Strain-Promoted 1,3-Dipolar Cycloaddition of Cycloalkynes and Organic Azides
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The Conformations of Cycloalkanes
The Conformations of Cycloalkanes Ring-containing structures are a common occurrence in organic chemistry. We must, therefore spend some time studying the special characteristics of the parent cycloalkanes. Cyclical connectivity imposes constraints on the range of motion that the atoms in rings can undergo. Cyclic molecules are thus more rigid than linear or branched alkanes because cyclic structures have fewer internal degrees of freedom (that is, the motion of one atom greatly influences the motion of the others when they are connected in a ring). In this lesson we will examine structures of the common ring structures found in organic chemistry. The first four cycloalkanes are shown below. cyclopropane cyclobutane cyclopentane cyclohexane The amount of energy stored in a strained ring is estimated by comparing the experimental heat of formation to the calculated heat of formation. The calculated heat of formation is based on the notion that, in the absence of strain, each –CH2– group contributes equally to the heat of formation, in line with the behavior found for the acyclic alkanes (i.e., open chains). Thus, the calculated heat of formation varies linearly with the number of carbon atoms in the ring. Except for the 6-membered ring, the experimental values are found to have a more positive heat of formation than the calculated value owning to ring strain. The plots of calculated and experimental enthalpies of formation and their difference (i.e., ring strain) are seen in the Figure. The 3-membered ring has about 27 kcal/mol of strain. It can be seen that the 6-membered ring possesses almost no ring strain. -
14.8 Organic Synthesis Using Alkynes
14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 666 666 CHAPTER 14 • THE CHEMISTRY OF ALKYNES The reaction of acetylenic anions with alkyl halides or sulfonates is important because it is another method of carbon–carbon bond formation. Let’s review the methods covered so far: 1. cyclopropane formation by the addition of carbenes to alkenes (Sec. 9.8) 2. reaction of Grignard reagents with ethylene oxide and lithium organocuprate reagents with epoxides (Sec. 11.4C) 3. reaction of acetylenic anions with alkyl halides or sulfonates (this section) PROBLEMS 14.18 Give the structures of the products in each of the following reactions. (a) ' _ CH3CC Na| CH3CH2 I 3 + L (b) ' _ butyl tosylate Ph C C Na| + L 3 H3O| (c) CH3C' C MgBr ethylene oxide (d) L '+ Br(CH2)5Br HC C_ Na|(excess) + 3 14.19 Explain why graduate student Choke Fumely, in attempting to synthesize 4,4-dimethyl-2- pentyne using the reaction of H3C C'C_ Na| with tert-butyl bromide, obtained none of the desired product. L 3 14.20 Propose a synthesis of 4,4-dimethyl-2-pentyne (the compound in Problem 14.19) from an alkyl halide and an alkyne. 14.21 Outline two different preparations of 2-pentyne that involve an alkyne and an alkyl halide. 14.22 Propose another pair of reactants that could be used to prepare 2-heptyne (the product in Eq. 14.28). 14.8 ORGANIC SYNTHESIS USING ALKYNES Let’s tie together what we’ve learned about alkyne reactions and organic synthesis. The solu- tion to Study Problem 14.2 requires all of the fundamental operations of organic synthesis: the formation of carbon–carbon bonds, the transformation of functional groups, and the establish- ment of stereochemistry (Sec. -
Isonitrile-Responsive and Bioorthogonally Removable Tetrazine Protecting Groups
UCLA UCLA Previously Published Works Title Isonitrile-responsive and bioorthogonally removable tetrazine protecting groups. Permalink https://escholarship.org/uc/item/0hc9j0mv Journal Chemical science, 11(1) ISSN 2041-6520 Authors Tu, Julian Svatunek, Dennis Parvez, Saba et al. Publication Date 2020 DOI 10.1039/c9sc04649f Peer reviewed eScholarship.org Powered by the California Digital Library University of California Chemical Science View Article Online EDGE ARTICLE View Journal | View Issue Isonitrile-responsive and bioorthogonally removable tetrazine protecting groups† Cite this: Chem. Sci., 2020, 11,169 a b c b All publication charges for this article Julian Tu, Dennis Svatunek, Saba Parvez, Hannah J. Eckvahl, have been paid for by the Royal Society Minghao Xu, ‡a Randall T. Peterson,c K. N. Houk b and Raphael M. Franzini *a of Chemistry In vivo compatible reactions have a broad range of possible applications in chemical biology and the pharmaceutical sciences. Here we report tetrazines that can be removed by exposure to isonitriles under very mild conditions. Tetrazylmethyl derivatives are easily accessible protecting groups for amines and phenols. The isonitrile-induced removal is rapid and near-quantitative. Intriguingly, the deprotection is especially effective with (trimethylsilyl)methyl isocyanide, and serum albumin can catalyze the elimination under physiological conditions. NMR and computational studies revealed that an imine-tautomerization step is often rate limiting, and the unexpected cleavage of the Si–C bond accelerates this step in the case with (trimethylsilyl)methyl isocyanide. Tetrazylmethyl-removal is compatible with use on biomacromolecules, in cellular environments, and in living organisms as demonstrated by cytotoxicity Creative Commons Attribution 3.0 Unported Licence. -
Comparing Models for Measuring Ring Strain of Common Cycloalkanes
The Corinthian Volume 6 Article 4 2004 Comparing Models for Measuring Ring Strain of Common Cycloalkanes Brad A. Hobbs Georgia College Follow this and additional works at: https://kb.gcsu.edu/thecorinthian Part of the Chemistry Commons Recommended Citation Hobbs, Brad A. (2004) "Comparing Models for Measuring Ring Strain of Common Cycloalkanes," The Corinthian: Vol. 6 , Article 4. Available at: https://kb.gcsu.edu/thecorinthian/vol6/iss1/4 This Article is brought to you for free and open access by the Undergraduate Research at Knowledge Box. It has been accepted for inclusion in The Corinthian by an authorized editor of Knowledge Box. Campring Models for Measuring Ring Strain of Common Cycloalkanes Comparing Models for Measuring R..ing Strain of Common Cycloalkanes Brad A. Hobbs Dr. Kenneth C. McGill Chemistry Major Faculty Sponsor Introduction The number of carbon atoms bonded in the ring of a cycloalkane has a large effect on its energy. A molecule's energy has a vast impact on its stability. Determining the most stable form of a molecule is a usefol technique in the world of chemistry. One of the major factors that influ ence the energy (stability) of cycloalkanes is the molecule's ring strain. Ring strain is normally viewed as being directly proportional to the insta bility of a molecule. It is defined as a type of potential energy within the cyclic molecule, and is determined by the level of "strain" between the bonds of cycloalkanes. For example, propane has tl1e highest ring strain of all cycloalkanes. Each of propane's carbon atoms is sp3-hybridized. -
Text Related to Segment 5.02 ©2002 Claude E. Wintner from the Previous Segment We Have the Value of the Heat of Combustion Of
Text Related to Segment 5.02 ©2002 Claude E. Wintner From the previous segment we have the value of the heat of combustion of an "unstrained" methylene unit as -157.4 kcal/mole. On this basis one would predict that combustion of "unstrained" cyclopropane should liberate 3 X 157.4 = 472.2 kcal/mole; however, when cyclopropane is burned, a value of 499.8 kcal/mole is measured for the actual heat of combustion. The difference of 27.6 kcal/mole is interpreted as representing the higher internal energy ("strain energy") of real cyclopropane as compared to a postulated strain-free "model." ("Model" in this usage speaks of a proposal, or postulate.) These facts are graphed conveniently on an energy diagram as follows: "Strain Energy" represents the error units: kcal/mole not to scale in the "strain-free model" real cyclopropane + 4.5 O2 27.6 "strain-free model" of cyclopropane 499.8 observed heat of combustion + 4.5 O2 472.2 3CO2 + 3H2O heat of combustion predicted for "strain-free model" Note that this estimate of the strain energy in cyclopropane amounts to 9.2 kcal/mole of strain per methylene group (dividing 27.6 by 3, because of the three carbon atoms). Comparable values in kcal/mole for other small and medium rings are given in the following table. As one might expect, in general the strain decreases as the ring is enlarged. units: kcal/mole n Total Strain Strain per CH2 3 27.6 9.2 (CH2)n 4 26.3 6.6 5 6.2 1.2 6 0.1 0.0 ! 7 6.2 0.9 8 9.7 1.2 9 12.6 1.4 10 12.4 1.2 12 4.1 0.3 15 1.9 0.1 Without entering into a discussion of the relevant bonding concepts here, and instead relying on geometry alone, interpretation of the source of the strain energy in cyclopropane and cyclobutane is to some extent self-evident. -
S1 Supporting Information Copper-Catalyzed
Supporting Information Copper-Catalyzed Semihydrogenation of Internal Alkynes with Molecular Hydrogen Takamichi Wakamatsu, Kazunori Nagao, Hirohisa Ohmiya*, and Masaya Sawamura* Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan Table of Contents Instrumentation and Chemicals S1 Characterization Data for Alkynes S1–S2 Procedure for the Copper-Catalyzed Semihydrogenation of Alkynes S2 Characterization Data for Alkenes S3–S5 References S5 NMR Spectra S6–S31 Instrumentation and Chemicals NMR spectra were recorded on a JEOL ECX-400, operating at 400 MHz for 1H NMR and 100.5 13 1 13 MHz for C NMR. Chemical shift values for H and C are referenced to Me4Si and the residual solvent resonances, respectively. Mass spectra were obtained with Thermo Fisher Scientific Exactive, JEOL JMS-T100LP or JEOL JMS-700TZ at the Instrumental Analysis Division, Equipment Management Center, Creative Research Institution, Hokkaido University. TLC analyses were performed on commercial glass plates bearing 0.25-mm layer of Merck Silica gel 60F254. Silica gel (Kanto Chemical Co., Silica gel 60 N, spherical, neutral) was used for column chromatography. Materials were obtained from commercial suppliers or prepared according to standard procedure unless otherwise noted. CuCl was purchased from Aldrich Chemical Co., stored under nitrogen, and used as it is. NatOBu, octane and 6-dodecyne 1a were purchased from TCI Chemical Co., stored under nitrogen, and used as it is. Diphenylacetylene 1j was purchased from Wako Chemical Co., stored under nitrogen, and used as it is. 1,4-Dioxane was purchased from Kanto Chemical Co., distilled from sodium/benzophenone and stored over 4Å molecular sieves under nitrogen. -
The Synthesis of a Polydiacetylene to Create a Novel Sensory Material
SELDE, KRISTEN A., M.S. The Synthesis of a Polydiacetylene to Create a Novel Sensory Material. (2007) Directed by Dr. Darrell Spells. 47pp. Sensory materials that respond to chemical and mechanical stimuli are under development in many laboratories. There are many significant uses of polydiacetylene compounds as sensory material. They have been applied to drug delivery, drug design, biomolecule development, cosmetics, and national security. In this study, experiments were carried out toward the development of a novel sensory material based on the established synthetic research on polydiacetylene compounds. Synthetic routes toward sensory materials with different head groups, different carbon chains lengths, and the incorporation of molecular imprints were explored. Diacetylene moieties, which can be used for polymer vesicle formation, were prepared by two main routes. In one route, 1-iodo-1-octyne and 1-iodo-1-dodecyne were prepared as starting materials for the synthesis of two diacetylene compounds (Diacetylene I and Diacetylene II). In the other route, a mesityl alkyne was used to prepare 5-iodo-1-pentyne, which was then used to prepare a triethylamino alkyne. This in turn was used to synthesize a diacetylene (Diacetylene III). Although each diacetylene product was formed, purification by column chromatography was found to be difficult. Experiments in vesicle formation, with and without molecular imprints, were also carried out using commercially available diacetylenes . THE SYNTHESIS OF A POLYDIACETYLENE TO CREATE A NOVEL SENSORY -
Stabilization of Anti-Aromatic and Strained Five-Membered Rings with A
ARTICLES PUBLISHED ONLINE: 23 JUNE 2013 | DOI: 10.1038/NCHEM.1690 Stabilization of anti-aromatic and strained five-membered rings with a transition metal Congqing Zhu1, Shunhua Li1,MingLuo1, Xiaoxi Zhou1, Yufen Niu1, Minglian Lin2, Jun Zhu1,2*, Zexing Cao1,2,XinLu1,2, Tingbin Wen1, Zhaoxiong Xie1,Paulv.R.Schleyer3 and Haiping Xia1* Anti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8p-electron anti- aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon. The compounds are characterized using X-ray crystallography, and their computed energies and magnetic properties reveal aromatic character. Hence, the incorporation of the osmium centre not only reduces the ring strain of the parent pentalyne, but also converts its Hu¨ckel anti-aromaticity into Craig-type Mo¨bius aromaticity in the metallapentalynes. The concept of aromaticity is thus extended to five-membered rings containing a metal–carbon triple bond. Moreover, these metal–aromatic compounds exhibit unusual optical effects such as near-infrared photoluminescence with particularly large Stokes shifts, long lifetimes and aggregation enhancement. romaticity is a fascinating topic that has long interested Results and discussion both experimentalists and theoreticians because of its ever- Synthesis, characterization and reactivity of osmapentalynes. Aincreasing diversity1–5. The Hu¨ckel aromaticity rule6 applies Treatment of complex 1 (ref. 32) with methyl propiolate to cyclic circuits of 4n þ 2 mobile electrons, but Mo¨bius topologies (HC;CCOOCH3) at room temperature produced osmapentalyne favour 4n delocalized electron counts7–10. -
Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids
W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 2015 Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids Jessica S. Lampkowski College of William & Mary - Arts & Sciences Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Organic Chemistry Commons Recommended Citation Lampkowski, Jessica S., "Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids" (2015). Dissertations, Theses, and Masters Projects. Paper 1539626985. https://dx.doi.org/doi:10.21220/s2-r9jh-9635 This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Development of a Solid-Supported Glaser-Hay Reaction and Utilization in Conjunction with Unnatural Amino Acids Jessica Susan Lampkowski Ida, Michigan B.S. Chemistry, Siena Heights University, 2013 A Thesis presented to the Graduate Faculty of the College of William and Mary in Candidacy for the Degree of Master of Science Chemistry Department The College of William and Mary May, 2015 COMPLIANCE PAGE Research approved by Institutional Biosafety Committee Protocol number: BC-2012-09-13-8113-dyoung01 Date(s) of approval: This protocol will expire on 2015-11-02 APPROVAL PAGE This -
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. -
A. Discovery of Novel Reactivity Under the Sonogashira Reaction Conditions B. Synthesis of Functionalized Bodipys and BODIPY-Sug
A. Discovery of novel reactivity under the Sonogashira reaction conditions B. Synthesis of functionalized BODIPYs and BODIPY-sugar conjugates Ravi Shekar Yalagala, M.Phil Department of Chemistry Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Faculty of Mathematics and Science, Brock University St. Catharines, Ontario © 2016 ABSTRACT A. During our attempts to synthesize substituted enediynes, coupling reactions between terminal alkynes and 1,2-cis-dihaloalkenes under the Sonogashira reaction conditions failed to give the corresponding substituted enediynes. Under these conditions, terminal alkynes underwent self-trimerization or tetramerization. In an alternative approach to access substituted enediynes, treatment of alkynes with trisubstituted (Z)- bromoalkenyl-pinacolboronates under Sonogashira coupling conditions was found to give 1,2,4,6-tetrasubstituted benzenes instead of Sonogashira coupled product. The reaction conditions and substrate scopes for these two new reactions were investigated. B. BODIPY core was functionalized with various functional groups such as nitromethyl, nitro, hydroxymethyl, carboxaldehyde by treating 4,4-difluoro-1,3,5,7,8- pentamethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene with copper (II) nitrate trihydrate under different conditions. Further, BODIPY derivatives with alkyne and azido functional groups were synthesized and conjugated to various glycosides by the Click reaction under the microwave conditions. One of the BODIPY–glycan conjugate was found to form liposome upon rehydration. The photochemical properties of BODIPY in these liposomes were characterized by fluorescent confocal microscopy. ii ACKNOWLEDGEMENTS I am extremely grateful to a number of people. Without their help, this document would have never been completed. First and foremost, I would like to thank my supervisor and mentor Professor Tony Yan for his guidance and supervision to make the thesis possible. -
Bioorthogonal Chemistry
Bioorthogonal Chemistry Rachel Whittaker February 13, 2013 Wednesday Literature Talk Outline What is It and Why Do We Care? Historical Background Staudinger Ligation Copper-free Click Chemistry Tetrazine Cycloadditions Other Examples Future Directions What Are We Talking About Here? “But what if the challenge [of synthesis] were inverted, wherein the target structure was relatively simple but the environment in which the necessary reactions must proceed was so chemically complex and uncontrollable that no two functional groups could combine reliably and selectively under such conditions?” – Carolyn Bertozzi, UC Berkley Acc. Chem Res., 2011, 44, 651. What Is It? Bioorthogonal chemistry- chemical reactions that neither interact with nor interfere with a biological system. Acc. Chem. Res., 2011, 44, 666. So Why Do We Care? Takes classic organic reactions and redesigns them with biological systems in mind Allows for more efficient/ non-toxic drug delivery, biological imaging, and material science Acc. Chem. Res., 2011, 44, 666. Requirements of Bioorthogonality 1. Functional groups used must be inert to biological moieties 2. FG’s must be selective for one another and nontoxic to organisms 3. Reaction must work in biological media 4. Must have very fast kinetics, particularly at low -4 -1 - concentrations and in physiological condtions (k2> 10 M s 1) 5. Helpful, but not required, if at least one FG is small Acc. Chem. Res., 2011, 44, 666. Types of Bioorthogonal Transformations* 1. Nucleophilic Additions 2. 1,3-Dipolar Cycloadditions