...
October 18, 2016: Organic & Biomolecular Chemistry
Ying Wang, Yang Wang, Kai Jiang, Qian Zhang, Dong Li
A simple and efficient transition-metal-free oxidative halogenation (Cl, Br) of the C5 C-H bond of 8-aminoquinoline amides has been developed. This method employed low-cost and innoxious sodium halides as halogenation reagents and oxone as an oxidant. The reactions demonstrated air and moisture tolerance, and good functional group compatibility, giving highly selective C5-halogenated products in good to excellent yields.
October 18, 2016: Organic & Biomolecular Chemistry
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