DOCSLIB.ORG

The Development of Carbon-Carbon Bond Forming Reactions of Aminal

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Development of Carbon-Carbon Bond Forming Reactions of Aminal Tetrahedron 71 (2015) 1448e1465 Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet The development of carbonecarbon bond forming reactions of aminal radicals David A. Schiedler, Jessica K. Vellucci, Yi Lu, Christopher M. Beaudry * Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331-4003, USA article info abstract Article history: Aminal radicals were generated and used in synthetic reactions for the first time. Aminal radicals are Received 20 October 2014 formed from aminals by radical translocation using AIBN and a stoichiometric hydrogen atom donor, or Received in revised form 18 December 2014 by SmI2 reduction of N-acyl amidines or amidinium ions in the presence of a proton source. Aminal Accepted 18 December 2014 radicals were found to participate in inter- and intramolecular CeC bond forming reactions with electron Available online 10 January 2015 deficient alkenes. Chemical yields were as high as 99%. Ó 2014 Elsevier Ltd. All rights reserved. Keywords: Aminal radicals Alkaloids Samarium iodide Radical translocation 1. Introduction electron lone pair on the adjacent nitrogen atom and react with alkenes to give products of CeC bond formation.9 This reactivity has Many biologically active molecules, including pharmaceuticals, proven useful for the synthesis of heterocycles as well as in the total contain one or more nitrogen atoms. As a result, nitrogen-rich synthesis of alkaloids.10 Carbon-centered radicals bearing two ad- compounds, such as alkaloids and pharmaceuticals, make com- jacent heteroatoms, such as acetal radical 2, are also known to pelling synthetic targets.1 However, the complex reactivity of ni- undergo CeC bond forming reactions with alkenes (Scheme 1, Eq. trogen can be problematic in synthesis. The ability to quaternize, 2). Additionally, N,S- and N,O-acetal radicals (3) have been pre- the Lewis basic lone pair, and the weakly acidic NeH protons found sumed as intermediates in CeC bond forming reactions (Scheme 1, in nitrogen-containing molecules often give rise to undesired Eq. 3).11 reactivity. Carbon-centered radicals bearing two adjacent nitrogen atoms In order to mask the complex Lewis acidebase reactivity of ni- (i.e., aminal radicals) have been implicated as intermediates in the trogen, synthetic chemists often resort to the use of protective free radical and radiative damage of DNA nucleotide bases,12 they groups.2 Other strategies, which have proven successful for the have been experimentally generated and studied spectroscopi- synthesis of nitrogen-containing structures include opting to install cally,13 and long-lived aminal radicals have been isolated.14 Appli- nitrogen late in the synthesis3 or in the form of a less reactive cations of aminal radicals include their use as photochromic dyes15 functional group (e.g., as a nitro4 or nitrile5 group). An alternative and as tools for mechanistic investigations.16 Although there are means to circumvent the pitfalls of alkaloid synthesis is the use of reports of fragmentation,17 protonation,18 and dimerization re- single electron reactivity (i.e., free radical reactions). Free radicals actions of aminal radicals, there had been no reports of their syn- are known to tolerate heteroatom lone pairs, and NeH bonds are thetic utility prior to recent work from our laboratory.19 resistive to homolytic cleavage.6 As a result, free radical reactions Having considered the known reactivity of acetal and a-ami- have been used successfully for key CeC bond forming reactions in noalkyl radicals, the creation of a new reaction was envisioned the synthesis of complex alkaloids (e.g., Scheme 1, Eq. 1).7 wherein an aminal radical would undergo addition to an alkene to The addition of carbon-centered radicals bearing heteroatoms give the product of CeC bond formation. Computational studies to CeC multiple bonds has been known for over 50 years.8 a- indicated that aminal radicals are 1e2 kcal/mol more stable than Aminoalkyl radicals, such as 1 (Scheme 1), gain stability from the analogous a-aminoalkyl radicals.20 This suggested that it would be possible to selectively generate aminal radicals in the presence of carbon atoms bearing a single nitrogen atom. Based on these con- * Corresponding author. Tel.: þ1 541 737 6746; fax: þ1 541 737 2062; e-mail siderations, we postulated that aminal radical intermediates would address: [email protected] (C.M. Beaudry). be well suited for the construction of the carbon framework in http://dx.doi.org/10.1016/j.tet.2014.12.067 0040-4020/Ó 2014 Elsevier Ltd. All rights reserved. D.A. Schiedler et al. / Tetrahedron 71 (2015) 1448e1465 1449 Scheme 1. Selected transformations involving radical intermediates bearing a-heteroatoms. nitrogen-rich molecules. For example, Fig. 1 shows a selection of aminals, which do not bear an electron-withdrawing group, biologically active aminal containing natural products, which have a deuterium labeling study on the translocation reactions of ami- attracted the interest of many synthetic chemists.21 Furthermore, nals, which do not bear an electron-withdrawing group, and ap- commercial pharmaceuticals quinethazone and metolazone also plications of the translocation method to acyclic aminals relevant to possess the aminal functional group. the synthesis of indole alkaloids. 2. Results and discussion In 1958, Juveland reported the generation of a-aminoalkyl radical intermediate 4 under peroxide initiated conditions (Scheme 2, Eq. 1).22 Treatment of piperidine with di-tert-butylperoxide in the presence of 1-octene yielded 2-octyl piperidine. Extension of this method to the generation of aminal radicals could involve the treatment of an aminal with di-tert-butylperoxide in the presence of a suitable radical acceptor (Scheme 2, Eq. 2). Tetrahy- droisoquinazoline (5) was chosen because it was easy to prepare, it is chromatographically stable, and it contains a chromophore, which allowed for facile monitoring of reaction progress. Following Juveland’s procedure, 5 was heated in the presence of di-tert-butylperoxide and 1-octene in a sealed tube. The reaction produced an intractable mixture of products and none of the de- sired product 6 was observed. In an effort to affect cleaner re- activity, modified reaction conditions were investigated. Lowering the reaction temperature resulted in no reaction. Performing the Fig. 1. Selected aminal containing alkaloids and pharmaceuticals. reaction neat, tethering the radical acceptor to the substrate, or using activated alkenes as radical acceptors all resulted in the for- Herein we give a full account of the development of aminal mation of a complex mixture of products.23 radical reactivity for use in synthesis. In addition to expanded Based on these results, two plausible explanations were for- discussions of the results previously reported, we describe our mulated. Either the desired aminal radical 7 was generated, and it initial efforts to generate aminal radicals under peroxide initiated was reacting in an unselective manner to give the observed de- conditions, the efforts to optimize translocation reactions of composition, or aminal radical 7 had not been generated and the 1450 D.A. Schiedler et al. / Tetrahedron 71 (2015) 1448e1465 Scheme 2. Extension of Juveland’s method. observed degradation was arising from other reaction pathways. competent. However, in addition to the desired product 13, iso- Unable to easily distinguish between these possibilities, an alter- meric product 14,27 over addition product 15, and dehalogenated native method for the generation of aminal radicals was sought. product 16 were observed (Table 1). Formation of the undesired Ideally, this method would incorporate a functional handle that product 14 is competitive with the formation of desired product 13 could be used to determine whether aminal radicals were being as a result of the stability of the a-aminobenzylic radical from generated. which it presumably arises. The formation of dehalogenated 16 was Radical translocation24 of 2-iodobenzyl (IBn) protected amine 8 not surprising given that similar reaction conditions have been 28 with AIBN and Bu3SnH in the presence of methyl acrylate gives used to perform radical dehalogenation. Although Curran re- alkylated product 9 (Scheme 3).25 Reactions of this type proceed ported the oxidation of 2-iodobenzyl ethers under similar reaction through the generation of a phenyl radical (10) followed by 1,5-H conditions,29 no amidine formation was observed. atom transfer to form an a-aminoalkyl radical intermediate 11. Having successfully demonstrated that aminal radical in- The a-aminoalkyl radical then adds to the olefin and gives 9 after H termediates could be generated and added to alkenes using the atom abstraction from Bu3SnH. radical translocation method, efforts were turned to reaction op- Scheme 3. Protective radical translocation. The application of radical translocation as a means to generate timization. Variation of the Bu3SnH equivalents had little effect on aminal radicals was particularly attractive because it would provide the product distribution; however, the yield of 13 decreased when a functional handle through which problematic reactivity might be less than 2 equiv were added (Table 1, entries 1e3). Adjustment of diagnosed. Specifically, the loss of iodide is diagnostic for the for- the acrylate equivalents showed that only trace amounts of the mation of a phenyl radical. Deuteration experiments could be used desired products
Load more

Recommended publications
  • Fluorescent Aminal Linked Porous Organic Polymer for Reversible Iodine Capture and Sensing Muhammad A
    www.nature.com/scientificreports OPEN Fluorescent aminal linked porous organic polymer for reversible iodine capture and sensing Muhammad A. Sabri1, Mohammad H. Al‑Sayah2, Susan Sen2, Taleb H. Ibrahim1 & Oussama M. El‑Kadri2* A novel triazene-anthracene-based fuorescent aminal linked porous organic polymer (TALPOP) was prepared via metal free-Schif base polycondensation reaction of 9,10-bis-(4,6-diamino-S‑triazin‑ 2-yl)anthracene and 2-furaldehyde. The polymer has exceptional chemical and thermal stabilities and exhibit good porosity with Brunauer–Emmett–Teller surface area of 401 m2g−1. The combination of such porosity along with the highly conjugated heteroatom-rich framework enabled the polymer to exhibit exceptional iodine vapor uptake of up to 314 wt % and reversible iodine adsorption in solution. Because of the inclusion of the anthracene moieties, the TALPOP exhibited excellent 3 −1 detection sensitivity towards iodine via forescence quenching with Ksv value of 2.9 × 10 L mol . The cost efective TALPOP along with its high uptake and sensing of iodine, make it an ideal material for environmental remediation. Nuclear energy is becoming one of the most feasible alternative sources to meet the ever-increasing energy demand and minimize the emission of greenhouse gases because of its high-density energy, minimal carbon footprints, and low operation cost1–4. Despite such advantages, the potential emissions of radioactive material 129 131 3 14 85 (such as I and I, H, CO2, and Kr) from nuclear energy power plants is a major drawback of this tech- nology due to the serious environmental and health efect of these materials4,5.
    [Show full text]
  • Synthesis and Structural Studies of a New Class of Quaternary Ammonium
    Rivera et al. Chemistry Central Journal 2011, 5:55 http://journal.chemistrycentral.com/content/5/1/55 RESEARCHARTICLE Open Access Synthesis and structural studies of a new class of quaternary ammonium salts, which are derivatives of cage adamanzane type aminal 1, 3, 6, 8-tetraazatricyclo[4.3.1.13,8]undecane (TATU) Augusto Rivera1*, John Sadat-Bernal1, Jaime Ríos-Motta1, Michal Dušek2 and Lukáš Palatinus2 Abstract Background: Novel mono N-alkyl quaternary ammonium salts (3a-f) were prepared using the Menschutkin reaction from the cage adamanzane type aminal 1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecane (TATU) and alkyl iodides, such as methyl, ethyl, propyl, butyl, pentyl and hexyl iodide (2a-f), in dry acetonitrile at room temperature. Results: The structures of these new quaternary ammonium salts were established using various spectral and electrospray ionization mass spectrometry (ESI-MS) analyses. Compound (3b) was also analyzed using X-ray crystallography. Conclusion: It was noted that alkyl chain length did not significantly affect the reaction because all employed alkyl iodide electrophiles reacted in a similar fashion with the aminal 1 to produce the corresponding mono N- quaternary ammonium salts, which were characterized by spectroscopic and analytical techniques. Background amines with haloalkyls [7]. We found that no reaction Cage aminals of the adamanzane type are tricyclic ter- occurred when N-alkylation was attempted using alkyl tiary tetraamines, which can act as bases or as nucleo- bromides and chlorides. Compound 1 reacts with alkyl philes. The main subject of research in our laboratory iodides in dry acetonitrile at room temperature to pro- (Universidad Nacional, Bogotá) is the reactivity of these duce mono N-alkyl ammonium quaternary salts (3a-f) polyamine bases toward nucleophiles and electrophiles.
    [Show full text]
  • Synthesis of Monocyclic Diaziridines and Their Fused Derivatives
    Special Issue Reviews and Accounts ARKIVOC 2008 (i) 128-152 Synthesis of monocyclic diaziridines and their fused derivatives Nina N. Makhova,* Vera Yu. Petukhova, and Vladimir V. Kuznetsov N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47, Leninsky prosp., 119991 Moscow, Russian Federation E-mail: [email protected] Abstract Diaziridines and their fused analogues have a wide-range potential as a test subjects for theoretical and practical application. This review covers our investigations focused on the development of optimal methods for the synthesis of monocyclic and fused diaziridine derivatives. Several approaches to the preparation of monocyclic diaziridine derivatives were developed: (1) a synthesis of 3,3-di- and 1,3,3-trialkylmono- and α,ω-bis(diaziridin-1-yl)alkanes from ketoxime O-sulfonates and ammonia, and primary aliphatic amines, respectively, as well as of practically previously inaccessible 3-monoalkyldiaziridines from ammonium salts of aldoxime O-sulfonic acids and ammonia (2) a synthesis of diaziridines from carbonyl compounds, primary aliphatic amines, and aminating reagents in water (or a water–MeOH mixture) at controlled pH of the medium, as well as from carbonyl compounds, amines and N-chloroalkylamines in aprotic solvents in the presence of K2CO3, and (3) a synthesis of 1,2,3-trialkyldiaziridines from N- chloroalkylamines without carbonyl compounds in the presence of primary aliphatic amines at high pressure. As regards fused diaziridine derivatives, general and simple methods were developed to prepare four types of these structures: 1,5-diazabicyclo[3.1.0]hexanes, 1,6- diazabicyclo[4.1.0]heptanes, 1,3,5-triazabicyclo[3.1.0] hexanes, including the parent compound and 2,4-nonsubstituted structures, and 1,3,6-triazabicyclo[3.1.0]hexanes, the latter being previously unknown.
    [Show full text]
  • Derivatives of the Triaminoguanidinium Ion, 6. Aminal-Forming Reactions with Aldehydes and Ketones [9]
    Z. Naturforsch. 2020; 75(3)b: 317–326 Jan Szabo and Gerhard Maas* Derivatives of the triaminoguanidinium ion, 6. Aminal-forming reactions with aldehydes and ketones https://doi.org/10.1515/znb-2019-0216 [9]. Some years ago, we started to study the chemistry of Received December 5, 2019; accepted January 19, 2020 salts 3, which in particular were expected to undergo mul- tiple functionalization based on the nucleophilicity of the Abstract: Cyclic aminals (N,N-acetals) could be prepared benzyl-NH nitrogen atom. Thus, 3-Cl was found to undergo by the reaction of N,N′,N″-triaminoguanidinium sul- threefold N-carbamoylation with various arylisocyanates fate, N,N′,N″-tris(benzylamino)guanidinium chloride or and thiocarbamoylation (leading to thiourea derivatives) N,N′,N″-tris(benzylamino)guanidine with formaldehyde with arylisothiocyanates [10]. In a similar manner, triple or acetone. In all cases, 1,2,4,5-tetrazinane derivatives N-acylation with acid chlorides produced N,N′,N″-tris(N- were obtained, which were structurally confirmed by X-ray acyl-N-benzylamino)guanidines, which under the action crystal structure determinations. In two cases, 1:1 cocrys- of aqueous NaOH could be transformed into mesoionic tals of two different tetrazinane products were isolated. On 1,2,4-triazolium-3-aminides [11]. Reactions of salts 3 with the other hand, the reaction of N,N′,N″-tris(benzylamino) aldehydes or ketones have not been reported so far. guanidinium chloride with benzaldehyde yielded a The presence of three amino groups in the cations of 3-(2-benzylidenehydrazin-1-yl)-1H-1,2,4-triazole.
    [Show full text]
  • Synthesis and Characterization of Covalent Adaptable Networks
    Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 3-19-2018 Synthesis and Characterization of Covalent Adaptable Networks Comprised of Dynamic Imine and Aminal Covalent Bonds Albert Chao Louisiana State University and Agricultural and Mechanical College, [email protected] Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Organic Chemistry Commons, and the Polymer Chemistry Commons Recommended Citation Chao, Albert, "Synthesis and Characterization of Covalent Adaptable Networks Comprised of Dynamic Imine and Aminal Covalent Bonds" (2018). LSU Doctoral Dissertations. 4506. https://digitalcommons.lsu.edu/gradschool_dissertations/4506 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. SYNTHESIS AND CHARACTERIZATION OF COVALENT ADAPTABLE NETWORKS COMPRISED OF DYNAMIC IMINE AND AMINAL COVALENT BONDS A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Chemistry by Albert Chao B.A., University of Cincinnati, 2010 May 2018 Acknowledgements I would like to thank my advisor Prof. Donghui Zhang for her guidance, mentorship, and financial support on the projects I have worked on during the past 5 years in graduate school at Louisiana State University. Prof. Donghui Zhang allowed me to think independently and develop projects from the beginning to the end. When I lost interest on each project, her patience and encouragement always turned failure into success.
    [Show full text]
  • Exploiting Intramolecularity: Exploring Aldehyde-Catalyzed Intermolecular Hydroaminations and Mixed Aminal Chemistry by Didier A
    Exploiting Intramolecularity: Exploring Aldehyde-Catalyzed Intermolecular Hydroaminations and Mixed Aminal Chemistry By Didier Alexandre Bilodeau Thesis submitted to the Faculty of Graduate and Postdoctoral Studies University of Ottawa In partial fulfillment of the requirements for the M.Sc. degree in the Ottawa-Carleton Chemistry Institute University of Ottawa Candidate Supervisor Didier Alexandre Bilodeau Dr. André M. Beauchemin © Didier Alexandre Bilodeau, Ottawa, Canada, 2018 Abstract Hydroamination reactions are very attractive to form new C-N bonds, though broadly applicable synthetic methods do not exist. The hydroamination of unactivated alkenes is especially difficult to accomplish given its negative reaction entropy, as well as potentially being a thermodynamically unfavourable transformation with some substrates. Thus, previously reported systems have often consisted of biased intramolecular systems or metal-catalyzed intermolecular variations operating at low temperatures. Recently, our group discovered that intermolecular Cope-type hydroamination of unactivated alkenes is achievable through the use of aldehydes as catalysts. These organocatalysts act solely through promoting the pre-association of reacting partners, hydroxylamines and allyl amines, in order to induce temporary intramolecularity; thus allowing for very mild reaction conditions and access to important 1,2-Diamine motifs. Aldehyde Catalyzed Intermolecular Cope-Type Hydroamination Catalysis through Temporary Intramolecularity This thesis presents studies expanding upon initial reports of aldehyde-catalyzed Cope-type intermolecular hydroamination. In the scope of these studies standard conditions were developed to compare aldehyde catalytic activity. These evaluations led to further strengthening our understanding of hypothesized trends in aldehydes’ catalytic efficiencies, ii notably the impact of electronic, steric and solvent effects. Furthermore, the possibility of using a catalytic precursor species for hydroamination was evaluated.
    [Show full text]
  • Copper-Catalysed Amination of Alkyl Iodides Enabled by Halogen-Atom Transfer
    ARTICLES https://doi.org/10.1038/s41929-021-00652-8 Copper-catalysed amination of alkyl iodides enabled by halogen-atom transfer Bartosz Górski1,3, Anne-Laure Barthelemy 1,3, James J. Douglas 2, Fabio Juliá 1 ✉ and Daniele Leonori 1 ✉ Despite the fact that nucleophilic displacement (SN2) of alkyl halides with nitrogen nucleophiles is one of the first reactions introduced in organic chemistry teaching, its practical utilization is largely limited to unhindered (primary) or activated (α-carbonyl, benzylic) substrates. Here, we demonstrate an alternative amination strategy where alkyl iodides are used as radical precursors instead of electrophiles. Use of α-aminoalkyl radicals enables the efficient conversion of the iodides into the corresponding alkyl radical by halogen-atom transfer, while copper catalysis assembles the sp3 C–N bonds at room temperature. The process provides SN2-like programmability, and application in late-stage functionalization of several densely functionalized pharmaceuticals demonstrates its utility in the preparation of valuable N-alkylated drug analogues. itrogen-rich molecules form the structural basis of almost species10. The potential of these two elementary steps to assemble a every pharmaceutical and agrochemical lead, as well as broad array of sp3 C–Y bonds (Y = C, N, O, S, halogen) represents a many other high-value products like food additives and powerful opportunity for modular fragment coupling11. N 1 organic materials . A large fraction of these chemotypes contain Despite these prominent features, copper catalysis has seen lim- bonds between nitrogenated residues and saturated carbons, which ited applications to the amination of unactivated alkyl halides12,13. makes the development of methods for sp3 C–N bond construction As shown in Fig.
    [Show full text]
  • Spontaneous Macrocyclization Through Multiple Dynamic Cyclic Aminal Formation Chemcomm
    Volume 57 Number 10 4 February 2021 Pages 1167–1268 ChemComm Chemical Communications rsc.li/chemcomm ISSN 1359-7345 COMMUNICATION Ezequiel Pérez-Inestrosa, Ignacio Alfonso et al . Spontaneous macrocyclization through multiple dynamic cyclic aminal formation ChemComm View Article Online COMMUNICATION View Journal | View Issue Spontaneous macrocyclization through multiple dynamic cyclic aminal formation† Cite this: Chem. Commun.,2021, 57, 1190 a bc bc Daniel Carbajo,‡ Antonio Jesu´s Ruiz-Sa´nchez, ‡ Francisco Na´jera, bc a Received 29th October 2020, Ezequiel Pe´rez-Inestrosa * and Ignacio Alfonso * Accepted 30th December 2020 DOI: 10.1039/d0cc07184f rsc.li/chemcomm The use of aminals in dynamic covalent chemistry is slightly under- diamines and carbonyl compounds. This reversible reaction explored, probably due to their inherent instability. Here we report has been applied to the synthesis of open-chain unsym- the spontaneous [2+2] macrocyclization of tetrakis(aminals). Their metrical aminals,14 the controlled evaporation of volatile car- unexpected stability and structural modularity, the dynamic nature of bonyl compounds,8,22 induce movement through a molecular 23 Creative Commons Attribution-NonCommercial 3.0 Unported Licence. the connections and their water tolerance make them appealing systems track and the preparation of a dynamic chemical network that for future applications as stimulus-responsive materials. self-directs its amplification.24 Inspired by a previous research25 we envisioned to study the Dynamic covalent chemistry (DCvC) has experienced an important reaction between amino and aldehyde building blocks allowing development in the last two decades, based on the use of reversible a large structural and functional diversity, including the possible covalent bonds to generate exchanging mixtures under formation of dynamic aminals.
    [Show full text]
  • CELSS Experiment Model and Design Concept of Gas Recycle System
    CELSS Experiment Model and Design Concept of Gas Recycle System Keiji Nitta and Mitsuo Oguchi Nat~onalAerospace Laboratory Tokyo, Japan Syuji Kanda Submar~ne Deslgnlng Department Kawasak~Heavy lndustr~esLtd Kobe, Japan ABSTRACT the strawman CELSS experiment concept and is described in next section. In order to prolong the duration of manned missions around the earth and to expand the 2. CELSS EXPERIMENT CONCEPT human existing region from the earth to other planets such as a Lunar Base or a manned Mars The CELSS is the technology for making a flight mission, the CELSS becomes an essential stable ecology among animals and plants factor of the future technology to be developed without re-supply of materials and using a through utilization of Space Station. special controlled environment. Therefore The preliminary SELI (System Engineering the CELSS would be divided into two sections; and Integration) efforts regarding CELSS have the environmental control section and the been carried out by the Japanese CELSS concept cultivating and breeding section of plants study group for clarifying the feasibility of and animals. In the environment control hardware development for Space Station section, at least three major systems, shown Experiments and for getting the time phased Fig. 1, should be installed for sustaining mission sets after Fy ,1992. The results of the gas environment, for water recycle and these studies are breifly summarized and for decomposing waste materials into a thereafter, the design and utilization methods fertilizer solution. of a Gas Recycle System for CELSS experiments In the cultivating and breeding section, are discussed. the Algae and higher plant cultivation systems for converting carbon dioxide to oxygen and for producing food are to be installed.
    [Show full text]
  • Organic & Biomolecular Chemistry
    Organic & Biomolecular Chemistry Accepted Manuscript This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/obc Page 1 of 9 Journal Name Organic & Biomolecular Chemistry Dynamic Article Links ► Cite this: DOI: 10.1039/c0xx00000x www.rsc.org/xxxxxx ARTICLE TYPE Mechanisms of Imine Exchange Reactions in Organic Solvents Maria Ciaccia a and Stefano Di Stefano*a Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX DOI: 10.1039/b000000x Manuscript 5 The state of the art in the mechanisms operating in imine chemistry in organic solvents is critically discussed in the present review. In particular, the reaction pathways involved in imine formation, transimination and imine metathesis in organic media are taken into account, with aim at organizing the poor and sometimes scattered information available in the literature.
    [Show full text]
  • Metampicillin Is a Cyclic Aminal Produced by Reaction of Ampicillin
    www.nature.com/scientificreports OPEN Metampicillin is a cyclic aminal produced by reaction of ampicillin with formaldehyde Raphael Reinbold 1,4, Tobias John 1,4, Paolo Spingardi 1, Akane Kawamura 1,2, Christopher J. Schofeld 1* & Richard J. Hopkinson 1,3* Metampicillin is a β-lactam antibiotic that is prepared by the reaction of ampicillin with formaldehyde. Although metampicillin has been studied for treatment of infections in animals and humans, its structure has been unclear. We report NMR studies revealing that metampicillin contains a formaldehyde-derived cyclic aminal. NMR time-course experiments with excess formaldehyde in solution show formation of another product with an additional exocyclic hemiaminal group formed by reaction with the cyclic aminal nitrogen. The exocyclic hemiaminal group is readily removed by reaction with the formaldehyde scavenger 1,3-cyclohexanedione, whereas the cyclic aminal methylene exhibits greater stability. The overall results assign the structure of metampicillin as containing a cyclic aminal and further reveal the potential for complexity in the reaction of formaldehyde with biomedicinally relevant molecules. Metampicillin is a β-lactam antibiotic approved for use in human medicine as recognised by the World Health Organization1, and which is also used in veterinary medicine according to the European Medicines Agency 2. It is prepared by the reaction of ampicillin (1) and formaldehyde (HCHO)3. Metampicillin is considered to be a prodrug that releases 1 afer acid-catalysed fragmentation in the stomach. Metampicillin accumulates in bile 4 and is reported to be more stable in serum than in aqueous acidic conditions 5. Whilst in most infections the clinical efcacy of metampicillin is comparable to that of 1, its accumulation in bile leads to greater efcacy in treatment of biliary infections6.
    [Show full text]
  • Enantioselective Direct Α‑Amination of Aldehydes Via a Photoredox Mechanism: a Strategy for Asymmetric Amine Fragment Coupling Giuseppe Cecere, Christian M
    Communication pubs.acs.org/JACS Enantioselective Direct α‑Amination of Aldehydes via a Photoredox Mechanism: A Strategy for Asymmetric Amine Fragment Coupling Giuseppe Cecere, Christian M. König, Jennifer L. Alleva, and David W. C. MacMillan* Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States *S Supporting Information ABSTRACT: The direct, asymmetric α-amination of aldehydes has been accomplished via a combination of photoredox and organocatalysis. Photon-generated N- centered radicals undergo enantioselective α-addition to catalytically formed chiral enamines to directly produce stable α-amino aldehyde adducts bearing synthetically useful amine substitution patterns. Incorporation of a photolabile group on the amine precursor obviates the need to employ a photoredox catalyst in this trans- formation. Importantly, this photoinduced transformation allows direct and enantioselective access to α-amino aldehyde products that do not require postreaction manipulation. central goal in organic synthesis is the development of A methods to enantioselectively build C−N bonds within complex molecular structures. In particular, aldehydes, acids, and alcohols bearing α-amine substitution are widely distributed among pharmaceutically active compounds, and their broad representation has prompted the invention of a number of 1,2 Design plan. A detailed catalytic cycle for our proposed catalysis strategies for stereogenic nitrogen installation. In this asymmetric aldehyde amination is presented in Scheme 1. We α context, -amino aldehydes represent a valuable structural motif, postulated that an electrophilic N-based radical 1 might be mainly because of their capacity to serve as versatile synthetic generated under mild conditions from an amine substrate 3 handles en route to a diverse range of complex N-containing bearing a photolabile leaving group.
    [Show full text]