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Published online: 1st March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)52
A Fluorous Proline Catalyst Immobilized on Teflon® for Highly Stereoselective Asymmetric Aldol Reactions

Kazuki Ishihara, Riho Obayashi, Mizuki Ohira, Yuki Kobayashi, Kotaro Ishihara, Yamato Kato, Narisa Takeuchi, Risa Mizuno, Takayuki Shioiri, and Masato Matsugi*

*Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan

Abstract

An immobilized fluorous-tagged proline catalyst and its application as a recycling system in highly stereoselective asymmetric aldol reactions is described. The introduction of acidic sulfonamide groups bearing multifluorous tags at the carboxy position proved to be more effective than the introduction of bulky substituents on the proline backbone to achieve high stereoselectivity. The Teflon®-immobilized proline catalyst could be recovered and reused at least five times while maintaining high levels of catalytic activity and stereoselectivity.

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Published online: 25th February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)56
Regio-Complementary Preparation of 6- and 7-Fluoro-1,2,3,4-tetrahydroquinolines via the Cyclization of Catecholamines Followed by Deoxyfluorination

Kazuyuki Saito, Wang Zhou, Shohei Sato, Keita Takubo, Kazunori Furutsu, Ahmed A. B. Mohamed, Euis Maras Purwati, Takashi Ikawa, and Shuji Akai*

*Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka 565–0871, Japan

Abstract

We herein report a regioselective preparation of 6- and 7-fluoro-1,2,3,4-tetrahydroquinolines by applying the deoxyfluorination strategy, developed by the authors. This method includes the cyclization of catecholamines bearing an N-protecting group to form 7-hydroxy-1-azaspiro[4.5]deca-6,9-dien-8-ones and 6,7-dihydroxy-1,2,3,4-tetrahydroquinolines followed by deoxyfluorination, in which the nature of the N-protecting group has a significant effect on both the cyclization and the regioselectivity of the deoxyfluorination reaction.

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Published online: 22nd February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)54
Polyfluoroarene-Capped Thiophene Derivatives via Fluoride-Catalyzed Nucleophilic Aromatic Substitution

Kotaro Kikushima, Kana Matsuki, Yuna Yoneda, Takayuki Menjo, Kosuke Kaneko, Tomonori Hanasaki, and Toshifumi Dohi*

*College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan

Abstract

Arylthiophene derivatives are potential components of functional materials, including organic electronics. Herein, we describe a nucleophilic aromatic substitution reaction of polyfluoroarenes using silylthiophenes as nucleophiles in the presence of a catalytic amount of a fluoride salt. Various polyfluoroarene-capped thiophene derivatives were synthesized via double arylation under transition metal-free conditions. A fluoride ion activates a silylthiophene to trigger a nucleophilic aromatic substitution, subsequently affording the coupling product along with elimination of the fluoride ion, which serves as a promoter of the catalytic reaction.

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Published online: 22nd February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)64
A Theoretical Study of Product Selectivity in Rhodium Catalyzed Oxidative Coupling Reaction Caused by the Solvation Effect

Masahiro Higashi,* Naoto Shibata, Suguru Takeno, Tetsuya Satoh, Masahiro Miura, and Hirofumi Sato*

*Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoudai-katsura, Nishikyo, Kyoto 615-8510, Japan

Abstract

Solvation effects in the direct oxidative coupling of 1-phenylpyrazole with alkynes in the presence of rhodium catalyst was theoretically studied by means of the reference interaction site model self-consistent field with spatial electron density distribution (RISM-SCF-SEDD) method, which provides both of quantum chemical and statistical mechanical information on the solvation system. This reaction gives naphthalene and quinoline derivatives whose yields depend on the solvent environment. The computational results showed that the path for the naphthalene derivative is exothermic independently of solvent environment. On the other hand, the reaction energy of the reductive elimination for the quinoline derivative is considerably affected by solvation and endothermic in N,N- dimethylformamide (DMF) solution, indicating that the reaction is not preferable in DMF solution. The detailed analysis of solvation free energy and solvation structure are also reported.

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Published online: 17th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)61
Diastereo- and Enantioselective Intramolecular 1,6-C–H Insertion Reaction of Diaryldiazomethanes Catalyzed by Chiral Dirhodium(II) Carboxylates

Motoki Ito, Yuji Kondo, Ryosuke Namie, Yoshihiro Natori, Koji Takeda, Hisanori Nambu, Masahiro Anada,* Yasunori Yamamoto, and Shunichi Hashimoto*

*Faculty of Pharmacy, Musashino University, 1-1-20 Shin-machi, Nishitokyo-shi, Tokyo, Japan

Abstract

A highly diastereo- and enantioselective intramolecular 1,6-C–H insertion reaction of diaryldiazomethanes possessing an ether group has been achieved with the use of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] as a catalyst, providing exclusively 3-substituted cis-3,4-dihydro-4-phenyl-1H-isochromans in up to 99% ee with no evidence of tandem ylide formation–rearrangement.

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Published online: 15th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)60
Total Synthesis of (±)-4-Deoxyblennolide C via Spirochromanone

Takuya Kumamoto,* Sho Hasegawa, Kanna Adachi, and Kazuaki Katakawa

*Department of Synthetic Organic Chemistry, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku, Hiroshima, 734-8553, Japan

Abstract

We report the total synthesis of (±)-4-deoxyblennolide C, a deoxy analogue of xanthone antibiotics blennolide C isolated from the fermentation broth of Blennoria sp. The synthesis involves construction of a quaternary carbon during the formation of spirochromanone through the aldol reaction of o-hydroxyacetophenones and cyclohexenone, oxidative cleavage of the alkene moiety, and the construction of a xanthone framework by Dieckmann condensation.

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Published online: 10th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)57
Chiral Phosphine Oxide-Catalyzed Enantioselective Ring Opening of Oxetanes

Shunsuke Kotani,* Yuka Tashima, Hiroki Tanaka, Shohei Aoki, and Makoto Nakajima*

*Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, Japan

Abstract

Chiral phosphine oxide as a Lewis base could effectively catalyze the enantioselective ring opening of 3-substituted oxetanes with silicon tetrachloride in the presence of N,N-diisopropylethylamine, affording the corresponding 2-substituted 1,3-chlorohydrins in high yields and good enantioselectivities.

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Published online: 10th February, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)65
Synthetic Studies on Didymeline Using Spirocyclization of Phenols with Diazo Functionality

Mitsuru Ikeda, Hiroki Nakayama, Ayaka Kanda, Shingo Harada,* and Tetsuhiro Nemoto*

*Pharmaceutical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo, Chiba, Japan

Abstract

Didymeline is an alkaloid with an azaspiro tricyclic skeleton with various functionalities. Despite the fact that its unique architecture is synthetically attractive, its total synthesis has never been achieved before. Herein, we present synthetic studies on the core structure of Didymeline. Accordingly, a spiro ring system was constructed through dearomatization of a phenol derivative with α-diazoamide unit. Based on the resulting 2-azaspiro[4,5]decane variant, a tricyclic molecule was synthesized via base-promoted intramolecular ring closure. For an asymmetric synthesis, an enantioselective dearomatization was also examined under silver catalysis, which led to the formation of an all-carbon substituted quaternary stereogenic center.

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Published online: 8th February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)53
Divergent Total Synthesis of Azalamellarins D and N

Tsutomu Fukuda,* Seiya Okutani, Mayu Sumi, Kazuhito Miyagi, Gen Onodera, and Masanari Kimura

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

Abstract

Lamellarins are polycyclic marine alkaloids with potent cytotoxic activities against cancer cell lines. A divergent synthesis of azalamellarins D and N, lactam congeners of the marine natural products lamellarins D and N, has been achieved via the pentacyclic 14-bromo-8,9-dihydro-benzo[7,8]indolizino[3,2-c]- quinolin-6(5H)-one intermediate. The pentacyclic intermediate can be synthesized from methyl 1-(benzensulfonyl)-3-bromo-1H-pyrrole-2-carboxylate via the Suzuki–Miyaura cross-coupling and intramolecular direct arylation as key reactions.

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Published online: 8th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)46
Deprotection of the Carbazole PMB Group Using Hypervalent Iodine Reagent Combined with N-Hydroxyphthalimide

Kana Yoshikawa, Takanori Tabata, Kazuma Fujimura, Natsumi Kuraoka, Akira Nakamura, Yasuyoshi Miki, and Tomohiro Maegawa*

*School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashi-osaka, Osaka, 577-8502, Japan

Abstract

We developed a novel method for deprotecting the N-PMB group of carbazoles. The combination of PhI(OAc)2 and N-hydroxyphthalimide cleaved the N-PMB group with moderate to good yields depending on the substituents on the carbazole ring.

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Published online: 5th February, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)58
Planar Chiral [2.2]Paracyclophane-Based Bis(thiourea)-Catalyzed Highly Diastereo- and Enantioselective Michael Addition Reaction of Nitroethane to Nitrostyrenes

Shinji Kitagaki,* Eriko Shimo, Sawa Takeda, Rintaro Fukai, Naohiro Kojima, Shun Yoshioka, Naoko Takenaga, and Keisuke Yoshida

*Laboratory of Medicinal Chemistry, Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan

Abstract

To demonstrate the utility of [2.2]paracyclophane as a chiral organocatalyst backbone, we evaluated a planar chiral pseudo-ortho- [2.2]paracyclophane-based bis(thiourea) catalyst in the Michael addition reaction of nitroethane to nitrostyrenes. The catalyst produced the desired 1,3-dinitro compounds in high yields and high diastereo- and enantioselectivities.

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Published online: 1st February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)62
Computational Study for the Aromatic Nucleophilic Substitution of 4-Dimethylamino-3-trifluoroacetyl- quinoline with Various Nucleophiles

Norio Ota, Souma Nakagawa, Yasuhiro Kamitori, and Etsuji Okada*

*Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan

Abstract

The aromatic nucleophilic substitutions of 4-dimethylamino- 3-trifluoroacetylquinoline 1 with amines, thiols, and alcohols are elucidated on the basis of DFT calculations. Our calculation results suggest that the reaction of 1 with amines giving N-N exchanged products 4 occurs via Meisenheimer type adducts V whereas the ones with thiols and alcohols proceed via the enol type adducts VII and IX to afford N-S and N-O exchanged products 8 and 9, respectively. It is also clarified that the conditions required for the successful substitution are not controlled by the activation energies on these processes, but by the energy changes on the processes from 1 to each intermediates, V, VII, and IX.

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Published online: 1st February, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)69
IBX Oxidations for the Synthesis of Substituted 2H-Pyrans

David R. Williams,* Seth A. Bawel, Nazanin Haddadpour, and Sarah Maier

*Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, IN 47405-7102, U.S.A.

Abstract

Facile oxidation of highly substituted 3,5-hexadien-1-ols using 3-iodoxybenzoic acid (IBX) in DMSO has resulted in a one-pot preparation of 2,3,4,6-tetrasubstituted 2H-pyrans. Cycloisomerizations of the 1-oxatriene moiety, produced in the oxidation, spontaneously occur via a disrotatory oxa-electrocyclization. The 2H-pyran products of Table 1 features three differentiated carbonyl substituents.

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Published online: 28th January, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)51
Total Synthesis of Urolithin C 3-Glucuronide

Katsunori Itaya, Ishtiaq Jeelani, and Hitoshi Abe*

*Department of Applied Chemistry, Faculty of Engineering, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

Urolithin is a metabolite of a class of compounds known as polyphenolswhich are found in various fruits, including pomegranates, nuts and strawberries. Urolithin is a biologically-active compound which has anti-inflammatory, antioxidant and anticancer properties. Our laboratory has focused on the use of a palladium-catalyzed intramolecular biaryl coupling reaction to yield urolithin C 3-glucuronide (uro-C 3-glur). The total synthesis of uro-C 3-glur has been accomplished in 11 steps starting from the commercially-available 3,4-dimethoxybenzaldehyde. We now report full details of the total synthesis of urolithin C 3-glucuronide (1).

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Published online: 25th January, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)49
Stereoselective Synthesis of Diastereomeric Berberine Alkaloids, O-Methylcorytenchirine and Coralydine

Misaki Kirii, Junpei Matsuoka, Akari Miyawaki, Kiyoshi Tomioka, and Yasutomo Yamamoto*

*Faculty of Pharmaceutical Sciences, Department of Medicinal Chemistry, Doshisha Women’s College of Liberal Arts, Kodo, Kyotanabe, Kyoto 610-0395, Japan

Abstract

Racemic total synthesis of diastereomeric berberine alkaloids, O-methylcorytenchirine and coralydine, was achieved from the common isoquinoline intermediate of norlaudanosine. The relative stereochemistry of C8-C14 was successfully constructed by favorable axial attack of nucleophiles to the iminium of dihydroprotoberberines.

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Published online: 25th January, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)67
Synthesis of 1-Azaazulenes Using Ring-Opening Cyclization of Spirocyclopropane with Amine

Hisanori Nambu,* Yuta Onuki, Koga Yamazaki, and Takayuki Yakura

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

Abstract

Synthesis of 1-azaazulenes using ring-opening cyclization of spirocyclopropane with a primary amine was accomplished. The reaction of cycloheptane-1,3-dione-2-spirocyclopropane with 2,4-dimethoxybenzylamine in refluxing acetonitrile resulted in a 94% yield of 1,2,3,6,7,8- hexahydrocyclohepta[b]pyrrol-4(5H)-one. The obtained product was successfully converted into 1-azaazulenes by deprotecting the amino-protecting group followed by oxidation.

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Published online: 22nd January, 2021

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)7
Conformational Control in Stereoselective Chemical Reactions: From Amino Acids to Iminosugars

Ari Koskinen*

*Department of Chemistry and Material Sciences, Aalto University, Finland

Abstract

Two alternative synthetic strategies for the synthesis of vicinal amino alcohols from naturally occurring amino acids have been investigated, viz. one going through diastereoselective addition of organometallic species to an amino aldehyde and one going through α’-chiral α,β-enones and their diastereoselective reduction. Based on these investigations we were able to develop a synthetic strategy towards all diastereomers of deoxynojirimycin starting from naturally occurring serine through a divergent route with a late stage intermediate that can be prepared in large quantities and in enantiomerically pure form.

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Published online: 19th January, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)47
N-Glycosylation of Thio-glycoside Derived from Odorless Thiols Using Hypervalent Iodine(III) Reagent

Koji Morimoto, Kana Yanase, Tohru Kamitanaka, and Tetsuya Kajimoto*

*School of Pharmacy, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, Japan

Abstract

A general and efficient protocol for direct N-glycosylation using inexpensive and readily available thioglycosides prepared from an odorless sulfur source was established. The use of easily available reactants and the mild reaction conditions make this protocol feasible for practical applications.

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Published online: 19th January, 2021

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)4
Lesinurad – There are More Ways than One of Synthesizing the Drug

Piotr P. Graczyk* and Sven Nerdinger*

*Early Stage Development, Sandoz GmbH, Biochemiestrasse 10, 6250 Kundl, Austria

Abstract

Over the last several years significant efforts have been devoted, particularly in China, to develop new syntheses of Lesinurad. Virtually all key bonds in this molecule can now be created in many different ways, often in a very high yield. Although almost all of the chemistry examples presented in this review come from patent applications and as such have not been subjected to rigorous peer review, they may serve as an inspiration to solve analogous synthetic problems. However, the readers are encouraged to pay particular attention to the very recent trends in the literature which use multicomponent reactions and flow chemistry to minimize the environmental impact and achieve high yields of API at the same time.

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Published online: 19th January, 2021

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)5
Azido, Cyano, and Nitrato Cyclic Hypervalent Iodine(III) Reagents in Heterocycle Synthesis

Naoko Takenaga,* Hideyasu China, Ravi Kumar, and Toshifumi Dohi*

*Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan

Abstract

In recent years, synthetic applications of cyclic hypervalent iodine reagents have undergone significant developments. Among them, benziodoxol(on)es containing azido, cyano, and nitrato ligands have been found to be useful synthetic tools for the preparation of functionalized heterocyclic compounds. This review aims to summarize recent synthetic applications of benziodoxol(on)es as effective heteroatom-introducing reagents.

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Published online: 12th January, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)66
Facile Preparation of 1-Hydroxy-1,2-Benziodoxol-3(1h)-one 1-Oxide (IBX) and Dess–Martin Reagent Using Sodium Hypochlorite under Carbon Dioxide

Kazunori Miyamoto,* Tomohide Okada, Takashi Toyama, Shinji Imamura, and Masanobu Uchiyama*

*Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

Abstract

We have developed a safe, convenient, and inexpensive method for preparation of the widely used oxidizing agent 1-hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide (IBX), by treatment of 2-iodobenzoic acid with aqueous sodium hypochlorite under CO2 at room temperature. As the only by-product is NaCl, this reaction can be utilized for one-pot synthesis of 1,1,1-triacetoxy-1,2-benziodoxol-3(1H)-one (Dess-Martin reagent) in excellent yield.

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Published online: 5th January, 2021

Review | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)33
Umpolung of Electron-Rich Heteroarenes with Hypervalent Iodine Reagents

Pamela Pal,(a) Jerome Waser,(b)*and Raj Kumar Nandi(a)*


* a Department of Chemistry, Diamond Harbour Women’s University, Sarisha, West Bengal-743368, India
* b ISIC-SB-LCSO, Ecole Polytechnique Federale de Lausanne (EPFL), Av. Forel 2, BCH 1402, Switzerland

Abstract

Five-membered heterocycles are well known for their innate nucleophilicity. In contrast, reaction of these heterocycles as electrophiles is less established and has become only recently an intensively investigated research area in synthetic chemistry. The use of hypervalent iodine reagents for the umpolung of the nucleophilic reactivity has been especially successful. This review provides a comprehensive overview regarding the generation of electrophilic intermediates from electron-rich heterocycles using hypervalent iodine reagents. The functionalization with different heteroatoms, arenes or heteroarenes nucleophiles is then described.

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Published online: 24th December, 2020

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)45
Generation of Monoaryl-λ3-iodanes from Arylboron Compounds through ipso-Substitution

Ayako Nakano, Yukino Okabe, Keitaro Matsuoka, Narumi Komami, Keito Watanabe, Masahiro Kojima, Tatsuhiko Yoshino, and Shigeki Matsunaga*

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

Abstract

Monoaryl-λ3-iodanes serve as versatile oxidants and arylating reagents in organic synthesis. In addition to the oxidation of iodoarenes, electrophilic substitution reactions using iodine tricarboxylates have been used for the synthesis of monoaryl-λ3-iodanes. Here, we report that ipso-substitution reactions of aryltrifluoroborates with iodine tris(trifluoroacetate) in DMF or DMA smoothly produced monoaryl-λ3-iodanes, which were readily converted to aryliodonium ylides. We also demonstrated that sequential C–H borylation and the ipso-substitution efficiently introduced the I(III) group under steric control.

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Published online: 23rd December, 2020

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)43
Dihalogenative Cyclization for the Synthesis of 4-Bromo-1-bromoalkyl-5-aryl/alkyl/alkenyl-pyrazoles

Motohiro Yasui, Maki Hasegawa, Keiji Konishi, Norihiko Takeda, and Masafumi Ueda*

*Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan

Abstract

A copper-mediated domino reaction involving cyclization, bromination, and nucleophilic substitution of N,N-disubstituted hydrazones, which are labile under oxidative conditions, to synthesize 4-bromo-1-bromoalkyl-5-aryl/alkyl/alkenyl-pyrazoles, is achieved. This method features the simultaneous construction of pyrazoles and two C-Br bonds, which are synthetically useful.

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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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