DOCSLIB.ORG

Carbene-Carbene Rearrangements: Evidence for a Cyclopropene Intermediate

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Carbene-Carbene Rearrangements: Evidence for a Cyclopropene Intermediate CARBENE-CAREENE REARRANGEMENTS: EVIDENCE FOR A CYCLOPROPENE INTERMEDIATE By THOMAS TYLER COBURN A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREI-IENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1973 ACKNOVJLEDGEMEKTS The author wishes to express his appreciation to Professor William M. Jones for the assistance and direction he offered during the course of this work. Dr. Jones' contribution as an excellent teacher and as a personal friend cannot be stated adequately. Advice, assistance, and experience extended by fellow members of the research group, especially Kenneth Krajca, Russell LaBar, and John Mykytka, are gratefully acknowledged. The author also acknowledges v/ith appreciation the enthusiastic support and good humor of his wife, Susan, and children, Matthew and Katherine, while on their "Florida Vacation" during which time this v;ork v;as accomplished. Financial assistance provided by a National Science Foundation Science Faculty Fellov/ship and a University of Florida Graduate Council Fellowship made the work possible and is gratefully acknowledged. 11 TABLE OF CONTENTS Page ACKNOWLEDGEI-IENTS ii LIST OF TABLES vi i LIST OF FIGURES viii ABSTRACT jLx INTRODUCTION 1 CHAPTER I. A Norcaradiene-Bisnorcaradiene 7 II. Destabilization of the Cyclopropene Interme- diate: Carbene-Carbene Rearrangements in the Acenaphthylcarbene-Phenalenylidene System 13 III. The Precursor to a Stabilized Cyclopropene Intermediate: Dibenzo [a, c] cycloheptatrienyli- dene; A Comparison of Its Properties with Those of Less Stabilized Intermediates 20 CONCLUSION 59 EXPERIMENTAL 65 General g5 Acenaphthylene-1-carboxaldehyde (20^) 67 7,7-Dichlorodibenzo [a,c]bicyclo [4.1.0]heptane (34^)... 68 6-Chloro-5tf-dibenzo [cj c7]cyclohepten-5-ol (3_5) 69 6-Chloro-5A'-dibenzo [a,c;] cyclohepten-5-one (36) 70 6-Chloro-6 , 7-dihydro-5//-dibenzo [a^o] cyclohepten- 5-one (37_) 70 6,7-Dihydro-5/?-dibenzo [a,c]cyclohepten-5-one (39) 72 111 . Page Mixtures of 6-Chloro-6 ,7-dihydro-5^-diben70 [a^ e]- cycloh.epten-5-one {32) and 6 ,7-Dihydro--5A'- dibenzo [a, e]cyclohepten-5-one (39^) from Catalytic Reduction 73 5Z?-Diben20 [a^ a]cyclohepten-5-one (38j 73 Preparation of Tosylhydrazones 7 4 Preparation of Sodium Salts of Tosylhydrazones 75 Thermolysis and Photolysis of Aldehyde and Kf^tone Tosylhydrazone Sodium Salts 76 5- Preparative-scale Photolysis of Diazo-2 , 3 , 4 , tetraphenylcyclopentadiene in Benzene at lOQO 77 Small-scale Photolysis of Diazo-2 , 3 ,4 , 5-tetra- phenylcyclopentadiene in Benzene at 100° 78 Pyrolysis of Tropone Tosylhydrazone Sodium Salt in the Presence of 2 ,3 , 4 , S-Tetraphcnyl- cyclopentadienone 79 Photolysis of 1,2 ,3 ,4-Tetraphenyl-7i:/-benzocyclo- /- heptene (9^) and 5 , 6 ,7 , 8-Tetraphenyl-7 benzocycloheptene (10^) 79 Room Temperature Photolysis of Diazo-2 , 3 , 4 , 5-Tetra- phenylcyclopentadiene in Benzene 80 Pyrolysis of Phenalen-1-one Tosylhydrazone Sodium ' 80 Salt (_19 ) in Dioxane Pyrolysis of Acenaphthylene-1-carboxaldehyde Tosyl- hydrazone Sodium Salt (21^') in Dioxane 82 "Hot Tube" Pyrolysis of Phenalen-1-one Tosyl- 83 hydrazone Sodium Salt (19^' ) "Hot Tube" Pyrolysis of Phenalen-1-one Benzene- sulfonylhydrazone Sodium Salt 84 "Hot Tube" Pyrolysis of Acenaphthylene-1-carbox- 85 aldehyde Tosylhydrazone Sodium Salt i21_' ) 9- (2,4 ,6-Cycloheptatrien-l-yl)phenanthrene (£2) 86 IV Page Low Temperature Photolysis of 5 "-Dibenzo [a, c]- cyclohepten-5-one Tosylhydrazone Sodium Salt (£1 ' ) in Tetrahydrof uran 88 Low Temperature Photolysis of the Sodium Salt of 5//-Dibenzo [a, c?]cyclohepten-5-one Tosylhydra- zone (4_1 ' ) in the Presence of Styrene 88 Low Temperature Photolysis of the Sodium Salt of 5//-Dibenzo [a^ c7]cyclohepten-5-one Tosylhydra- zone (£1') in the Presence of Dimethyl Fumarate 89 Low Temperature Photolysis of 5^-Dibenzo [a, c]- cyclohepten-5-one Tosylhydrazone Sodium Salt (£1') in the Presence of 1 , 3-Cyclopentadiene. 89 Low Temperature Photolysis of 5//-Dibenzo [a, c] cyclo- hepten-5-one Tosylhydrazone Sodium Salt (41*) with Subsequent Addition of 1 , 3-Cyclopentadiene 90 Generation of Dibenzo [a^ c] cycloheptatrienylidene (32) in the Presence of Furan 91 Photolysis of 1,7- (o-Biphenylenyl) -endo-2, 5-epoxy- norcar-3-ene (4_4) 93 Pyrolysis of 1 ,7- (o-Biphenylenyl) -e^^do-2 , 5-epoxy- norcar-3-ene ( 4_4 ) in Benzene 94 Pyrolysis of 5£?-Dibenzo [a, c] cyclohepten-5-one Tosylhydrazone Sodium Salt {4_1 ' ) in the Presence of 2 , 3 ,4 , 5-Tetraphenylcyclopenta- dienone 95 Thermal Rearrangement of 10 , 11 , 12 , 13-Tetraphenyl- 9//-Cyclohepta [ ^ phenanthrene (£6) 96 Low Temperature Photolysis of 4 , S-Bonzotropone Tosylhydrazone Sodium Salt (5_3 ' ) in the Presence of 1, 3-Cyclopentadiene 97 2 7 2 8 ' ' Pyrolysis of e«do-5 , 6-Benzotetracyclo [7 . 2 . 1. .0 ]- dodeca-3,5,10-triene (£8) 98 Low Temperature Photolysis of 3 , 4-Benzotropone Tosylhydrazone Sodium Salt (S^' ) in the Presence of 1 , 3-Butadiene 98 , Page Low Temperature Photolysis of l-Vinyl-6 , 7-benzo- spiro[2.6]nona-4,6,8-triene (50) 100 Pyrolysis of 4 ,5-Benzotropone Tosylhydrazone Sodium Salt (53^') in the Presence of 2 , 3 , 4 , 5-Tetra- pheny Icyclopentadienone 101 Pyrolysis of Tropone Tosylhydrazone Sodium Salt in Furan 103 Generation of Phenanthrylcarbene (32) in the Presence of Furan 104 Low Temperature Photolysis of the Sodium Salt of 5ff-Dibenzo [a, c] cyclohepten-5-one Tosylhydra- zone (4]^') in the Presence of Diethylamine. 106 Photolysis of Phenyl Azide in the Presence of Butylamine 106 Photolysis of Phenyl Azide in the Presence of Furan 108 REFERENCES 109 BIOGRAPHICAL SKETCH 115 VI LIST OF TADLtS Table Page 1 Solvent Effect on the Reduction of 6-Chloro- 5//-dibenzo [a,c]cyclohepten-5-onc (3£) 24 2 Nmr Spectral Properties of £6 and Similar Compounds 33 3 Nmr Spectra (t) 4 2 4 H-nmr (t) 42 5 Nmr Spectral Properties of 50 and Similar Compounds 45 6 Hydrocarbons from Reactions with Tetracyclone. 49 7 Effect of Added Shift Reagent on H-nmr Spectra of Adduct 4_4 92 8 Effect of Added Shift Reagent on "^H-nmr Spectra of Adduct 57^ 104 Vll LIST OF FIGURES Figure Page 1 Mechanisms of Rearrangement 2 2 Isomerization of 3-Naphthylcarbene 5 3 A Mechanistic Hypothesis 8 A Delocalization Energies 21 5 Synthetic Scheme 23 6a Nmr Spectra of 3^9 25 6b Nmr Spectra of 3_7 26 7 Nmr Spectra of 4_4_ with Increasing Amounts of Eu(fod)3 Present 34 8 H-nrar Spectra of Adducts 44 9 A Two-step Mechanism for Adduct Formation 46 10 H-nmr Spectra of _57 with Increasing Amounts of Eu(fod)3 Present 52 Vlll , - Abstract of Dissertation Presented to the Graduate Council of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy FOR CARBENE-CARBE1:E REARRANGEr^NTS : EVIDENCE A CYCLOPROPENE INTERMEDIATE BY Thomas Tyler Coburn August, 1973 Chairman: V7illiara M. Jones Major Department; Chemistry Evidence is presented that implicates a fused cyclo- propene intermediate in the interconversion of aromatic capable of carbenes and arylcarbenes. A carbene potentially rearrangement with the requisite fused cyclopropene inter- mediate incorporated into an annelated bicyclo [3 . 1. 0] hex-6- strained ene structure (acenaphthylcarbene) is sufficiently phase to avoid rearrangement in solution, although gas isomerization (410°) still occurs. When the required 0] rearrangement intermediate has an annelated bicyclo [4 . 1. hept-7-ene structure (dibenzo [a, c] cycloheptacrienylidene) rearrangement takes place readily in solution at room tempera- ture and below. Annelated cycloheptatrienylidenes in which the loss in resonance energy accompanying cyclopropene forma- ix , most susceptible tion is minimized to the greatest extent are carbenes to reorganization. In the case of unsymmetrical relative the direction of rearrangement is controlled by the stabilities of the two potential cyclopropene intermediates. A convenient, high yield synthesis of 5ff-dibenzo- [a,£;]cyclohepten-5-one is developed, and the properties of dibenzo[a,c?]cycloheptatrienylidene are examined. Dibenzo- [a,c]cycloheptatrienylidene and 4 ,5-benzocycloheptatrienylidene rearrange rapidly in solution, and when the rearrangements adducts of take place in the presence of dienes, Diels-Alder structure the cyclopropene intermediates are obtained. The of their of these adducts can be deduced from a comparison compounds •^H-nmr spectral properties with those of model previously characterized. The molecular geometry of the is single furan adduct of dibenzo [a, c] cycloheptatrienylidene determined from an analysis of lanthanide- induce proton nmr yield shifts. Both carbenes react with cyclopentadiene to cycloaddi- only the endo-anti isomer expected to result from tion of 3-monosubstituted cyclopropenes with this diene. Furan adducts are obtained under both thermal (125 ) and photochemical (30° and -60°) conditions. Tetracyclone adducts result from thermal generation of the carbenes, and cyclopentadiene and butadiene adducts are obtained from low temperature (-60°) reactions of the cyclopropene intermediate which forms from the photolytically generated carbene. The adducts are shown not to be secondary photo-products, and irreversible a two step thermal process is ruled out. Also, X competitive with rearrangement is cyclopropene formation explanation of the experimental Shown to be an unsatisfactory results. been previously Cyoloheptatrienylidene, which has to solution, reacts with dienes Shown not to rearrange in result from a two step process. give adducts that apparently cyoloheptatrienylidene with tetra- The thermal reaction of evidence that cyclopropene trap- cyclone offers no conclusive the f uran-cycloheptatrienylidene ping occurs. Although structure for formation by adduct has the correct gross transition state would be cyclopropene trapping, an endo .Icycloheptatrienylidene reacts demanded. Since dibenzo la, and transition state and since steric with furan via an e.o reason for to indicate any . secondary orbital effects fail cycloaddition, a two step mechanism the differing modes of reaction is suggested. for the cyoloheptatrienylidene ring expand in Phenanthryloarbene, which does not indication of cyclopropene solution, fails to give any solutions containing dienes.
Load more

Recommended publications
  • Measuring and Predicting Sooting Tendencies of Oxygenates, Alkanes, Alkenes, Cycloalkanes, and Aromatics on a Unified Scale
    Measuring and Predicting Sooting Tendencies of Oxygenates, Alkanes, Alkenes, Cycloalkanes, and Aromatics on a Unified Scale Dhrubajyoti D. Dasa,1, Peter St. Johnb,1, Charles S. McEnallya,∗, Seonah Kimb, Lisa D. Pfefferlea aYale University, Department of Chemical and Environmental Engineering, New Haven CT 06520 bNational Renewable Energy Laboratory, Golden CO 80401 Abstract Soot from internal combustion engines negatively affects health and climate. Soot emissions might be reduced through the expanded usage of appropriate biomass-derived fuels. Databases of sooting indices, based on measuring some aspect of sooting behavior in a standardized combustion environment, are useful in providing information on the comparative sooting tendencies of different fuels or pure compounds. However, newer biofuels have varied chemical structures including both aromatic and oxygenated functional groups, making an accurate measurement or prediction of their sooting tendency difficult. In this work, we propose a unified sooting tendency database for pure compounds, including both regular and oxygenated hydrocarbons, which is based on combining two disparate databases of yield-based sooting tendency measurements in the literature. Unification of the different databases was made possible by leveraging the greater dynamic range of the color ratio pyrometry soot diagnostic. This unified database contains a substantial number of pure compounds (≥ 400 total) from multiple categories of hydrocarbons important in modern fuels and establishes the sooting tendencies of aromatic and oxygenated hydrocarbons on the same numeric scale for the first time. Using this unified sooting tendency database, we have developed a predictive model for sooting behavior applicable to a broad range of hydrocarbons and oxygenated hydrocarbons. The model decomposes each compound into single-carbon fragments and assigns a sooting tendency contribution to each fragment based on regression against the unified database.
    [Show full text]
  • Transport of Dangerous Goods
    ST/SG/AC.10/1/Rev.16 (Vol.I) Recommendations on the TRANSPORT OF DANGEROUS GOODS Model Regulations Volume I Sixteenth revised edition UNITED NATIONS New York and Geneva, 2009 NOTE The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. ST/SG/AC.10/1/Rev.16 (Vol.I) Copyright © United Nations, 2009 All rights reserved. No part of this publication may, for sales purposes, be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, electrostatic, magnetic tape, mechanical, photocopying or otherwise, without prior permission in writing from the United Nations. UNITED NATIONS Sales No. E.09.VIII.2 ISBN 978-92-1-139136-7 (complete set of two volumes) ISSN 1014-5753 Volumes I and II not to be sold separately FOREWORD The Recommendations on the Transport of Dangerous Goods are addressed to governments and to the international organizations concerned with safety in the transport of dangerous goods. The first version, prepared by the United Nations Economic and Social Council's Committee of Experts on the Transport of Dangerous Goods, was published in 1956 (ST/ECA/43-E/CN.2/170). In response to developments in technology and the changing needs of users, they have been regularly amended and updated at succeeding sessions of the Committee of Experts pursuant to Resolution 645 G (XXIII) of 26 April 1957 of the Economic and Social Council and subsequent resolutions.
    [Show full text]
  • Structure-Based Discovery and Synthesis of Potential Transketolase Inhibitors
    Supplementary Materials Structure-Based Discovery and Synthesis of Potential Transketolase Inhibitors Jingqian Huo 1,†, Bin Zhao 2,†, Zhe Zhang 1, Jihong Xing 3, Jinlin Zhang 1,*, Jingao Dong 1,3,* and Zhijin Fan 2,4,* 1 College of Plant Protection, Agricultural University of Hebei, Baoding 071001, China; [email protected] (J.H.); [email protected] (Z.Z.) 2 State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, P. R. China; [email protected] 3 College of life science, Agricultural University of Hebei, Baoding 071000, China; [email protected] 4 Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China * Correspondence: [email protected] (J.Z.); [email protected] (J.D.); [email protected] (Z.F.) † These authors contributed equally to this work. Table of Contents Table S1. The docking affinity of the compounds with transketolase. Figure S1. The binding mode between the small molecules and transketolase. Figure S2. Molecular structure of compound 4b. The appearance, yields, melting points and spectral data of the synthesized compounds. Table S1. The docking affinity of the compounds with transketolase ZINC Affinity ZINC Affinity ZINC Affinity ZINC Affinity ZINC Affinity Compd. (kcal/mol) Compd. (kcal/mol) Compd. (kcal/mol) Compd. (kcal/mol) Compd. (kcal/mol) 12007063 -9.1 05776152 -8.7 12929396 -8.6 67603588 -8.5 41585313 -8.5 19961402 -9 72020240 -8.7 95353804 -8.6 72472311 -8.5 46127235 -8.5 12126699 -9 16283531 -8.7 95353805 -8.6 72472321 -8.5 49169766 -8.5 23186631 -8.8 08654961 -8.6 95381421 -8.6 72472332 -8.5 05175849 -8.5 12130512 -8.8 58191888 -8.6 12130884 -8.6 21941633 -8.5 19706239 -8.5 Molecules 2018, 23, 2116; doi:10.3390/molecules23092116 www.mdpi.com/journal/molecules Molecules 2018, 23, 2116 2 of 11 a b c d e f Figure S1.
    [Show full text]
  • Secondary Organic Aerosol Formation from the Ozonolysis of Cycloalkenes and Related Compounds*
    252 Chapter 7 Secondary Organic Aerosol Formation from the Ozonolysis of Cycloalkenes and Related Compounds* * This chapter is reproduced by permission from “Secondary organic aerosol formation from ozonolysis of cycloalkenes and related compounds” by M.D. Keywood, V. Varutbangkul, R. Bahreini, R.C. Flagan, J.H. Seinfeld, Environmental Science and Technology, 38 (15): 4157-4164, 2004. Copyright 2004, American Chemical Society. 253 7.1. Abstract The secondary organic aerosol (SOA) yields from the laboratory chamber ozonolysis of a series of cycloalkenes and related compounds are reported. The aim of this work is to investigate the effect of the structure of the hydrocarbon parent molecule on SOA formation for a homologous set of compounds. Aspects of the compound structures that are varied include the number of carbon atoms present in the cycloalkene ring (C5 to C8), the presence and location of methyl groups, and the presence of an exocyclic or endocyclic double bond. The specific compounds considered here are cyclopentene, cyclohexene, cycloheptene, cyclooctene, 1-methyl-1-cyclopentene, 1-methyl-1- cyclohexene, 1-methyl-1-cycloheptene, 3-methyl-1-cyclohexene, and methylene cyclohexane. SOA yield is found to be a function of the number of carbons present in the cycloalkene ring, with increasing number resulting in increased yield. Yield is enhanced by the presence of a methyl group located at a double-bonded site but reduced by the presence of a methyl group at a non-double bonded site. The presence of an exocyclic double bond also leads to a reduced yield relative to the equivalent methylated cycloalkene. On the basis of these observations, the SOA yield for terpinolene relative to the other cyclic alkenes is qualitatively predicted, and this prediction compares well to measurements of SOA yield from the ozonolysis of terpinolene.
    [Show full text]
  • Benzofuran Synthesis Through Iodocyclization Reactions: Recent Advances
    MOJ Bioorganic & Organic Chemistry Mini Review Open Access Benzofuran synthesis through iodocyclization reactions: recent advances Abstract Volume 1 Issue 7 - 2017 Recent advancements (2014-17) in the benzofuran synthesis through iodocyclization Saurabh Mehta have been summarized. The successful use of various iodinating agents, bases, additives Department of Applied Chemistry, Delhi Technological etc. make iodocyclization a versatile and efficient methodology. The methodology has University, India been applied for the synthesis of more complex benzofuran derivatives, and may open interesting avenues in the area of heterocyclic chemistry (Figure 1). Correspondence: Saurabh Mehta, Department of Applied O-LG Chemistry, Delhi Technological University, Bawana Road, Delhi, + O R1 I 1 2 110042 India, Tel +9188 0066 5868, R R Email [email protected], [email protected] R2 I Received: December 17, 2017 | Published: December 29, 2017 LG = H, Me or other Protecting group 1 R = H, Me, OMe, I, CO2Me, etc. R2 = H, aryl, alkyl, alkenyl, etc. Figure 1 Keywords: annulations, alkyne, benzofuran, iodocyclization, heterocycle Introduction derivatives were obtained in high yields (84%−100%) under mild conditions. The authors demonstrated that the choice of bis(2,4,6- Benzo[b]furan is a privileged heterocyclic scaffold. Several collidine)iodonium hexafluorophosphate [I(coll)2PF6] as the compounds containing this scaffold have interesting biological iodinating agent was necessary for the success of the reaction. Also, 1 activities, such as anti-cancer, anti-viral, anti-inflammatory, etc. Few the ethoxyethyl ether group acted as a protecting group as well as a 2 derivatives are even used as commercial drugs, such as Amiodarone, good leaving group.
    [Show full text]
  • Epoxidation of Cyclopentene, Cyclohexene and Cycloheptene by Acetylperoxyl Radicals
    Epoxidation of Cyclopentene, Cyclohexene and Cycloheptene by Acetylperoxyl Radicals J. R. Lindsay Smith, D. M. S. Smith, M. S. Stark* and D. J. Waddington Department of Chemistry, University of York, York, YO10 5DD, United Kingdom To further the current understanding of how peroxyl radicals add to C=C double bonds,eg. 1-3 a series of cyclic alkenes (cyclopentene, cyclohexene and cycloheptene) were reacted with acetylperoxyl radicals over the temperature range 373 - 433 K, via the co- oxidation of acetaldehyde, the cyclic alkene and a reference alkene. The resulting epoxides were monitored by GC-FID, allowing the determination of the Arrhenius parameters given in Table 1 for these addition reactions. 3 -1 -1 -1 Alkene log10(A / dm mol s ) Eact / kJ mol cyclopentene 9.7±0.6 31.2±5.0 cyclohexene 7.7±0.7 17.4±5.3 cycloheptene 8.8±0.8 25.5±6.5 cis-2-butene4 8.1±0.5 22.9±3.8 Table 1: Arrhenius parameters for the addition of acetylperoxyl radicals to cyclic alkenes and cis-2-butene. Parameters for cis-2-butene are also given for comparison,4 as it would be expected that a relatively unstrained cycloalkene would behave in a similar manner to this non-cyclic alkene; this is indeed found to be so, with no statistically significant difference between cyclohexene and cis-2-butene. Indeed the measured activation energy for cyclohexene fits in well with correlation between charge transfer ( Ec) and activation energy that is known to exist for the addition of acetylperoxyl to acyclic mono-alkenes.1 Cyclopentene however does have a significantly larger pre-exponential factor and activation energy than either cyclohexene or cis-2-butene.
    [Show full text]
  • A SCF MO Treatment of Some Tropone Derivatives* M
    CROATICA CHEMICA ACTA 42 (1 97 0) 1 <CCA-565 539.19:547.5 Original Scientific Paper A SCF MO Treatment of Some Tropone Derivatives* M. J. S. Dewar and N. Trinajstić** Department of Chemistry, The University of Texas, Austin, Texas 78712, U.S.A. R e c e iv e d A u g u s t 9, 1969 Recent work in these laboratories has led to the development of a semiempirical SCF MO treatment which seems to give extremely good results for ground States of conjugated molecules of ali kinds composed of carbon, hydrogen, nitrogen and oxygen. We have now applied this treatment to a problem of current interest, namely the structures of tropolone and tropone deri­ vatives. The calculations lead to the conclusion that neither of these ring systems is in itself aromatic, while tropone is now re- cognized to be polyenoid, tropolone still seems to be generally regarded as aromatic. This belief, however, arose from the behavior of tropolone derivatives in strong acid solution, where they exist as hydroxy tropylium derivatives, or in alkali where they form mesomeric anions. Calculated heats of formation, resonance ener- gies, and bond lengths are reported. INTRODU CTION Some time ago one of us1 concluded on the basis of available Chemical <evidence that stipitatic acid and colchicine must contain a novel aromatic system, tropolone (I), containing a seven-membered ring. Subsequent work not only confirmed this conclusion but also led to the synthesis of tropolone2 itself, and of the related tropone3 (II); both these compounds seemed to show stability characteristics of typical aromatic systems, and it was quickly realized that this might be due to the fact that both I and II can be regarded as deri­ vatives of the tropylium ion, C7H7+, which Hiickel4 in 1931 had predicted to be aromatic, a prediction which has been fully confirmed.5 However although an enormous amount of experimental work has been carried out since then on the synthesis and properties of numerous tropone and tropolone derivatives, very few theoretical studies seem as yet to have been reported.
    [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]
  • An Update on Natural Occurrence and Biological Activity of Benzofurans
    Acta Scientific MEDICAL SCIENCES (ISSN: 2582-0931) Volume 4 Issue 10 October 2020 Review Article An Update on Natural Occurrence and Biological Activity of Benzofurans Kavita Khatana* and Anjali Gupta Received: June 28, 2020 Department of Chemistry, School of Basic and Applied Sciences, Galgotias Published: September 21, 2020 University, Greater Noida, UP, India © All rights are reserved by Kavita Khatana. *Corresponding Author: Kavita Khatana, Department of Chemistry, School of Basic and Applied Sciences, Galgotias University, Greater Noida, UP, India. Graphical Abstract Figure a Abstract Benzofuran and its derivatives are the major group amongst the natural collection of biologically active heterocyclic compounds. Their wide range of pharmacological activities and imaginable applications in medicinal and pharmaceutical chemistry have at- tracted various research scholars, medicinal chemists and pharmacologists. This review emphasizes the progress and development . ofKeywords: benzofuran Benzofuran; derivatives Antioxidant; in various biological Antiviral; activities Antimicrobial; with an Anticancer update of current research findings during a decade Introduction physiological and industrial world. In reference to pharmaceutical Heterocyclic ring systems have emerged as powerful scaf- industry, over 60% of the top retailing drugs contain at least one folds for many biological evaluations. Heterocyclic compounds heterocyclic motif as a part of overall topography of the compound. Benzofurans and its derivatives are important class of heterocyclic have significant role in medicinal and pharmacological chemistry, Citation: Kavita Khatana and Anjali Gupta. “An Update on Natural Occurrence and Biological Activity of Benzofurans”. Acta Scientific Medical Sciences 4.10 (2020): 114-123. An Update on Natural Occurrence and Biological Activity of Benzofurans 115 compounds, which are known to possess various biological proper- 3-(hydroxymethyl)-7-methoxy-2,3-dihydrobenzo furan-5-yl) ties.
    [Show full text]
  • How Ingredients Influence Furan and Aroma Generation in Sponge Cake Mayela Cepeda-Vázquez, Barbara Rega, Nicolas Descharles, Valérie Camel
    How ingredients influence furan and aroma generation in sponge cake Mayela Cepeda-Vázquez, Barbara Rega, Nicolas Descharles, Valérie Camel To cite this version: Mayela Cepeda-Vázquez, Barbara Rega, Nicolas Descharles, Valérie Camel. How ingredients influence furan and aroma generation in sponge cake. Food Chemistry, Elsevier, 2018, 245, pp.1025 - 1033. 10.1016/j.foodchem.2017.11.069. hal-01868629 HAL Id: hal-01868629 https://hal-agroparistech.archives-ouvertes.fr/hal-01868629 Submitted on 5 Oct 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. How ingredients influence furan and aroma generation in sponge cake AUTHORS Mayela Cepeda-Vázquez, Barbara Rega, Nicolas Descharles, Valérie Camel* UMR Ingénierie Procédés Aliments, AgroParisTech, Inra, Université Paris-Saclay, 91300 Massy, France * Corresponding author. AgroParisTech, 16 rue Claude Bernard, F-75231, Paris Cedex 05, France Tel. +33 (0) 1 44 08 17 25 email addresses: [email protected]; [email protected]; [email protected]; [email protected] * ABSTRACT A wide range of compounds can be formed during thermal processing of food, some of which are relevant for aroma (e.g. furfural), while others are of great health-concern (e.g.
    [Show full text]
  • Cycloalkanes, Cycloalkenes, and Cycloalkynes
    CYCLOALKANES, CYCLOALKENES, AND CYCLOALKYNES any important hydrocarbons, known as cycloalkanes, contain rings of carbon atoms linked together by single bonds. The simple cycloalkanes of formula (CH,), make up a particularly important homologous series in which the chemical properties change in a much more dramatic way with increasing n than do those of the acyclic hydrocarbons CH,(CH,),,-,H. The cyclo- alkanes with small rings (n = 3-6) are of special interest in exhibiting chemical properties intermediate between those of alkanes and alkenes. In this chapter we will show how this behavior can be explained in terms of angle strain and steric hindrance, concepts that have been introduced previously and will be used with increasing frequency as we proceed further. We also discuss the conformations of cycloalkanes, especially cyclo- hexane, in detail because of their importance to the chemistry of many kinds of naturally occurring organic compounds. Some attention also will be paid to polycyclic compounds, substances with more than one ring, and to cyclo- alkenes and cycloalkynes. 12-1 NOMENCLATURE AND PHYSICAL PROPERTIES OF CYCLOALKANES The IUPAC system for naming cycloalkanes and cycloalkenes was presented in some detail in Sections 3-2 and 3-3, and you may wish to review that ma- terial before proceeding further. Additional procedures are required for naming 446 12 Cycloalkanes, Cycloalkenes, and Cycloalkynes Table 12-1 Physical Properties of Alkanes and Cycloalkanes Density, Compounds Bp, "C Mp, "C diO,g ml-' propane cyclopropane butane cyclobutane pentane cyclopentane hexane cyclohexane heptane cycloheptane octane cyclooctane nonane cyclononane "At -40". bUnder pressure. polycyclic compounds, which have rings with common carbons, and these will be discussed later in this chapter.
    [Show full text]
  • Alkenes and Alkynes
    02/21/2019 CHAPTER FOUR Alkenes and Alkynes H N O I Cl C O C O Cl F3C C Cl C Cl Efavirenz Haloprogin (antiviral, AIDS therapeutic) (antifungal, antiseptic) Chapter 4 Table of Content * Unsaturated Hydrocarbons * Introduction and hybridization * Alkenes and Alkynes * Benzene and Phenyl groups * Structure of Alkenes, cis‐trans Isomerism * Nomenclature of Alkenes and Alkynes * Configuration cis/trans, and cis/trans Isomerism * Configuration E/Z * Physical Properties of Hydrocarbons * Acid‐Base Reactions of Hydrocarbons * pka and Hybridizations 1 02/21/2019 Unsaturated Hydrocarbons • Unsaturated Hydrocarbon: A hydrocarbon that contains one or more carbon‐carbon double or triple bonds or benzene‐like rings. – Alkene: contains a carbon‐carbon double bond and has the general formula CnH2n. – Alkyne: contains a carbon‐carbon triple bond and has the general formula CnH2n‐2. Introduction Alkenes ● Hydrocarbons containing C=C ● Old name: olefins • Steroids • Hormones • Biochemical regulators 2 02/21/2019 • Alkynes – Hydrocarbons containing C≡C – Common name: acetylenes Unsaturated Hydrocarbons • Arene: benzene and its derivatives (Ch 9) 3 02/21/2019 Benzene and Phenyl Groups • We do not study benzene and its derivatives until Chapter 9. – However, we show structural formulas of compounds containing a phenyl group before that time. – The phenyl group is not reactive under any of the conditions we describe in chapters 5‐8. Structure of Alkenes • The two carbon atoms of a double bond and the four atoms bonded to them lie in a plane, with bond angles of approximately 120°. 4 02/21/2019 Structure of Alkenes • Figure 4.1 According to the orbital overlap model, a double bond consists of one bond formed by overlap of sp2 hybrid orbitals and one bond formed by overlap of parallel 2p orbitals.
    [Show full text]