HETEROCYCLES

■ Contents

■ 5-Aminotetrazole as a Building Block for Multicomponent Reactions (Review)

Anton V. Dolzhenko*

*School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan 47500, Malaysia

Abstract

5-Aminotetrazole is a useful building block in organic synthesis, including various multicomponent reactions (MCRs). In MCRs, 5-aminotetrazole usually plays a role of 1,3-binucleophilic reagent, but in some reactions, the only reactive centre is an exocyclic amino group of 5-aminotetrazole. This review systematises MCRs involving 5-aminotetrazole forming a background for further investigations in this area.

■ Copper Accelerated One-Pot Sequential Tandem Synthesis of Tetrahydropurinoisoquinoline Derivatives

Pradip Kumar Maji* and Ayan Mahalanobish

*Department of Chemistry, Bidhan Chandra College , Asansol, Burdwan, 713304, WB, India

Abstract

Copper catalyzed efficient and operationally simple tandem synthesis of purino[8,9-a]isoquinolinedione from 5,6-diamino-1,3-dimethyluracil and in situ generated alkenyl aldehyde has been described. In this cascade reaction C-C and C-N bonds are formed through Sonogashira coupling, 5-endo cyclization, and 6-endo cyclization in a same reaction vessel.

■ Synthesis and Biological Evaluation of Triazolyl Monastrol Analogues Using Cu-Catalyzed Click Chemistry

Hani Mutlak A. Hassan,* Iuliana Denetiu, Kaltoom Sakkaf, Khalid A. Khan, Peter N. Pushparaj, and Kalamegam Gauthaman

*King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21589 80216, Saudi Arabia

Abstract

The synthesis of triazolyl monastrol analogues through a Cu(I)-catalyzed [3+2] azide-alkyne cycloaddition (CuAAC) reactions and their biological evaluation against cancer cell lines is described.

■ Synthesis of Azulene-Substituted Tetraarylpyrroles by Reaction of 1-Azulenyl Ketones with Benzoin and Ammonium Acetate

Taku Shoji,* Sho Takagaki, Miwa Tanaka, Takanori Araki, Shuhei Sugiyama, Ryuta Sekiguchi, Akira Ohta, Shunji Ito, and Tetsuo Okujima

*Department of Chemistry, Faculty of Science, Shinshu University, Asahi 3-1-1, Matsumoto, Nagano 390-8621, Japan

Abstract

Tetraarylpyrroles with a 1-azulenyl substituent were prepared by the reaction of 1-azulenyl ketones, which have various aryl-substituents at their α-position, with benzoin in the presence of ammonium acetate as a nitrogen source of the pyrrole ring. Optical property of the tetraarylpyrroles obtained by the reaction was clarified by UV/Vis spectroscopy and/or time-dependent density functional theory (TD-DFT) calculations

■ Efficient Synthesis of Seven-Membered Cyclic Ethers Using Pd(II) Catalyst

Masahiro Miyazawa,* Yusuke Yano, Chiaki Hayashi, Masatake Okuno, Kenta Hara, Yoshiro Hirai, and Hajime Yokoyama

*Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract

We report a palladium(II)-catalyzed intramolecular cyclization of oct-2-ene-1,8-diol derivatives to afford seven-membered cyclic ethers without the need for high dilution and without dimer formation.

■ Choline Chloride Catalyzed Eco-Friend and Effective One-Pot Synthesis of 9-Arylacridine-1,8-dione and Hexahydroquinoline via Hantzsch Type Reaction

Shengxue Mao, Fei Li, Yue Lv, Chengwei Lv,* and Shijun Yu*

*School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, China

Abstract

Choline chloride was utilized to efficiently catalyzed Hantzsch type reaction for the synthesis of 9-arylacridine-1,8-dione and hexahydroquinoline derivatives. The optimized catalytic system benefits from facile operation and separation procedures, in good to excellent yields, and for wide substrate tolerance. This methodology is of interest also due to employing simple and inexpensive choline chloride as catalyst and environmentally benign ethanol as solvent without the use of any harmful organic solvent and toxic metal catalyst.

■ Three New Lactone-Type Diterpenoid Alkaloids from Aconitum rotundifolium Kar. & Kir.

Firas Obaid Arhema Frejat, Wenliang Xu, Lianhai Shan, and Xianli Zhou*

*School of Life Science and Engineering, Southwest Jiaotong University, NO.111, North Second Ring Road Chengdu 610031, Sichuan, China

Abstract

Three new lactone-type C19-diterpenoid alkaloids, rotundifosines A – C (1 - 3) along with two known diterpenoid alkaloids, heterophyllidine (4) and chellespontine (5) were isolated from the whole plant of Aconitum rotundifolium Kar. & Kir. Their structures were established on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. Compounds 1–3 were evaluated for cytotoxicity against MCF-7, MDA-MB-231, 786-0 and HepG2 human cancer cell lines.

■ Selenium Dioxide Mediated Benzylic sp3 C-H Oxidation in Acetic Acid: Synthesis of Lophine Derivatives from α-Methylene Ketones via a Domino Multicomponent Reaction

Vineet Jeena* and Mncedisi Mazibuko

*School of Chemistry and Physics, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, 3209, South Africa

Abstract

We report a selenium dioxide/acetic acid catalysed one-pot conversion of α-methylene ketones to 1,2-diaryldiketones as a key step to successfully access lophine derivatives in a domino multicomponent reaction.

■ Synthesis of (5,6-Dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl)-methanamine

Zhong-Gang Bai, Hui Qi, Qun-Zheng Zhang, Yu Ma, Qing Pan, and Xun-Li Zhang*

*College of Chemistry and Chemical Engineering, Xi’an Shiyou University, 18, 2nd Dianzi Road, Xi’an, Shanxi 710065, China

Abstract

This short paper reports the development of a new method for the synthesis of (5,6-dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl)methanamine. Pyrazole was initially protected with an N-SEM protective group, followed by alkylation at C-5 position with 1-bromo-3-chloropropane. Following SEM deprotection, the intramolecular ring was closed and then a bromine atom (Br) was introduced with N-bromosuccinimide (NBS) by electrophilic aromatic substitution (SEAr), forming 3-bromo-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole. The Br group was subsequently converted into aldehyde group, then into oxime. The final step of hydrogenation resulted in the desired product. The overall yield through the 8-step reaction process was found to be 29.4%. The intermediates and final product were identified by HPLC-MS and 1H NMR. This development provides a novel synthetic route to the formation of 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole skeleton.

■ A Convenient Synthesis of Isotellurazoles via Deoxygenation of Isotellurazole Te-Oxide Oligomers by Using a Combination of Ph3P/I2

Yusuke Taneichi, Kazuaki Shimada,* and Toshinobu Korenaga

*Department of Chemistry and Biosciences, Faculty of Science and Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan

Abstract

Ynones and ynals bearing a variety of substituent were converted into isotellurazole Te-oxide oligomers through a convenient procedure via formation and ring closure of β-(N,N-dimethylcarbamoyltellurenyl)alkenyl ketones or aldehydes, and the subsequent conversion of A into the corresponding isotellurazoles B was carried out efficiently by treating with Ph3P/I2 under a rather mild reaction condition.

■ AgNTf2-Mediated Arylation of Bromopyrroloindolines

Soichiro Sato, Azusa Hirayama, Tohma Adachi, Daichi Kawauchi, Hirofumi Ueda, and Hidetoshi Tokuyama*

*Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan

Abstract

The silver(I)-mediated arylation of bromopyrroloindolines was developed. The selection of silver salts was crucial to obtain arylated compounds in high yields. Among the various tested silver(I) salts, AgNTf2 was the most effective agent for arylation. Reactions using various electron-rich aromatic compounds revealed that the developed conditions are suitable for the arylation of a broad range of aromatic compounds, including benzene derivatives, furan, thiophene, and pyrrole.

■ Ultrasound Promoted Efficient Construction of Polycyclic-Fused Pyrazolo[4,3-c]pyridines via Domino Reaction

Ting Zhou, Dao-Lin Wang,* Jiao Xu,* Liang Yan, and Wei Ma

*College of Chemistry and Chemical Engineering, Bohai University, 19, Keji Rd., New Songshan District, Jinzhou City, Liaoning Province 121001, China

Abstract

Ultrasonic-accelerated rapid protocol for the synthesis of polycyclic-fused pyrazolo[4,3-c]pyridines via SN2/Thorpe-Ziegler/Thorpe- Guareschi domino reactions of 4-acetyl-5-bromomethyl-1-phenyl-1H-pyrazole with salicylonitriles (2-mercaptobenzonitrile or 3-cyanopyridine-2(1H)-thiones). Ultrasound‐based methodology performed better than the conventional process in rates and yields.