Complexes with Benzoxazole and Benzothiazole Ligands As Efficient Heterogenous Photocatalysts for Organic Dyes Degradation

Total Page:16

File Type:pdf, Size:1020Kb

Complexes with Benzoxazole and Benzothiazole Ligands As Efficient Heterogenous Photocatalysts for Organic Dyes Degradation catalysts Article Co(II/III) Complexes with Benzoxazole and Benzothiazole Ligands as Efficient Heterogenous Photocatalysts for Organic Dyes Degradation Martyna Szyma ´nska 1 , Włodzimierz Czepa 1,2, Cezary Hołubowicz 3, Renata Swisłocka´ 4 , Teresa Łuczak 1 , Maciej Kubicki 1 , Joanna Karpi ´nska 3 , Marta A. Fik-Jaskółka 1,* and Violetta Patroniak 1,* 1 Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Pozna´nskiego8, 61-614 Pozna´n,Poland; [email protected] (M.S.); [email protected] (W.C.); [email protected] (T.Ł.); [email protected] (M.K.) 2 Centre for Advanced Technologies, Adam Mickiewicz University, Uniwersytetu Pozna´nskiego10, 61-614 Pozna´n,Poland 3 Faculty of Chemistry, University of Białystok, Ciołkowskiego 1K, 15-245 Białystok, Poland; [email protected] (C.H.); [email protected] (J.K.) 4 Faculty of Construction and Environmental Engineering, Bialystok University of Technology, Wiejska 45e, 15-351 Białystok, Poland; [email protected] * Correspondence: martafi[email protected] (M.A.F.-J.); [email protected] (V.P.) Received: 8 October 2019; Accepted: 30 October 2019; Published: 1 November 2019 Abstract: The problem of pollution in the current world is growing, however people’s awareness of environmental protection and ecology is also increasing. The aim of the study is to present three new Schiff base compounds with Co(II/III) ions and to assess their photocatalytic activity. The study was supported by cyclic voltammetry technique. In due course the complex 2 revealed as the most effective in AR18 degradation, even more than commercially available TiO2. The search for new photocatalysts able to decompose harmful organic dyes into environmentally friendly basic substances is becoming a new trend in the area of chemistry development. Keywords: Schiff base; cobalt(II/III) complexes; photocatalysis; cyclic voltammetry; redox processes 1. Introduction Nowadays the natural environment is becoming more and more exposed to the threat of pollution. In the past decades the growing food, textile, chemical etc., industries have led to the alarming level of the Earths’ contamination. Currently, the trend is to maintain the high efficiency of the factories and to decrease the amount of post-production and post-usage waste. Both, the big industries and consumers joined the pro-Earth movement and support the low-waste lifestyle to prevent further contaminations [1]. However, since the level of pollution is already very high, it is important to develop new and efficient ways to decrease it. Notably, over 100,000 organic dyes is used worldwide in the manufactures [2,3]. One of the challenges is the removal of the organic dyes, used in textile, paper, polymer, cosmetics, and food industry from wastewater [4]. Organic dyes, such as Reactive Blue 21 and Acid Red 18 and the products of their cleavage exhibit carcinogenic and mutagenic effects when present in high concentrations [5–7]. In fact, the list and usage protocols of textile dyes that decompose to toxic amines are not regulated yet [8]. Therefore, there is a strong need to find a way to efficiently reduce the amount of dyes already present in the environment. The significance of adsorption of noxious compounds is dropping, since it does not neutralize dyes to non-toxic compounds, but only removes it from water [9]. The challenge is to decompose Catalysts 2019, 9, 913; doi:10.3390/catal9110913 www.mdpi.com/journal/catalysts Catalysts 2019, 9, 913 2 of 16 the compounds to its harmless derivatives that can be achieved by catalytic degradation. The perfect catalysts exhibiting efficient decomposition of organic dyes should be cheap, as well as easy to obtain and to operate [10]. In particular, photocatalysis is a modern green chemistry approach which breaks down organicCatalysts 2019 pollutants, 9, x FOR PEER into REVIEW simple, non-toxic compounds such as water, carbon dioxide,2 of and16 other simple inorganiccatalysts exhibiting anions efficient under thedecomp influenceosition of organic photocatalyst dyes should and be UV cheap, irradiation as well as oreasy even to obtain visible light. It is alreadyand to shownoperate that[10]. In photocatalysis particular, photocatalysis is a useful is a and modern promising green chemistry tool for approach efficient which degradation breaks dyes from wastewaterdown organic [11 pollutants,12]. into simple, non-toxic compounds such as water, carbon dioxide, and other simple inorganic anions under the influence of photocatalyst and UV irradiation or even visible light. One of the most commonly used photocatalyst is titanium dioxide (TiO2)—a cheap, non-toxic, and It is already shown that photocatalysis is a useful and promising tool for efficient degradation dyes stable compound. Notably, TiO2 needs to be exposed to UV light to catalyze the degradation processes. UV from wastewater [11,12]. accounts only for ca. 2% of the sunlight, while visible light is ca. 45%. Therefore, a new class of catalysts with One of the most commonly used photocatalyst is titanium dioxide (TiO2)—a cheap, non-toxic, high photocatalyticand stable compound. activity inNotably, the presence TiO2 needs of visible to be exposed light is neededto UV lig andht to recently catalyze widely the degradation explored [13,14]. Dopingprocesses. of the TiO UV2 with accounts Schiff only base for complexes ca. 2% of the increases sunlight, thewhile photocatalytic visible light is activityca. 45%. Therefore, because of a thenew action in the widerclass range of catalysts of sunlight—both with high photocatalytic UV and visible activity light. in Thethe degradationpresence of visible of methylene light is needed blue in and the visible light usingrecently the modifiedwidely explored hybrid [13,14]. compounds Doping was of examinedthe TiO2 with by M.Schiff M. Momenibase complexes [15]. increases the photocatalytic activity because of the action in the wider range of sunlight—both UV and visible light. Since the d-electron metal ions may adsorb visible light, some of the complexes exhibit enhanced The degradation of methylene blue in the visible light using the modified hybrid compounds was photocatalyticexamined performance by M. M. Momeni toward [15]. organic compound degradation. Therefore, there is a number of papers presentingSince the outstanding d-electron metal effi ionsciency may of adsorb the process visible light, in the some presence of the complexes of complexes exhibit enhanced with such metal ions asphotocatalytic Zn(II), Co(II), performance Ni(II), Cu(II), toward Fe(II) organic [16– compound19]. degradation. Therefore, there is a number of Onepapers of the presenting degradation outstanding pathways efficiency bases of the on process the oxidation in the presence mechanism of complexes called withFenton such metal reaction —a ions as Zn(II), Co(II), Ni(II), Cu(II), Fe(II) [16–19]. well-known reaction utilizing H2O2 and iron ions. The homogenous catalyst under electromagnetic One of the degradation pathways bases on the oxidation mechanism called Fenton reaction—a radiation produces hydroxyl radicals providing effective decomposition of organic species [20]. This reaction well-known reaction utilizing H2O2 and iron ions. The homogenous catalyst under electromagnetic is widelyradiation used forproduces destroying hydroxyl hazardous radicals providing organics effe includingctive decomposition aromatic amines, of organic surfactants, species [20]. andThis organic dyes [21reaction–23]. Therefore, is widely suchused for an approachdestroying inspireshazardous the organics development including of aaromatic class of amines, new efficient surfactants, compounds with photocatalyticand organic dyes activity. [21–23]. An Therefore, example such could an beapproach the mechanism inspires the of development the methylene of a blueclass decolorizationof new efficient compounds with2+ photocatalytic3 activity. An example could be the2+ mechanism3 of the process in the presence of Co , HCO −, and H2O2 forming the Fenton-like Co -HCO −-H2O2 system that 2+ 3- was presentedmethylene by blue Li et decolorization al. [24,25]. Thanks process to in this,the presence organic of impurities Co , HCO could, and beH2O oxidized2 forming easily. the Fenton- Moreover, in like Co2+-HCO3--H2O2 system that was presented by Li et al. [24,25]. Thanks to this, organic impurities another case peroxide decomposition was catalyzed by Co2+ ions [26]. could be oxidized easily. Moreover, in another case peroxide decomposition was catalyzed by Co2+ Asions the [26]. degradation of organic dyes is promoted by electron transfer, to better understand photocatalyticAs behaviorthe degradation of cobalt of organic complexes, dyes is cyclic promoted voltammetry by electron (CV) transfer, was performed. to better understand CV is avaluable techniquephotocatalytic for investigation behavior of of a varietycobalt complexes, of redox processes. cyclic voltammetry Moreover, (CV) it might was performed. provide a wideCV is range of characterizationavaluable technique showing for its investigation potential in of photocatalytic a variety of redox reactions processes. including Moreover, stability it might of provide the compounds, a wide range of characterization showing its potential in photocatalytic reactions including stability of presence of intermediates during redox reactions, and reversibility of the processes [27]. the compounds, presence of intermediates during redox reactions, and reversibility of the processes Because[27]. of the previous research in our group [28], we decided to check the photocatalytic
Recommended publications
  • Synthesis and Consecutive Reactions of Α-Azido Ketones: a Review
    Molecules 2015, 20, 14699-14745; doi:10.3390/molecules200814699 OPEN ACCESS molecules ISSN 1420-3049 www.mdpi.com/journal/molecules Review Synthesis and Consecutive Reactions of α-Azido Ketones: A Review Sadia Faiz 1,†, Ameer Fawad Zahoor 1,*, Nasir Rasool 1,†, Muhammad Yousaf 1,†, Asim Mansha 1,†, Muhammad Zia-Ul-Haq 2,† and Hawa Z. E. Jaafar 3,* 1 Department of Chemistry, Government College University Faisalabad, Faisalabad-38000, Pakistan, E-Mails: [email protected] (S.F.); [email protected] (N.R.); [email protected] (M.Y.); [email protected] (A.M.) 2 Office of Research, Innovation and Commercialization, Lahore College for Women University, Lahore-54600, Pakistan; E-Mail: [email protected] 3 Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia, Serdang-43400, Selangor, Malaysia † These authors contributed equally to this work. * Authors to whom correspondence should be addressed; E-Mails: [email protected] (A.F.Z.); [email protected] (H.Z.E.J.); Tel.: +92-333-6729186 (A.F.Z.); Fax: +92-41-9201032 (A.F.Z.). Academic Editors: Richard A. Bunce, Philippe Belmont and Wim Dehaen Received: 20 April 2015 / Accepted: 3 June 2015 / Published: 13 August 2015 Abstract: This review paper covers the major synthetic approaches attempted towards the synthesis of α-azido ketones, as well as the synthetic applications/consecutive reactions of α-azido ketones. Keywords: α-azido ketones; synthetic applications; heterocycles; click reactions; drugs; azides 1. Introduction α-Azido ketones are very versatile and valuable synthetic intermediates, known for their wide variety of applications, such as in amine, imine, oxazole, pyrazole, triazole, pyrimidine, pyrazine, and amide alkaloid formation, etc.
    [Show full text]
  • Heterocycles 2 Daniel Palleros
    Heterocycles 2 Daniel Palleros Heterocycles 1. Structures 2. Aromaticity and Basicity 2.1 Pyrrole 2.2 Imidazole 2.3 Pyridine 2.4 Pyrimidine 2.5 Purine 3. Π-excessive and Π-deficient Heterocycles 4. Electrophilic Aromatic Substitution 5. Oxidation-Reduction 6. DNA and RNA Bases 7. Tautomers 8. H-bond Formation 9. Absorption of UV Radiation 10. Reactions and Mutations Heterocycles 3 Daniel Palleros Heterocycles Heterocycles are cyclic compounds in which one or more atoms of the ring are heteroatoms: O, N, S, P, etc. They are present in many biologically important molecules such as amino acids, nucleic acids and hormones. They are also indispensable components of pharmaceuticals and therapeutic drugs. Caffeine, sildenafil (the active ingredient in Viagra), acyclovir (an antiviral agent), clopidogrel (an antiplatelet agent) and nicotine, they all have heterocyclic systems. O CH3 N HN O O N O CH 3 N H3C N N HN N OH O S O H N N N 2 N O N N O CH3 N CH3 caffeine sildenafil acyclovir Cl S N CH3 N N H COOCH3 nicotine (S)-clopidogrel Here we will discuss the chemistry of this important group of compounds beginning with the simplest rings and continuing to more complex systems such as those present in nucleic acids. Heterocycles 4 Daniel Palleros 1. Structures Some of the most important heterocycles are shown below. Note that they have five or six-membered rings such as pyrrole and pyridine or polycyclic ring systems such as quinoline and purine. Imidazole, pyrimidine and purine play a very important role in the chemistry of nucleic acids and are highlighted.
    [Show full text]
  • Further Studies on the Synthesis Of
    FURTHER STUDIES ON THE SYNTHESIS OF ARYLETHMOLMINES By Robert Simonoff in Thesis submitted to the Faculty of the Graduate School of the University of Maryland in partial fulfillment of the requirements for the degree of Doctor of Philosophy 1945 UMI Number: DP70015 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMI Dissertation Publishing UMI DP70015 Published by ProQuest LLC (2015). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ACKNOWLEDGEMENT The author wishes to express his appreciation for the encouragement and assistance given by Dr, Walter H. Hartung under whose direction this work has been carried out* TABLE OF CONTENTS Page INTRODUCTION.................................................... 1 REVIEW OF THE LITERATURE Previous Methods of Synthesis of Arylethanolamines Hydrogenolytic Debenzylation. ................. ......17 EXPERIMENTAL Synthesis of Ketones .................... .33 Synthesis of Amines.......... ........ ......... ....... ....... 38 Nitrosation of Ketones.• •«••••••.......... 40 Decomposition of Arylglyoxylohydroxamyl
    [Show full text]
  • Heterocyclic Chemistrychemistry
    HeterocyclicHeterocyclic ChemistryChemistry Professor J. Stephen Clark Room C4-04 Email: [email protected] 2011 –2012 1 http://www.chem.gla.ac.uk/staff/stephenc/UndergraduateTeaching.html Recommended Reading • Heterocyclic Chemistry – J. A. Joule, K. Mills and G. F. Smith • Heterocyclic Chemistry (Oxford Primer Series) – T. Gilchrist • Aromatic Heterocyclic Chemistry – D. T. Davies 2 Course Summary Introduction • Definition of terms and classification of heterocycles • Functional group chemistry: imines, enamines, acetals, enols, and sulfur-containing groups Intermediates used for the construction of aromatic heterocycles • Synthesis of aromatic heterocycles • Carbon–heteroatom bond formation and choice of oxidation state • Examples of commonly used strategies for heterocycle synthesis Pyridines • General properties, electronic structure • Synthesis of pyridines • Electrophilic substitution of pyridines • Nucleophilic substitution of pyridines • Metallation of pyridines Pyridine derivatives • Structure and reactivity of oxy-pyridines, alkyl pyridines, pyridinium salts, and pyridine N-oxides Quinolines and isoquinolines • General properties and reactivity compared to pyridine • Electrophilic and nucleophilic substitution quinolines and isoquinolines 3 • General methods used for the synthesis of quinolines and isoquinolines Course Summary (cont) Five-membered aromatic heterocycles • General properties, structure and reactivity of pyrroles, furans and thiophenes • Methods and strategies for the synthesis of five-membered heteroaromatics
    [Show full text]
  • Most Common Benzoxazole Derivatives As Antimicrobial Agent (1990-2018)
    Sarah Sattar Jabbar*et al. /International Journal of Pharmacy & Technology ISSN: 0975-766X CODEN: IJPTFI Available Online through Review Article www.ijptonline.com MOST COMMON BENZOXAZOLE DERIVATIVES AS ANTIMICROBIAL AGENT (1990-2018) Sarah Sattar Jabbar* Department of Pharmaceutical Chemistry, Collage of Pharmacy, University of Baghdad, Baghdad, Iraq. Email: [email protected] Received on: 20-10-2018 Accepted on 29-11-2018 Abstract: In this review, it was aimed to identify antimicrobial activity of newly synthesized benzoxazole derivatives which were synthesized and assayed for antibacterial and antifungal activity in previous study and showed a better antimicrobial effect that could be more effective against resistant pathogens. Benzoxazole derivatives have been extensively studied in the past few decades. The benzoxazole have shown significant antimicrobial activity against a wide variety of microorganisms like fungi, Gram +ve and Gram –ve bacteria. The review focuses out various important synthetic derivatives of benzoxazole which may in turn helpful to the information seekers to develop some novel derivatives of medicinal interest possessing benzoxazole moiety that could be better agents in term of efficacy and safety. Key word: benzoxazole , benzoxazole derivatives , Antimicrobial Agent Introduction Bacterial infection is a major category of human disease, for which many antibacterial compounds were developed. The dramatically rising prevalence of multidrug-resistant microbial infection in the past few decades has become a serious health care problem. Under these circumstances, the development of novel class of antimicrobial agent is going on. Benzoxazole plays an important role in medicinal chemistry and exhibit wide range of biological activities. The main objective of the medicinal chemistry is to synthesize the compounds that show promising activity as therapeutic agents with lower toxicity.
    [Show full text]
  • Influence of Roasting Process in Six Coffee Arabica Cultivars
    295 A publication of CHEMICAL ENGINEERING TRANSACTIONS VOL. 75, 2019 The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Sauro Pierucci, Laura Piazza Copyright © 2019, AIDIC Servizi S.r.l. ISBN 978-88-95608-72-3; ISSN 2283-9216 DOI: 10.3303/CET1975050 Influence of Roasting Process in Six Coffee Arabica Cultivars: analysis of Volatile Components Profiles a a a b Fabrizio Sarghini* , Evelina Fasano , Angela De Vivo , Maria Cristina Tricarico aUniversity of Naples Federico II, Department of Agricultural Sciences, Naples, Italy b Kimbo Spa, Italy [email protected] The complex composition of coffee aroma depends on the several factors regarding green coffee such as species and variety of the beans, origin , seeds size, colour (Toci and Farah, 2014). The most important coffee varieties are known to be Coffea arabica with good organoleptic characteristics, and Coffea canephora , known as Robusta of inferior quality. Development of aroma compounds also is greatly dependent upon the degree of roasting (Lopez-Galilea et al., 2006). In the roasting process almost 840 volatile organic compounds (VOC) are evaluated (Saw et al., 2015). The aim of this work is to investigate of the aromatic profile of six Arabica cultivar from Africa, Central and South America at different roasting degrees (light, medium and dark) and to establish odordescriptor categories as indicators for the assessment of flavour differences. The three roasting degrees were obtained in laboratory considering as target the industrial products and coffee roasting intensity was evaluated by a polychromatic colorimeter. The aromatic compounds of espresso coffee were evaluated by static headspace gas mass chromatography.
    [Show full text]
  • Synthesis and Cytotoxic Evaluation of Benzoxazole/Benzothiazole-2-Imino-Coumarin Hybrids and Their Coumarin Analogues As Potenti
    ORIGINAL ARTICLES Department of Chemical Technology of Drugs1, Medical University of Gdańsk, Gdańsk, Poland; Department of Pharmaceutical and Medicinal Chemistry2, Institute of Pharmacy, University of Greifswald, Greifswald, Germany Synthesis and cytotoxic evaluation of benzoxazole/benzothiazole-2- imino-coumarin hybrids and their coumarin analogues as potential anticancer agents A. MAKOWSKA1, L. WOLFF2, F. SĄCZEWSKI1,†, P. J. BEDNARSKI2,*, A. KORNICKA1,* Received July 9, 2019, accepted August 19, 2019 *Corresponding authors: Patrick J. Bednarski, Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, F.-L. Jahn Strasse 17, D-17489 Greifswald, Germany, [email protected] Anita Kornicka, Department of Chemical Technology of Drugs, Medical University of Gdańsk, Al. Gen. J. Hallera 107, 80-416 Gdańsk, Poland [email protected] †deceased 18.10.2018 Pharmazie 74: 648-657 (2019) doi: 10.1691/ph.2019.9664 Two series of 2-imino-coumarin based hybrids: 3-(benzoxazol-2-yl)-2H-chromen-2-imines 3-9 (series A-I) and 3-(benzothiazol-2-yl)-2H-chromen-2-imines 10-16 (series A-II), as well as their coumarin analogues: 3-(benzox- azol-2-yl)-2H-chromen-2-ones 17-21 (series B-I) and 3-(benzothiazol-2-yl)-2H-chromen-2-ones 22-28 (series B-II) were prepared as potential antitumor agents. The in vitro cytotoxic potency of the synthesized compounds was evaluated against five human cancer cell lines: DAN-G, A-427, LCLC-103H, RT-4 and SISO, and rela- tionships between structure and anticancer activity are discussed. Among the compounds tested, 3-(benzo[d] oxazol-2-yl)-N,N-diethyl-2-imino-2H-chromen-7-amine (6, series A-I) and 3-(benzo[d]thiazol-2-yl)-6-fluoro-2H- chromen-2-one (26, series B-II) exhibited the most potent cytotoxic activity with IC50 values ranging from <0.01 μM to 1.1 μM.
    [Show full text]
  • Research Journal of Pharmaceutical, Biological and Chemical Sciences
    ISSN: 0975-8585 Research Journal of Pharmaceutical, Biological and Chemical Sciences Synthesis Some New Benzoxazole Derivatives and Their Cytotoxicity to Human Cancer Cell Lines. Ahmed A. Fadda*, Ehab Abdel-Latif, Eman H. Tawfik, and Raaben M. Mohammed. Department of Chemistry, Faculty of Science, Mansoura University, ET-35516 Mansoura, Egypt. ABSTRACT A new series of benzoxazole derivatives were synthesized based on the reaction of 2- mercaptobenzoxazole as a core compound with some chloroacetamide derivatives and hydrazine. The structures of the newly synthesized compounds were secured by IR, 1H NMR, MS and elemental analyses. The synthesized benzoxazole compounds have been evaluated for their cytotoxic effects toward four human cancer cell lines. They displayed moderate to strong cytotoxic effects against the tested cancer cell lines. Compounds 11 and 12 showed the stronger cytotoxic effects against hepatocellular carcinoma (IC50 5.5±0.22 μg/ml) and breast cancer (IC50 5.6±0.32 μg/ml) cell lines, respectively. Keywords: 2-Mercaptobenzoxazole, N-chloroacetylamino-acetanilide, hydrazine hydrate, 2- hydrazinylbenzoxazole, ninhydrin, piperonal, anticancer activity. *Corresponding author January – February 2016 RJPBCS 7(1) Page No. 1820 ISSN: 0975-8585 INTRODUCTION Oxazole derivatives are well-known five-membered nitrogen containing heterocyclic compounds. They are highly versatile intermediates used for the synthesis of several organic molecules, including amino acids, peptides, antimicrobial or antitumor compounds, immunomodulators, heterocyclic precursors for biosensors coupling, and photosensitive composition devices for proteins [1-3]. Benzoxazole and its derivatives are known to exhibit high therapeutic efficiency as antibacterial, antifungal, antitumor, anti-tubercular, anti- inflammatory and HIV-1 reverse transcriptase inhibitory activities [4-8]. 2-Mercaptobenzoxazoles have emerged as a potent medicinal scaffold and have remained the focus of drug discovery due to their important therapeutic values [9].
    [Show full text]
  • Pyrazines in Drug Discovery
    Pyrazines in Drug Discovery Overview At least eight pyrazine-containing drugs have been approved by Key Points the FDA. In medicinal chemistry, pyrazine has been employed as bioisostere of benzene, pyridine, and pyrimidine. For pyrazine-containing kinase inhibitors, the pyrazine nitrogen atom May serves as a hydrogen frequently serves as a hydrogen bond acceptor to interact with bond acceptor to interact with an amino acid in the hinge region of the kinase protein. an amino acid in the hinge region of the kinase protein Bridging Molecules for Innovative Medicines 1 PharmaBlock designs and Structurally, pyrazine is a planar hexagon, similar to benzene, in both synthesizes over 1391 bond angles and lengths. Its C–N bonds are shorter and C–N–C bond Pyrazines and 159 angles are smaller than their phenyl counterparts. Pyrazine products are in stock. CLICK HERE to find detailed product information on webpage. Pyrazine’s Bond Lengths and Angles With 6 π-electrons, pyrazine is an electron-deficient (also known as electron-poor) aromatic heterocycle because of the increased electro negativity of the nitrogen atoms. Due to the presence of the electronegative nitrogen atoms, the electron density on the ring carbons is less than one. The lone-pair electrons do not take part in the delocalization for aromaticity so this molecule can act as a mild base. Its first pKa1 = 0.65 and second pKa2 = 5.78. Basic dissociation constants (pKa1) of pyrazine, some pyrazine derivatives, and other 1 diazines are listed below: Pyrazine-containing Drugs There are approximately eight pyrazine-containing drugs on the market in the US.
    [Show full text]
  • Streptomyces Monashensis Sp. Nov., a Novel Mangrove Soil
    www.nature.com/scientificreports Corrected: Author Correction OPEN Streptomyces monashensis sp. nov., a novel mangrove soil actinobacterium from East Received: 13 September 2018 Accepted: 21 January 2019 Malaysia with antioxidative Published online: 28 February 2019 potential Jodi Woan-Fei Law1, Hooi-Leng Ser1,2,3, Nurul-Syakima Ab Mutalib 4, Surasak Saokaew 1,5,6, Acharaporn Duangjai1,5,7, Tahir Mehmood Khan2,8, Kok-Gan Chan 9,10, Bey-Hing Goh2,3,5 & Learn-Han Lee1,3,5 A new Streptomyces species discovered from Sarawak mangrove soil is described, with the proposed name – Streptomyces monashensis sp. nov. (strain MUSC 1JT). Taxonomy status of MUSC 1JT was determined via polyphasic approach. Phylogenetic and chemotaxonomic properties of strain MUSC 1JT were in accordance with those known for genus Streptomyces. Based on phylogenetic analyses, the strains closely related to MUSC 1JT were Streptomyces corchorusii DSM 40340T (98.7%), Streptomyces olivaceoviridis NBRC 13066T (98.7%), Streptomyces canarius NBRC 13431T (98.6%) and Streptomyces coacervatus AS-0823T (98.4%). Outcomes of DNA–DNA relatedness between strain MUSC 1JT and its closely related type strains covered from 19.7 ± 2.8% to 49.1 ± 4.3%. Strain MUSC 1JT has genome size of 10,254,857 bp with DNA G + C content of 71 mol%. MUSC 1JT extract exhibited strong antioxidative activity up to 83.80 ± 4.80% in the SOD assay, with signifcant cytotoxic efect against colon cancer cell lines HCT-116 and SW480. Streptomyces monashensis MUSC 1JT (=DSM 103626T = MCCC 1K03219T) could potentially be a producer of novel bioactive metabolites; hence discovery of this new species may be highly signifcant to the biopharmaceutical industry as it could lead to development of new and useful chemo-preventive drugs.
    [Show full text]
  • Haloselectivity of Heterocycles Will Gutekunst
    Baran Group Meeting Haloselectivity of Heterocycles Will Gutekunst Background SN(ANRORC) Addition of Nuclophile, Ring Opening, Ring Closure Polysubstituted heterocycles represent some of the most important compounds in the realm of pharmaceutical and material sciences. New and more efficient ways to selectively produce these Br Br molecules are of great importance and one approach is though the use of polyhalo heterocycles. Br NaNH2 N N Consider: Ar N 3 Ar2 NH3(l), 90% NH2 3 Halogenations H NH2 H N CO2Me Ar H 3 Suzuki Couplings 1 N CO2Me - Br H Ar 3 Ar2 1 Triple Halogenation NH2 NH CO Me N N 2 Ar1 H 1 Triple Suzuki Coupling N CO2Me N NH H NH2 Ar H 3 Ar2 1 Triple C-H activation? CO Me N 2 Ar1 H N CO2Me Cross Coupling H Virtually all types of cross coupling have been utilized in regioselective cross coupling reactions: Nucleophilic Substitution Kumada, Negishi, Sonogashira, Stille, Suzuki, Hiyama, etc. SNAr or SN(AE) In all of these examples, the oxidative addition of the metal to the heterocycle is the selectivity determining steps and is frequently considered to be irreversible. This addition highly resembles a nucleophilic substitution and it frequently follows similar regioselectivities in traditional S Ar reactions. Nu N The regioselectivity of cross coupling reaction in polyhalo heterocycles do not always follow the BDE's Nu of the corresponding C-X bonds. N X N X N Nu 2nd 2nd Meisenheimer Complex 1st Br Br 88.9 83.2 S (EA) Br 88.9 N 87.3 Br O O via: st OMe 1 Br NaNH , t-BuONa 2 N N pyrrolidine + Merlic and Houk have determined that the oxidative addition in palladium catalyzed cross coupling N N THF, 40ºC N reactions is determined by the distortion energy of the C-X bond (related to BDE) and the interaction of N the LUMO of the heterocycle to the HOMO of the Pd species.
    [Show full text]
  • Food and Drug Administration, HHS § 178.3297
    Food and Drug Administration, HHS § 178.3297 Substances Limitations Sodium 2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate For use only: (CAS Reg. No. 85209–91–2). 1. As a clarifying agent at a level not exceeding 0.30 percent by weight of olefin polymers complying with § 177.1520(c) of this chapter, items 1.1, 3.1, or 3.2 (where the copolymers complying with items 3.1 and 3.2 contain not less than 85 weight percent of polymer units derived from polypropylene). The finished polymers contact foods only of types I, II, IV-B, VI-B, VII-B, and VIII as identified in table 1 of § 176.170(c) of this chapter and limited to conditions of use B through H, de- scribed in table 2 of § 176.170(c), or foods of all types, lim- ited to conditions of use C through H described in table 2 of § 176.170(c). 2. As a clarifying agent at levels not exceeding 0.10 percent by weight of polypropylene complying with § 177.1520(c) of this chapter, items 1.1(a) or 1.1(b) and of olefin polymers com- plying with § 177.1520(c) of this chapter, items 3.1(a), 3.1(b), 3.1(c), 3.2(a), or 3.2(b) (where the copolymers contain not less than 85 weight percent of the polymer units derived from polypropylene.) The finished polymers shall be used in contact with foods only under conditions of use A through H described in Table 2 of § 176.170(c) of this chapter.
    [Show full text]