DOCSLIB.ORG

Pericyclic Reactions 2012-2013

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pericyclic Reactions 2012-2013 DAMIETTA UNIVERSITY CHEM-405: PERICYCLIC REACTIONS LECTURE 1 Dr Ali El-Agamey 1 LEARNING OUTCOMES LECTURES 1-2 Understand the meaning of phase, regioselectivity, regiospecificity, stereoselectivity, stereospecificity. various types of pericyclic reactions. Realize common features among pericyclic reactions. Identify molecular orbital diagram of various systems. 2 1 Lecture 1-2: -Phase, Electron wave functions, Molecular orbitals, Regioselectivity, Regiospecificity, Stereoselectivity, Stereospecificity. - Types of Pericyclic Reactions, Various approaches to explain the pericyclic reactions, The Frontier Orbital Approach, Common Features among Pericyclic Reactions, Molecular Orbital Description of Various Systems. Lecture 3-4: -Electrocyclic reactions (Principle of microscopic reversibility, conrotatory and disrotatory motions; Torquoselectivity; Forbidden electrocyclic reactions). - Electrocyclic reactions of cations and anions (Pentadienyl cation; Pentadienyl anion; Allyl cations; oxyallyl cations; Allyl anion; Aziridines; 1,3-Dipoles). -Woodward-Hoffmann rules for electrocyclic reactions. Lecture 5: -Cycloaddition reactions (Energy consequences of the interaction between orbitals; [4 + 2] cycloaddition; [2 + 2] cycloaddition; suprafacial addition; antrafacial addition). -Factors affecting the rate of the Diels-Alder reaction (The diene; Electron-demand in Diels-Alder reactions; Lewis-acid catalysis). 3 Lecture 6-7: -Recognizing a Diels–Alder Product. -Diels-Alder Reaction (Regioselectivity; Stereospecificity; Stereoselectivity: endo vs exo; Stereoselectivity: Why endo). -Factors Affecting endo/exo Product Ratio (Steric Factors; Reversibility; Temperature; Lewis-Acid Catalysis; Pressure; Solvent used (Hydrophobic Effects)). -Cycloreversions. -[4 + 2] Cycloadditions of Cations and Anions (Oxyallyl-Diene; Allyl Cation-Diene; Allyl Anion-Alkene). -Woodward-Hoffmann Rules for [i + j] Cycloadditions. -[2 + 2] Cycloaddition (Promoted by Light; Alkene and a Ketene; Alkene and Ph3P=CH2 or R2Ti=CH2). Lecture 8: -Cycloadditions Involving more than Six Electrons. -Not all Cycloadditions are Pericyclic. -1,3-Dipolar Cycloadditions (Regioselectivity) -Examples of 1,3-Dipoles (Nitrones; Azomethine Ylids; Nitrile Oxides; Ozone). -[π2s + π2s + π2s] Cycloadditions. 4 2 Lecture 9-10: -Sigmatropic Reactions (Migration of Hydrogen; Migration of Carbon). -The Woodward-Hoffmann rules for [1,n] sigmatropic rearrangements. Lecture 11: -Ene reaction. Lecture 12: -Problems Reading J Morrison et al, Organic Chemistry, Oxford University Press, 2001. J Clayden et al, Organic Chemistry, Oxford University Press, 2001. RB Grossman, The art of writing reasonable organic reaction mechanism, Springer, 2003. B Miller, Advanced organic chemistry: reactions and mechanisms, Prentice Hall, 1998. I Fleming, Pericyclic reactions, Oxford University Press, 1999. S Sankararaman, Pericyclic reactions, Wiley-VCH, 2005. PS Kalsi, Organic reactions, NEW AGE, 2010. 5 Wave functions: Phase Standing waves. Plus and minus signs show relative phases. 6 3 Wave functions: Phase The places where the amplitude is zero are called nodes and they lie in a plane called the nodal plane (perpendicular to the plane of the paper). Wave function gives the amplitude as a function of distance along the standing wave. 7 Two ways of combining waves: in-phase and out-of-phase 8 4 Electron wave functions Electrons in atoms are best described as waves. Electron wave functions gives the amplitude as a function, not of a single coordinate, but of the three coordinates necessary to describe motion in three dimensions. It is these electron wave functions that we call orbitals. Like a standing wave, an electron wave can have nodes, where the amplitude is zero. On the opposite sides of a node the amplitude has opposite signs, that is, the wave is of opposite phases. 9 Electron wave functions Between the two lobes of a p orbital lie a nodal plane, perpendicular to the axis of the orbital. The two lobes are of opposite phases. 10 5 Electron wave functions Within the 2s orbital but not within the 1s orbital, there is a region where there is no electron density at all (radial node). 11 Electron wave functions 12 6 Molecular orbitals: LCAO method One way to construct molecular orbitals (MOs) is to combine the atomic orbitals of the atoms that make up the molecule. This approach is known as the Linear Combination of Atomic Orbitals (LCAO). Atomic orbitals can combine in the same way- in-phase or out-of- phase. 13 Molecular orbitals (s atomic orbitals) 14 7 Molecular orbitals: breaking bonds The electron in the antibonding orbital cancels out the bonding of the electron in the bonding orbital. Therefore, since there is no overall bonding holding the two atoms together, they can drift apart as two separate atoms with their electrons in 1s atomic orbitals. 15 Molecular orbitals: breaking bonds 16 8 Molecular orbitals: Helium Any bonding due to the electrons in the bonding orbital is cancelled out by the electrons in the antibonding orbital. 17 He2 does not exist. Molecular orbitals (p atomic orbitals) An antibonding orbital has a nodal plane perpendicular to the bond axis, and cutting between the atomic nuclei. 18 9 Molecular orbitals (p atomic orbitals) 19 Regioselectivity Regioselective: Term describing a reaction that can produce two (or more) constitutional isomers but gives one of them in greater amounts than the other. In other words, a regioselective reaction selects for a particular constitutional isomer. a regioselective reaction 20 10 Regioselectivity (1) Dehydration of alcohols: (2) Dehydrohalogenation of alkyl halides: (3) The addition of HX: 21 Regiospecificity A regiospecific reaction: is a reaction that gives exclusively or nearly exclusively one of several possible isomeric products i.e. a reaction that is 100% regioselective is termed regiospecific. 22 11 Stereoselectivity A stereoselective reaction: is one in which a single starting material can yield two or more stereoisomeric products, but gives one of them in greater amounts than any other i.e. a stereoselective reaction selects for a particular stereoisomer. a stereoselective reaction e.g. Alcohol dehydrations: 23 Stereospecificity A stereospecific reaction: is a reaction in which the reactant can exist as stereoisomers and each stereoisomeric reactant leads to a different stereoisomeric product or a different set of stereoisomeric products.1 a stereospecific reaction In the preceding reaction, stereoisomer A forms stereoisomer B but does not form D, so the reaction is stereoselective in addition to being stereospecific.1 All stereospecific reactions, therefore, are also stereoselective.1 A stereoselective reaction is not necessarily stereospecific.1 24 12 Reactions of Organic Compounds A pericyclic reaction, a reaction that has a cyclic transition structure in which all bond-forming and bond-breaking takes place in concert, without the formation of an intermediate.125 Pericyclic Reaction I An intramolecular reaction in which a new σ bond is formed between the ends of a conjugated π system and leads to the formation of a cyclic compound 26 13 Electrocyclic Reactions Are Reversible 27 Pericyclic Reaction II Two different π bond-containing molecules react to form a cyclic compound 28 14 Pericyclic Reaction III A σ bond is broken in the reactant, a new σ bond is formed in the product, and the π bonds rearrange 29 30 15 Note • The electrocyclic reactions and sigmatropic rearrangements are intramolecular reactions • The cycloaddition reactions are usually intermolecular reactions • Common features among the three pericyclic reactions • are concerted reactions • are highly stereoselective 31 32 16 The scientific method has four major elements: observation, law, theory, and hypothesis. 33 Normally Experiments Theory Theory Rarely Experiments (e.g. mathematics) Predictions 34 17 • Three approaches have been employed to explain the pericyclic reactions and these are: 1- Frontier orbitals 2- Correlation diagrams 3- Aromatic transition states 35 The Frontier orbital Approach1 • It is common in chemistry for the chemical properties of atoms to be approximated by considering only the properties of the highest occupied orbitals (the valence orbitals). The lower orbitals can be ignored. • A similar approach can be employed with molecules. Ignore lower-energy orbitals, and consider only the properties of the frontier orbitals. • Frontier MOs: the Highest Occupied Molecular Orbitals (HOMO) and Lowest Unoccupied Molecular Orbitals (LUMO).2 36 18 A Molecular Orbital Description of Ethene 37 Four p atomic orbitals interact to give the four π MOs of 1,3-butadiene LUMO HOMO LUMO HOMO 38 19 Note The normal electronic state of a molecule is known as its ground state The ground state electron can be promoted from its HOMO to its LUMO by absorption of light (excited state) In a thermal reaction the reactant is in its ground state; in a photochemical reaction, the reactant is in its excited state A photochemical reaction takes place when a reactant absorbs light A thermal reaction takes place without the absorption of light 39 Questions Define the type of pericyclic reactions for the following reactions and determine if they are 4n + 2 or 4n systems. 40 20 Questions 41 DAMIETTA UNIVERSITY CHEM-405: PERICYCLIC REACTIONS LECTURE 2 Dr Ali El-Agamey 42 21 • Three approaches have been employed to explain the pericyclic reactions and these are: 1- Frontier orbitals 2- Correlation diagrams 3- Aromatic transition states 43 A Molecular
Load more

Recommended publications
  • UCLA Electronic Theses and Dissertations
    UCLA UCLA Electronic Theses and Dissertations Title Computational Studies on the Reactivity, Selectivity and Molecular Dynamics of Cycloaddition Reactions Permalink https://escholarship.org/uc/item/1jk894mq Author Yu, Peiyuan Publication Date 2017 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA Los Angeles Computational Studies on the Reactivity, Selectivity and Molecular Dynamics of Cycloaddition Reactions A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Chemistry by Peiyuan Yu 2017 © Copyright by Peiyuan Yu 2017 ABSTRACT OF THE DISSERTATION Computational Studies on the Reactivity, Selectivity and Molecular Dynamics of Cycloaddition Reactions by Peiyuan Yu Doctor of Philosophy in Chemistry University of California, Los Angeles, 2017 Professor Kendall N. Houk, Chair The first part of this dissertation describes computational studies of higher-order cycloadditions with a focus on elucidating the origins of periselectivity. These reactions involve ambimodal transition states (TS) and bifurcations of potential energy surface. Chapter 1 describes density functional theory (DFT) studies of a transannular [6+4] cycloaddition proposed in the biosynthesis of heronamide A, in which an unbridged 10- membered ring is formed. Ring and steric strains are found to be essential in controlling the product stability that makes this reaction feasible. Chapter 2 presents an Environment-Perturbed Transition State Sampling method to explore the mechanism of the enzyme SpnF-catalyzed Diels–Alder. A [6+4] cycloaddition is also involved and enzyme enhances the formation of [4+2] product, with respect to the counterparts in the gas phase and in water. Chapter 3 explores the mechanisms and selectivities of the cycloadditions of tropone to dimethylfulvene discovered ii in 1967 by Houk.
    [Show full text]
  • 11 Concerted Pericyclic Reactions
    11 Concerted Pericyclic Reactions Introduction There are many reactions in organic chemistry that give no evidence of involving intermediates when subjected to the usual probes for studying reaction mechanisms. Highly polar transition states do not seem to be involved either,since the rates of the reactions are often insensitive to solvent polarity. Efforts to detect free-radical intermedi- ates in these reactions by spectroscopic or chemical means have not been successful,and the reaction rates are neither increased by initiators nor decreased by inhibitors of free- radical reactions. This absence of evidence of intermediates leads to the conclusion that the reactions are single-step processes in which bond making and bond breaking both contribute to the structure at the transition state,although not necessarily to the same degree. Such processes are called concerted reactions. There are numerous examples of both unimolecular and bimolecular concerted reactions. An important group of concerted reactions are the concerted pericyclic reactions.1 A pericyclic reaction is characterized as a change in bonding relationship that takes place as a continuous concerted reorganization of electrons. The word ``concerted'' speci®es that there is a single transition state and that there are no intermediates in the process. To maintain continuous electron ¯ow,pericyclic reactions must occur through cyclic transi- tion states. Furthermore,the cyclic transition state must correspond to an arrangement of the participating orbitals that can maintain a bonding interaction between the reacting atoms throughout the course of the reaction. We shall see shortly that these requirements make pericyclic reaction highly predictable in terms of such features as relative reactivity, stereospeci®city,and regioselectivity.
    [Show full text]
  • Pericyclic Reactions Notes
    - 1 - PERICYCLIC REACTIONS NOTES Pericyclic reactions cannot be treated adequately by “curly-arrow” formalisms and a knowledge of molecular orbital theory is crucial to their understanding. They are reactions in which “all first order changes in bonding relationships takes place in concert on a closed curve” (Woodward & Hoffmann). More simply, the term “pericyclic” covers all concerted reactions involving a cyclic flow of electrons through a single transition state. Pericyclic reactions can be predicted and controlled to a great degree, which makes them very useful in synthesis. There are broadly four classes of pericyclic reaction: Sigmatropic – These are unimolecular isomerisations, and involve the movement of a σ-bond from one position to another. An illustration would be the first step of the Claisen Rearrangement: Note the nomenclature of this reaction, being described as a [i,j] shift. For example, this following is a [1,7] shift: Electrocyclic – These are unimolecular. They are characterised by ring opening or closing with a σ- bond forming at one end. Ring closing is more common, since this is formation of a σ-bond at the expense of a π-bond, but ring strain can lead to opening. Two examples are: Cycloaddition – This is the largest class of pericyclic reaction. It is characterised by two fragments coming together to form two new σ-bonds in a ring. Some examples are Diels-Alder and Ozonolysis reactions, which are described below. Chelotropic reactions are a specific type of cycloaddition, where the two bonds are made or broken at the same atom. The classic example of this is carbene addition to a double bond.
    [Show full text]
  • Diels–Alder Reaction
    Diels–Alder reaction In organic chemistry, the Diels–Alder reaction is a chemical reaction Diels–Alder reaction between a conjugated diene and a substituted alkene, commonly termed the Named after Otto Paul Hermann dienophile (also spelled dieneophile[1]), to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a Diels concerted mechanism. More specifically, it is classified as a thermally- Kurt Alder allowed [4+2] cycloaddition with Woodward–Hoffmann symbol [π4s + π2s]. Reaction type Cycloaddition It was first described by Otto Diels and Kurt Alder in 1928. For the Reaction discovery of this reaction, they were awarded the Nobel Prize in Chemistry in 1950. Through the simultaneous construction of two new carbon–carbon bonds, the Diels–Alder reaction provides a reliable way to form six- membered rings with good control over the regio- and stereochemical outcomes.[2][3] Consequently, it has served as a powerful and widely applied tool for the introduction of chemical complexity in the synthesis of natural conjugated (substituted) Diene products and new materials.[4][5] The underlying concept has also been applied to π-systems involving heteroatoms, such as carbonyls and imines, + which furnish the corresponding heterocycles; this variant is known as the (substituted) Alkene hetero-Diels–Alder reaction. The reaction has also been generalized to other ring sizes, although none of these generalizations have matched the ↓ formation of six-membered rings in terms of scope or versatility. Because of (substituted) Cyclohexene the negative values of ΔH° and ΔS° for a typical Diels–Alder reaction, the Identifiers microscopic reverse of a Diels–Alder reaction becomes favorable at high temperatures, although this is of synthetic importance for only a limited range Organic Chemistry diels-alder-reaction of Diels-Alder adducts, generally with some special structural features; this Portal [6] reverse reaction is known as the retro-Diels–Alder reaction.
    [Show full text]
  • 02CY0507 Subject Name: Advanced Organic Chemistry - I M.Sc
    Syllabus for Master of Science Organic Chemistry Subject Code: 02CY0507 Subject Name: Advanced Organic Chemistry - I M.Sc. Sem - III Objectives: The objective of the course is to study some important rearrangements and to study different pericyclic reactions. To create an interest of students to learn advanced concepts in organic chemistry. Credits Earned: 6 Credits Course Outcomes: After completion of this course, student will be able to understand Advanced concepts of Pericyclic reactions. Molecular rearrangements, mechanism and their applications. Recognise and comment on aromatic concept of organic compounds. Pre-requisite of course: Students should have knowledge of basic concepts of organic chemistry at UG and PG 1st year level. Teaching and Examination Scheme Tutorial/ Practical Teaching Scheme (Hours) Theory Marks Marks Total Credits Term ESE Internal Marks Theory Tutorial Practical IA Viva (V) work (E) (I) (TW) 5 - 2 6 50 30 20 25 25 150 Syllabus for Master of Science Organic Chemistry Contents: Unit Topics Contact Hours 1 Pericyclic Reaction Introduction, Types of pericyclic reaction, Aromaticity in context of pericyclic reaction, Woodward-Hoffmann rules and pericyclic reactions, Conservation of molecular orbital symmetry, symmetry characteristics of molecular orbitals, correlation diagram of electrocyclic reaction, Correlation diagram and FMO 20 method of cycloaddition reaction, orbital symmetry in cycloaddition reaction (Correlation diagram), Frontier molecular orbital method, Cope and Claisen Rearrangement, Examples
    [Show full text]
  • Pericyclic Reactions
    Pericyclic Reactions II M. Sc. Chemistry (Organic Chemistry) Semester-III Paper – I ORGANIC REACTION MECHANISMS-I & PERICYCLIC REACTIONS Presented By : K.N.S.SWAMI., M. Sc., SET Guest Faculty in Chemistry P. R. Government College (Autonomous), Kakinada. Contents Pericyclic Reactions-I (A)Molecular orbital symmetry, frontier orbitals of ethylene, 1,3 Butadiene, 1,3,5- Hexatriene, allyl system, classification of pericyclic reactions FMO approach, Wood word- Hoffman correlation diagram method and perturbation of molecular (PMO)approach for the explanation of pericyclic reactions under thermal and photochemical conditions. (B)Electrocyclic Reactions: Con-rotatory and dis-rotatory motions (4n) and (4n+2), allyl systems Introduction Chemical reactions Bond formation or breaking Intermediate Ionic intermediates such as Transition State Free radical cation, anion, ion pair, etc. formation intermediate Electrophilic - cation Rearrangements Free radical reactions Nucleophilic - anion Pericyclic reactions Thermal Photochemical Ionic intermediates Chemical reaction such as cation, Free radical Mechanism anion, zwitter ion, intermediate etc Heat Factors – solvent, Transition State Not Source of energy Catalyst, reagent, formation influenced Structural changes Light 1. Proceeds in single cyclic transition state. 2. Reactions not influenced by any solvent, reagent, structural changes, catalysts, etc. 3. These are highly stereospecific in nature. 4. These reactions are initiated either by heat or light. Such class of reactions are called as pericyclic reactions. Reactions are either carried out thermally or photochemically. The chemical reaction in which starting material is converted into a single stereo-isomeric product is called as stereospecific or regiospecific reaction. Pericyclic Reactions Pericyclic reactions (pericyclic means shifting of electrons around the circle) are first explained by the scientist Hoffman and Woodward in 1965.
    [Show full text]
  • Orbital Symmetry Control of Pericyclic Reactions
    ORBITAL SYMMETRY CONTROL OF PERICYCLIC REACTIONS CHEMISTRY 650 SPRING 2002 R. MAGID BOOKS AND REVIEW ARTICLES (UPDATED APRIL 24, 2006) As a means of organizing the review literature for this course, books and articles are grouped beginning on p. 3 under the following headings: I. Books: General discussions of orbital symmetry theory and pericyclic reactions. II. Books: Specific reactions that are controlled by orbital symmetry. III. Books: Theoretical treatments related to orbital symmetry. IV. Reviews: General discussions of pericyclic reactions: theory and experimental data. V. Reviews: Specific reactions that are controlled by orbital symmetry. A. Electrocyclic reactions B. Cycloadditions C. Sigmatropic reactions D. Miscellaneous reactions E. Reactions in two or more of categories A-D VI. Reviews: Theoretical treatments related to orbital symmetry. Most of the books in I-III are on reserve in the main library. Some are in the Chemistry Department Reading Room (room 653). Those that the library doesn't have may often be found in the extensive(??) private collection of RMM. Within each heading, the articles have been arranged more or less chronologically; where it appeared appropriate to collect articles on similar topics, this was done. Nearly all of these articles are written in English. Those that aren't can be identified by their foreign language titles. Discussions of orbital symmetry are now appearing in nearly all of the new undergraduate and graduate organic texts. A partial listing of some of the better of these brief introductory treatments follows: Introductory Texts 1. Morrison, R. T.; Boyd, R. N. Organic Chemistry, 6th ed.; Allyn and Bacon: Boston, 1992; Chapter 28.
    [Show full text]
  • A Detailed Study on Pericyclic Reactions 1Raj Kumar Pandey, 2Dr
    ISSN: 2348-0033 (Online) ISSN : 2249-4944 (Print) IJEAR VOL . 3, ISSU E 1, JA N - JUN E 2013 A Detailed Study on Pericyclic Reactions 1Raj Kumar Pandey, 2Dr. Neelima Jain CMJ University, Shillong, Meghalaya, India Abstract result of a compounding of the long-established sigma designation In organic chemistry, there exist Pericyclic reactions, stereochemistry from single carbon-carbon bonds and the Greek word tropos, of which depends on symmetry of MOs (Molecular Orbitals) and meaning turn. In this type of rearrangement reaction, a substituent not on the overall symmetry of the molecules. So, in this paper, moves from one part of a π-bonded system to another part in an we have done a detailed study on Pericyclic Reactions. intramolecular reaction with simultaneous rearrangement of the π system. Fig. 3 shows Sigmatropic rearrangement. Keywords Pericyclic Reactions, Molecular Orbits, Organic Chemistry, Stereo Chemistry I. Introduction Pericyclic reactions are concerted reaction that proceeds via a cyclic transition state having no distinct intermediates in the reaction, in this type of reaction, Bond forming and bond breaking steps are simultaneous but not necessarily synchronous [2]. Fig. 3: Sigmatropic rearrangement There are various methods to analyze Pericyclic reactions. Some of them are as follows: D. Group Transfer Reactions • Orbital symmetry correlation method (Woodward, Hoffmann, The concerted transfer of a group from one molecule to another Longuet-Higgins and Abrahamson) due to concomitant movement of a σ-bond (from one molecule to • The frontier orbital method (Woodward, Hoffmann and another) and formation of a new σ-bond (between two molecules) Fukui) at the expense of a π-bond is generally referred to as group transfer • Transition state aromaticity method (Dewar and Zimmerman) Pericyclic reaction.
    [Show full text]
  • Fused and Spiro Furanones from Tetronic Acid Synthons: Oxa and Azacycles Featuring the Butenolide Ring
    Fused and spiro furanones from tetronic acid synthons: Oxa and azacycles featuring the butenolide ring Vorgelegt von Juan-Manuel URBINA-GONZALEZ Dissertation zur Erlangung des Doktorgrades der Fakultät für Biologie, Chemie und Geowissenschaften Universität Bayreuth Bayreuth, 2006 Fused and spiro furanones from tetronic acid synthons: Oxa and azacycles featuring the butenolide ring Vorgelegt von Juan-Manuel URBINA-GONZALEZ Dissertation zur Erlangung des Doktorgrades der Fakultät für Biologie, Chemie und Geowissenschaften Universität Bayreuth Bayreuth, 2006 Erklärung Hiermit erkläre ich, dass ich die vorliegende Arbeit selbst verfasst und keine anderen als die angegebenen Quellen und Hilfsmittel verwendet habe. Ich habe nicht versucht (mit oder ohne Erfolg), eine Dissertation einzureichen oder mich der Doktorprufung zu unterziehen. Bayreuth, den 25. April, 2006 Juan Manuel Urbina González Acknowledgements Thanks to Prof. Dr. Rainer Schobert for his help, support and patience as supervisor throughout my PhD. Thanks to my colleagues: Dr. Gary J. Gordon, Dr. Carsten Jagusch, Dr. Claire M. Melanophy, Gillian Mullen, Ralf Stehle, Andreas Stangl, Bernhard Biersack, Alexander Gmeiner, Georg Rapp and Sebastian Knauer (PhD colleagues). To my colleagues in the lab Dr. Thomas Schmalz, Arno Bieser, Thomas Baumann, Andrea Schlenk, Ellen Wiedemann and Antje Grotemeier. Also to my students in Hauptpraktikum: André Wicklein, Sigrun Polier, Andreas Spoerl (†), Martin Hoffmann and Michael Mueller for their work. Thanks to the staff of OC1: Werner Kern, Rosie and Michael Glaessner, Kerstin Hannemann and Dr. Claus Hoelzel for their friendliness and help. I would also like to acknowledge the kindness of the Unverzagt’s group members especially Daniel, Nelson, Markus and Stefano. And heartfelt thanks to each of my family members who support me through the distance and have always been there for me.
    [Show full text]
  • Thermal Pericyclic Reaction Pericyclic Reactions
    AOR No10 (2016.7.15) Thermal Pericyclic Reaction Pericyclic Reactions 6.1 The Four Classes of Pericyclic Reactions 1. Cycloadditions (bimolecular) Cheletropic reaction Otto Paul Hermann Diels Kurt Alder (1876 – 1954) (1902 – 1958) “protection of diene” 2. Electrocyclic reactions (Unimolecular) [1,7]-shift -50 kJ/mol Mislow rearrangement 3. Sigmatropic rearrangement (Unimolecular) [2,3]-shift Claisen rearrangement [3,3]-shift 4. Group transfer reaction (Bimolecular) 6.2 Evidence for the Concertedness of Bond Making and Breaking “ene reaction” No intermediates Diels-Alder reactions: exothermic high negative entropy of activation, -150 to -200 J K-1 mol-1, with a low enthalpy of activation Sauer, Angew. Chem., Int. Ed. Engl. 1980, 19, 779 Metalla-ene reaction Little effect by solvent polarity Stereochemistry Isotope effect Substituent effect M = Li, Mg, Pd [4 + 2] 6.3 Symmetry-allowed and Symmetry-forbidden Reaction 6.3.1 The Woodward-Hoffmann Rules Class by Class 6.3.1.1. Cycloadditions [2 + 2] Diels-Alder reaction: [4 + 2] cycloaddition “number of electrons” 1,3-Dipolar cycloaddition Rule of cycloadditions X,Y,Z,A,B = (C, N, O, S) A thermal pericyclic cycloaddition is allowed if the total number of electrons involved can be expressed in the form (4n+2), where n is an integer. If the total number of electrons can be expressed in 10-electrons [8 + 2] the form (4n) it is forbidden. (4n + 2) electrons [6 + 4] Suprafacial-Suprafacial Suprafacial-Antarafacial 4n (allowed) (4n + 2) Antarafacial-Antarafacial [14 + 2] trans Rule of cycloadditions 6.3.1.2 Electrocyclic Reactions 4n, 4n+2 Ring strain, aromaticity, stabilization of charge by substituent If the total number of electrons involved can be expressed in the form (4n+2), where n is an integer, a thermal pericyclic cycloaddition is symmetry allowed when both components react in a suprafacial manner (or both components react in an antarafacial manner).
    [Show full text]
  • Metal-Mediated Vinylogous Nazarov Cyclization Reaction
    University of Windsor Scholarship at UWindsor Electronic Theses and Dissertations Theses, Dissertations, and Major Papers 9-13-2019 Metal-Mediated Vinylogous Nazarov Cyclization Reaction Somaiah Khalid Almubayedh University of Windsor Follow this and additional works at: https://scholar.uwindsor.ca/etd Recommended Citation Almubayedh, Somaiah Khalid, "Metal-Mediated Vinylogous Nazarov Cyclization Reaction" (2019). Electronic Theses and Dissertations. 7798. https://scholar.uwindsor.ca/etd/7798 This online database contains the full-text of PhD dissertations and Masters’ theses of University of Windsor students from 1954 forward. These documents are made available for personal study and research purposes only, in accordance with the Canadian Copyright Act and the Creative Commons license—CC BY-NC-ND (Attribution, Non-Commercial, No Derivative Works). Under this license, works must always be attributed to the copyright holder (original author), cannot be used for any commercial purposes, and may not be altered. Any other use would require the permission of the copyright holder. Students may inquire about withdrawing their dissertation and/or thesis from this database. For additional inquiries, please contact the repository administrator via email ([email protected]) or by telephone at 519-253-3000ext. 3208. METAL-MEDIATED VINYLOGOUS NAZAROV CYCLIZATION REACTION By Somaiah Khalid Almubayedh A Dissertation Submitted to the Faculty of Graduate Studies through the Department of Chemistry and Biochemistry in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy at the University of Windsor Windsor, Ontario, Canada © 2019 Somaiah K. Almubayedh Metal-Mediated Vinylogous Nazarov Cyclization Reaction by Somaiah Khalid Almubayedh APPROVED BY: _____________________________ R. Dembinski, External Examiner Oakland University _____________________________ I.
    [Show full text]
  • GLOSSARY of TERMS USED in THEORETICAL ORGANIC CHEMISTRY (IUPAC Recommendations 1999)
    Pure Appl. Chem., Vol. 71, No. 10, pp. 1919±1981, 1999. Printed in Great Britain. q 1999 IUPAC INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY ORGANIC CHEMISTRY DIVISION COMMISSION ON PHYSICAL ORGANIC CHEMISTRY GLOSSARY OF TERMS USED IN THEORETICAL ORGANIC CHEMISTRY (IUPAC Recommendations 1999) Prepared for publication by VLADIMIR I. MINKIN Institute of Physical & Organic Chemistry, Rostov State University, 194/2 Stachka St., 344090 Rostov on Don, Russia Membership of the Commission during the period (1991±1999) the report was drafted was as follows: Chairman: 1987±1993, P. Muller (Switzerland); 1993±1997, T. T. Tidwell (Canada); 1997±1998, Ch. L. Perrin (USA); 1998±1999. Secretary: 1991±1996, W. Drenth (Netherlands); 1996±1999, E. Baciocchi (Italy). Titular Members: J.-L. M. Abboud (Spain, 1998±1999); J. M. McBride (USA, 1987±1993), V. I. Minkin (Russia, 1992±1999); Ch. L. Perrin (USA, 1994±1997); M.-F. Ruasse (France, 1998±1999); J. Shorter (UK, 1989±1997); Z. Rappoport (Israel, 1992±1999); Y. Takeuchi (Japan, 1992±1997); Associate Members: J.-L. M. Abboud (Spain, 1996±1997); P. N. I. Ahlberg (Sweden, 1991±1993); E. Baciocchi (Italy, 1994±1995); S. Fukuzumi (Japan, 1998±1999); E. Halevi (Israel, 1989±1993); S. S. Kim (South Korea, 1996±1999); A. Kirby (UK, 1994±1997); D. Lenoir (Germany, 1998±1999); R. Louw (the Netherlands, 1998±1999); O. M. Nefedov (Russia, 1991±1993); N. S. Nudelman (Argentina, 1998±1999); Ch. L. Perrin (USA, 1991±1993); D. J. Raber (USA, 1992±1999); M.-F. Ruasse (France, 1994±1997); H.-U. Siehl (Germany (1994±1999), P. Tundo (Italy, 1998±1999); P. Van Brandt (Belgium, 1987±1993); J.
    [Show full text]