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Organic & Biomolecular Chemistry

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https://read.qxmd.com/read/30768102/recent-advances-in-the-synthesis-of-c2-spiropseudoindoxyls
#1
REVIEW
Yanling Ji, Xianghong He, Cheng Peng, Wei Huang
Compared with the numerous reviews on the construction of C3 spirooxindoles, few reviews have examined the synthesis of structurally analogous C2-spiropseudoindoxyl derivatives. This scaffold has attracted substantial attention from synthetic chemists because of its relevance to medicinal chemistry. This review summarizes the recent progress in the synthesis of many heterocycle and carbocycle fused spiropseudoindoxyl compounds. The article is divided into sections according to the type of catalysis, including metal catalysis, high-iodine reagent mediation, and organic catalysis...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768099/%C3%AE-%C3%AE-unsaturated-butenolides-in-an-organocatalytic-doubly-annulative-cascade-for-the-preparation-of-3-4-dihydrocoumarins
#2
Dorota Kowalczyk-Dworak, Łukasz Albrecht
A new, organocatalytic doubly annulative cascade utilizing α,β-unsaturated butenolides and imines (derived from salicyl aldehydes and α-amino-γ-lactones) as starting materials is described. The developed strategy is based on two annulative processes: (1) initial [3 + 2]-dipolar cycloaddition allowing for the construction of a pyrrolidine ring; and (2) the butenolide-ring-opening reaction leading to the introduction of a 3,4-dihydrocoumarin framework. Target polycyclic compounds have been obtained with excellent chemical and stereochemical efficiencies...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768098/applications-of-chiral-naphthyloxycyclohexanols-in-deracemization-of-%C3%AE-substituted-carboxylic-acids-by-dynamic-thermodynamic-resolution
#3
Aditya N Khanvilkar, Sudeep G Samanta, Ashutosh V Bedekar
Two derivatives of trans-2-naphthyloxycyclohexanol were synthesized, their enantiomers were separated by enzyme mediated kinetic resolution and their absolute configuration was established by synthesizing their diastereomers with esters of known chiral description. Chiral alcohols were then used as chiral auxiliaries for the preparation of esters by coupling with racemic α-halo acids. During the coupling reactions with DCC and a suitable base, an efficient dynamic thermodynamic resolution was observed and the products were isolated in high diastereomeric purity...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768092/synthesis-and-antitumor-activities-of-aquayamycin-and-analogues-of-derhodinosylurdamycin-a
#4
Padam P Acharya, Hem Raj Khatri, Sandip Janda, Jianglong Zhu
Total syntheses of aquayamycin (3) and a number of analogues of angucycline antitumor antibiotic derhodinosylurdamycin A bearing various 2-deoxy sugar subunits (4-7) have been achieved. These molecules (3-7) were synthesized based on a convergent strategy for the synthesis of derhodinosylurdamycin A (2) previously reported from our group. In particular, our recently developed mild cationic gold-catalyzed glycosylation with S-but-3-ynyl thioglycoside donors was employed for the synthesis of analogues (6 and 7) bearing disaccharide subunits containing α-l-olivoside and α-l-olioside moiety, respectively...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768089/convenient-access-to-5-membered-cyclic-iminium-ions-evidence-for-a-stepwise-4-2-cycloaddition-mechanism
#5
Jared L Freeman, Margaret A Brimble, Daniel P Furkert
In situ generation and reaction of novel 5-membered N-tosyl cyclic α,β-unsaturated iminium ions from readily prepared stable precursors is demonstrated. Formal iminium Diels-Alder cycloaddition proceeded in good yield via a stepwise rather than concerted cycloaddition process, confirmed through the isolation of a Mukaiyama-Michael type intermediate. Relative stereochemistry was determined upon subsequent intramolecular cyclisation under Lewis acid catalysis to afford formal endo 5,6-spirobicyclic adducts, as confirmed by crystallography...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768088/regioselectivity-enhancement-in-synthesis-of-70-fullerene-derivatives-by-introduction-of-a-branched-structure
#6
Fukashi Matsumoto, Shuhei Sumino, Toshiyuki Iwai, Takatoshi Ito
Regio-purity in [70]fullerene derivatives is of great importance to improve the power conversion efficiencies of organic photovoltaics. We found that the introduction of a branched structure to [70]PCBM enhanced the yield of α-isomers. The effect of the steric group in the reaction mechanism was theoretically investigated and a difference in the activation energies within specific pathways was revealed.
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768085/chemoselective-syntheses-of-spirodihydrofuryl-and-spirocyclopropyl-barbiturates-via-cascade-reactions-of-barbiturate-based-olefins-and-acetylacetone
#7
Xuebin Yan, Pei Shao, Xixi Song, Chaofei Zhang, Chang Lu, Songtao Liu, Yanli Li
The Michael addition initiated ring closure reaction of barbiturate-based olefins and acetylacetone with NBS has been explored. The efficient and chemoselective approach for the synthesis of barbiturate-fused spirocycles was established. Spirodihydrofuryl barbiturates and spirocyclopropyl barbiturates were synthesized selectively via cascade reactions under different basic conditions in moderate to excellent yields. The structure of 2-(4-chlorophenyl)-1,1-diacetyl-5,7-dimethyl-5,7-diazaspiro[2,5]octane-4,6,8-trione was confirmed by single crystal X-ray diffraction analysis...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768084/naphthalimide-containing-conjugated-polyelectrolytes-with-different-chain-configurations
#8
Yu Chen, Ying Tan, Chunyan Tan, Yunpeng Lu, Yuzong Chen, Yuyang Jiang
Several donor-acceptor type conjugated polyelectrolytes containing naphthalimide are developed. Different polymer chain configurations of the backbones of polymers lead to different photophysical properties. The para-substituted polymers show extended conformations with quite low quantum yields in high polarity solvents because of twisted intramolecular charge transfer features, while the meta-substituted polymers can form helices and demonstrated significantly improved quantum yields in water and methanol, as well as achieving sensitive, ultrafast and ratiometric detection of trace methylene blue in water...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768082/recent-advances-in-metal-free-aerobic-c-h-activation
#9
REVIEW
André Shamsabadi, Vijay Chudasama
Herein we describe recent developments in selective, metal-free, dioxygen-induced C-H activation. This method of activating C-H bonds is an attractive alternative to traditional methodologies as it uses dioxygen, an inherently sustainable and widely accessible oxidant, in place of expensive or toxic metals and/or hazardous peroxides. Reactions developed on the basis of using aerobic C-H activation are also discussed.
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30768080/correction-bioactive-spiropyrrolizidine-oxindole-alkaloid-enantiomers-from-isatis-indigotica-fortune
#10
Si-Fan Liu, Bin Lin, Yu-Fei Xi, Le Zhou, Li-Li Lou, Xiao-Xiao Huang, Xiao-Bo Wang, Shao-Jiang Song
Correction for 'Bioactive spiropyrrolizidine oxindole alkaloid enantiomers from Isatis indigotica fortune' by Si-Fan Liu et al., Org. Biomol. Chem., 2018, 16, 9430-9439.
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30766987/copper-catalyzed-tandem-annulation-enol-nucleophilic-addition-to-access-multisubstituted-indoles
#11
Wangze Song, Ming Li, Junnan He, Junhao Li, Kun Dong, Yubin Zheng
A method to access various multisubstituted indoles from propargylic alcohols and readily available enol nucleophiles by copper-catalyzed tandem annulation/enol nucleophilic addition has been developed. Compared to the expensive metal catalysts such as platinum, gold, silver, and palladium used previously, the most economical copper(i) catalyst could achieve this reaction efficiently. The fused heterocyclic compounds, pyrrolo[1,2-a] indoles, could be afforded by further transformation of the products. The allyl cation intermediate may be involved in the mechanism...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30766975/tert-butyl-nitrite-mediated-radical-cyclization-of-tetrazole-amines-and-alkynes-toward-tetrazolo-1-5-a-quinolines
#12
Teng Liu, Yi-Gang Ji, Lei Wu
A general and efficient radical cyclization of 1H-tetrazol-5-amines and alkynes toward tetrazolo[1,5-a]quinolines is established for the first time. The annulation mediated by tert-butyl nitrite takes place expeditiously within 10 minutes under mild conditions. Without using external additives or excitation, the tetrazolo[1,5-a]quinoline derivatives are obtained in moderate to good yields, along with high regioselectivities for unsymmetrical alkynes and broad functional tolerance features. The reaction is exemplified to occur via a radical process, with aryl radicals synergistically generated from tert-butyl nitrite, water and tetrazolate-diazonium salts...
February 15, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30762860/on-water-iodine-mediated-direct-construction-of-1-3-benzothiazines-from-ortho-alkynylanilines-by-regioselective-6-exo-dig-cyclization
#13
Kapil Mohan Saini, Rakesh K Saunthwal, Shiv Kumar, Akhilesh K Verma
Herein, we report the 6-exo-dig ring closure of ortho-alkynylanilines with readily available aroyl isothiocyanate. An environmentally benign, metal- and base-free, iodine promoted cascade synthesis of highly functionalized (benzo[1,3]thiazin-2-yl)benzimidic acids has been accomplished via in situ generated ortho-alkynylthiourea. The established methodology employs the abundant chemical feedstock of ortho-alkynylanilines and aroyl isothiocyanates and could be applied in the late-stage synthesis of pharmaceutically active 1,3-benzothiazine containing molecules...
February 14, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30762859/ir-iii-catalyzed-4-2-cyclization-of-azobenzene-and-diazotized-meldrum-s-acid-for-the-synthesis-of-cinnolin-3-2h-one
#14
Gongutri Borah, Pitambar Patel
The first report on Ir(iii)-catalyzed C-H alkylation/cyclization of azobenzene with diazotized Meldrum's acid is described for the synthesis of cinnolin-3(2H)-one derivatives under mild conditions. Controlled experiments led to the isolation of intermediate ortho-alkylated product of azobenzene, which was converted to both cinnolin-3(2H)-one-4-carboxylic acid and its ester derivative. Additionally, the iridacyclic complex of azobenzene was isolated and found to be an active intermediate in the catalytic cycle...
February 14, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30762067/ru-ii-catalysed-synthesis-of-1h-isothiochromenes-by-oxidative-coupling-of-benzylthioethers-with-internal-alkynes
#15
Esteban P Urriolabeitia, Sara Ruiz
The synthesis of 1H-isothiochromenes by oxidative coupling of benzyl(tert-butyl)thioethers with internal alkynes, catalysed by Ru(ii), has been achieved. The reaction occurs by S-directed C-H activation at the ortho position of the aryl ring, promoted by ruthenium, migratory insertion of the alkyne, 1,2-thio-Wittig rearrangement of the tert-butyl group and reductive elimination by C-S coupling between the resulting anionic sulfide and the vinylic carbon.
February 14, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30762059/indium-and-zinc-catalyzed-enantioselective-amide-propargylation-of-aldehydes-with-stannylated-allenyl-amides
#16
Tetsuya Sengoku, Ikuhei Ikeda, Keisuke Ai, Masaki Takahashi, Hidemi Yoda
The catalytic enantioselective propargylation of aldehydes with newly prepared stannyl allenyl amides is described. The reaction has been accomplished by using catalytic amounts of indium chloride, zinc chloride, and a chiral BINOL derivative, affording amide-functionalized homopropargyl alcohols in excellent yields and enantioselectivities.
February 14, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30762058/modular-dna-based-hybrid-catalysts-as-a-toolbox-for-enantioselective-hydration-of-%C3%AE-%C3%AE-unsaturated-ketones
#17
Ji Hye Yum, Soyoung Park, Ryota Hiraga, Izumi Okamura, Shunta Notsu, Hiroshi Sugiyama
The direct addition of water to a carbon-carbon double bond remains a challenge, but such a reaction is essential for the development of efficient catalysts that enable direct access to chiral alcohols. We now report on the enantioselective hydration of α,β-unsaturated ketones, catalyzed by modular DNA-based hybrid catalysts, affording β-hydroxy ketones with up to 87% enantiomeric excess. Oligonucleotides containing an intrastrand bipyridine ligand were readily synthesized by a straightforward process using an automated solid-phase synthesis...
February 14, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30758386/synthesis-of-quinazolin-4-1h-ones-via-amination-and-annulation-of-amidines-and-benzamides
#18
Fangpeng Hu, Xinfeng Cui, Zihui Ban, Guoqiang Lu, Nan Luo, Guosheng Huang
Quinazolinones have broad applications in the biological, pharmaceutical and material fields. Studies on the synthesis of these compounds are therefore widely conducted. Herein, a novel and highly efficient copper-mediated tandem C(sp2)-H amination and annulation of benzamides and amidines for the synthesis of quinazolin-4(1H)-ones is proposed. This synthetic route can be useful for the construction of quinazolin-4(1H)-one frameworks.
February 13, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30758364/enantioselective-synthesis-of-chiral-heterocyclic-biaryls-via-asymmetric-suzuki-miyaura-cross-coupling-of-3-bromopyridine-derivatives
#19
Wang Xia, Zhen-Wei Zhang, Yongsu Li, Xiaoding Jiang, Hao Liang, Yaqi Zhang, Rihui Cao, Liqin Qiu
A series of chiral heterocyclic biaryls with a pyridyl moiety were prepared in moderate to good yields with up to 92% ee via asymmetric Suzuki-Miyaura coupling. The chiral-bridged biphenyl monophosphine ligand L1 was found to be much more effective in the reaction enantioselection than its counterpart binaphthyl monophosphine ligands.
February 13, 2019: Organic & Biomolecular Chemistry
https://read.qxmd.com/read/30758363/cytosporins-a-d-novel-benzophenone-derivatives-from-the-endophytic-fungus-cytospora-rhizophorae-a761
#20
Hong-Xin Liu, Hai-Bo Tan, Kai Chen, Li-Yun Zhao, Yu-Chan Chen, Sai-Ni Li, Hao-Hua Li, Wei-Min Zhang
Four novel benzophenone derivatives, cytosporins A-D (1-4), hemiterpene-conjugated phenolics with an unprecedented benzo[b][1,5]dioxocane skeleton, were isolated from Cytospora rhizophorae A761. The structures of the new compounds were fully characterized on the basis of extensive spectroscopic analysis. The deduced structure represents the first example of natural meroterpenoids which bear a benzo[b][1,5]dioxocane framework embodying hemiterpene and benzophenone moieties. Moreover, compounds 1-4 were evaluated for in vitro antimicrobial activity...
February 13, 2019: Organic & Biomolecular Chemistry
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