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Published online: 1st March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)63
■ Design and Synthesis of Novel Orexin Antagonists via Structural Simplification of the Morphinan Skeleton

Sayaka Ohrui,* Yoko Irukayama-Tomobe, Yukiko Ishikawa, Masashi Yanagisawa, and Hiroshi Nagase

*C1232 Kanagawa Science Park R & D Building, Research Foundation ITSUU Laboratory, 3-2-1 Sakado, Takatsu-ku, 213-0012 Kawasaki, Kanagawa, Japan

Abstract

Herein, we report novel orexin antagonists with a spiro-type piperidine skeleton designed and synthesized via removal of the unnecessary sites of orexin 1 receptor (OX1R) antagonists with a morphinan skeleton for binding to OX1R. In addition, while decahydroisoquinoline compounds with an A-ring did not show antagonistic activity for OX1R, spiro-type piperidine compounds with a dihydroindene structure showed antagonistic activities. This suggests that the lipophilic site corresponding to the A-ring of the morphinan skeleton is important for determining the antagonistic activity toward OX1R.

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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: 26th February, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-21-14414
■ Synthesis of Anti-insomnia Drug Suvorexant

Hongshun Yuan, Lei Guo,* and Xianhua Pan*

*School of Perfume and Aroma Technology, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai, 201418, China.

Abstract

Suvorexant is the first dual orexin receptor antagonist for treating insomnia. Although numerous methods have been developed to construct suvorexant, a generally efficient, mild, facile synthesis platform for the conversion of simple starting material to this highly enantioselective scaffold via successive C–N bond forming steps remains in high demand. Here we report an efficient synthetic route without using chiral HPLC separation, resolution, enzyme catalysis or transition metal catalysis, and the total yield is up to 37%.

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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: 24th February, 2021

Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14402
■ 3,5-Disubstituted Tetrahydro-2H-1,3,5-thiadiazine-thiones Ester Derivatives and Their Antimicrobial Evaluation

Irfan Ullah, Jamshed Hashim,* Nuzhat Arshad,* Muhammad Yaseen, Rasool Khan, Tahseen Iqbal, Syeda Zehra Hamid, Afshan Kanwal, and Iqbal Safi

*H.E.J. Research Institute of Chemistry, ICCBS, University of Karachi, Karachi-75270, Pakistan

Abstract

A diverse set of 3,5-disubstitited tetrahydro-2H-1,3,5-thiadiazine-thiones (THTT) and their ester derivatives were synthesized in good to excellent yields. The ester derivatives were screened for their antibacterial and antifungal potential and compared with their acidic counterparts. Structure-activity relationship revealed that the THTTs with N-3 carboxylic functionality have very promising potential against all tested pathogens in general. However, ester analogues showed suppressed or no activities against the same pathogens thus indicate that these compounds can be used as a template study for the development of improved antimicrobial agents/prodrugs.

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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: 18th February, 2021

Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14398
■ Synthesis of 4-Hydroxyaurones and Their Herbicidal Activities

Mei Xia, Min Zhang,* Jianfen Ding, Jiankai Hong, Yuting Shen, and Liuqing Yang*

*School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu, China

Abstract

A series of 4-hydroxyaurone derivatives 4a-4v were synthesized and characterized by 1H NMR, 13C NMR, and elemental analysis. Their herbicidal activities against four species of plants were evaluated in a greenhouse by both pre- and post-emergence treatments at a dosage of 750 g a.i. ha-1. The bioassay revealed that 4-hydroxyaurones exhibited moderate to good herbicidal activities against dicotyledons plants for post-emergence treatment. For instance, (Z)-4-hydroxy-2-(4-nitrobenzylidene)benzofuran-3(2H)-one (4m), demonstrated 74.5% inhibitory activity against Amaranthus retroflexus L., higher than that of the positive control herbicide acetochlor. Thus, compound 4m may serve as a new possible leading compound for the discovery of post-emergence herbicide.

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Published online: 18th February, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-21-14409
■ A Simple Synthesis and Antimicrobial Activity of Some New 1,2,4-Triazolopyrimidine Derivatives

Kamelia M. El-mahdy* and Azza M. El-kazak

*Department of Chemistry, Faculty of Education, Ain Shams University, Roxy 11757, Cairo, Egypt

Abstract

The synthesis of new 1-(7-oxo-5-phenyl-1,7-dihydro[1,2,4]triazolo-[1,5-a]pyrimidin-2-yl)guanidine (2) by reaction 2,3-diamino-6-phenylpyrimidin-4(3H)-one (1) with cyanoguanidine was achieved. Compound 2 reacted with malononitrile to produce diaminopyrimidine derivative 3 which upon treatment with CS2 resulted in the formation of 1,3,5-triazine 4. Cyclization of compound 1 with either benz[c]acridine-7-carboxylic acid or mandelic acid in presence of phosphoryl chloride was investigated. Moreover, 2-[chloro(phenyl)methyl]-5-phenyl[1,2,4]triazolo[1,5-a]pyrimidin-7(1H)-one (6) was used as a valuable scaffold to construct various fused and attached heterocyclic rings via simple reactions. The antimicrobial activity of the synthesized compounds were tested. Spectral and analytical data of the newly synthesized compounds were all in good agreement with the proposed chemical structures.

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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: 9th February, 2021

Paper | Regular issue | Prepress
DOI: 10.3987/COM-21-14411
■ Synthesis of Some Macrocyclic Diimines from Mono-, Di-, Tri-, and Tetra-Indolyl Dialdehydes

Kittya Somphol, Naresh Kumar, and David StC. Black*

*School of Chemistry, The University of New South Wales, Sydney 2052, Australia

Abstract

Reactions of a range of diamines with a variety of dialdehydes containing one, two, three, or four indole rings are described. In certain cases, high yields can be obtained to deliver macrocyclic diimines containing one, two, three, or four indole rings. The range of macrocyclic diimines incorporates compounds with 15-, 17-, 18-, 19-, 20-, 21-, 22-, 23-, 24-, 25-, 28-, 30-, 31-, and 32-membered rings. A feature of most of these successful reactions is the use of isopropanol as the solvent.

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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: 8th February, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-21-14404
■ Catalytic and Diastereoselective Cascade Reaction for the Preparation of cis-1,3-Disubstituted Isoindoline-Aminal Hybrid Compounds

Tetsuya Tsujihara,* Takeyuki Suzuki, and Tomikazu Kawano*

*School of Pharmacy, Iwate Medical University, 1-1-1 Idaidori, Yahaba, Iwate 028-3694, Japan

Abstract

A convenient and catalytic method for the diastereoselective construction of cis-1,3-disubstituted isoindoline skeletons is described. In the presence of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene as a base catalyst and under mild conditions, the direct aminalization of N-protected imines bearing a Michael acceptor using the aniline derivatives and the subsequent intramolecular aza-Michael reaction proceeded successfully in a short reaction time. A series of cis-1,3-disubstituted isoindoline-aminal hybrid compounds are obtained in moderate to good yield (44%–93%) with complete diastereocontrol.

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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: 4th February, 2021

Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14384
■ Microwave-Assisted and Solvent-Free Synthesis of Quinoline Derivatives and Their Fluorescence Properties

Xiaobin Zhang, Xiumei Ma, Yun Ai, Yuanyuan Ren, Xiao Bai, Huan Chen, Ying Zhou, Wenyu Li, Cuiling Wang,* and Yifeng Liu

*College of Life Sciences, Northwest University, No. 229, Taibai North Road, Xi'an, Shaanxi 710069, China

Abstract

A protocol for the microwave-assisted Friedländer synthesis of quinoline derivatives under solvent-free conditions has been developed. According to this modified method, quinoline derivatives were synthesized by condensation of 2-aminobenzophenone with the corresponding carbonyl compounds in the presence of phosphomolybdic acid for 8 min in a 320 W microwave with yields ranging from 61% to 90%. The fluorescence properties of the synthesized compounds were studied, and all compounds showed good fluorescence properties. The substituted groups and the concentrations of quinolines and solvents had significant effects on the compounds’ fluorescence properties. This method provides a convenient way to obtain quinolines, and is beneficial to the application of these compounds.

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Published online: 3rd February, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14400
■ Efficient Synthesis of Acrylates Bearing an Aryl or Heteroaryl Moiety: One-Pot Method from Aromatics and Heteroaromatics Using Formylation and the Horner-Wadsworth-Emmons Reaction

Tatsuro Yasukata* and Takaharu Matsuura

*API R&D Laboratory, CMC R&D Division, Shionogi & Co., Ltd., 1-3 Kuise Terajima 2-chome, Amagasaki, Hyogo 660-0813, Japan

Abstract

Acrylates bearing an aryl or heteroaryl moiety were efficiently prepared by a one-pot process employing a sequence of lithiation, formylation and the Horner-Wadsworth-Emmons reaction starting from aromatic and heteroaromatic compounds. This method can efficiently introduce an acrylate moiety into aromatic and heteroaromatic compounds.

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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: 1st February, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14396
■ Acetate/Acetic Acid-Assisted One-Pot Synthesis of (Diarylmethylene)imidazolone from Amide or Thioamide

Masahiro Ikejiri,* Atsufumi Watanabe, Mari Katsuda, Mayu Funakoshi, Aki Fujisaka, and Kazuyuki Miyashita*

*Faculty of Pharmacy, Osaka Ohtani University, Nishikiori-Kita 3-11-1, Tondabayashi, Osaka 584-8540, Japan

Abstract

With the aim of extending the library of green fluorescent protein chromophore analogs, a facile one-pot synthesis of 5-(diarylmethylene)imidazolones from the corresponding amide or thioamide is described. Isolation of unstable imidate intermediates is not required, thereby circumventing the drawback of previous approaches. A reaction mechanism in which both acetate and acetic acid promote the imidazolone formation is proposed.

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Published online: 29th January, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14388
■ Construction and Biological Evaluations of Some Novel Chromeno[2,3-b]pyridines and Chromeno[2,3-b]quinolines Using 6-Methylchromone-3-carbonitrile

Magdy A. Ibrahim* and Nasser M. El-Gohary

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

Abstract

Reaction of 6-methylchromone-3-carbonitrile (1) with acetylacetone under basic conditions afforded 3-acetyl-2,7-dimethyl-5H-chromeno[2,3-b]pyridin-5-one (2) which utilized as a starting substrate. Condensation of compound 2 with a variety of amines and hydrazines produced chromeno[2,3-b]pyridines linked variable compounds in the same molecular frame. Condensation reaction of compound 2 with variable carbon nucleophilic reagents namely; malononitrile, ethyl cyanoacetate, malononitrile dimer, 1H-benzimidazol-2-ylacetonitrile and dimedone produced heteroannulated chromeno[2,3-b]quinolines 18-22. The synthesized compounds were screened in vitro for their antimicrobial activity and revealed remarkable inhibitory effects against the selected microorganisms. Structures of the newly synthesized products have been deduced upon the help of elemental analysis and spectral data (IR, 1H NMR, 13C NMR and mass spectra).

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Published online: 29th January, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14401
■ Stepwise Reactions between Cyclic 1,4-Diazadienes and Ketenes: Characteristics and Mechanism

Kazuhide Nakahara,* Koki Yamaguchi, and Hisao Kansui

*Department of Integrative Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan

Abstract

The reaction of unsymmetrical monophenyl cyclic 1,4-diazadienes with ketene derivatives yields new structures via 1,5-sigmatropic reactions. These structures were determined and confirmed by single-crystal X-ray analysis. The reaction mechanism was investigated by density functional theory calculations. The result of the calculation indicated whether the reaction was a cyclization reaction or a 1,5-shift rearrangement based on the stability of the intermediate conformation.

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Published online: 29th January, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14403
■ Synthesis of Pyrazolo[4,3-c]quinolines and the C-C Bond Cleavage during Reductive Cyclization

Nisha Devi, Antriksh Gupta, Raghuram Gujjarappa, Chandi C. Malakar,* and Virender Singh*

*Department of Chemistry, National Institute of Technology Manipur, Langol, Imphal-795004, Manipur, India

Abstract

An efficient synthesis of o-nitrophenyl tethered pyrazole-4-carbaldehydes was achieved via Vilsmeier-Haack formylation of hydrazone derivatives which were subjected to Claisen-Schmidt condensation and Morita-Baylis-Hillman (MBH) reaction with various methyl ketones and activated alkenes respectively to generate the corresponding chalcones and MBH adducts. However, successive Fe-mediated reductive cyclization was followed by an unusual C-C bond cleavage which afforded the pyrazolo[4,3-c]quinolines devoid of diverse substituents at C-4 position.

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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: 28th January, 2021

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14382
■ DBU-Catalyzed Highly Efficient Synthesis of 1,4-Dihydropyridine Derivatives from Arylidenemalononitriles and β-Enamino Imides

Wei Han, Kazuya Nakajima, Masashi Kajitani, and Takeshi Oriyama*

*Department of Chemistry, Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan

Abstract

Various 1,4-dihydropyridine derivatives were efficiently synthesized from arylidenemalononitriles and β-enamino imides using DBU (3 mol%) as the catalyst at room temperature. This mild, straightforward high-yielding protocol was atom-economy, time-economy, with a low catalyst load, and without the need for reflux.

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Published online: 28th January, 2021

Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14383
■ Efficient Approach towards the Polysubstituted 4H-Pyran Hybrid Quinolone Derivatives and Subsequent Copper-Catalyzed Hydroxylation of Haloarenes

Vipin Kumar, Dharmender Singh, Raghuram Gujjarappa, Chandi C. Malakar,* and Virender Singh*

*Department of Chemistry, National Institute of Technology Manipur, Langol, Imphal-795004, Manipur, India

Abstract

A proficient and feasible approach towards polysubstituted quinolone conjugated 4H-pyrans has been elucidated. The illustrated phenomenon concern with the base-mediated multicomponent reaction and subsequent copper-catalyzed hydroxylation of C-X bond emerging in an amide functionality. The developed reaction conditions showcased considerable substrate scope and functional group tolerance by giving the desired products in good yields.

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Published online: 27th January, 2021

Paper | Regular issue | Prepress
DOI: 10.3987/COM-20-14372
■ The Electronic Structure of Thioxanthylium Scaffolds

Koki Hirano, Akira Yasuda, Takahiro Sasamori, Kosei Shioji, Kentaro Okuma, and Noriyoshi Nagahora*

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

Abstract

A new series of thioxanthylium trifluoromethanesulfonates has been synthesized via a trifluoromethanesulfonic-acid-induced cyclization of thioether precursors. The electronic structure of these thioxanthylium salts were determined by UV−vis absorption spectroscopy, and theoretically investigated by density functional theory calculations.

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