HETEROCYCLES

■ Contents

■ Synthetic Methods for Phosphorus Compounds Containing Chromone and Thiochromone Rings

Tarik E. Ali,* Mohammed A. Assiri, Somaia M. Abdel-Kariem, and Ibrahim S. Yahia

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

Abstract

The chromone and thiochromone rings are prominent heterocyclic substructures present in numerous natural and pharmacologically active compounds. To date, many chromone analogues containing phosphorus compounds are interest in several laboratories due to their potent pharmacological activities. This review compiles all the available literature data on the synthesis of phosphorus compounds containing chromone and thiochromone rings as well as their available biological properties starting from their appearance up to the end of 2019.

■ Mini Review: Antioxidant Application of Metal-Organic Frameworks and Their Composites

Shaikha S. Alneyadi*

*Department of Chemistry, College of Science, UAE University Al-Ain, 15551 UAE

Abstract

Metal–organic frameworks (MOFs) are porous coordination materials composed of multidentate organic ligands and metal ions or metal clusters. MOFs have great potential as medical materials for biological, environmental, and food antimicrobial fields. In recent years, MOFs have been applied to various antioxidant fields due to their continued release capability, porosity, and structural flexibility in combination with many chemicals and/or materials such as nanoparticles, antioxidant, and polymers. This review offers a detailed summary of the antioxidant applications of MOFs and their composites, focusing on the combination types of MOF composites and their antioxidant effects in different applications described in 2015-2020. These applications are illustrated by the examples discussed in this review.

■ 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.

■ 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.

■ 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.

■ 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.

■ 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.

■ 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.

■ 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.

■ 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%.