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Published online: 23rd December, 2020

Review | Regular issue | Prepress
DOI: 10.3987/REV-20-948
Imidazole Chemistry in Crop Protection

Clemens Lamberth*

*Syngenta Crop Protection AG, Research Chemistry, Schaffhauserstrasse 101, CH-4332 Stein, Switzerland

Abstract

An overview is given of the significance of the imidazole scaffold in crop protection chemistry. The main herbicidally, fungicidally and insecticidally active imidazole classes are presented, together with their synthesis routes, modes of action and biological efficacies. Also, partially and fully saturated imidazole derivatives, such as imidazolines and imidazolidines, oxygenated derivatives, such as imidazolinones and hydantoins as well as annulated derivatives, such as benzimidazoles, are covered. In addition, also the role of imidazoles as intermediates or reagents in the synthesis of other agrochemicals is reported.

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Published online: 21st December, 2020

Review | Regular issue | Prepress
DOI: 10.3987/REV-20-949
Recent Advances in Synthetic Transformations with Robust Yet Reactive B(Dan) Moiety

Jialun Li and Hiroto Yoshida*

*Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.

Abstract

Recent advances in the direct B(dan)-installing reactions (dan = naphthalene-1,8-diaminato) into organic frameworks by utilizing (pin)B–B(dan) or H–B(dan) as a B(dan) source, and the direct cross-coupling of dan-substituted organoboron compounds therefrom are described.

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Published online: 18th December, 2020

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)42
Catalytic Asymmetric Ring-Opening of σ-Symmetric Cyclic Carbonates with Chiral Amino Sulfonamide Catalysts

Michiyasu Nakao, Tomomi Shozui, Daisuke Inoue, Takahito Ihara, Syuji Kitaike, and Shigeki Sano*

*Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78 Sho-machi, Tokushima 770-8505, Japan

Abstract

Enantioselective ring-opening of σ-symmetric six-membered cyclic carbonates with benzyl alcohol catalyzed by 20 mol% of chiral amino sulfonamide catalysts afforded chiral acyclic carbonates in up to 79% ee.

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Published online: 10th December, 2020

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)44
An Arylative Aziridination Process toward Aspidosperma Alkaloids

Kouassi Signo, Elsa Deruer, Siomenan Coulibali, and Sylvain Canesi*

*Laboratoire de Méthodologie et Synthèse de Produits Naturels, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, H3C 3P8, Québec, Canada.

Abstract

An arylative aziridination process has been developed from dibrominated phenols containing a Fukuyama sulfonamide on the lateral chain. A two-step procedure involving the formation of a dienone by a phenol oxidation reaction mediated by a hypervalent iodine reagent (Kita reaction) followed by an intramolecular arylative aziridination process was used. This second step occurred under mild conditions via a Michael–Smiles ring-closure cascade, producing sulfur dioxide as the only byproduct. Additionally, a stereoselective approach was observed with tyrosine derivatives. This transformation respects the rules of green chemistry and atom economy. These new polyfunctionalized scaffolds could offer several synthetic possibilities for the total synthesis of natural products such as the main core of Aspidosperma alkaloids.

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Published online: 3rd December, 2020

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)41
Preparation of Optically Pure Dinuclear Cobalt(III) Complex with Λ-Configuration as a Dianionic Chiral Catalyst

Mohamed S. H. Salem, Ankit Kumar, Makoto Sako, Tsukasa Abe, Shinobu Takizawa,* and Hiroaki Sasai*

*The Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan

Abstract

The disodium salt of enantiomerically pure dimeric Λ-cobalt(III) complex 1 was prepared in one-pot from sodium triscarbonatocobaltate(III) and Schiff base ligand (Ra,S,S)-2 formed by the condensation of (R)-3,3ʹ-diformyl-2,2ʹ-dihydroxy-1,1ʹ-binaphthyl 3 with (S)-tert-leucine 4. Preliminary screening of 1 as a chiral catalyst was conducted for the bromocyclization of a tryptamine derivative.

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Published online: 3rd December, 2020

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)40
Concise Synthesis of an Amide-Functionalized [7]Helicene-like Molecule via Intramolecular Amidation

Yongning Xing, Masanori Nikaido, Takuya Murai, Shohei Hamada, Yusuke Kobayashi, Takahiro Sasamori, Takeo Kawabata, and Takumi Furuta*

*Department of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan

Abstract

A concise synthesis of an amide-functionalized [7]helicene-like molecule was achieved via the intramolecular amidation of an in-situ-generated biaryl δ-amino acid derivative. An X-ray analysis of racemic mixture of this helicene-like molecule revealed a helically twisted π-system and that the (M)- and (P)-isomers associate pairwise via hydrogen-bonding interactions, which results in a one-dimensional columnar packing in the crystal structure.

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Published online: 30th November, 2020

Review | Regular issue | Prepress
DOI: 10.3987/REV-20-944
Highly Oxidized γ-Lactam-Containing Natural Products: Total Synthesis and Biological Evaluation

Kosaku Tanaka III,* Hiroshi Kogen, and Kenichi Kobayashi*

*Graduate School of Pharmaceutical Sciences, Health Sciences University of Hokkaido; 1757 Kanazawa, Tobetsu-cho, Ishikari-gun, Hokkaido 061-0293, Japan

Abstract

γ-Lactam is a ubiquitous structure found in the natural products. A number of highly oxidized γ-lactam-containing natural products are produced by various fungi. These compounds often show a wide range of biological activities because their multiple internal reaction sites, which arise from the high oxidation state of the compounds, can react with biological nucleophiles. Due to their high reactivity and dense functionality, total syntheses of these molecules require strict control of the inherent reactivity and the appropriate design of synthetic intermediates. This review focuses on the recent total syntheses of some highly oxidized γ-lactam-containing natural products, including fused bicyclic (epolactaene, NG-391, lucilactaene, L-755,807), spirocyclic (azaspirene, pseurotin A, E, and F2, cephalimysin A–C, FD-838, and berkeleyamide D), and tricyclic (rubrobramide and talaramide A) skeletons, and on the structure-activity relationship studies of related molecules.

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Published online: 27th November, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)39
Intramolecular Transamidation-Cyclization of N-(α-Oxoacetyl) Diamine: Influence of Solvent, Acidity and Substituents

Takashi Kouko, Hiroaki Miyazawa, Hideki Hikita, Hiromi Totsuka, Kazuhiro Higuchi,* and Tomomi Kawasaki*

*Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan

Abstract

We studied the selective formation of 3,5- and 2,5-pyrazinone via a transamidation-cyclization reaction. The equilibrium between acyl amides changed depending on the solvent, acidity, and substituents. Furthermore, selective transformation of 2,5-pyrazinone was accomplished by using a substrate with a secondary amine.

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Published online: 26th November, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)37
Synthesis, Structure, and π-Donor Properties of Tris(Ethyleledioxy)Benzene and Bis(Ethyleledioxy)Thiophene

Ryoji Watanabe, Tohru Nishinaga,* Yoshiyuki Kuwatani, and Masahiko Iyoda*

*Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan

Abstract

Tris(ethylenedioxy)benzene 3 and bis(ethylenedioxy)thiophene 4 have been synthesized starting from 2,3-dibromo-1,4-dioxene in 25 and 38% overall yields, respectively. These ethylenedioxy-fused benzene and thiophene can be easily oxidized to produce the corresponding radical cations 3•+ and 4•+ because of their high-lying HOMO levels. Interestingly, the radical cation 3•+ exhibits a fairly strong fluorescent emission at λmax 602 and 590 nm (φF = 0.40 in MeCN and 0.50 in H2SO4).

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Published online: 20th November, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)34
Synthesis and Blue Dyeing Ability for Polypropylene Fabrics of Various 3,7-Bis(Dialkylamino)Phenoxazin-5-Ium Salts and the Sulfur and Selenium Analogs

Takumi Yoshida* and Masahito Segi*

*Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan

Abstract

3,7-Bis(dialkylamino)phenoxazin-5-ium salts having different amino groups (dimethylamino, diethylamino, dipropylamino, dibutylamino, and pyrrolidyl) and counter anions (chloride, bromide, iodide, hydrogensulfate, and nitrate) were synthesized in up to 80% isolated yield as blue cationic dyes. In addition, 3,7-bis(diethylamino)phenothiazin-5-ium and 3,7-bis(diethylamino)phenoselenazin-5-ium iodides were also synthesized in 20% and 17% isolated yields, respectively. Polypropylene fabrics were dyed with the above synthesized blue cationic dyes. As an evaluation result, it has been found that the moderate size such as diethylamino groups at the 3 and 7 positions of phenoxazinium salts is suitable for the dyeing ability.

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Published online: 20th November, 2020

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)3
Recent Advances in Synthetic Strategies for the C4a,C9a-Fused Tetracyclic Hydrocarbazole Core Structure of Minfiensine and Related Akuammiline Alkaloids

Keisuke Hosoya, Keita Iida, Minami Odagi,* and Kazuo Nagasawa*

*Department of Biotechnology and Life Science, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan

Abstract

The Strychnos alkaloid minfiensine and its analogs among the akuammiline alkaloids have a variety of biological activities, including anti-tumor and analgesic activities, and have therefore attracted considerable synthetic interest. Here we provide an overview of recent advances in methodologies for the construction of the characteristic tetracyclic hydrocarbazole core structure containing a fused pyrrolidine ring at C4a and C9a.

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Published online: 13th November, 2020

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)38
De Novo Approach to Izidines via a Gold-Catalyzed Hydroamination–N-acyliminium Ion Cyclization of Acyclic Ynamides

Kenji Sugimoto,* Shota Mizuno, Misaki Shirato, Kosuke Tanabe, and Yuji Matsuya*

*Faculty of Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama, 930-0194, Japan.

Abstract

A gold(I)-catalyzed novel domino reaction of acyclic ynamides yielding nitrogen-fused bicyclic skeletons was described. The reaction with 10 mol% JohnPhosAuNTf2 and stoichiometric amount of PhCO2H enables constructions of quinolizidine and indolizidine skeleton having tetrasubstituted carbon center. Especially in the case of quinolizidine synthesis, the quaternary stereogenic center could be furnished under highly diastereoselective manner.

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Published online: 9th November, 2020

Review | Regular issue | Prepress
DOI: 10.3987/REV-20-943
Systematic Search for Transition States in Complex Molecules: Computational Analyses of the Regio- and Stereoselective Interflavan Bond Formation in Flavan-3-Ols

Daisuke Urabe* and Keisuke Fukaya

*Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan

Abstract

This review describes our recent work on a systematic search for transition states in transformations of complex molecules. The method features a combination of a conformational search method using constrained models to create a large library of transition-state candidates, and subsequent density functional theory (DTF)-based transition state calculations for the candidates. The method is applicable to calculation of transition states for inter- and intramolecular interflavan bond formation in flavan-3-ols to reproduce experimental results for highly regio- and stereoselective C-C bond formation. The specific roles of van der Waals interactions in the transition states can be visualized by NCIPLOT mapping to show the importance of weak but attractive interactions for selective interflavan bond formation.

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Published online: 9th November, 2020

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)35
Design, Synthesis, Physical Properties and Indoleamine 2, 3-Dioxygenase 1 Inhibitory Activity of Substitued Indole Derivatives with N-H, N-Metohymethyl, or N-Mehylthiomethyl Group toward Fragment-Based Drug Discovery

Kenta Hayami, Yuichi Kuboki, Katsumi Ohta, Bangzhong Lin, Megumi Fumimoto, Kazuto Nunomura, Jun-Ichi Haruta , Kenichi Murai, Hiromichi Fujioka, Akira Asai, and Mitsuhiro Arisawa*

*Graduate School of Pharmaceutical Science, Osaka University, 1-6 Yamadaoka, Suita, Osaka 560-0871, Japan

Abstract

We designed and prepared N-H, N-CH2OMe(MOM), and N-CH2SMe (MTM) forms of various substituted indoles, using a docking study, as a small fragment library toward fragment-based drug discovery (FBDD) and evaluated their indoleamine 2, 3-dioxygenase 1 (IDO1) inhibitory activities and physical properties.

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Published online: 29th October, 2020

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)32
Hybrid Catalysis of 8-Quinolinecarboxaldehyde and Brønsted Acid for Efficient Racemization of α-Amino Amides and Its Application in Chemoenzymatic Dynamic Kinetic Resolution

Kohsuke Ohmatsu, Mari Kiyokawa, Yuto Shirai, Yuya Nagato, and Takashi Ooi*

*Institute of Transformative Bio-Molecules (WPI-ITbM), and Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Nagoya, 464-8601, Japan

Abstract

The combination of 8-quinolinecarboxaldehyde and benzoic acid proved to be an effective catalyst system for the racemization of N-unprotected α-aryl- or α-alkyl-substituted α-amino amides. Application of this system to chemoenzymatic dynamic kinetic resolution provided an efficient access to enantiomerically pure N-acetyl-α-amino amides in good to high yields.

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Published online: 29th October, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)28
Synthesis of 1-Methoxy-1H-indoles with a Heterocyclic Moiety via Unstable Indole Isothiocyanate by Using Enzyme from Brassicaceae Plant

Kaori Ryu, Seikou Nakamura,* Koya Miyagawa, Souichi Nakashima, and Hisashi Matsuda*

*Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan

Abstract

A synthesis of five 1-methoxy-1H-indole derivatives with imidazole, pyrazole, 1H-1,2,3-triazole, and 1H-1,2,4-triazole moieties was achieved by focusing on the formation mechanism of plant constituents. The objective 1-methoxy-1H-indole derivatives were obtained in situ (in one step) through the reaction of an unstable 3-(isothiocyanatomethyl)-1-methoxy-1H-indole, which was derived from neoglucobrassicin and plant enzyme myrosinase, and a heterocyclic compound. We have great hopes that this method would be useful for the development of medicinal seeds.

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Published online: 28th October, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)29
Stereoselective Alkylation of Oxathiazinane N,O-Ketals for the Construction of Aza-Quaternary Carbon Centers

Hisanori Nambu, Eri Tanaka, Mai Okada, Chiaki Hirosawa, Narumi Noda, Tomoya Fujiwara, and Takayuki Yakura*

*Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan

Abstract

Stereoselective construction of aza-quaternary carbon centers was achieved using the alkylation of oxathiazinane N,O-ketals prepared by Rh(II)-catalyzed C–H amination of sulfamates. The addition of alkyl Grignard reagents into N,O-ketals in the absence of any Lewis acid proceeded stereoselectively to provide the corresponding alkylated products with an aza-quaternary carbon center in high yields. The obtained product could be converted into an α-amino alcohol derivative, which is a potential synthetic intermediate for sphingofungin F and its derivatives.

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Published online: 27th October, 2020

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)1
Recent Advances in the Microwave Assisted Synthesis of Benzofuran and Indole Derivatives

Thaipparambil Aneeja, Sankaran Radhika, C M A Afsina, and Gopinathan Anilkumar*

*School of Chemical Sciences, Mahatma Gandhi University, Priyadarsini Hills, Kottayam, Kerala , India

Abstract


Abstract – Microwave (MW) assisted syntheses are environment friendly, efficient, rapid and convenient methodology for the synthesis of organic compounds. Benzene ring fused to a five membered ring containing N or O atom exhibits wide range of biological activities. Benzofuran is present in polymers, pharmaceuticals, and bioactive natural products. Benzofuran is significant as insecticides, herbicides, anti-inflammatory and anti-viral agents. Indoles are well known scaffold showing noteworthy activities like anti-tumor, anti-viral, anti-microbial and anti-oxidant. Indole derivatives are valuable moiety in different therapeutically active drug molecules. On account of the biological significance of benzofuran and indole scaffold, this review describes the recent advances in microwave assisted synthesis of benzofurans and indoles, and covers literature from 2012-2020.

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Published online: 27th October, 2020

Review | Regular issue | Prepress
DOI: 10.3987/REV-20-939
Attractive Organic Cocrystal Materials in Optics

Xiao Han,* Linyu Wang, and Gaiqing Xi

*College of Chemical Engineering & Material, Hebei Key Laboratory of Heterocyclic Compounds, Handan University, Handan 056005, Hebei, China

Abstract

Since the beginning of this century, organic molecule solid material, one of favorable choices for constructing high-performance optoelectronic devices/circuits, has showed the impressive perspective in organic optoelectronics. Especially, because of the long-range order, absent grain boundary and extremely low defect density, organic single-crystal material support a great platform for fundament and application researches. Herein, cocrystal engineering, one simply collaborative strategy, shows offers the unique advantages, involving facile and low-cost synthesis procedure, easily achieving rare and multifunctional properties, tunable structure, morphology and size. It is extremely suitable to construct functional organic molecule solid material, especially novel multifunctional organic single-crystal materials. In this mini review, a overview of organic cocrystal is presented to introduce its attractive future in optics, such as OFET, lasing, nonlinear optics, optical waveguide material, stimuli-responsive material and other potential applications.

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Published online: 26th October, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)30
Synthesis and Structure-Activity Relationship Study of 1,12-Dicarba-closo-dodecaborane-based Triol Derivatives as Nonsecosteroidal Vitamin D Analogs

Shinya Fujii, Ryota Sekine, Atsushi Kano, Hiroyuki Masuno, Emiko Kawachi, Tomoya Hirano, and Hiroyuki Kagechika*

*Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10, Surugadai, Kanda, Chiyoda-ku 101-0062, Japan

Abstract

The secosteroidal hormone 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] is a specific ligand of nuclear vitamin D receptor (VDR), and novel vitamin D analogs are promising candidates for multiple clinical applications. We previously developed a series of 1,12-dicarba-closo-dodecaborane (p-carborane) derivatives as nonsecosteroidal VDR agonists. Here, we report the synthesis and structure-activity relationship of p-carborane-based nonsecosteroidal vitamin D analogs bearing a nitrogen or a sulfur atom in the linker structure. Biological evaluation revealed that the structure–activity relationships of amine derivatives and sulfide derivatives are different, and therefore the choice of the linker structure significantly affects the activity. We also found that benzylamine structure could be a lead scaffold for novel vitamin D analogs. The structure–activity relationships presented here should be helpful in further development of nonsecosteroidal vitamin D analogs.

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Published online: 22nd October, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)36
Preparation of 2-Aryl-3-Silyl- and 2-Aryl-3-Germyl-1,3-Butadienes via Arylnickelation and Zinciomethylation

Nana Yoshino, Betemariam Sharewa, Zenichi Ikeda, and Seijiro Matsubara*

*Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo, Kyoto 615-8510, Japan

Abstract

Benzyl 3-silyl(or germyl)propargyl ether, aryl iodide, and bis(iodozincio)methane were assembled in the presence of a nickel catalyst to efficiently give 2-aryl-3-silyl(germyl)-1,3-butadienes via arylnickelation, zinciomethylation, and 1,4-elimination of zinc benzyloxide. As a ligand, an electron-deficient phospine such as tris(2-furyl)phosphine was effective.

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Published online: 22nd October, 2020

Review | Regular issue | Prepress
DOI: 10.3987/REV-20-940
Synthetic Approaches for Heteroannulated Chromones Fused Various Heterocyclic Systems

Salsabeel H. Hashiem, Magdy A. Ibrahim, Al-Shimaa Badran,* Nasser M. El-Gohary, and Hassan A. Allimony

*Department of Chemistry, Faculty of Education, Ain Shams University, Roxy 11711, Cairo, Egypt

Abstract

The main focus of this review summarized the different methods utilized for the synthesis of chromone annulated with different heterocyclic rings such as pyrroles, furans, pyrazole, imidazole, benzene, naphthalene, quinolone……and others.

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Published online: 21st October, 2020

Review | Regular issue | Prepress
DOI: 10.3987/REV-20-935
The Interrupted Pummerer Reaction: Design of Sulfoxides and Their Utility in Organic Synthesis

Kazuhiro Higuchi* and Masanori Tayu

*Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan

Abstract

Acid anhydride-activated sulfoxides can undergo a variety of cascade reactions after reacting with nucleophiles on its sulfur atom. Originally regarded as an abnormal phenomenon that occurs under Pummerer reaction conditions, the reports of the reaction increased gradually, and research regarding sulfoxide reactivity has advanced. In recent years, the term ‘interrupted Pummerer reaction’ has been introduced, and the transformation has been actively incorporated into the development of new research areas. Such studies have yielded numerous valuable sulfoxides, which contribute to the precise reaction control and to the generation of practical products. Notably, the outcome of the interrupted Pummerer reaction is characteristic for each nucleophile.

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Published online: 20th October, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)31
Mn(III)-Based Oxidative Cyclization of 2-((2-Arylamino)Ethyl)Malonates: Synthesis of Quinolines via Dihydroquinolinedicarboxylates

Takayuki Nagashimada, Masahiro Morikawa, Kengo Ohki, and Hiroshi Nishino*

*Department of Chemistry, Graduate School of Science, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555, Japan

Abstract

The synthesis of quinolines from aniline derivatives via the Mn(III)-based oxidative cyclization of 2-(2-(arylamino)ethyl)malonates is described. The 2-(2-(arylamino)ethyl)malonates were prepared in two steps from the substituted anilines. The cyclization of nineteen arylaminoethylmalonates protected by the N-acyl and N-alkoxycarbonyl groups easily proceeded in the formal 6-endo mode regardless of the presence of halo, methyl, and methoxy groups on the aromatic ring, and the corresponding tetrahydroquinolinedicarboxylates were produced in high yields except for the 2,4-dimethoxyphenyl-substituted aminoethylmalonate which occurred by ipso-cyclization. The tetrahydroquinolinedicarboxylate could be transformed into quinoline via decarboxylation and deprotective hydrolysis. The characteristic phenomenon in the NMR spectrum of the tetrahydroquinolinedicarboxylates is also discussed.

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Published online: 19th October, 2020

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)24
Rhodium-Catalyzed Crossed [2+2+2] Cycloaddition with Ynamides: Key-Strategy for the Concise Total Synthesis of 3-Oxygenated Carbazole Alkaloids

Carole Alayrac* and Bernhard Witulski*

*Laboratoire de Chimie Molèculaire et Thioorganique (LCMT) , National Graduate School of Engineering and Research Center, France

Abstract

Total syntheses of a set of naturally occurring 3-oxygenated carbazole alkaloids - 6-chlorohyellazole, carazostatin, carbazomycins A and B - are described. The key-strategy underlines a highly chemo- and regioselective rhodium-catalyzed [2+2+2] cyclotrimerization between appropriately tailored yne-ynamides and 1-methoxypropyne that is stirred by the interplay of stereoelectronic and steric effects allowing the introduction of four ring substituents of the natural carbazoles within a single step and making the overall syntheses short and efficient.

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Published online: 23rd September, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)27
Dirhodium(Ii)-Catalyzed ortho C–H Amination of N-Alkyldiarylamines

Motoki Ito,* Mamiko Mori, Tomoya Nakagawa, Miki Hori, Kazuhiro Higuchi, and Shigeo Sugiyama*

*Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588,

Abstract

Dirhodium(II)-catalyzed ortho C–H amination of N-alkyldiarylamines has been developed. The C(sp2)–H amination proceeded with high preference over C(sp3)–H amination to provide N-aryl-o-phenylenediamines in up to 80% yield. With the use of unsymmetric diarylamines as substrates, selective amination of one of two distinct aromatic rings was also achieved.

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Published online: 16th September, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)23
Synthesis of (Trifluoromethyldiazirinyl)phenylboronic Acid Derivatives for Photoaffinity Labeling

Manami Hashinoki, Natsumi Kurokawa, Yuta Murai, Zetryana Puteri Tachrim, Yasuko Sakihama, Takeyuki Suzuki, and Makoto Hashimoto*

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

Abstract

Trifluoromethylphenyldiazirine is one of the most reliable photophores for photoaffinity labeling during functional analysis of biologically active compounds. Phenylboronic acid derivatives containing trifluoromethyldiazirinyl moiety have not yet been reported. The construction of the photophore was achieved using (3-formylphenyl)boronic acid and (4-formylphenyl)boronic acid pinacol esters effectively.

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Published online: 11th September, 2020

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)26
Transition Metal-Free O-Arylation of Quinoxalin-2-ones with Diaryliodonium Salts

Masami Kuriyama,* Yuki Mochizuki, Tsubasa Miyagi, Kosuke Yamamoto, Yosuke Demizu, and Osamu Onomura*

*Graduate School of Biomedical Sciences, Nagasaki University, 1-14, Bunkyo-machi, Nagasaki 852-8521, Japan

Abstract

The transition metal-free O-arylation reactions of quinoxalin-2-ones with diaryliodonium salts have been achieved, and desired 2-aryloxyquinoxalines were readily obtained in moderate to high yields. This method proved to be compatible with a series of diaryliodonium salts as well as a set of quinoxalin-2-ones.

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Published online: 9th September, 2020

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)19
An Alternative Approach to the Development of Near-Infrared Fluorescent Dyes Based on Fluorescein

Akane Katori, Akari Yamagami, Sae Wakabayashi, Kouji Kuramochi, Ayumi Imayoshi, and Kazunori Tsubaki*

*Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Japan

Abstract

In xanthene dyes the upper aryl moiety is often a benzene ring, but in this work an L-shaped dibenzoxanthene dye (4) was synthesized with a five-membered (benz)imidazole ring as the upper aryl moiety. Although 4 was designed with the π-face of the dibenzoxanthene and the π-plane of the aryl moiety as coplanar, the reactivity of the compound at the triaryl carbon was quite high and easily attacked by solvent, such as methanol. The consequent discoloration is caused not only by the external exposure of the triaryl carbon, but also by the greatly reduced LUMO level and increased reactivity to nucleophilic attack when the π-system of the xanthene ring is expanded. The introduction of the 2,6-dimethylphenyl group was found to be effective to avoid nucleophilic attack by solvent. A compound, labeled 9c, with a 2,6-dimethylphenyl group as the aryl moiety, had sufficient stability to solvent, an emission maximum at 828 nm in DMF, and a fluorescence quantum yield of 8%.

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Published online: 4th September, 2020

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)25
Palladium on Carbon–Catalyzed Oxidative Transformation of Benzylic Ethers

Ryoya Takakura, Shoko Kuwata, Kouki Nakano, Naoki Yasukawa, Hironao Sajiki,* and Yoshinari Sawama*

*Laboratory of Organic Chmistry, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi 501-1196, Japan

Abstract

Palladium on carbon (Pd/C)-catalyzed oxidative transformations of primary and secondary benzylic ethers in ethylene glycol as a solvent and reagent in an oxygen atmosphere produced the corresponding hydroxyethyl esters and cyclic ketals, respectively. Commercially-available and heterogeneous Pd/C was easily removed by filtration, and molecular oxygen was used as a clean oxidant.

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