Organic Chemistry Frontiers

Total Page:16

File Type:pdf, Size:1020Kb

Organic Chemistry Frontiers ORGANIC CHEMISTRY FRONTIERS View Article Online REVIEW View Journal | View Issue Recent developments in 1,6-addition reactions of para-quinone methides (p-QMs) Cite this: Org. Chem. Front., 2020, 7, 1743 Jia-Yin Wang, Wen-Juan Hao,* Shu-Jiang Tu * and Bo Jiang * In recent years, para-quinone methides (p-QMs) have emerged as attractive and versatile synthons in organic synthesis owing to their high reactivity. Consequently, p-QM chemistry has attracted increasing attention and remarkable advances have been achieved. Among the numerous transformations involving p-QMs, catalytic reactions play a pivotal role, and a variety of catalytic systems mediated by Lewis acids, Brønsted acids, bases, transition metals, N-heterocyclic carbenes, and other catalysts have been estab- lished for performing 1,6-conjugate addition reactions. Various molecular scaffolds have been con- Received 30th March 2020, structed using p-QMs to obtain the core structures of numerous natural and synthetic substances of Accepted 28th May 2020 chemical and biomedical relevance. In this review, we provide a comprehensive overview of recent pro- DOI: 10.1039/d0qo00387e gress in this rapidly growing field by summarizing the 1,6-conjugate addition and annulation reactions of rsc.li/frontiers-organic p-QMs with consideration of their mechanisms and applications. 1. Introduction cal processes, such as lignin biosynthesis,2 adrenergic recep- tors,3 enzyme inhibition,4 and DNA alkylation5 and cross- para-Quinone methides (p-QMs; Fig. 1, type A) are ubiquitous linking.6 Owing to their unique structural assembly compris- structural motifs present in a wide variety of biologically active ing reactive carbonyl and olefinic moieties, p-QMs undergo natural products.1 p-QMs also play numerous roles in biologi- resonance between neutral and zwitterionic structures (Fig. 1, type B) and display remarkable chemical reactivity as versatile acceptors for 1,6-addition reactions, including Michael Published on 28 May 2020. Downloaded 10/5/2021 3:33:54 PM. School of Chemistry & Materials Science, Jiangsu Key Laboratory of Green Synthetic addition and radical addition. As Michael acceptors, p-QMs Chemistry for Functional Materials, Jiangsu Normal University, Xuzhou 221116, P. R. China. E-mail: [email protected], [email protected], have been successfully subjected to 1,6-addition or annulation [email protected]; Fax: +8651683500065; Tel: +8651683500065 reactions with carbon-, phosphorus-, and nitrogen-centered Jia-Yin Wang was born in 1993 Wen-Juan Hao was born in 1983 in Jiangsu Province (China). He in Jiangsu province, China. She received his BS in 2016 at received her B.S. in 2006 and M. Xuzhou Institute of Technology. S. in 2009 at Jiangsu Normal He received his MS in 2019 at University under the supervision Jiangsu Normal University under of Prof. Shu-Jiang Tu, Ph.D. in the supervision of Prof. Shu- 2014 at Soochow University with Jiang Tu and Prof. Bo Jiang. Prof. Shu-Jun Ji and then joined Currently, he is pursuing his the School of Chemistry and PhD at Nanjing University under Materials Science at Jiangsu the supervision of Prof. Guigen Normal University as a lecturer Li and Prof. Bo Jiang (JSNU). His and is currently promoted to Jia-Yin Wang research interests include radical Wen-Juan Hao Associate Professor. She was as a triggered bicyclization and asym- Visiting Scholar at Nanyang metric transformation. Technological University from July 2016 to January 2017 in Singapore with Prof. Choon Hong Tan. Her research interest includes synergistic catalysis, heterocyclic syntheses, and radical domino reactions. This journal is © the Partner Organisations 2020 Org. Chem. Front.,2020,7,1743–1778 | 1743 View Article Online Review Organic Chemistry Frontiers Fig. 1 p-QMs and their resonance structures. nucleophiles under various catalytic systems. Interestingly, p-QMs have also been exploited as highly reactive radical acceptors for capturing various carbon- and nitrogen-centered radicals via radical addition/cyclization or radical cross-coup- ling. These transformations provide numerous elegant and Fig. 2 p-QMs and their derivatives. practical methods for the formation of a variety of carbon– carbon and carbon–heteroatom bonds, permitting the syn- thesis of important molecules that are difficult to obtain by tegic design, reaction discovery, and fundamental character- other approaches. Since two pioneering works describing the istics of the 1,6-conjugate addition and annulation reactions of synthesis of diarylmethines from p-QMs via 1,6-conjugate p-QMs with an emphasis on achiral transformations in con- addition were independently reported by Fan7a and sideration with recent asymmetric advances. Jørgensen,7b several reaction modes of p-QMs have been thoroughly explored,8 including [2 + 1], [4 + 1], [3 + 2], [4 + 2], [4 + 3], and double annulations involving various p-QM sub- strates containing different functional groups and substitution 2. Chemistry of p-QMs patterns (Fig. 2, 1a–1h), resulting in new three-, five-, and six- membered and polycyclic systems. In the past years, Li, 2.1. 1,6-Addition of nucleophiles to p-QMs Bernardi, Enders, and Tortosa independently highlighted 2.1.1. Catalyst-free 1,6-addition. Environmentally benign 9 achievements in the asymmetric transformations of p-QMs. and sustainable synthetic approaches to target compounds Undoubtedly, implementing catalytic approaches involving of have attracted increasing attention in recent years, with con- p-QMs is one large research field, which includes both chiral siderable research effort devoted to the development of reac- and achiral aspects. Owing to the increasing attention that tion conditions for green and sustainable chemistry, such as Published on 28 May 2020. Downloaded 10/5/2021 3:33:54 PM. p-QM chemistry has received in recent years, especially with metal-free catalysis,10 catalyst-free synthesis, and the utiliz- respect to non-asymmetric transformations, there is a strong ation of green solvents.11 In this context, Anand and co- demand to summarize these recent advances. Therefore, the workers reported a straightforward strategy for the 1,6-conju- purpose of this review is to provide our perspective on the stra- gate addition of dialkylzinc reagents to p-QMs 1a under con- Shu-Jiang Tu was born in 1957 Bo Jiang was born in 1981 in in Jiangsu (China) and received Jiangsu (China). He received his his B.S. in 1983 at Jiangsu B.S. in 2004 and M.S. in 2007 at Normal University. He was Jiangsu Normal University under appointed as Assistant Professor the supervision of Prof. Shu- at the Xuzhou Normal University Jiang Tu, Ph.D. in 2010 at in 1999 and was promoted to Soochow University with Prof. Full Professor in 2003. His Shu-Jiang Tu and Prof. Guigen current interests are the develop- Li. He joined Jiangsu Normal ment of new synthetic methods, University as a lecturer and was green chemistry, and microwave promoted to Full Professor in multicomponent syntheses. 2019. He was as an Associate Shu-Jiang Tu Bo Jiang Research Professor at Texas Tech University from Aug. 2015 to Feb. 2017 in USA with Prof. Guigen Li. His research interest includes asymmetric catalysis, radical transformations, and the innovation of synthetic methods. 1744 | Org. Chem. Front.,2020,7,1743–1778 This journal is © the Partner Organisations 2020 View Article Online Organic Chemistry Frontiers Review tinuous-flow conditions in a microreactor (Scheme 1).12 Upon injection of a toluene solution of p-QMs 1a and 2.0 equivalents − of dialkylzinc reagent at a flow rate of 5 μL min 1 (residence time in the microreactor = 10 min), the reactants were smoothly transformed into unsymmetrical alkyl diaryl- methanes 2 at room temperature. This protocol was generally applicable to a wide range of p-QMs 1a and dialkylzinc reagents without any catalyst or promoter. In 2017, Kang et al. synthesized diaryl diazaphosphonates 4 via 1,6-hydrophosphonylation of p-QMs 1a with N-heterocyclic phosphine (NHP)-thioureas 3 under catalyst- and additive-free conditions.13 This transformation proceeded smoothly in ff CHCl3 at room temperature over 16 h to a ord 20 examples of Scheme 3 1,6-Addition of sulfonyl hydrazides to p-QMs. the desired product (Scheme 2a). When the 2,6-diisopropyl- phenyl-substituted NHP-thiourea 3 was employed under the optimized reaction conditions, the reaction did not proceed. (Scheme 3a). Various types of sulfonyl hydrazides 8 bearing On the basis of control experiments, the authors proposed a either aryl or alkyl groups were well tolerated in this conjugate plausible reaction pathway (Scheme 2b). The 1,6-conjugate addition reaction, and the authors proposed a plausible addition between the p-QM 1a and the bifunctional NHP- mechanism for this catalyst-free transformation. In the first thiourea 3, which is activated by hydrogen bond formation step, the sulfinyl anion is formed from sulfonyl hydrazide 8 in with the thiourea Brønsted acid, generates the diazaphospho- the presence of water with the release of N . The resonance ff 2 nium intermediate 5. Subsequent proton transfer (PT) a ords structure of the sulfinyl anion, sulfur-centered anion 10, the anionic thiourea intermediate 6, which undergoes intra- undergoes 1,6-conjugate addition to the p-QM 1a to afford molecular nucleophilic substitution to furnish the final intermediate 11. The desired product 9 is formed upon proton product 4 alongside thiazolidine 7. transfer from hydronium ions to the intermediate 11 Subsequently, the Liu group developed a 1,6-conjugate (Scheme 3b).14 The similar unsymmetrical
Recommended publications
  • The Observed Chemical Structure of L1544? ?? S
    Astronomy & Astrophysics manuscript no. Maps_L1544 c ESO 2017 July 20, 2017 The observed chemical structure of L1544? ?? S. Spezzano, P. Caselli, L. Bizzocchi, B. M. Giuliano, and V. Lattanzi Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany July 20, 2017 ABSTRACT Context. Prior to star formation, pre-stellar cores accumulate matter towards the centre. As a consequence, their central density increases while the temperature decreases. Understanding the evolution of the chemistry and physics in this early phase is crucial to study the processes governing the formation of a star. Aims. We aim at studying the chemical differentiation of a prototypical pre-stellar core, L1544, by detailed molecular maps. In contrast with single pointing observations, we performed a deep study on the dependencies of chemistry on physical and external conditions. Methods. We present the emission maps of 39 different molecular transitions belonging to 22 different molecules in the central 6.25 arcmin2 of L1544. We classified our sample in five families, depending on the location of their emission peaks within the core. Furthermore, to systematically study the correlations among different molecules, we have performed the principal component analysis (PCA) on the integrated emission maps. The PCA allows us to reduce the amount of variables in our dataset. Finally, we compare the maps of the first three principal components with the H2 column density map, and the Tdust map of the core. Results. The results of our qualitative analysis is the classification of the molecules in our dataset in the following groups: (i) the c-C3H2 family (carbon chain molecules like C3H and CCS), (ii) the dust peak family (nitrogen-bearing species + like N2H ), (iii) the methanol peak family (oxygen-bearing molecules like methanol, SO and SO2), (iv) the HNCO peak family (HNCO, propyne and its deuterated isotopologues).
    [Show full text]
  • Exhaustive Product Analysis of Three Benzene Discharges by Microwave Spectroscopy Michael C
    pubs.acs.org/JPCA Article Exhaustive Product Analysis of Three Benzene Discharges by Microwave Spectroscopy Michael C. McCarthy,* Kin Long Kelvin Lee, P. Brandon Carroll, Jessica P. Porterfield, P. Bryan Changala, James H. Thorpe, and John F. Stanton Cite This: J. Phys. Chem. A 2020, 124, 5170−5181 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information ABSTRACT: Using chirped and cavity microwave spectroscopies, automated double resonance, new high-speed fitting and deep learning algorithms, and large databases of computed structures, the discharge products of benzene alone, or in combination with molecular oxygen or nitrogen, have been exhaustively characterized between 6.5 and 26 GHz. In total, more than 3300 spectral features were observed; 89% of these, accounting for 97% of the total intensity, have now been assigned to 152 distinct chemical species and 60 of their variants (i.e., isotopic species and vibrationally excited states). Roughly 50 of the products are entirely new or poorly characterized at high resolution, including many heavier by mass than the precursor benzene. These findings provide direct evidence for a rich architecture of two- and three-dimensional carbon and indicate that benzene growth, particularly the formation of ring−chain molecules, occurs facilely under our experimental conditions. The present analysis also illustrates the utility of microwave spectroscopy as a precision tool for complex mixture analysis, irrespective of whether the rotational spectrum of a product species is known a priori or not. From this large quantity of data, for example, it is possible to determine with confidence the relative abundances of different product masses, but more importantly the relative abundances of different isomers with the same mass.
    [Show full text]
  • A Study of the C3H2 Isomers and Isotopologues: first Interstellar Detection of HDCCC?
    A&A 586, A110 (2016) Astronomy DOI: 10.1051/0004-6361/201527460 & c ESO 2016 Astrophysics A study of the C3H2 isomers and isotopologues: first interstellar detection of HDCCC? S. Spezzano1;3, H. Gupta2;??, S. Brünken3, C. A. Gottlieb4, P. Caselli1, K. M. Menten5, H. S. P. Müller3, L. Bizzocchi1, P. Schilke3, M. C. McCarthy4, and S. Schlemmer3 1 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany e-mail: [email protected] 2 California Institute of Technology, 770 S. Wilson Ave., M/C 100-22, Pasadena, CA 91125, USA 3 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany 4 Harvard-Smithsonian Center for Astrophysics, and School of Engineering & Applied Sciences, Harvard University, Cambridge, MA 02138, USA 5 Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany Received 28 September 2015 / Accepted 12 November 2015 ABSTRACT The partially deuterated linear isomer HDCCC of the ubiquitous cyclic carbene (c-C3H2) was observed in the starless cores TMC- 1C and L1544 at 96.9 GHz, and a confirming line was observed in TMC-1 at 19.38 GHz. To aid the identification in these narrow line sources, four centimetre-wave rotational transitions (two in the previously reported Ka = 0 ladder and two new ones in the Ka = 1 ladder) and 23 transitions in the millimetre band between 96 and 272 GHz were measured in high-resolution laboratory spectra. Ten spectroscopic constants in a standard asymmetric top Hamiltonian allow the main transitions of astronomical interest −1 in the Ka ≤ 3 rotational ladders to be calculated to within 0.1 km s in radial velocity up to 400 GHz.
    [Show full text]
  • Gas Phase Synthesis of Interstellar Cumulenes. Mass Spectrometric and Theoretical Studies."
    rl ì 6. .B,1l thesis titled: "Gas Phase Synthesis of Interstellar Cumulenes. Mass Spectrometric and Theoretical studies." submitted for the Degree of Doctor of Philosophy (Ph.D') by Stephen J. Blanksby B.Sc.(Hons,) from the Department of ChemistrY The University of Adelaide Cì UCE April 1999 Preface Contents Title page (i) Contents (ii) Abstract (v) Statement of OriginalitY (vi) Acknowledgments (vii) List of Figures (ix) Phase" I Chapter 1. "The Generation and Characterisation of Ions in the Gas 1.I Abstract I 1.II Generating ions 2 t0 l.ru The Mass SPectrometer t2 1.IV Characterisation of Ions 1.V Fragmentation Behaviour 22 Chapter 2 "Theoretical Methods for the Determination of Structure and 26 Energetics" 26 2,7 Abstract 27 2.IT Molecular Orbital Theory JJ 2.TII Density Functional Theory 2.rv Calculation of Molecular Properties 34 2.V Unimolecular Reactions 35 Chapter 3 "Interstellar and Circumstellar Cumulenes. Mass Spectrometric and 38 Related Studies" 3.I Abstract 38 3.II Interstellar Cumulenes 39 3.III Generation of Interstellar Cumulenes by Mass Spectrometry 46 3.IV Summary 59 Preface Chapter 4 "Generation of Two Isomers of C5H from the Corresponding Anions' 61 ATheoreticallyMotivatedMassSpectrometricStudy.'. 6l 4.r Abstract 62 4.rl Introduction 66 4.III Results and Discussion 83 4.IV Conclusions 84 4.V Experimental Section 89 4.VI Appendices 92 Chapter 5 "Gas Phase Syntheses of Three Isomeric CSHZ Radical Anions and Their Elusive Neutrals. A Joint Experimental and Theoretical Study." 92 5.I Abstract 93 5.II Introduction 95 5.ru Results and Discussion t12 5.IV Conclusions 113 5.V Experimental Section ttl 5.VI Appendices t20 Chapter 6 "Gas Phase Syntheses of Three Isomeric ClHz Radical Anions and Their Elusive Neutrals.
    [Show full text]
  • On the Road to Carbene and Carbyne Complexes
    ON THE ROAD TO CARBENE AND CARBYNE COMPLEXES Nobel Lecture, 11 December 1973 by ERNST OTTO FISCHER Inorganic Chemistry Laboratory, Technical University, Munich, Federal Republic of Germany Translation from the German text INTRODUCTION In the year 1960, I had the honour of giving a talk at this university* about sandwich complexes on which we were working at that time. I think I do not have to repeat the results of those investigations today. I would like to talk instead about a field of research in which we have been intensely interested in recent years: namely, the field of carbene complexes and, more recently, carbyne complexes. If we substitute one of the hydrogen atoms in a hydrocarbon of the alkane type - for example, ethane - by a metal atom, which can of course bind many more ligands, we arrive at an organometallic compound in which the organic radical is bound to the metal atom by a σ-bond (Fig. la). The earliest compounds of this kind were prepared more than a hundred years ago; the first was cacodyl, prepared by R. Bunsen (1), and then zinc dialkyls were prepared by E. Frankland (2). Later V. Grignard was able to synthesise alkyl magnesium halides by treating magnesium with alkyl halides (3). Grignard was awarded the Nobel Prize in 1912 for this effort. We may further recall the organo-aluminium compounds (4) of K. Ziegler which form the basis for the low pressure polymerisation, for example of ethylene. Ziegler and G. Natta were together honoured with the Nobel Prize in 1963 for their work on organometallic compounds.
    [Show full text]
  • Transfer of Radiation Through Cyclopropenylidene and Ethylene Oxide
    A&A 402, 1–3 (2003) Astronomy DOI: 10.1051/0004-6361:20030229 & c ESO 2003 Astrophysics Transfer of radiation through cyclopropenylidene and ethylene oxide S. Chandra School of Physical Sciences, SRTM University, Nanded 431 606, India Received 29 June 1999 / Accepted 17 October 2002 Abstract. Cyclopropenylidene and ethylene oxide molecules are of astronomical importance as their observed lines, distributed throughout the observable microwave region, have a number of pairs having nearly equal frequencies, but different excitation energies and/or belonging to two different species of the molecule. Hence, these molecules may play important role in detecting physical conditions in cosmic objects. Therefore, in order to calculate intensities of the lines, we have investigated transfer of radiation through a cosmic object containing the molecule at a kinetic temperature of 10 K. Our results show that some lines of the molecule may be found in absorption against the cosmic 2.7 K background. Key words. ISM: molecules – molecular data – radiative transfer 1. Introduction The molecular data required as input for the present inves- tigation are: (i) Einstein A-coefficients for radiative transitions Cyclopropenylidene (C3H2), in astronomical objects, was iden- between the rotational energy levels accounted for, and (ii) rate tified by Thaddeus et al. (1985); they reported twelve emission coefficients for collisional transitions between the energy levels lines of the molecule, distributed throughout the observable mi- due to collisions with H2 molecules. crowave region. Ethylene oxide (C H O) has been observed by 2 4 Both cyclopropenylidene and ethylene oxide are b-type Dickens et al. (1997) in Sgr B2N; twelve emission lines of the asymmetric top molecules having a large electric dipole mo- molecule, distributed throughout the observable microwave re- ment of 3.325 D and 1.88 D, respectively, along their b-axis gion, have been reported by them.
    [Show full text]
  • COLL 1 Vibrationally Mediated Chemistry at the Gas-Surface
    COLL 1 Vibrationally mediated chemistry at the gas-surface interface Arthur L Utz(1), [email protected], 62 Talbot Ave, Medford MA 02155, United States ; Victoria Campbell(1); Deno DelSesto(1); Nan Chen(1); Eric Peterson(1); Eric Dombrowski(1); Yongli Huang(1). (1) Department of Chemistry, Tufts University, Medford MA 02155, United States Vibrationally energized polyatomic molecules are abundant under thermal processing conditions, and vibrational energy can play an important role in activating reactions at the gas-surface interface. Beam-surface scattering studies performed with laser-excited and internal state selected molecules provide insight into how vibrational excitation of the molecule and surface activate reaction. Observations of mode- and bond-selective reactivity reveal the extent of vibrational energy redistribution prior to reaction. Surface- temperature-dependent studies using internal-state-selected gas-phase reagents show that surface vibrations can play a dramatic role in promoting methane activation on Ni. The presentation will highlight recent results from our lab that explore the role of surface excitation and of vibrationally hot precursor molecules in promoting reaction at the gas- surface interface. COLL 2 Electronically nonadiabatic chemical dynamics at metal surfaces Alec M. Wodtke(1)(2), [email protected], Fassberg 11, Goettingen Lower Saxony 37077, Germany . (1) Department of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Goettingen Lower Saxony 37077, Germany (2) Department of Physical Chemistry, Georg August University of Goettingen, Goettingen Lower Saxony 37077, Germany Developing a predictive understanding of surface chemistry based on the first principles of Physics must include possible breakdown of the Born-Oppenheimer approximation.
    [Show full text]
  • Hutchinson-Dissertation-2016
    Development of Bifunctional Alkylating Agents for Association and Migration along DNA By Mark A. Hutchinson A dissertation submitted to Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy Baltimore, Maryland August 2016 © 2016 Mark A. Hutchinson All rights reserved Abstract Environmental toxins and a number of drugs have been shown to react with and cause damage to cellular components including DNA. Alkylation of DNA has been shown to result in mutations that may cause detrimental effects to the cell, including cancer. One class of DNA alkylating agents is quinone methides (QM). These compounds are highly electrophilic and are generated by a variety of anti-cancer compounds such as mitomycin C. In order to further understand their ability to alkylate DNA both their selectivity and mechanism of action must be studied. These intermediates have been shown to form from metabolism inside of cells and have been found to alkylate DNA in both an irreversible and reversible manner. The reversible DNA adducts may persistent enough to elicit a cellular response, but are difficult to observe for standard analysis. In order to study the QMs ability to alkylate DNA, a simple QM was used to observe reversible DNA adducts. These adducts could be irreversibly trapped through the use of bis[(trifluoroacetoxy)iodo]benzene (BTI). Once oxidized through the use of BTI, the reversible QM-DNA adducts could withstand lengthy analysis (>24 h) for detection by LC/MS analysis. Additionally, QMs have been synthesized as bifunctional alkylating agents capable of forming interstrand crosslinking within DNA (BisQM). Once crosslinked, BisQM is able to exploit the reversible nature of their DNA-adducts providing a potential to migrate along DNA.
    [Show full text]
  • Discovery of Benzyne, O-C6H4, in TMC-1 with the QUIJOTE Line Survey? J
    Astronomy & Astrophysics manuscript no. c6h4 ©ESO 2021 August 6, 2021 Letter to the Editor 1 Discovery of benzyne, o-C6H4, in TMC-1 with the QUIJOTE line survey? J. Cernicharo1, M. Agúndez1, R. I. Kaiser2, C. Cabezas1, B. Tercero3; 4, N. Marcelino1, J. R. Pardo1, P. de Vicente3 1 Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain e-mail: [email protected] 2 Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA 3 Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain 4 Observatorio Astronómico Nacional (OAN, IGN), Madrid, Spain Received; accepted ABSTRACT We report the detection, for the first time in space, of a new non-functionalised hydrocarbon cycle in the direction of TMC-1: o- 11 −2 C6H4 (ortho-benzyne). We derive a column density for this hydrocarbon cycle of (5.0±1.0)×10 cm . The abundance of this species is around 30 times lower than that of cyclopentadiene and indene. We compare the abundance of benzyne with that of other pure hydrocarbons, cycles or chains, and find that it could be formed from neutral-radical reactions such as C2H + CH2CHCCH and C + C5H5, and possibly through C4H + C2H4,C3H + CH2CCH2, and C3H2+C3H3. Hence, the rich content of hydrocarbon cycles observed in TMC-1 could arise through a bottom-up scenario involving reactions of a few radicals with the abundant hydrocarbons recently revealed by the QUIJOTE line survey. Key words. molecular data – line: identification – ISM: molecules – ISM: individual (TMC-1) – astrochemistry 1.
    [Show full text]
  • REACTIONS of HALOCYCLOPROPANES. The
    This dissertation has been microfilmed exactly as received 69-11,652 HOUSER, Charles W., 1934- REACTIONS OF HALOCYCLOPROPANES. The Ohio State University, Ph.D., 1968 Chemistry, organic University Microfilms, Inc., Ann Arbor, Michigan REACTIONS OF HALOCYCLOPROPANES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School o f The Ohio State U niversity By Charles W. Houser, B.A. ******** The Ohio State U niversity 1968 Approved hy /Adviser Department of Chemistry Dedicated to Jane and Brian i l ACKNOWLEDGMENTS The author wishes to express sincere appreciation to Professor Harold Shechter for the inception of this problem and for his helpful discussions throughout the course of this research. His editorial guidance during preparation of this manuscript is also gratefully acknowledged. National Science Foundation and Petroleum Research Fund are thanked for their financial assistance to this research. The author owes a special debt of gratitude to his wife, Jane, for her patience and encouragement during completion of this work. i i i VITA October 20, 1934 Born - Parkersburg, West Virginia 1954-1958 U. S. Marine Corps 1962 B.A., David Lipscomb College, Nashville, Tennessee 1962-1965 Teaching Assistant, The Ohio State University, Columbus, Ohio I965-I968 Research Associate, The Ohio State University, Columbus, Ohio iv CONTENTS Page ACKNOWLEDGMENTS.......................................................................................................... i i i VITA .........................................................................
    [Show full text]
  • Reactivities of Quinone Methides Versus O-Quinones in Catecholamine Metabolism and Eumelanin Biosynthesis
    International Journal of Molecular Sciences Review Reactivities of Quinone Methides versus o-Quinones in Catecholamine Metabolism and Eumelanin Biosynthesis Manickam Sugumaran Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA; [email protected]; Tel.: +1-617-287-6598 Academic Editor: David Arráez-Román Received: 18 August 2016; Accepted: 12 September 2016; Published: 20 September 2016 Abstract: Melanin is an important biopolymeric pigment produced in a vast majority of organisms. Tyrosine and its hydroxylated product, dopa, form the starting material for melanin biosynthesis. Earlier studies by Raper and Mason resulted in the identification of dopachrome and dihydroxyindoles as important intermediates and paved way for the establishment of well-known Raper–Mason pathway for the biogenesis of brown to black eumelanins. Tyrosinase catalyzes the oxidation of tyrosine as well as dopa to dopaquinone. Dopaquinone thus formed, undergoes intramolecular cyclization to form leucochrome, which is further oxidized to dopachrome. Dopachrome is either converted into 5,6-dihydroxyindole by decarboxylative aromatization or isomerized into 5,6-dihydroxyindole-2-carboxylic acid. Oxidative polymerization of these two dihydroxyindoles eventually produces eumelanin pigments via melanochrome. While the role of quinones in the biosynthetic pathway is very well acknowledged, that of isomeric quinone methides, however, remained marginalized. This review article summarizes the key role of quinone methides during the oxidative transformation of a vast array of catecholamine derivatives and brings out the importance of these transient reactive species during the melanogenic process. In addition, possible reactions of quinone methides at various stages of melanogenesis are discussed. Keywords: catecholamine metabolism; quinone methides; quinone isomerization; eumelanin biosynthesis; dihydroxyindole polymers; quinone reactivity 1.
    [Show full text]
  • Detection of Cyclopropenylidene on Titan
    EPSC Abstracts Vol. 14, EPSC2020-380, 2020, updated on 25 Sep 2021 https://doi.org/10.5194/epsc2020-380 Europlanet Science Congress 2020 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Detection of Cyclopropenylidene on Titan Conor Nixon1, Alexander Thelen1,2, Martin Cordiner1,3, Zbigniew Kisiel4, Steven Charnley1, Edward Molter5, Joseph Serigano6, Patrick Irwin7, Nicholas Teanby8, and Yi-Jehng Kuan9,10 1Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, United States of America ([email protected]) 2Universities Space Research Association, Columbia, MD 21046, USA 3Department of Physics, Catholic University of America, Washington, DC 20064, USA 4Institute of Physics, Polish Academy of Sciences, Al. Lotnik_ow 32/46, 02-668 Warszawa, Poland 5Department of Astronomy, University of California, Berkeley, CA 94720, USA 6Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA 7Atmospheric, Oceanic, and Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK 8School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK 9Department of Earth Sciences, National Taiwan Normal University, Taipei 116, Taiwan, ROC 10Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan, ROC Titan, Saturn’s largest moon, has long been known to harbor a thick atmosphere [1] that evolves a complex array of organic molecules through atmospheric photochemistry [2, 3]. Especially from the 1970s onwards, successive waves of investigation with ground-based telescopes, spacecraft including Voyager 1 and Cassini-Huygens, and space telescopes have revealed the molecular inventory of its atmosphere through remote sensing at UV to radio wavelengths, and in situ mass spectroscopy [4, 5].
    [Show full text]