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Regular & Special Issues

165 data found. 1 - 30 listed Next Last

Published online: 17th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)36
8-Methyl Derivatives of Aristeromycin, Neplanocin, 3-Deazaneplanocin and Related Analogs

Xueqiang Yin, Qi Chen, Wei Ye, Chong Liu, and Stewart W. Schneller*

*Molette Laboratory for Drug Discovery, Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, U.S.A.

Abstract

The promising biological properties of 8-methyladenosine prompted a study of the related carbocyclic analogs based on aristeromycin and neplanocin. These target compounds have been prepared from strategically protected parent carbocyclic nucleoside derivatives or built up from suitable cyclopentanols and cyclopentenols. Several of these nucleosides were evaluated against a variety of RNA and DNA viruses to determine the potential of the 8-methyl series as a source for new antiviral agents. Encouraging results towards Epstein-Barr virus, cowpox, vaccinia virus, Ebola, and the flaviviruses (dengue and yellow fever) suggests more extensive studies.

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Published online: 17th February, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)90
Selective Aryl Radical Transfers into N-Heteroaromatics from Diaryliodonoium Salts with Trimethoxybenzene Auxiliary

Toshifumi Dohi, Shohei Ueda, Akiko Hirai, Yusuke Kojima, Koji Morimoto, and Yasuyuki Kita*

*Research Organization of Science and Technology, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan

Abstract

We have found that a series of trimethoxybenzene-based diaryliodonium(III) salts I (ArI+Ar’X-, where Ar = various aryl groups, Ar’ = 2,4,6-trimethoxyphenyl, X- = counterion) can exclusively cause Ar-transfers during the base-induced radical couplings with N-heteroaromatic compounds 1 by working the trimethoxybenzene ring (Ar’) as an inert coupling auxiliary. By the treatment with N-heteroaromatics 1 as the solvent, the metal-free arylations utilizing the specific salts I initiated by solid NaOH upon heating selectively produced the corresponding biaryls 2 in good yields without the formation of the trimethoxybenzene (Ar’) coupling product.

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Published online: 17th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)62
Absorption and Fluorescence Properties of Chalcones Having Pyrrole or Indole Moiety

Yukino Shinozaki and Tatsuo Arai*

*Graduate School of Pure and Applied Science, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8571, Japan

Abstract

2'-Hydroxychalcone derivatives having pyrrole ring have been synthesized and their absorption and fluorescence properties have been examined in connection to intramolecular hydrogen bonding.

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Published online: 17th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)88
Synthesis and Crystal Structures of Dicobalt Hexacarbonyl Complexes of Dicationic Alkyne-Bridged Imidazolium and Triazolium Derivates

Simone Haslinger, Gerhard Laus, Stefan Oberparleiter, Klaus Wurst, Volker Kahlenberg, Sven Nerdinger,* Erwin Schreiner, and Herwig Schottenberger

*Sandoz GmbH, Biochemiestrasse 10, 6250 Kundl , Austria

Abstract

Dicationic alkyne-bridged imidazolium and triazolium chlorides were subjected to counter-ion replacement reaction with weakly coordinating anions, such as hexafluoridophosphate and bis(trifluoromethanesulfonyl)amide. The resulting low-melting salts were further functionalized to dicobalt hexacarbonyl adducts. Seven crystal structures were determined by X-ray diffraction. Interionic C–H...F and C–H...O contacts were observed.

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Published online: 16th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)82
Toward the Synthesis of (‒)-Codeine by Chiral Auxiliary-Mediated Nitrone Cycloaddition

Julia Rautschek and Peter Metz*

*Department of Chemistry, Organic Chemistry I, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany

Abstract

Application of a C2-symmetric dioxolane moiety as chiral auxiliary for an asymmetric intramolecular nitrone cycloaddition was studied as a possible key step for the enantioselective synthesis of (–)-codeine. A cycloaddition precursor bearing a 1,2-diphenylethylene acetal was selected that was readily accessible in ten steps from isovanillin. It underwent nitrone cycloaddition and after a consecutive transformation, an isoxazolidine intermediate with the absolute and relative configuration required for (–)-codeine was obtained.

Supporting Info. (1.5MB)PDF (475KB)

Published online: 16th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)49
Effect of Leaving Group Substituents on the Microfluidic Synthesis of [18F]3-Fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile ([18F]FPEB)

Thomas M. Moore, Murthy R. Akula, Lee Collier, Gilles Tamagnan, Caroline Papin, David Alagille, and George W. Kabalka*

*Departments of Chemistry and Radiology, University of Tennessee, Knoxville, Tennessee, 37996-1600, U.S.A.

Abstract

A commercial microfluidic reactor system has been used to synthesize the mGLUR5 receptor imaging agent [18F]FPEB. To study the effect of leaving group substituents on the synthesis of the desired compound, the chloro-, bromo-, iodo-, and nitro-substituted precursors for FPEB were evaluated. Precursor concentrations of 4 – 10 mg/mL were evaluated in various solvents, with temperature ranges between 120 and 220 oC, and total processing times of less than five minutes. Optimized incorporation yields ranged from 5% to 69.4% depending on the precursor used.

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Published online: 16th February, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)85
Azulene-Based Tetrathiafulvalenes: Preparation and Their Electron-Donating Ability

Ohki Sato,* Takahito Saito, Masami Aoki, and Atsushi Sakai

*Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338-8570, Japan

Abstract

The condensation reaction of dithiocarbonates derived from azuleno- and guaiazulenopentathiepin with vinylene trithiocarbonate and the ethylenedithio derivative in triethyl phosphite afforded azulene-based tetrathiafulvalenes [Az-TTF, Az-(EDT)TTF, GAz-TTF and GAz-(EDT)TTF], respectively. The vinylene derivatives (Az-TTF and GAz-TTF) showed slightly higher electron-donating ability than the corresponding ethylenedithio ones [Az-(EDT)TTF and GAz-(EDT)TTF] by CV measurement. GAz-TTFs produced charge transfer complexes with tetracyanoquinodimethane, respectively.

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Published online: 16th February, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)67
Halocyclizations and Cycloisomerizations of Bisaryl 1,6-Diynes

Kyle R. Strom, Anna C. Impastato, Jaime A. Duque, and John K. Snyder*

*Department of Chemistry, Boston University, Boston, Massachusetts 02215, U.S.A.

Abstract

N-Sulfonamide tethered bisaryl 1,6-diynes underwent cyclization in the presence of Ga(III) trihalide to give mixtures of halocyclization (HC) and Friedel-Crafts (FC) cycloisomerization products. The ratio of products was found to be dependent on the identity of the halide and diyne substrate. In contrast, under Bronsted acid conditions only Friedel-Crafts cycloisomerization products were obtained. The regiochemical preference of the cyclization under Bronsted acid catalysis was reversed under Lewis acid catalysis. Herein, we report our efforts to understand and make use of this disparity to access a range of vinyl halides and indenopyridines from readily accessible 1,6-diyne.

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Published online: 16th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)63
Synthesis of Lamellarins via Regioselective Assembly of 1,2-Diarylated [1]Benzopyrano[3,4-b]pyrrol-4(3H)-one Core

Tsutomu Fukuda,* Takatoshi Katae, Issei Harada, and Masatomo Iwao

*Division of Chemistry and Materials Science, Graduate School of Engineering, Nagasaki University, 1-14, Bunkyo-machi, Nagasaki 852-8521, Japan

Abstract

A modular synthesis of lamellarins has been developed. The key reactions in this synthesis are the assembly of 1,2-diarylated [1]benzopyrano[3,4-b]pyrrol-4(3H)-ones from a preexisting [1]benzopyrano[3,4-b]pyrrol-4(3H)-one core and the appropriate arylboronic acids. The obtained 1,2-diarylated [1]benzopyrano[3,4-b]pyrrol-4(3H)-ones could be easily converted into the corresponding lamellarin derivatives by intramolecular annulation between the pyrrole nitrogen and the C2 aromatic ring.

Supporting Info. (7.2MB)PDF (759KB)

Published online: 15th February, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)80
A Fischer Indolization Strategy toward the Total Synthesis of (–)-Goniomitine

Beau P. Pritchett, Jun Kikuchi, Yoshitaka Numajiri, and Brian M. Stoltz*

*The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Blvd. MC101-20, Pasadena, CA 91125, U.S.A.

Abstract

A Fischer indolization strategy toward the core of (–)-goniomitine is reported. Initial investigations into the Pd-catalyzed asymmetric allylic alkylation of dihydropyrido[1,2-a]indolone (DHPI) substrates are also discussed.

Supporting Info. (1.3MB)PDF (370KB)

Published online: 14th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)83
Catalytic Intramolecular [2+2+2] Cycloaddition of Peptide-Tethered Branched Triynes for the Synthesis of Cyclic Peptides

Shuhei Obinata, Yu-ki Tahara, Kyalo Stephen Kanyiva, and Takanori Shibata*

*Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan

Abstract

Rhodium-catalyzed intramolecular [2+2+2] cycloaddition of peptide-tethered branched triynes gave cyclic peptides in moderate to excellent yields. This is a new catalytic protocol for the synthesis of cyclic peptides containing various amino acids.

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Published online: 14th February, 2017

Communication | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)31
Growth Mechanism of Uncultured Actinobacterial Strain Leucobacter sp. ASN212 by Zinc Coproporphyrin

Ryogo Takai, Kengo Shigetomi, Yoichi Kamagata, and Makoto Ubukata*

*Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan

Abstract

We propose HemH as a primary target of Zn coproporphyrin, which stimulates the growth of uncultured Leucobacter sp. ASN212, based on the structure-activity relationship for transition-metal complexes of coproporphyrin.

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Published online: 14th February, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)71
A Short Synthetic Route to a Hybrid Molecule Benzosultine-Sulfone via [2+2+2] Cyclotrimerization Using Mo(CO)6

Sambasivarao Kotha* and Gaddamedi Sreevani

*Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400076, India

Abstract

Here, we report an improved and short synthetic route to benzosultine-sulfone via [2+2+2] cyclotrimerization as a key step, starting with dipropargyl ether and 1,4-dibromo-2-butyne with an overall yield of 16%.

Supporting Info. (607KB)PDF (525KB)

Published online: 14th February, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)76
Diastereoselective Synthesis of 2,4-Substituted Tetrahydroquinolines via Hf(OTf)4-Catalyzed Substitution/Cyclization of 2-Aminobenzyl Alcohols with Styrenes

Masahiro Noji,* Hiroto Kadowaki, Yuuki Kubota, Tomomi Yoshida, Noriko Saito, Subaru Yamaguchi, Ren Ohata, Keitaro Ishii, and Toshikatsu Takanami

*Department of Life and Pharmaceutical Sciences, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan

Abstract

An efficient and convenient stereoselective synthetic approach to 2,4-substituted 1,2,3,4-tetrahydroquinoline has been developed. This catalytic procedure involves a sequential reaction of 2-aminobenzyl alcohol with styrenes in the presence of Hf(OTf)4 catalyst followed by intramolecular cyclization of the resulting cation species to give a variety of cis-2,4-substituted tetrahydroquinolines in good yield and diastereoselectivity.

Supporting Info. (7.5MB)PDF (1.1MB)

Published online: 14th February, 2017

Review | Special issue | Prepress
DOI: 10.3987/REV-16-SR(S)1
Asymmetric Hydrogenation of Six-Membered Monocyclic N-Heteroaromatic Compounds

Atsuhiro Iimuro, Kosuke Higashida, Haruki Nagae, and Kazushi Mashima*

*Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan

Abstract

Six-membered chiral cyclic amines are important skeletal structures found in natural products as well as bioactive species. Asymmetric hydrogenation of six-membered N-heteroaromatic compounds is considered one of the most straightforward protocols for preparing six-membered chiral cyclic amines, because asymmetric hydrogenation is an atom economical reaction and applicable to industrial scales. In this review, we summarize the development of asymmetric hydrogenation of six-membered N-heteroaromatic compounds, such as pyridines, pyrazines, pyrimidines, and pyridones.

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Published online: 6th February, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)72
Diastereo- and Enantioselective Construction of 6,7-Dioxabicyclo[2.2.1]heptane Derivatives by a Dirhodium(II)-Catalyzed Intramolecular C–H Insertion Reaction

Taku Miyazawa, Kozue Imai, Motoki Ito, Koji Takeda, Masahiro Anada,* Shigeki Matsunaga, and Shunichi Hashimoto*

*Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan

Abstract

The first diastereo- and enantioselective construction of bridged bicyclic ring systems by an intramolecular C–H insertion reaction is described. With dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], Rh2(S-PTTL)4, the C–H insertion of α-alkyl-α-diazoesters containing an ethylene ketal moiety at the γ-position provided methyl 6,7-dioxabicyclo[2.2.1]heptane-3-carboxylate derivatives with up to 95% ee and perfect diastereoselectivity.

Supporting Info. (3.6MB)PDF (1.2MB)

Published online: 1st February, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)55
Preparation and Optical and Electrochemical Properties of Diphthalocyanine Linked with a TTF Unit

Takeshi Kimura,* Shomu Sasaki, and Shiduko Nakajo

*Center for Instrumental Analysis, Iwate University, Morioka, Iwate 020-8551, Japan

Abstract

4,4’,7,7’-Tetrabutyl-5,5’,6,6’-tetracyano-2,2’-bis(benzo-1,3-dithiol-2-ylidene) (3-Bu) was prepared and mixed with 4,5-bis(2,6-dimethylphenoxy)phthalonitrile (4), which was treated with lithium alkoxide at 120 °C to produce diphthalocyanine linked with a TTF unit. The structure of the product was determined by NMR and MALDI-TOF-MS. The optical and electrochemical properties were examined by UV-vis spectra and cyclic voltammetry.

Supporting Info. (1.2MB)PDF (201MB)

Published online: 1st February, 2017

Communication | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)51
Design and Synthesis of 4-Chlorocolchicine-Derived Prodrug Capable of Forming Nanoparticles by Self-Assembly

Mariko Kitajima, Akihiro Morita, Shimpei Endo, Noriyuki Kogure, Kenjirou Higashi, Kunikazu Moribe, and Hiromitsu Takayama*

*Laboratory of Biofunctional Molecular Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan

Abstract

We have designed and synthesized colchicine-derived prodrug 7, which is composed of a 4-chlorocolchicine derivative, a dipeptide side chain cleavable by cathepsin B, a spacer containing a disulfide bond, and hydrophobic vitamin E. Prodrug 7 was capable of forming nanoparticles by self-assembly. Mean particle diameter evaluated by dynamic light scattering measurement was ca. 205 nm.

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Published online: 31st January, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)50
Oxidative Desulfurization of Electron-Donating 5,5,7,7-Tetraaryl-5,7-dihydrodibenzo[c,e]thiepins and the Related Heterocycles: Generation of Dicationic Dyes upon Two-Electron Oxidation

Takanori Suzuki,* Takuma Kuroda, Hitomi Tamaoki, Sho Higasa, Tatsuo Nehira, Ryo Katoono, Yusuke Ishigaki, Kenshu Fujiwara, Takanori Fukushima, and Hidetoshi Yamada

*Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan

Abstract

Upon oxidation of the title heterocycle (1A) with dimethylamino groups, elemental sulfur is extruded to form dicationic dye (1B2+), from which the starting dibenzothiepin derivative was generated by the reaction with Na2S. The bay-region substituents enhance configurational stability, so that, the optically pure heterocycles [(M)-2A, (M)-3A)] can be obtained in terms of helicity of one-handedness by starting with the corresponding optically pure dicationic dyes [(R)-2B2+, (R)-3B2+)]. Similar oxidative desulfurization occurs in dibenzo-1,5-oxathiocin 4A, a structurally related 8-membered heterocycle.

Supporting Info. (377KB)PDF (1.2MB)

Published online: 31st January, 2017

Paper | Regular issue | Prepress
DOI: 10.3987/COM-16-13543
The Reactivity of 4’-Substituted Spiro[Isoindole-1,3’-Pyrazoles] Derivatives: Substitution/Elimination Reactions and Access to Biaryl Derivatives

Benedetta Maggio, Gianfranco Fontana, Maria Valeria Raimondi, Demetrio Raffa, Fabiana Plescia, Angela Maria Ingarra, and Giuseppe Daidone*

*STEBICEF, University of Palermo, Via Archirafi 32, 90123 Palermo, Italy

Abstract

This paper describes aspects of the chemistry of 4’-substituted spiro[isoindole-1,3’-pyrazoles]. These compounds underwent substitution and/or elimination reactions to afford some new spiro– as well as biaryl derivatives of potential pharmaceutical relevance. Mechanistic considerations are discussed as well.

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Published online: 31st January, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)84
Ammonium Hypoiodite-Catalyzed Peroxidative Dearomatization of Phenols

Muhammet Uyanik, Kohei Nishioka, and Kazuaki Ishihara*

*Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8603, Japan

Abstract

Here, we report the first transition metal-free peroxidative dearomatization of phenols using hypoiodite catalysis with TBHP. Hypoiodite salts are generated in situ from the corresponding quaternary ammonium iodides in the presence of TBHP, and the oxidative coupling reaction proceeds efficiently under mild conditions. The dearomatized products are versatile synthetic intermediates for further synthetic transformations to various complex structures including heterocycles. As a demonstration, the further oxidation of the unsaturated peroxide with TBHP afforded the corresponding peroxy epoxide in good yield.

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Published online: 31st January, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)26
Effective Separation of Am(III) from Cm(III) Using Modified BTPhen Ligands

Ashfaq Afsar, Alyn C. Edwards, Andreas Geist, Laurence M. Harwood,* Michael J. Hudson, James Westwood, and Roger C. Whitehead

*School of Chemistry, University of Reading, Whiteknights, Reading, Berkshire RG6 6AD, UK

Abstract

Electronic modulation of CyMe4-BTPhen with 5-bromo and 5-(4-hydroxyphenyl) substituents leads to enhanced separation of Am(III) from Cm(III) over 0.1 – 3 M HNO3 (SFAm/Cm = ca. 9 at 0.1 M HNO3). In addition, substituting bromine atoms at the 5 and 6 positions of the phenanthroline backbone provides a mean of separating Am(III) from Eu(III) (SFAm/Eu = ca. 240 at 3 M HNO3).

Supporting Info. (571KB)PDF (450KB)

Published online: 31st January, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-16-S(S)65
Syntheses and Photophysical Properties of Aminobenzopyranoxanthene Dyes Containing Various Alkyl Chains at Amine Moieties

Shinichiro Kamino,* Masaru Tanioka, Daisuke Sawada, and Shuichi Enomoto*

*Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama-shi, Okayama 700-8530, Japan

Abstract

Aminobenzopyranoxanthene (ABPX) dyes containing linear n-alkyl chains at amino groups were synthesized, and their cis and trans stereoisomers were isolated. Detailed spectrophotometric studies revealed that all the ABPX derivatives exhibited fluorescence emission in the far-red and near-infrared wavelength regions, and their fluorescence quantum efficiency increased with increasing n-alkyl chain length. Almost no differences in photophysical properties were observed between the cis and trans stereoisomers.

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Published online: 31st January, 2017

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-16-13625
A New Chromone Derivative From An Endophytic Fungus Xylaria sp. Isolated From Ardisia Crenata

Ken-ichi Nakashima,* Junko Tomida, Masanori Tabata, Takao Hirai, Yuji Morita, Yoshiaki Kawamura, and Makoto Inoue

*Laboratory of Medicinal Resources, Faculty of Pharmaceutical Sciences, Aichi Gakuin University, 1-100 Kusumoto-cho Chikusa-ku Nagoya city 464-8650, Japan

Abstract

A new chromone derivative, xylariacetal (1), and a known isocoumarin, mullein (2), were isolated from Xylaria sp. ECN-008, which was derived from the leaves of Ardisia crenata. The structure of the new compound was identified by various spectroscopic techniques including 1D- and 2D-NMR. Xylariacetal (1) exhibits a characteristic tricyclic structure with an acetal moiety.

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Published online: 30th January, 2017

Review | Special issue | Prepress
DOI: 10.3987/REV-16-SR(S)6
Synthetic Methods for Ring-Fluorinated Pyrrole Derivatives

Takeshi Fujita and Junji Ichikawa*

*Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan

Abstract

The synthesis of pyrrole ring-fluorinated heterocyclic compounds has been increasingly studied in response to the rising demand for these compounds as potential drugs, agrochemicals, and advanced materials. The approaches to their synthesis are grouped into two categories in terms of how the fluorine substituents are introduced: (i) direct fluorination of the existing pyrrole and related rings and (ii) the construction of pyrrole rings via fluorine-containing precursors. This review overviews recent synthetic methods for ring-fluorinated pyrrole derivatives according to the types of reactions.

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Published online: 30th January, 2017

Paper | Regular issue | Prepress
DOI: 10.3987/COM-16-13583
Expeditious Synthesis of Carboxylic Esters and High-Yielding Macrolactones Using Trifluoromethyl-Substituted Benzoic Anhydrides with 4-(Dimethylamino)pyridine: an Evaluation of The Reactivities of Aromatic Acid Anhydrides as Dehydration Reagents Compared with 2-Methyl-6-nitrobenzoic Anhydride

Isamu Shiina* and Takayuki Tonoi

*Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan

Abstract

Trifluoromethyl-substituted benzoic anhydrides as structural congeners of 2-methyl-6-nitrobenzoic anhydride (MNBA) were prepared and investigated for comparative reactivity in the synthesis of carboxylic esters and macrolactones. 2-Fluoro-6-(trifluoromethyl)benzoic anhydride (FTFBA) was found to be a promising dehydrating agent in the presence of 4-(dimethylamino)pyridine (DMAP), and was successfully employed in the synthesis of threo-aleuritic acid lactone in good yield with high chemoselectivity.

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Published online: 27th January, 2017

Review | Regular issue | Prepress
DOI: 10.3987/REV-16-849
Tetrazolecarbaldehydes and Their Derivatives

Dietrich Moderhack*

*Institute of Medicinal and Pharmaceutical Chemistry, Technical University, Braunschweig, Beethovenstrasse 55, D-38106, Germany

Abstract

This article summarizes the preparative chemistry of the three classes of tetrazolecarbaldehydes (A–C) including derivatives. Certain comparisons between A–C and their closest analogues, the 1,2,4-triazolecarbaldehydes (D–F), are drawn.

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Published online: 27th January, 2017

Paper | Regular issue | Prepress
DOI: 10.3987/COM-16-13623
One-Pot and Efficient Synthesis of 5-Aminopyrazole-4-carbonitriles Catalyzed by Potassium Phthalimide

Hamzeh Kiyani* and Maryam Bamdad

*School of Chemistry, Damghan University, Cheshmeh Ali Road, Daneshgah square, Damghan 36715-364, Iran

Abstract

The potassium phthalimide (PPI) has been found to be an efficient, recyclable, inexpensive, commercially available, and easy to handle catalyst for the synthesis of 5-aminopyrazole-4-carbonitriles through the one-pot, three-component reaction of easily available starting reactants involving aldehydes, phenylhydrazine, and malononitrile. This reaction was performed in a mixture of ethanol-water as a green reaction media at 50 °C. The present eco-friendly three-component cyclocondensation offers main benefits including, time-saving, mild conditions, minimize the amount of waste, good atom efficiency, avoiding the hazardous organic solvents or catalysts, and the ease of the work-up.

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Published online: 27th January, 2017

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-16-13632
Facile and Short-Step Synthesis of 5-Substituted 2,3,4,5-Tetrahydrobenz[f][1,4]Oxazepines Using a Modified Pictet-spengler Reaction

Toshiaki Saitoh, Michikazu Kitabatake, Takuya Sugimoto, Hiromu Kawakubo, Kunihiko Mohri, and Yoshie Horiguchi*

*Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3-3165, Higashi-tamagawagakuen, Machida, Tokyo 194-8543, Japan

Abstract

5-Substituted 2,3,4,5-tetrahydrobenz[f][1,4]oxazepines (6) were synthesized using a modified Pictet-Spengler reaction of formyliminium ion (4) as the key step. Cyclization of 4 proceeded readily by using trifluoroacetic acid as a catalyst, giving N-formyl 5-substituted 2,3,4,5-tetrahydrobenz[f][1,4]oxazepines (5) in 26–78% yield. The imination of 2-phenoxyethaneamine (1) with aldehydes, formylation of the resulting imines (3), and the acid-catalyzed cyclization steps could be carried out in a one-pot procedure. Hydrolysis of 5 with hydrochloric acid gave the 5-substituted 2,3,4,5-tetrahydrobenz[f][1,4]oxazepines (6) in high yields.

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Published online: 26th January, 2017

Review | Special issue | Prepress
DOI: 10.3987/REV-16-SR(S)4
Direct Enantioselective Alkynylation of α-Ketoesters and α-Ketiminoesters Catalyzed by [Bis(oxazoline)phenyl]rhodium(III) Complexes

Kazuhiro Morisaki, Hiroyuki Morimoto, Kazushi Mashima, and Takashi Ohshima*

*Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan

Abstract

This review summarizes our studies of the direct enantioselective alkynylation of α-ketoesters and α-ketiminoesters catalyzed by [bis(oxazoline)phenyl]rhodium(III) ((phebox)Rh(III)) complexes. The reactions provide chiral α-tetrasubstituted propargyl alcohols and propargylamines under proton-transfer conditions in high yield and with high enantioselectivity. The unique nature of (phebox)Rh(III) complexes allows the reactions to occur in the presence of various functional groups, including an electrophilic aldehyde functionality. Mechanistic studies revealed that the generation of (alkynyl)Rh(III) complexes limited the overall reactivity, which led us to use (trimethylsilylethynyl)(phebox)Rh(III) complexes as efficient pre-catalysts. The use of (trimethylsilylethynyl)(phebox)Rh(III) complexes reduced catalyst loading to as low as 0.5 mol%, and expanded the substrate scope to unprecedented α-ketiminophosphonate and cyclic N-sulfonyl α-ketiminoesters.

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165 data found. 1 - 30 listed Next Last