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Most Cited Articles

The Top 20 Cited Articles

The most cited articles are updated on a monthly basis and available as Last 3 Years. Citation data is obtained through CrossRef's Cited-Linking service.

Note: The Top 20 Citations are published across all volumes.

Paper | Regular issue | Vol 81, No. 4, 2010, pp.935-942
Published online: 9 February, 2010
DOI: 10.3987/COM-09-11890
A Highly Effective One-Pot Synthesis of Quinolines from 2-Alkynylnitrobenzenes

Kentaro Okuma,* Saori Ozaki, Jun-ichi Seto, Noriyoshi Nagahora, and Kosei Shioji

*Department of Chemistry, Faculty of Sciences, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan

Abstract

A highly effective one-pot synthesis of poly-substituted quinolines from 2-alkynylnitrobenzenes using inexpensive reagents has been developed. Reaction of 2-alkynylnitrobenzenes with Sn/HCl in EtOH resulted in the formation of 2-aminophenyl ketones and subsequently condensed in situ with ketones to form tri-substituted quinolines in 80-97% yields.

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Short Paper | Regular issue | Vol 91, No. 9, 2015, pp.1809-1815
Published online: 4 August, 2015
DOI: 10.3987/COM-15-13285
Viridobrunnines A and B, Antimicrobial Phenoxazinone Alkaloids from A Soil Associated Streptomyces sp.

Xiu Mei Zhang, Xu Liu, Zhe Wang, Zhen Hua Tian, and Wei Dong Xie*

*Department of Pharmacy, Marine College, Shangdong University at Weihai, Wenhua Xilu 180, Weihai 264209, China

Abstract

Chemical investigation of a Streptomyces sp. strain designated A1302 isolated from soil sample led to the discovery of two new phenoxazinone alkaloids, viridobrunnines A and B (1 - 2), along with two known analogues exfoliazone (3) and chandrananimycin D (4). Their structures were established by means of spectroscopic methods. The antibacterial and antifungal activity of isolated compounds was assayed. Viridobrunnine B (2) exhibited potent antibacterial activity against Bacillus subtilis with inhibition zone from 13 mm to 15 mm.

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Paper | Special issue | Vol 70, No. 1, 2006, pp.461-476
Published online: 2 November, 2006
DOI: 10.3987/COM-06-S(W)44
Synthetic Approaches to Polyhydroxy Indolizidines and Related Azabicyclic Scaffolds

Stephen Hanessian,* Eric Therrien, Jayakumar S. Warrier, and Guillaume Charron

*Department of Chemistry, University of Montreal, 2900 Edouard-Montpetit, Montréal, Québec H3C 3J7, Canada

Abstract

Approaches to the synthesis of unnatural polyhydroxylated indolizidines are described. Key reactions involve addition of 2-(trimethylsilyloxy)furan to iminium salts, and ring-closure metathesis as second alternative.

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Review | Special issue | Vol 88, No. 2, 2014, pp.827-844
Published online: 1 October, 2013
DOI: 10.3987/REV-13-SR(S)4
The Halogen/Magnesium-Exchange Using iPrMgCl·LiCl and Related Exchange Reagents

Nadja M. Barl, Veronika Werner, Christoph Sämann, and Paul Knochel*

*Department of Chemistry, Institute of Organic Chemistry, Ludwig-Maximilians-University of Munich, Butenandtstr. 5-13 Haus F, D-81377 Munich, Germany

Abstract

We have described the regio- and chemoselective preparation of various (hetero)aryl-Grignard reagents via halogen/magnesium-exchange along with applications of these organometallics in various reactions. The LiCl-mediated halogen/magnesium-exchange proceeds readily under mild conditions and offers the opportunity to convert not only organic iodides, but less activated organic bromides, as well. Furthermore, this exchange tolerates a broad spectrum of sensitive functionalities such as triazenes, methyl esters, silylated cyanohydrins, alcohols and acrylates. Electron-rich aryl derivatives can be converted into the corresponding Mg-species by using more activated bis-alkylmagnesium compounds. Subsequent functionalization reactions such as cross-couplings, allylations, acylations, addition reactions to ketones, cyclization reactions, fluorinations, disulfenylations, aminations as well as sulfoxide/magnesium-exchange reactions have been performed, readily furnishing highly functionalized derivatives as well as biologically active heterocycles.

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Review | Special issue | Vol 69, No. 1, 2006, pp.593-620
Published online: 18 August, 2006
DOI: 10.3987/REV-06-SR(O)3
Fluorine-Containing 2-Functionalized 1,3-Dicarbonyl Compounds for Heterocyclic Synthesis

Yanina V. Burgart, Victor I. Saloutin,* and Oleg N. Chupakhin

*Institute of Organic Synthesis of Urals Division of Russian Academy of Sciences, 22/20, S. Kovalevskoy/Akademicheskaya Str., Ekaterinburg, GSP-147, Russia

Abstract

Data on the synthesis and chemical transformations of 2-functionalized fluoroalkyl-containing 1,3-dicarbonyl compounds are reviewed. Reactions giving fluorinated heterocycles are discussed. The heterocyclization of non-substituted fluoroalkylated 1,3-dicarbonyl compounds with the same dinucleopiles is considered for the sake of comparison.

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Paper | Regular issue | Vol 92, No. 1, 2016, pp.45-54
Published online: 14 December, 2015
DOI: 10.3987/COM-15-13332
Brevisulcatic Acids from a Marine Microalgal Species Implicated in a Toxic Event in New Zealand

Raku Irie, Rina Suzuki, Kazuo Tachibana, Patrick T. Holland, D. Tim Harwood, Feng Shi, Paul McNabb, Veronica Beuzenberg, Fumiaki Hayashi, Huiping Zhang, and Masayuki Satake*

*Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

Abstract

Ladder-frame polyethers, known as brevisulcatic acids (BSXs) -1 (1), -2 (2), -4 (3), -5 (4) and -7 (5), were isolated from the dinoflagellate Karenia brevisulcata as potential causative toxins of a harmful algal event in New Zealand in 1998. The structures of 2, 4, and 5 were elucidated in this study. Brevisulcatic acids possessed a common fused nine ether-ring backbone, with a size and sequence determined to be 8/6/8/9/7/7/6/6/6. Rings B, C, H, I and J of the brevisulcatic acids were similar to those of brevetoxin A, a well-known polyether toxin. BSX-5 (4) had a γ-lactone as the 5-membered A-ring, analogous to brevetoxin A, while in BSX-2 (2) and BSX-7 (5) the lactone was present in its seco-acid form. In addition to this backbone variation, there were also some structural difference in side-chain substituents, with 2 and 4 having a 2-methylenepropionic acid unit, and 5 a 2-methylenepropanol unit. Cytotoxicity of 4 against neuroblastoma cells indicated that not only the structures but also activity of brevisulcatic acids are similar to those of brevetoxin A. This indicates that brevisulcatic acids potentially played a significant role in the toxicity observed during the only documented Karenia brevisulcata bloom to date.

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Short Paper | Special issue | Vol 88, No. 1, 2014, pp.817-825
Published online: 1 August, 2013
DOI: 10.3987/COM-13-S(S)66
Selective Synthesis of Benzyl Enol Ethers of β-Dicarbonyl Compounds in Basic Condition and the Application towards Synthesis of Naphthoquinones

Kazuaki Katakawa, Dai Yonenaga, Tomoyo Terada, Naoya Aida, Airi Sakamoto, Keishi Hoshino, and Takuya Kumamoto*

*Research Institute of Pharmaceutical Sciences, Musashino University, 1-1-20 Shinmachi Nishitokyo Tokyo, Japan

Abstract

Selective synthesis of benzyl enol ether of β-tetronic acids and β-dicarbonyl compounds in basic condition was examined. Benzylation of α-methyl-β-tetronic acid with benzyl tosylate in the presence of potassium carbonate gave the corresponding benzyl enol ether exclusively. The reaction of β-tetronic acid and cyclic 1,3-diketones gave the O-benzyl adducts preferentially than the C,O-dibenzylated ones. Diels-Alder reaction of furan derived the benzyl enol ether of α-methyl-β-tetronic acid and benzyne furnished the functionalized napthoquinone derivatives.

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Review | Special issue | Vol 40, No. 1, 1995, pp.477-500
Published online: 1 January, 1970
DOI: 10.3987/REV-94-SR2
Cyclic Carboxylic Imide Structures as Structure Elements of High Stability. Novel Developments in Perylene Dye Chemistry

Heinz Langhals

*Institut für Organische Chemie, Universität München, Karlstrasse 23, D-80333 München, Germany

Abstract

Cyclic carboxylic imides are structure elements in aromatic heterocycles with high persistency. Their attachment to perylene leads to the perylene dyes; the synthesis and unique properties of the dyes are reported and discussed. An extension of the principle to other aromatics is made.

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Paper | Special issue | Vol 82, No. 2, 2011, pp.1527-1540
Published online: 5 October, 2010
DOI: 10.3987/COM-10-S(E)108
Deconstructing Quinine. Part 1. Toward an Understanding of the Remarkable Performance of Cinchona Alkaloids in Asymmetric Phase Transfer Catalysis

Scott E. Denmark* and Robert C. Weintraub

*245 Roger Adams Laboratory Box 18-5 , Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, U.S.A.

Abstract

A study of catalyst structure-activity/selectivity relationships for Cinchona alkaloid-based asymmetric phase transfer catalysis (APTC) is described. An array of substituent modifications at C(9) and the quinuclidine nitrogen were introduced to examine the role of steric and electronic effects on rate and selectivity. The synthesis of the catalysts began with manipulation of the C(9) hydroxyl group followed by alkylation of the quinuclidine nitrogen to generate the quaternary ammonium salt. Catalysts that contained large substituents attached to the quinuclidinium nitrogen were found to be the most selective and those in which the hydroxyl group was protected generally afforded faster catalysts. The presence of a polar group at C(9) significantly impacted catalyst activity.

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Communication | Special issue | Vol 61, No. 1, 2003, pp.97-100
Published online: 20 October, 2003
DOI: 10.3987/COM-03-S62
Montmorillonite Impregnated with Bismuth Nitrate: Microwave-assisted Facile Nitration of β-Lactams

Bimal K. Banik,* Susanta Samajdar, Indrani Banik, Sze Sze Ng, and Jennie Hann

*The University of Texas, M. D. Anderson Cancer Center, Department of Molecular Pathology, Box 89, 1515 Holcombe Boulevard, Houston, Texas 77030, U.S.A.

Abstract

A facile synthesis of nitro substituted β-lactams over montmorillonite impregnated with bismuth nitrate under microwave irradiation has been accomplished in excellent yield.

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Paper | Special issue | Vol 77, No. 2, 2009, pp.1307-1321
Published online: 28 October, 2008
DOI: 10.3987/COM-08-S(F)116
New [11C]Phosgene Based Synthesis of [11C]Pyrimidines for Positron Emission Tomography

Koh-ichi Seki,* Ken-ichi Nishijima, Kimihito Sanoki, Yuji Kuge, Masayuki Takahashi, Hiromichi Akizawa, Nagara Tamaki, Leonard I. Wiebe, and Kazue Ohkura*

*Central Institute of Radio Isotope Science, Hokkaido University, Kita 15 Nishi 7, Kita-ku, Sapporo, Hokkaido 060-0815, Japan

Abstract

Thymine, 5-FU, and uracil were successfully synthesized through a procedure involving a cyclocondensation of triphosgene with newly developed α-substituted β-aminoacrylamides intermediates (1a, X = Me; 1b, X = F; 1c, X = H). The radioligands [2-11C]thymine and [2-11C]5-fluorouracil were synthesized in high radiochemical yields in 16-17 minutes from the end of bombardment by applying the cyclocondensation method with [11C]COCl2.

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Review | Special issue | Vol 28, No. 1, 1989, pp.489-519
Published online: 1 January, 1970
DOI: 10.3987/REV-88-SR1
Recent Developments of Free-Radical Substitutions of Heteroaromatic Bases

Francesco Minisci,* Elena Vismara, and Francesca Fontana

*Dipartimento di Chimica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy

Abstract

The most recent mechanistic and synthetic aspects of the substitution of protonated heteroaromatic bases by nucleophilic carbon-centered radicals are reviewed. From mechanistic point of view the following aspects are discussed; i ) Structurereactivity relationship; i i ) Rearomatization of the radical adducts; iii) Solvent and isotope effects; iv) Overlap area with ionic reactions. The synthetic developments concern the following topics: i) Selectivity with carbonyl radicals; ii) Alkyl iodides as sources of alkyl radicals; iii) Alkylation by carboxylic acids; iv) Vinylation by olefins; v) Oxyalkylation by ethers; vi) Catalytic processes; vii) Substitution with strongly nucleophilic radicals.

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Curriculum vitae | Special issue | Vol 74, No. 1, 2007, pp.13-14
Published online: 1 January, 1970
DOI: 10.3987/COM-08-S(W)CurriculumVitae
Curriculum Vitae

Ekkehard Winterfeldt

*Institute of Organic Chemistry, University of Hannover, Schneiderberg 1B, D-30167 Hannover, Germany

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Paper | Special issue | Vol 82, No. 2, 2011, pp.1617-1631
Published online: 18 November, 2010
DOI: 10.3987/COM-10-S(E)125
Synthesis of 2- and 3-Indolylpyrroles via 1,3-Dipolar Cycloadditions of Münchnones and Nitroalkenes

Justin M. Lopchuk and Gordon W. Gribble*

*6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, U.S.A.

Abstract

A series of 2- and 3-indolylpyrroles were generated via 1,3-dipolar cycloadditions between (2-nitrovinyl)indoles and symmetrical and unsymmetrical 1,3-oxazolium-5-olates (münchnones).

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Short Paper | Regular issue | Vol 83, No. 6, 2011, pp.1371-1376
Published online: 14 April, 2011
DOI: 10.3987/COM-11-12176
An Efficient Arylation of Benzoazoles with Aryl Bromides by a Practical Palladium-Copper Cocatalytic System

Xue-Ming Yan, Xue-Rong Mao, and Zhi-Zhen Huang*

*School of Chemistry and Chemical Engineering , Nanjing University, Nanjing 210093, China

Abstract

A practical, efficient Pd(OAc)2/Cu(II)/PPh3 cocatalytic system has been developed. With only 1 mol% Pd(OAc)2, 20 mol% copper(II) salt, and 0.5 equiv of inexpensive PPh3 as ligand, the direct arylation of benzoazoles with aryl bromides could be performed smoothly in mild condition, affording the desired arylated benzoazoles in good yields (75-93%).

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Review | Special issue | Vol 80, No. 1, 2010, pp.63-82
Published online: 12 March, 2009
DOI: 10.3987/REV-09-SR(S)1
A New Type of Oxidation-Reduction Condensation by the Combined Use of Phenyl Diphenylphosphinite and Oxidant

Teruaki Mukaiyama,* Kiichi Kuroda, and Yuji Maruyama

*Tokyo Chemical Industry Co., Ltd., 6-15-5 (TCI) Toshima, Kita-ku, Tokyo 114-0003, Japan

Abstract

A new type of oxidationreduction condensation of alcohols with sulfur, nitrogen, and oxygen nucleophiles by the combined use of phenyl diphenylphosphinite (PhOPPh2) and oxidants such as azides or diethyl azodicarboxylate (DEAD) are described. In these reactions, chiral secondary and tertiary alcohols are converted into the corresponding chiral sulfides, azides, esters and ethers under mild and neutral conditions with almost complete inversion of stereochemical configuration.

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Paper | Special issue | Vol 86, No. 1, 2012, pp.331-342
Published online: 18 July, 2012
DOI: 10.3987/COM-12-S(N)14
Reaction of Grignard Reagents with Diisopropylaminoborane. Synthesis of Alkyl, Aryl, Heteroaryl and Allyl Boronic Acids from Organoc(diisopropyl)aminoborane by a Simple Hydrolysis

Christopher L. Bailey, Chris L. Murphy, Jacob W. Clary, Scott Eagon, Naomi Gould, and Bakthan Singaram*

*Department of Chemistry, University of California, 1156 High Street, Santa Cruz, CA 95064, U.S.A.

Abstract

Diisopropylaminoborane (BH2-N(iPr)2) is prepared by reacting lithium diisopropylaminoborohydride (iPr-LAB) with trimethylsilyl chloride (TMSCl). Aliphatic, aromatic, and heteroaromatic (diisopropylamino)boranes are readily synthesized at ambient temperature (0 °C) in 1h by the reaction of Grignard reagents with (BH2-N(iPr)2). Two contending reaction pathways have tentatively been identified. During the mechanistic investigation, bromomagnesium diisopropylaminoborohydride was identified as a byproduct. This borylation reaction can be carried out under Barbier conditions, where (BH2-N(iPr)2) traps the in situ formed Grignard reagent from the corresponding organic halide and magnesium metal. Simple acid hydrolysis of the product organo(diisopropylamino)borane leads to the corresponding boronic acid in good to excellent yield.

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Paper | Special issue | Vol 86, No. 2, 2012, pp.1419-1429
Published online: 2 October, 2012
DOI: 10.3987/COM-12-S(N)102
Tuning the Solubilities of Bis-triazinylphenanthroline Ligands (BTPhens) and Their Complexes

Dominic M. Laventine, Ashfaq Afsar, Michael J. Hudson, and Laurence M. Harwood*

*Department of Chemistry, University of Reading, Reading RG6 6AD, U.K.

Abstract

A series of bis-triazinylphenanthroline ligands (BTPhens) was synthesized by modifying the triazine substituents. It was found that varying these substituents altered the solubilities of the ligands in a number of non-polar solvents. Thus C5-BTPhen showed significantly higher solubility in octanol than C1-BTPhen. The high solubility of C5-BTPhen and its complexes was exploited to facilitate the NMR titration experiments. These experiments shown that the dominant species in solution were the 1:2 complexes [Ln(III)(BTPhen)2], even at high Ln concentrations, and that the relative stability of the 2:1 to 1:1 BTPhen-Ln complexes varied with different lanthanides. C5-BTPhen therefore shows considerable promise for a once-through selective actinide separation process.

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Short Paper | Special issue | Vol 90, No. 1, 2015, pp.625-630
Published online: 2 April, 2014
DOI: 10.3987/COM-14-S(K)12
Synthesis of Unprotected CH2-Skipped Piperazine-Pyridine Alternating Cycles with Azide End-Group

Andi Kipper, Indrek Kalvet, Kaido Tämm, Lauri Sikk, Peeter Burk, Kuldar Kõiv, and Uno Mäeorg*

*Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411, Estonia

Abstract

This work describes synthesis of CH2-skipped alternating piperazine-pyridine cycles with azide end-group starting from piperazine, 1-methylpiperazine and pyridine-2,6-dicarboxylic acid. This compound can be used to enhance binding efficiency by shielding repulsion between negatively charged phosphate groups in DNA-oligonucleotide hybridization techniques.

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Paper | Regular issue | Vol 63, No. 12, 2004, pp.2747-2767
Published online: 26 October, 2004
DOI: 10.3987/COM-04-10213
Stereoselective Synthesis of 1-Substituted 1,2,3,4-Tetrahydro-β-carbolines by Asymmetric Electrophilic α-Amidoalkylation Reactions

Ulrich Weber, Cornelia Hoesl, W. Ponikwar, M. Suter, Heinrich Nöth, and Klaus T. Wanner*

*Department of Pharmacy, Ludwig-Maximilians-University of Munich, Butenandtstr. 5-13 Haus C, D-81377 Munich, Germany

Abstract

An efficient procedure for the asymmetric synthesis of 1-substituted 1,2,3,4-tetrahydro-9-methyl-β-carbolines based on asymmetric electrophilic α-amidoalkylation reactions is described. Stereoselective addition of various organometallic reagents to a chiral N-acyl-β-carbolinium ion gave the corresponding 1-substituted 1,2-dihydro-β-carbolines in high yields and very good to excellent diastereomeric ratios. Catalytic hydrogenation followed by the removal of the chiral auxiliary via reductive cleavage of the amide bond proceeded with complete conservation of the absolute configuration at the newly created stereocenter leading to 1-substituted 1,2,3,4-tetrahydro-9-methyl-β-carboline derivatives in high yields. Their absolute stereochemistry was proven by X-Ray analysis. The 1-phenyl-substituted 1,2,3,4-tetrahydro-β-carbolines were evaluated for their affinity to the PCP binding site of the NMDA receptor.

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