Materials and biological applications of 1,2,3-selenadiazoles: a review

In recent years, chemistry of metal-nitrogen–bonded compounds have attracted tremendous attention mainly because of unusual properties resulting from such a bond involving carbon and other heteroatoms. M?N–bonded compounds, when containing group VI elements, especially selenium, has attracted great attention in materials chemistry. In addition, the increased interest in synthesis of N-containing bioactive compounds with other heteroatoms such as selenium, sulfur, etc is mainly because of their tremendous potential as antioxidants, additives, dyes for polymers, and as insecticides, in solvent extraction, and in nanotechnology. Thus, the synthesis and applications of 1,2,3-selenadiazoles have attracted recent interest of materials scientists, including nanotechnologists, pharmaceutical chemists, and organic chemists. The chemistry of 1,2,3-selenadiazoles is highly rich and has been practiced ever since its first report in 1972. Such N-containing Se-heterocycles form several types of selenadiazoles that are a rich source of selenium for semiconductor nanoparticles of metal selenides. The materials chemistry of such molecules has been documented for over three decades, and their great scope in semiconductors has emerged. This review article is an attempt to bring a variety of materials and biological application of 1,2,3-selenadiazoles for better understanding of the researchers.     

Selenium heterocycles. XXXV . Synthesis and pyrrolysis of aryloxy-, arylthio-, and arylseleno-1,2,3-selenadiazoles

A series of 4-substituted-5-arylthio-1,2,3-selenadiazoles, 4-substituted-5-arylseleno-1,2,3-selenadiazoles and 4-aryloxymethyl-1,2,3-selenadiazoles were synthesized. Pyrrolysis of these compounds afforded the corresponding acetylenes XI, XIII (X = S, Se) and XII, respectively. Oxidation of 4-substituted-5-arylthio-1,2,3-selenadiazoles (XIV) with m-chloroperbenzoic acid gave 4-substituted-5-arylsulfinyl-1,2,3-selenadiazoles (XV) and 4-substituted-5-arylsulfonyl-1,2,3-selenadiazoles (XVI).     

1,4-PENTADIEN-3-ONES. A SOURCE FOR SELENANO 1,2,3- SELENA AND THIADIAZOLES

The 4-Selenanols (2,3) and 4-selenanones (4) were obtained by the reaction of 1,4-pentadien-3-ones (1) with sodium hydrogen selenide under different conditions. The fused 1,2,3-selenadiazoles (6) and 1,2,3-thiadiazoles (7) were prepared from 4 on oxidative cyclization with SeO₂ and Hurd–Mori reaction with SOCl₂.     

Dodecacarbonyltriruthenium

Since the pioneering work of Mond and his coworkers the metal carbonyls and their derivatives have been under active study, and, as in other areas of inorganic chemistry, research activity has greatly increased in the last twenty years. Whereas hitherto our knowledge of the carbonyls of the heavier transition metals has been seriously hampered by a lack of good methods of synthesis, new preparative methods have recently been developed for Ru₃(CO)₁₂, and many new ruthenium carbonyl complexes are being discovered as its chemistry is explored.     

Bildung und fragmentierung von cycloalkeno-1,2,3-selenadiazolen

Cycloalkeno-1,2,3-selenadiazoles can be prepared from cycloalkanone-semicarbazones with SeO₂. Pyrolysis yields bis-cycloalkeno-1,4-diselenines and cycloalkynes, which can be trapped with tetraphenyl-cyclopentadienone. A detailed spectroscopic characterization of the 1,2,3-selenadiazoles and the 1,4-diselenines is given.     

Renaissance of Ring‐Opening Chemistry of Benzotriazoles: New Wine in an Old Bottle

1,2,3‐Benzotriazoles could undergo ring cleavage to form ortho‐amino arenediazonium or α‐diazo‐imine species via a Dimroth‐type equilibrium. Historically, the synthetic potential of this unique reactivity had remained underdeveloped. Recently, some new strategies have been developed to effect the ring‐opening chemistry of benzotriazoles in more practical manners. A wide range of conceptually novel and synthetically useful reactions have been developed, which enable the access to diverse valuable heterocycles and ortho‐amino arene derivatives. As one of the players in this field, our group has also contributed a series of intriguing transition‐metal‐catalyzed denitrogenative functionalizations of benzotriazoles. In this account, we aim to provide an overview of the ring‐opening chemistry of benzotriazoles, with a focus on relevant works published in the past decade. In order to show a whole picture of the research field, some pioneering works in its developing history will also be discussed briefly.     

4-(2-Hydroxyaryl)-1,2,3-selenadiazoles as Precursors of Benzofuran-2-selenolates

The reaction of selenium dioxide with o-hydroxyacetophenone semicarbazones gives 4-(2-hydroxyaryl)-1,2,3-selenadiazoles which undergo ready decomposition by the action of potassium carbonate to form benzofuran-2-selenolates. The latter can be alkylated with methyl iodide and benzyl chloride and arylated with 2,4-dinitrochlorobenzene. Intermediate formation of 2-(o-hydroxyphenyl)ethyneselenolate during decomposition of 1,2,3-selenadiazoles was proved by the isolation of methyl o-methoxyphenylethynyl selenide when the substrate was treated with potassium carbonate in the presence of methyl iodide.     

Synthesis and reactivity of 5-and 6-hydroxy-benzo[b]furan-2-selenolates

Treatment of 2,4-and 2,5-diacetoxyacetophenone semicarbazones with selenium dioxide gave 4-(2,4-and 2,5-diacetoxyphenyl)-1,2,3-selenadiazoles which were readily deacylated by the action of hydrochloric acid. 4-(2,4-and 2,5-Dihydroxyphenyl)-1,2,3-selenadiazoles thus obtained underwent decomposition in the presence of potassium carbonate in acetonitrile with formation of 5-and 6-hydroxybenzo[b]furan-2-selenolates which were subjected to alkylation.     

A Convenient Approach to 2-Aminobenzo[<Emphasis Type="Italic">b</Emphasis>]chalcogenophenes Based on Copper-Catalyzed Transformation of 4-(2-Bromophenyl)-1,2,3-chalcogenodiazoles in the Presence of a Base and Amines

The reactions of 4-(2-bromophenyl)-1,2,3-thia-and -selenadiazoles with amines in the presence of potassium carbonate and copper(I) iodide afforded 2-aminobenzo[b]chalcogenophenes. The corresponding thiaand selenamides, prepared by interaction of 4-(2-bromophenyl)-1,2,3-thia- and -selenadiazoles with amines in the absence of copper salt, were transformed into 2-aminobenzo[b]chalcogenophenes by the action of potassium carbonate and copper(I) iodide in DMF in different yields.     

Selenium heterocycles XXIII. Synthesis of 4,5-dihydrophenanthro[1,3-d]-1,2,3-selenadiazoles and 10,11 -dihydrophenanthro[1,2-d]-1,2,3-selenadiazoles

The selenium dioxide oxidation of a series of 1,2,3,4-tetrahydrophenanthrone and 1,2,3,4-tetrahydrophenanthren-4-one semicarbazones afforded 4,5-dihydrophenanthro[4,3-d]-1,2,3-selenadiazoles and 10,11-dihydrophenanthro[1,2-d]-1,2,3-selenadiazoles. The latter series which represent a new type of selenaazasteroidal compounds were pyrolyzed and gave the corresponding 1,4-deselenine derivatives.     

ZnII and PbII coordination chemistry of 2,6-bis(1,2,3-triazol-4-yl)pyridine (clickate) and the metal ion-dependent emission of ‘clickate’–appended anthracene

The effect of metal coordination of 2-(1-(9-anthryl)methyl-1,2,3-triazol-4-yl)-6-(1-n-octyl-1,2,3-triazol-4-yl)pyridine (2) on the emission of the appended anthryl group was investigated in acetonitrile. The tridentate 2,6-bis(1,2,3-triazol-4-yl)pyridyl ligand included in 2 is referred herein as ‘clickate’. Titrating zinc(II) perchlorate or zinc(II) chloride into the solution of fluorescent ligand 2 results in quenching, which is attributed to the formation of a dark 1:1 Zn^II complex of 2. Frontier molecular orbital analysis and cyclic voltammetric data support the occurrence of photoinduced electron transfer from the excited state of the anthryl group to the Zn^II-bound clickate moiety, which relaxes the excited fluorophore non-radiatively, i.e. quenches fluorescence. Fluorescence quenching of clickate 2 upon forming the Pb^II complex was also observed. The Zn^II/Pb^II-coordination chemistry of clickate was characterised via X-ray crystallography, isothermal titration calorimetry, ¹H NMR spectroscopy and absorption spectroscopy using the symmetrically substituted clickate 2,6-bis(1-n-octyl-1,2,3-triazol-4 yl)pyridine (1).     

Tributylstannyl radical-catalyzed reaction of 1,2,3-selenadiazoles with olefins or dienes

It was found that the reaction of 1,2,3-selenadiazoles derived from cyclic ketones with olefins or dienes was markedly promoted by a catalytic amount of tributylstannyl radical, which was generated in situ from tributylstannyl hydride or allyltributylstannane and AIBN, to give the corresponding dihydroselenophenes in moderate to good yields. In contrast, when 1,2,3-selenadiazoles prepared from linear and aromatic ketones were used as substrates, the same reaction did not take place, and alkynes were formed as the sole product.     

Expeditious synthesis of new 1,2,3-thiadiazoles and 1,2,3-selenadiazoles from 1,2-diaza-1,3-butadienes via Hurd-Mori-type reactions

Alpha-substituted hydrazones obtained from 1,2-diaza-1,3-butadienes and methylenic or methinic activated substrates gave rise to a wide range of cyclic compounds. In particular, in the presence of thionyl chloride as solvent-reagent, they were transformed into 1,2,3-thiadiazoles,(1) with selenium oxychloride in new 4-substituted 2,3-dihydro-1,2,3-selenadiazoles, while with selenium dioxide, they were transformed into 4-substituted 1,2,3-selenadiazoles. We have also examined the nucleophilic behavior of 1,2,3-thiadiazole 4a in the reaction with 1,2-diaza-1,3-butadienes that produced, under basic conditions, 4-hydrazono-1-(1,2,3-thiadiazolyl)pentane derivatives. This event represents an interesting example of stereoselective synthesis because it leads exclusively to the formation of the RR/SS racemic mixture. These latter compounds, treated with thionyl chloride, gave the corresponding 1,3-di-1,2,3-thiadiazolylpropane derivatives, while with sodium methoxide they afforded 1,2,3-thiadiazolyl-2-oxo-2,3-dihydro-1H-pyrrole systems.     

Fluorinated Derivatives of 4-Phosphino- and 4-Iminophosphorano-2,5-Dimethyl-2H-1,2,3-Diazaphospholes and Their Metal Complexes

Abstract

Although there has been considerable interest in the chemistry and metal complexation of low coordinate phosphines, there are very few examples of bisphosphine systems where both phosphorus atoms are trivalent and only one of the centers is two-coordinate^1,2. An example of such a system is the 4-phosphino-2,5-dimethyl-1,2,3-diazaphosphole obtained from acetone methylhydrazone and phosphorus trichloride³. This bisphosphine contains a two-coordinate endocyclic phosphorus and a three-coordinate exo phosphorus center. The exo phosphorus preferentially coordinates to metals but under certain conditions the two-coordinate phosphorus will also coordinate⁴.     

Three novel Schiff base transition metal(II) complexes induce gastric cancer cell death through ROS-mediated apoptotic pathway

Abstract

A new tridentate Schiff base ligand, 2-((2-(dimethylamino)ethylimino)methyl)-6-ethoxyphenol (HL₁), has been prepared by a one-pot condensation reactions, which was further used in the construction of three novel Schiff base transition metal(II) complexes, [Cu(L₁)(MeOH)](NO₃) (1), [Co(L₁)(MeOH)₂(N₃)] (2) and [Cu(L₁)(HCOO)]_n (3). Furthermore, a green hand-grinding technique has been implemented to reduce the particle size of the coordination complexes to generate the nanoscale compounds. The Scanning Electron Microscopy (SEM) studies reveal the formation of square and spherical particles for nano 1 and nanorod for nano 2 and 3. In addition, CCK-8 assay was conducted to detect the antiproliferative activity of nano 1–3 on human gastric cancer MGC-803 cells. The cell viability curves and IC₅₀ (half maximal inhibitory concentration) values indicated that only nano 1 has excellent anticancer activity on MGC-803 cells but not nano 2 and 3. The Annexin V-FITC/PI double staining assay and DCFH-DA staining were performed to detect the apoptosis of MGC-803 cancer cells.     

Integrating social and environmental justice into the chemistry classroom: a chemist’s toolbox

ABSTRACT

Although the chemical enterprise has provided numerous contributions to humanity, unintended consequences contribute to a disproportionate exposure of hazardous chemicals to certain populations based on race and socioeconomic status. Integrating concepts of social and environmental justice within chemistry curriculum provides an educational framework to help mitigate these impacts by training the next generation of chemists with justice-centered and green chemistry principles to guide their future work. Green and sustainable chemistry technologies can contribute to social equity and environmental justice. However, equity and social justice have only recently become a significant part of the green chemistry conversation. This article summarizes how the authors have explored issues of equity and environmental justice with the green and sustainable chemistry community. It offers a toolbox for college and university instructors containing foundational language, research, and idea-generation that can be used to strengthen the transition of a traditional chemistry curriculum toward a justice-centered one.     

Synthesis of Imidazolato and 2-Methyl-Imidazolato Derivatives of Tellurium(IV)

INTRODUCTION

The chemistry of S-N compounds has been well established^[1] in the past few years and the stability was accounted in terms of extensive π bonding^[2,3]. The diversity of these compounds tempted chemsits to explore analogous Se-N and Te-N compounds. However, the poor or even absence of π bonding with heavier Se and Te posed problem to synthesize such compounds in the past. The chemistry of Se-N and Te-N compounds has been developed extensively by introducing new synthetic precursors^[4] in the last decade or so. We have observed that N-trimethyl silylimidazole and 2-methyl silylimidazole are potential reagents for peperation of monomeric transition metal imidazolates and Tin(IV) imidazolate^[5,6]. We, therefore, thought worthwhile to synthesize amido derivatives of Te(IV) incorporating these π delocalised heterocycles which acts as potential 4e (both σ and π) donors.     

Reaction of 1,2,3-selenadiazoles with boranes

The complex formation of 1,2,3-selenadiazoles with boron trifluoride etherate and phenyldichloroborane has been studied. The molecular structure of the5-ethoxycarbonyl-4-methyl-1,2,3-selenadiazole has been confirmed by X-ray analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 289–293, February, 2007.     

Metal‐Free Route for the Synthesis of 4‐Acyl‐1,2,3‐Triazoles from Readily Available Building Blocks

Functionalized 1,2,3‐triazole heterocycles have been known for a long time and hold an extraordinary potential in diverse research areas ranging from medicinal chemistry to material science. However, the scope of therapeutically important 1‐substituted 4‐acyl‐1H‐1,2,3‐triazoles is much less explored, probably due to the lack of synthetic methodologies of good scope and practicality. Here, we describe a practical and efficient one‐pot multicomponent reaction for the synthesis of α‐ketotriazoles from readily available building blocks such as methyl ketones, N,N‐dimethylformamide dimethyl acetal, and organic azides with 100 % regioselectivity. This reaction is enabled by the in situ formation of an enaminone intermediate followed by its 1,3‐dipolar cycloaddition reaction with an organic azide. We effectively utilized the developed strategy for the derivatization of various heterocycles and natural products, a protocol which is difficult or impossible to realize by other means.     

Reoxidation of Transition‐metal Catalysts with O2

Transition‐metal catalyzed oxidation reactions are central components of organic chemistry. On behalf of green and sustainable chemistry, molecular oxygen (O₂) has been considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characters, and therefore offers attractive academic and industrial prospects. In recent years, some powerful organic oxidation methods have been continuously developed. Among them, the use of molecular oxygen (O₂) as a green and sustainable oxidant has attracted considerable attentions. However, the development of new transition metal‐catalyzed protocols using O₂ as an ideal oxidant is highly desirable but very challenging because of the low standard electrode potential of O₂ to reoxidize the transition‐metal catalysts. In this Account, we highlight some of our progress toward the use of transition‐metal catalyzed aerobic oxidation reactions. Through the careful selection of ligand and the acidic additives, we have successfully realized the reoxidation of Cu, Pd, Mn, Fe, Ru, Rh, and bimetallic catalysts under O₂ or air atmosphere (1 atm) for the oxidative coupling, oxygenation reactions, oxidative C‐H/C‐C bond cleavage, oxidative annulation, and olefins difunctionalization reactions. Most of the reactions can tolerate a range of functional groups. These methods provide new strategies for the green synthesis of alkynes, (α ‐keto)amides/esters, ketones/diones, O/N‐heterocycles, β ‐azido alcohols, and nitriles. The high efficiency, low cost, and simple operation under air make these methodologies very attractive and practical. We will also discuss the mechanisms of these reactions which might be useful to promote the new type of aerobic oxidative reaction design.