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  • 1.
    Beşev, Magnus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Radical Cyclization Approaches to Pyrrolidines2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Five-membered rings are readily prepared by 5-exo-trig radical cyclization. This thesis is concerned with novel methodology for pyrrolidine synthesis. We have synthesised selenium containing radical precursors from aziridines and α-phenylseleno ketones, and cyclized them to 2,4- and 3,4-disubstituted pyrrolidines. A few examples of 5-exo-dig cyclization were also demonstrated. In another study we investigated the capacity of the nitrogen protecting group to direct diastereoselectivity in the formation of 2,4-disubstituted pyrrolidines. The diphenylphosphinoyl protecting group directed cyclization to occur in a highly cis-selective manner. When cyclizations were performed at 17 oC, cis/trans-ratios as high as 24/1 were obtained. In contrast, cyclization of the unprotected pyrrolidine precursor afforded the trans-diastereomer as the major product (cis/trans = 1/3.3 – 1/20). We also examined the use of a hydroxyl auxiliary for controlling diastereoselectivity in radical cyclization. The required selenium containing radical precursors were synthesised from 2-cyanoaziridines by addition of organometallic reagents, reduction of the resulting aziridine ketone, and benzeneselenol ring-opening of the aziridine. Cyclization at 17 oC produced 2,4-disubstituted pyrrolidines substantially enriched in the trans-isomer (cis/trans = 1/9 – 1/12). Novel radical cyclization approaches to thiazolines and pyrrolines were also tried.

    The thesis also describes attempts to improve the Hassner aziridine synthesis by employing stannous chloride as a functional group tolerant reducing agent.

  • 2.
    Bäckvall, Jan-Erling
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Andersson, Pher
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Stone, Guy
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Syntheses of (±)-α- and (±)- γ- Lycorane via a Stereocontrolled Organopalladium Route1991In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 56, no 9, p. 2988-2993Article in journal (Refereed)
    Abstract [en]

    Total syntheses of (+/-)-alpha-and (+/-)-gamma-lycorane are described. The key steps in the syntheses are the stereocontrolled palladium-catalyzed intramolecular 1,4-chloroamidation of 12 to 13 and the subsequent anti-stereoselective copper-catalyzed S(N)2' reaction of allylic chloride 13 with [3,4-(methylenedioxy)phenyl]magnesium bromide to give 14. Hexahydroindole 14 has the required relative stereochemistry between carbons 3a, 7, and 7a for alpha-lycorane (1a) and was transformed to the latter via 15 and 16. The epimeric gamma-lycorane (2) was obtained by performing the Bischler-Napieralski cyclization on 14, which led to a highly stereoselective isomerization to give exclusively 17. Compound 17 was subsequently transformed to 2. The overall yield from ester 8 to (+/-)-alpha- and (+/-)-gamma-lycorane was 40 and 36%, respectively.

  • 3.
    Engman, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Al-Maharik, Nawaf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    McNaughton, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Birmingham, A
    Uppsala University.
    Powis, G.
    Uppsala University.
    Thioredoxin Reductase and Cancer Cell Growth Inhibition by Organotellurium Compounds that could be Selectively Incorporated into Tumor Cells2003In: Bioorganic & Medicinal Chemistry, ISSN 0968-0896, E-ISSN 1464-3391, Vol. 11, no 23, p. 5091-5100Article in journal (Refereed)
    Abstract [en]

    The thioredoxins are small ubiquitous redox proteins with the conserved redox catalytic sequence-Trp-Cys-Gly-Pro-Cys-Lys, where the Cys residues undergo reversible NADPH dependent reduction by selenocysteine containing flavoprotein thioredoxin reductases. Thioredoxin expression is increased in several human primary cancers including lung, colon, cervix, liver, pancreatic, colorectal and squamous cell cancer. The thioredoxin/thioredoxin reductase pathway therefore provides an attractive target for cancer drug development. Organotellurium steroid, lipid, amino acid, nucleic base, and polyamine inhibitors were synthesized on the basis that they might be selectively or differentially incorporated into tumor cells. Some of the newly prepared classes of tellurium-based inhibitors (lipid-like compounds 3b and 3e, amino acid derivative 5b, nucleic base derivative 8b, and polyamine derivatives 14a and 14b) inhibited TrxR/Trx and cancer cell growth in culture with IC(50) values in the low micromolar range.

  • 4.
    Engman, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    McNaughton, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Gajewska, Malgorzata
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Kumar, Sangit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Birmingham, Anne
    Powis, Garth
    Thioredoxin reductase and cancer cell growth inhibition by organogold(III) compounds2006In: Anti-Cancer Drugs, ISSN 0959-4973, E-ISSN 1473-5741, Vol. 17, no 5, p. 539-544Article in journal (Refereed)
    Abstract [en]

    Thioredoxin (Trx) expression is increased in several human primary cancers associated with aggressive tumor growth and decreased patient survival, and the Trx/Trx reductase (TrxR) system therefore provides an attractive target for cancer drug development. Various gold(III) compounds with none, one, two or three carbon-gold bonds were evaluated for their capacity to inhibit TrxR and the growth of MCF-7 cancer cells in vitro. Compounds with up to two carbon-gold bonds were often potent inhibitors of TrxR with IC50 values as low as 2 nmol/l. In the presence of Trx and insulin the inhibiting capacity was much lower. However, the inhibitory concentrations of the compounds did not correlate with the ability to kill cells. Out of the organometallics tested, only compound 8 with two carbon-gold bonds was able to inhibit colony formation by MCF-7 breast cancer cells at low micromolar concentrations (IC50=1,6umol/l). Unfortunately, the compound did not show any anti-tumor activity against MCF-7 breast cancer and HT-29 colon cancer zenografts in scid mice.

  • 5.
    Erdélyi, Máté
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Towards the Development of Photoswitchable β-Hairpin Mimetics2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Peptide secondary structure mimetics are important tools in medicinal chemistry, as they provide analogues of endogeneous peptides with new physicochemical and pharmacological properties. The β-hairpin motif has been shown to be involved in numerous physiological processes, among others in regulation of eucariotic gene transcription. This thesis addresses the design, synthesis and conformational analysis of photoswitchable β-hairpin mimetics.

    The developmental work included the establishment of an improved procedure for cross coupling of aryl halides with terminal alkynes. Microwave mediated Sonogashira couplings in closed vessels were optimized under homogeneous and solid-phase conditions furnishing excellent yields for a large variety of substrates within 5 – 25 minutes. In addition, microwave heating was shown not to have any non-conventional effect on the reaction rate.

    Furthermore, the most important factors affecting β-hairpin stability were evaluated. Studies of tetrapeptide and decapeptide analogues revealed the essential role of the β-turn in initiation of hairpin folding. Moreover, hydrogen bonding was shown to be the main interchain stabilizing force, whereas hydrophobic interactions were found to be relatively weak. Nevertheless, hydrophobic packing appears to provide an important contribution to the thermodynamic stability of β-hairpins.

    Photoswitchable peptidomimetics were prepared by incorporation of various stilbene moieties into tetra- and decapeptides. Synthesis, photochemical isomerisation and spectroscopic conformational analysis of the compounds were performed.

    List of papers
    1. Rapid Homogeneous-Phase Sonogashira Coupling Reactions Using Controlled Microwave Heating
    Open this publication in new window or tab >>Rapid Homogeneous-Phase Sonogashira Coupling Reactions Using Controlled Microwave Heating
    2001 In: Journal of Organic Chemistry, Vol. 66, no 12, p. 4165-4169Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91463 (URN)
    Available from: 2004-03-11 Created: 2004-03-11Bibliographically approved
    2. Rapid Microwave Promoted Sonogashira Coupling Reactions on Solid Phase
    Open this publication in new window or tab >>Rapid Microwave Promoted Sonogashira Coupling Reactions on Solid Phase
    2003 (English)In: Journal of Organic Chemistry, Vol. 68, no 16, p. 6431-6434Article in journal (Refereed) Published
    Abstract [en]

    A microwave-enhanced, rapid, and efficient solidphase version of the Sonogashira reaction is presented. It has been applied to the coupling of aryl iodides and bromides with various acetylene derivatives giving excellent yields in 15 to 25 min. The scopes of homogeneous, solventless, and solid-phase conditions for Sonogashira coupling of aryl halides are compared.

    National Category
    Organic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-91464 (URN)10.1021/jo034284s (DOI)
    Available from: 2004-03-11 Created: 2004-03-11 Last updated: 2011-01-05
    3. Insight into β-Hairpin Stability: A Structural and Thermodynamic Study of Diastereomeric β-Hairpin Mimetics
    Open this publication in new window or tab >>Insight into β-Hairpin Stability: A Structural and Thermodynamic Study of Diastereomeric β-Hairpin Mimetics
    2002 In: New Journal of Chemistry, Vol. 26, p. 834-843Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91465 (URN)
    Available from: 2004-03-11 Created: 2004-03-11Bibliographically approved
    4. Synthesis and Conformational Analysis of Novel Stibene-type Peptidomimetics
    Open this publication in new window or tab >>Synthesis and Conformational Analysis of Novel Stibene-type Peptidomimetics
    Show others...
    Article in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-91466 (URN)
    Available from: 2004-03-11 Created: 2004-03-11Bibliographically approved
    5. Synthesis and Conformational Analysis of Novel β-Hairpin mimetics. Factors Affecting Stability and Incorporation of a Photoswitchable Dipeptide Mimic
    Open this publication in new window or tab >>Synthesis and Conformational Analysis of Novel β-Hairpin mimetics. Factors Affecting Stability and Incorporation of a Photoswitchable Dipeptide Mimic
    Article in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-91467 (URN)
    Available from: 2004-03-11 Created: 2004-03-11Bibliographically approved
  • 6.
    Erdélyi, Máté
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Gogoll, Adolf
    Rapid Microwave Promoted Sonogashira Coupling Reactions on Solid Phase2003In: Journal of Organic Chemistry, Vol. 68, no 16, p. 6431-6434Article in journal (Refereed)
    Abstract [en]

    A microwave-enhanced, rapid, and efficient solidphase version of the Sonogashira reaction is presented. It has been applied to the coupling of aryl iodides and bromides with various acetylene derivatives giving excellent yields in 15 to 25 min. The scopes of homogeneous, solventless, and solid-phase conditions for Sonogashira coupling of aryl halides are compared.

  • 7.
    Ericsson, Cecilia
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Synthesis of Tetrahydrofuran and Pyrrolidine Derivatives Utilising Radical Reactions: Organochalcogenides in Reductive, Carbonylative and Group-Transfer Cyclisation2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes free-radical reactions for the construction of tetrahydrofuran and pyrrolidine derivatives. The studies are concerned with (i) diastereoselectivity in radical cyclisation, (ii) construction of tetrahydrofuran-3-ones and pyrrolidin-3-ones via radical carbonylation/cyclisation and (iii) synthesis of tetrahydrofuran derivatives via group-transfer cyclisation of organochalcogen compounds.

    (i) Diastereoselectivity in the synthesis of tetrahydrofuran derivatives via radical cyclisation was controlled by addition of Lewis acids. In the synthesis of 2,4-disubstitued tetrahydrofurans, the trans-isomer was formed as the major product in the unperturbed reaction. Upon addition of trialkylalumiums the diastereoselectivity was reversed. In a similar fashion, exo/endo-diastereoselectivity in the synthesis of bicyclic 2,3,4-trisubstituted tetrahydrofurans could also be controlled.

    (ii) Procedures for construction of tetrahydrofuran-3-ones and pyrrolidin-3-ones were presented. Epoxides were ring-opened with benzeneselenolate or benzenetellurolate and the resulting β-hydroxyalkyl phenyl chalcogenides were vinylated using ethyl propiolate/NMM or E-1,2-bis(phenylsulfonyl)ethylene/NaH. The corresponding nitrogen analogues were accessed by N-vinylation of aziridines followed by benzeneselenolate ring-opening. The two types of organochalcogen radical precursors were then treated with TTMSS/AIBN under an atmosphere of carbon monoxide (80 atm) to afford tetrahydrofuran-3-ones and pyrrolidin-3-ones, respectively, in high yields.

    (iii) Microwaves were found to induce group-transfer cyclisation of β-allyloxyalkyl aryl chalcogenides. Short time heating (3-10 min) at 250 oC in ethylene glycol was required to obtain tetrahydrofuran derivatives in 60-91% yield.

    List of papers
    1. Diastereocontrol by Trialkylaluminums in the Synthesis of Tetrahydrofurans via Radical Cyclisation
    Open this publication in new window or tab >>Diastereocontrol by Trialkylaluminums in the Synthesis of Tetrahydrofurans via Radical Cyclisation
    2001 In: Organic Letters, Vol. 3, p. 3459-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91437 (URN)
    Available from: 2004-02-26 Created: 2004-02-26Bibliographically approved
    2. Construction of Tetrahydrofuran-3-ones from Readily Available Organochalcogen Precursors via Radical Carbonylation/Reductive Cyclization
    Open this publication in new window or tab >>Construction of Tetrahydrofuran-3-ones from Readily Available Organochalcogen Precursors via Radical Carbonylation/Reductive Cyclization
    2002 In: Organic Letters, Vol. 4, p. 3-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91438 (URN)
    Available from: 2004-02-26 Created: 2004-02-26Bibliographically approved
    3. Radical Carbonylation/Reductive Cyclization for the Construction of Tetrahydrofuran-3-ones and Pyrrolidin-3-ones
    Open this publication in new window or tab >>Radical Carbonylation/Reductive Cyclization for the Construction of Tetrahydrofuran-3-ones and Pyrrolidin-3-ones
    2003 In: Journal of Organic Chemistry, Vol. 68, p. 8386-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-91439 (URN)
    Available from: 2004-02-26 Created: 2004-02-26Bibliographically approved
    4. Microwave-Assisted Group-Transfer Cyclisation of Organotellurium Compounds
    Open this publication in new window or tab >>Microwave-Assisted Group-Transfer Cyclisation of Organotellurium Compounds
    Article in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-91440 (URN)
    Available from: 2004-02-26 Created: 2004-02-26Bibliographically approved
  • 8.
    Gayet, Arnaud
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Development of New Chiral Bicyclic Ligands: Applications in Catalytic Asymmetric Transfer Hydrogenation, Epoxidations, and Epoxide Rearrangements2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the synthesis and application of new chiral bicyclic ligands and their application in asymmetric catalysis. The studies involved: [i] The development of novel chiral bicyclic amino sulfur ligands and their use in transfer hydrogenation. [ii] The development of the kinetic resolution of racemic epoxide through the use of chiral lithium amides. [iii] The synthesis and application of chiral bicyclic amine in the organocatalysed epoxidation of alkenes. [iv] Development and application of new chiral diamine ligands in the rearrangement of epoxides into allylic alcohols.

    [i] The preparation of two-series of amino thiol ligands based on the structure of camphor is described, together with their application in the iridium-catalysed asymmetric transfer hydrogenation of acetophenone using isopropanol as the hydrogen source. Excellent activity and good enantioselectivity have been achieved using 2 mol% of chiral ligand in combination with [IrCl(COD)]2.

    [ii] The chiral diamines (1S,3R,4R)-3-(pyrrolidine-1-ylmethyl)-2-aza-bicyclo[2.2.1]heptane and its (2R,5R)-dimethylpyrrolidine derivative were applied to the kinetic resolution of a variety of racemic 5-7 membered cycloalkene oxides with lithium diisopropylamide (LDA) as the bulk base. Using 5 mol% of the chiral diamines, both unreacted epoxides and allylic alcohols could be produced in enantiomeric excess up to 99%.

    [iii] The synthesis of chiral bicyclic amines and their use in the organocatalysed epoxidation of alkene has been described. Using a substoichiometric amount of the chiral amines and aldehydes as ligands precursors, with Oxone® as oxidant, a good activity but moderate enantioselectivity was observed for the epoxidation of trans-stilbene.

    [iv] The preparation of 6-substituted-7-bromo-aza-bicyclo[2.2.1]heptanes via nucleophilic addition of organocopper reagents to 3-bromo-1-azoniatricyclo[2.2.1.0]heptyle bromide has been described. These compounds have been utilised as chiral building blocks in the preparation of novel chiral diamine ligands, which have been successfully applied to the catalysed asymmetric rearrangement of epoxide into the corresponding allylic alcohol.

    List of papers
    1. Novel Catalytic Kinetic Resolution Of Racemic Epoxides to Allylic alcohols
    Open this publication in new window or tab >>Novel Catalytic Kinetic Resolution Of Racemic Epoxides to Allylic alcohols
    2002 In: Organic Letters, ISSN 1523-7060, Vol. 4, no 22, p. 3777-3779Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92519 (URN)
    Available from: 2005-01-10 Created: 2005-01-10Bibliographically approved
    2. Development of new camphor based N,S chiral ligands and their application in transfer hydrogenation
    Open this publication in new window or tab >>Development of new camphor based N,S chiral ligands and their application in transfer hydrogenation
    2004 In: Organic & Biomolecular Chemistry, ISSN 1477-0520, Vol. 2, no 13, p. 1887-1893Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92520 (URN)
    Available from: 2005-01-10 Created: 2005-01-10Bibliographically approved
    3. Synthesis of 6-Substituted 7-Bomoazabicyclo[2.2.1]heptanes via Nucleophilic Addition to 3-Bromo-1-azoniatricyclo[2.2.1.0]-heptane Bromide
    Open this publication in new window or tab >>Synthesis of 6-Substituted 7-Bomoazabicyclo[2.2.1]heptanes via Nucleophilic Addition to 3-Bromo-1-azoniatricyclo[2.2.1.0]-heptane Bromide
    2005 (English)In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 347, no 9, p. 1242-1246Article in journal (Refereed) Published
    Abstract [en]

    We describe herein an efficient method for the preparation of a functionalised bicyclic framework (6-substituted 7-bromo-aza-bicyclo[2.2.1]heptane) through the selective opening of the aziridium 2 with organocuprates in up to 90% yield. These interesting chiral building blocks were then utilised as novel ligands in the rearrangement of epoxides to afford chiral allylic alcohols.

    National Category
    Organic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-92521 (URN)10.1002/adsc.200404322 (DOI)
    Available from: 2005-01-10 Created: 2005-01-10 Last updated: 2017-12-14Bibliographically approved
  • 9.
    Gayet, Arnaud
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Andersson, Pher G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Synthesis of 6-Substituted 7-Bomoazabicyclo[2.2.1]heptanes via Nucleophilic Addition to 3-Bromo-1-azoniatricyclo[2.2.1.0]-heptane Bromide2005In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 347, no 9, p. 1242-1246Article in journal (Refereed)
    Abstract [en]

    We describe herein an efficient method for the preparation of a functionalised bicyclic framework (6-substituted 7-bromo-aza-bicyclo[2.2.1]heptane) through the selective opening of the aziridium 2 with organocuprates in up to 90% yield. These interesting chiral building blocks were then utilised as novel ligands in the rearrangement of epoxides to afford chiral allylic alcohols.

  • 10.
    Guliashvili, Tamaz
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Synthesis and Reactivity Studies of Zwitterionic Silenes and 2-Silenolates2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes synthesis and reactivity studies of 2-amino-2-siloxysilenes and 2-silenolates, species that are strongly influenced by reversed Si=C bond polarization, i.e. an Siδ-=Cδ+ polarization as compared to the natural Siδ+=Cδ- polarization. Because of the reversed polarization, the 2-amino-2-siloxysilenes are zwitterions and the 2-silenolates are predominantly described by the resonance structure with the negative charge at Si.

    Transient zwitterionic 2-amino-2-siloxysilenes are formed thermolytically from carbamylpolysilanes (tris(trimethylsilyl)silylamides) and trapped with 1,3-dienes in nearly quantitative yields. These silenes have structure and reactivity characteristics that differ from earlier studied Si=C bonded compounds. They are thermodynamically stable toward dimerization and react with 1,3-dienes to give exclusively [4+2] cycloadducts. Their reactions with 1,3-dienes proceed in accordance with inverse electron demand (IED) Diels-Alder reactions which is explained by the electron-rich nature of these silenes. The 2-amino-2-siloxysilenes are also less reactive toward alcohols than earlier silenes. Hence, alcohols do not react with 2-amino-2-siloxysilenes but with the silene precursor, the carbamylpolysilanes, leading to alkoxysilanes in high yields. The latter reaction represents a novel base-free synthetic protocol for protection of primary and secondary alcohols with the fluoride resistant but photolabile tris(trimethylsilyl)silyl group.

    Another class of formally Si=C bonded compounds, metal 2-silenolates, has been formed in high yields using a novel facile method. Reaction of acyl- and carbamylpolysilanes with potassium tert-butoxide in tetrahydrofurane gives potassium 2-silenolates. The potassium 2-silenolates are stable at room temperature, in contrast to earlier lithium 2-silenolates that degrade rapidly at ambient temperature. The first crystallisable complex of a 2-silenolate was formed and characterized by X-ray crystallography. This 2-silenolate has a pyramidal central Si (ΣSi = 317.8°), and an Si-C single rather than Si=C double bond (r(SiC) = 1.926 Å). The potassium 2-silenolates give exclusively Si alkylated products with alkyl halides and only [4+2] cycloadducts with 1,3-dienes.

    List of papers
    1. Evidence for Formation of Silenes Strongly Influenced by Reversed Si=C Bond Polarity
    Open this publication in new window or tab >>Evidence for Formation of Silenes Strongly Influenced by Reversed Si=C Bond Polarity
    Show others...
    2002 In: Organic Letters, ISSN 1523-7060, Vol. 4, no 11, p. 1915-1918Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92331 (URN)
    Available from: 2004-11-03 Created: 2004-11-03Bibliographically approved
    2. Formation of Transient Zwitterionic Silenes and Their Diels-Alder Reactions with 1,3-Dienes: Mechanism and Stereoselectivity
    Open this publication in new window or tab >>Formation of Transient Zwitterionic Silenes and Their Diels-Alder Reactions with 1,3-Dienes: Mechanism and Stereoselectivity
    Show others...
    In: Journal of Americal Chemical Society, ISSN 0002-7863Article in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-92332 (URN)
    Available from: 2004-11-03 Created: 2004-11-03Bibliographically approved
    3. The First Unsuccesful attempt to Add Alcohols to a Silene
    Open this publication in new window or tab >>The First Unsuccesful attempt to Add Alcohols to a Silene
    In: Organometallics, ISSN 0276-7333Article in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-92333 (URN)
    Available from: 2004-11-03 Created: 2004-11-03Bibliographically approved
    4. The First Isolable 2-Silenolate
    Open this publication in new window or tab >>The First Isolable 2-Silenolate
    2003 In: Angewandte Chemie International Eddition, ISSN 1433-7851, Vol. 42, no 14, p. 1640-1642Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92334 (URN)
    Available from: 2004-11-03 Created: 2004-11-03Bibliographically approved
    5. Potassium 1-N,N-Dialkylamino-2,2-bis(trimethylsilyl)-2-Silenolates: Heavy Enolates with Remarkable Stability
    Open this publication in new window or tab >>Potassium 1-N,N-Dialkylamino-2,2-bis(trimethylsilyl)-2-Silenolates: Heavy Enolates with Remarkable Stability
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-92335 (URN)
    Available from: 2004-11-03 Created: 2004-11-03 Last updated: 2010-01-13Bibliographically approved
  • 11.
    Holmberg, Pär
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry.
    Karlsson, John
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Enzymatic Kinetic Resolution of 1-(3-furyl)-3-buten-1ol2005In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 16, p. 2397-2399Article in journal (Other academic)
    Abstract [en]

    The enzymatic kinetic resolution of 1-(3-furyl)-3-buten-1-ol was investigated via the enantioselective hydrolysis of the corresponding acetate. Pseudomonas fluorescens (Fluka) was found to give the highest enantiomeric ratios of the 11 lipases screened. At 51% conversion, the ee value (eep) for the product was found to be 89%, giving an enantiomeric ratio (Ep) of 58, while the ee value (ees) for the substrate was 89%, giving an enantiomeric ratio (Ep) of 38.

  • 12.
    Karimi, Farhad
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    [11C]Carbon Monoxide in Palladium- / Selenium-Promoted Carbonylation Reactions: Synthesis of 11C-Imides, Hydrazides, Amides, Carboxylic Acids, Carboxylic Esters, Carbothioates, Ketones and Carbamoyl Compounds2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    [11C]Carbon monoxide in low concentrations has been used in palladium- or seleniummediated carbonylation reactions such as the synthesis of 11C-imides, hydrazides, amides, carboxylic acids, esters, carbothioates, ketones and carbamoyl compounds.

    In these reactions aryl iodides have been used in most cases. However, less reactive aryl triflate, chloride and bromides were activated using tetrabutylammonium iodide.

    The reactivities of nucleophiles may have influence on the radiochemical yield of the 11Clabelled compounds. Carboxyamination of aryl halides using aniline derivatives yielded 10% of the corresponding 11C-amide. However, the radiochemical yields increased significantly when the aniline derivatives were treated with lithium bis(trimethylsilyl)amide. In contrast, this reagent did not improve the radiochemical yields when primary amines such as methylamine and benzylamine were used. In these cases the radiochemical yields were improved by using pempidine.

    11C-Esterification usually gave low yields. However, the radiochemical yields of 11C-esters could be improved by using magnesium bromide and pempidine.

    An excess of ligand may have a significant impact on palladium-promoted carbonylation reaction. The radiochemical yields of 11C-ketones were improved when using excess amounts of tri-o-tolylphosphine.

    (13C)Carbon monoxide may be utilized for the synthesis of 13C-substituated compounds in order to confirm the position of 11C-labelling.

  • 13.
    Meng, QS
    et al.
    Uppsala University.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Thibblin, Alf
    Uppsala University.
    Concerted and stepwise solvolytic elimination and substitution reactions: Stereochemistry and substituent effects1997In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 119, no 6, p. 1217-1223p. 1217-1223Article in journal (Refereed)
    Abstract [en]

    Solvolysis of the R,R and R,S isomers 2a-X and 2b-X, respectively, (X = I, Br, OBs) in 25 vol % acetonitrile in water gives the elimination products 4, 5a, and 5b along with the substitution products 2a-OH, 2b-OH, 2a-NHCOMe, and 2b-NHCOMe. The rates of e

  • 14.
    Nordin, Sofia
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Asymmetric Transfer Hydrogenation of Aromatic Ketones: Catalyst Development and Mechanistic Studies2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the development and evaluation of new chiral Ru(arene)(amino alcohol) catalysts for the transfer hydrogenation of aromatic ketones using isopropanol as the hydrogen source. Two mechanistic studies of the Ru(arene)(amino alcohol) catalyzed transfer hydrogenation of acetophenone were also conducted.

    The Ru(arene)[(1S,3R,4R)-3.(Hydroxymethyl)-2-azabicyclo[2.2.1]heptane] catalyst was optimized for catalytic asymmetric transfer hydrogenation of aromatic ketones. The effect of substituents on the arene ligand on both selectivity and reactivity was investigated. The performance of the catalyst was also optimized by altering the structure of the chiral amino alcohol ligand. These optimizations resulted in a highly active and selective catalyst, Ru(p-cymene)[(R)-1-[(1S,2R,6S,7R,9R)-4,4-Dimethyl-3,5-dioxa-8-aza-tricyclo[5.2.1.00,0]dec-9-yl]-ethanol], for asymmetric transfer hydrogenation of aromatic ketones. This catalyst was capable of reducing acetophenone in 96% ee in 4 minutes at room temperature at a substrate to catalyst ratio of 200. Full conversion was reached even at a substrate to catalyst ratio of 5000 and the high enantioselectivity of 96% ee was maintained. A range of prochiral aromatic ketones with electron withdrawing or electron donating substituents in any position on the aromatic ring were reduced in short reaction times and with high enantioselectivity, up to 99% ee. Bulky aryl alkyl ketones were also reduced with high enantioselectivity.

    A combined quantum chemical and kinetic investigation of the Ru(arene)(amino alcohol) catalyzed transfer hydrogenation of acetophenone was conducted. Three possible mechanisms were studied and the quantum chemical calculations indicated that the mechanism was concerted. In addition, a kinetic isotope study for the Ru(arene)(amino alcohol) catalyzed transfer hydrogenation of acetophenone was conducted. The determination of the kinetic isotope effect of the proton and hydride transfer showed that the proton and the hydride transfer were both rate-limiting and occurred in the same step. This result supports the proposed concerted mechanism.

    List of papers
    1. Ru(arene)(amino alcohol)-Catalyzed Transfer Hydrogenation of Ketones: Mechanism and Origin of Enantioselectivity
    Open this publication in new window or tab >>Ru(arene)(amino alcohol)-Catalyzed Transfer Hydrogenation of Ketones: Mechanism and Origin of Enantioselectivity
    1999 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 121, no 41, p. 9580-9588Article in journal (Refereed) Published
    Abstract [en]

    The mechanism of the Ru(arene)(amino alcohol)-catalyzed transfer hydrogenation of ketones using isopropyl alcohol as the hydrogen source has been studied by means of hybrid density functional methods (B3PW91). Three mechanistic alternatives were evaluated, and it was shown that the reaction takes place via a six-membered transition state, where a metal-bound hydride and a proton of a coordinated amine are transferred simultaneously to the ketone. Further calculations provided a general rationale for the rate of the reaction by comparison of steric effects in the ground and transition states of the ruthenium hydride complex. It was found that the TS has a strong preference for planarity, and this in turn is dependent on the conformational behavior of the O,N-linkage of the amino alcohol ligand. Finally, a general model, rationalizing the enantioselectivity of the reaction, was developed. Experimental studies of both rate and enantioselectivity were used in order to support the computational results.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-89926 (URN)10.1021/ja9906610 (DOI)
    Available from: 2002-05-17 Created: 2002-05-17 Last updated: 2017-12-14Bibliographically approved
    2. Evidence for Concerted Proton and Hydride Transfer in the Ru(cymene)(amino alcohol)-Catalyzed Transfer Hydrogenation
    Open this publication in new window or tab >>Evidence for Concerted Proton and Hydride Transfer in the Ru(cymene)(amino alcohol)-Catalyzed Transfer Hydrogenation
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-89927 (URN)
    Available from: 2002-05-17 Created: 2002-05-17 Last updated: 2010-01-13Bibliographically approved
    3. New Expidient Route to Both Enantiomers of Nonproteinogenic Amino Acid Derivatives from the Unsaturated 2-Aza-bicyclo Moiety. D. A
    Open this publication in new window or tab >>New Expidient Route to Both Enantiomers of Nonproteinogenic Amino Acid Derivatives from the Unsaturated 2-Aza-bicyclo Moiety. D. A
    Show others...
    1999 In: J. Org. Chem., Vol. 64, p. 2276-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-89928 (URN)
    Available from: 2002-05-17 Created: 2002-05-17Bibliographically approved
    4. 2-Azanorbornyl alcohols: Very efficient Ligands for Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of Aromatic Ketones. D. A
    Open this publication in new window or tab >>2-Azanorbornyl alcohols: Very efficient Ligands for Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation of Aromatic Ketones. D. A
    Show others...
    1999 In: J. Org. Chem., Vol. 65, p. 3116-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-89929 (URN)
    Available from: 2002-05-17 Created: 2002-05-17Bibliographically approved
    5. Highly Diastereoselective Reaction of 2-Azanorbornyl Enolates with Electrophiles. D. A
    Open this publication in new window or tab >>Highly Diastereoselective Reaction of 2-Azanorbornyl Enolates with Electrophiles. D. A
    1999 In: Org. Lett., Vol. 1, p. 1595-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-89930 (URN)
    Available from: 2002-05-17 Created: 2002-05-17Bibliographically approved
    6. Remote Dipole Effects as a Means to Accelerate Ru(Amino alcohol)-Catalyzed Transfer Hydrogenations of Ketones.
    Open this publication in new window or tab >>Remote Dipole Effects as a Means to Accelerate Ru(Amino alcohol)-Catalyzed Transfer Hydrogenations of Ketones.
    Show others...
    2001 In: Chem. Eur. J, Vol. 7, p. 1431-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-89931 (URN)
    Available from: 2002-05-17 Created: 2002-05-17Bibliographically approved
  • 15.
    Roth, Peter
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Asymmetric transfer hydrogenation of aromatic ketones and azirines with NH-ligands2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Ru(arene)[(1S, 3R, 4R)-3-(Hydroxymethyl)-2-azabicyclo[2.2.1]heptane catalyst was optimized as ligand in the asymmetric transfer hydrogenation of ketones and resulted in increased activity and enantioselectivity of the catalyst. Dioxolane substitution at the rear end of the amino alcohol ligand and introduction of a (R)-methyl substituent yielded a catalyst that reduced acetophenone in 96% enantiomeric excess in 90 minutes with a substrate to catalyst molar ratio of 5000. A diversity of substituted aromatic ketones was reduced with excellent rate and enantioselectivity. Based on experimental and computational results, a study of the origin of the enantioselectivity was conducted. A combination of electrostatic, steric, dispersion forces and solvation effects was suggested to be the cause of the stereo discrimination. A set of amino sulfides built upon the 2-azabicyclo and the cyclohexane structures were prepared and tested as ligands in the enantioselective transfer hydrogenation of acetophenone with [IrCl(COD)]2 as metal precursor. With this type of catalysts, the reaction rates were good but the enantioselectivity unsatisfactory with 70% as the highest obtained enantiomeric excess. The first enantioselective reduction of aromatic 2H-azirines was accomplished by using the asymmetric transfer hydrogenation protocol. Aromatic azirines were reduced to yield chiral aziridines with up to 72% enantiomeric excess and good yields. The enantioselectivity and reactivity of the reaction were strongly influenced by substituents on the aromatic and aliphatic moiety of the substrate.

  • 16.
    Ryberg, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Concerted or Stepwise?: β-Elimination, Nucleophilic Substitution, Copper Catalysed Aziridination and Ruthenium Catalysed Transfer Hydrogenation Studied by Kinetic Isotope Effects and Linear Free-Energy Relationships2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the use of kinetic isotope effects, linear free energy relationships and stereochamical studies to distinguish between different mechanistic alternatives and to obtain information about transition state structure.

    In the first part fluorine and deuterium kinetic isotope effects were determined for the base promoted HF elimination from 4-fluoro-4-(4’-nitrophenyl)butane-2-on. During this work a new method for the determination of fluorine kinetic isotope effects was developed. The results from the study demonstrates that the reaction proceeds via an E1cBip mechanism.

    In the second part the transition state structure for the SN2 reaction between ethyl chloride and cyanide ion in DMSO was studied. Kinetic isotope effects for six different positions in the reacting system, both in cyanide and ethyl chloride, were determined. The experimental isotope effects were then compared with the theoretically predicted isotope effects.

    The third part describes the use of Hammett type free-energy relationships and stereochemical evidence to study the mechanism of the copper catalysed alkene aziridination. The results from the study support a model that involves the simultaneous presence of two different copper nitrene intermediates. One which reacts non-stereospecifically via a radical intermediate and one which reacts stereospecifically via a concerted mechanism.

    In the fourth part a mechanistic study of the Ru(aminoalcohol) catalysed transfer hydrogenation of acetophenone in isopropanol is described. Kinetic isotope effects were determined for both proton and hydride transfer. The observation of significant primary deuterium kinetic isotope effects for both proton and hydride transfer support a mechanism where the proton and hydride are transferred simultaneously in a concerted mechanism.

  • 17.
    Shanks, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Al-Maharik, Nawaf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Malmström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Engman, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Eriksson, Petter
    Stenberg, Bengt
    Reitberger, Torbjörn
    Improved Antioxidant Formulations for Polymeric Materials: Synergistic Protective Effects in Combinations of Organotellurium Compounds with Conventional Phenolic Antioxidants or Thiols2003In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 81, no 2, p. 261-271Article in journal (Refereed)
    Abstract [en]

    As judged by differential scanning calorimetry experiments at 190 °C and chemiluminescence measurements at 150 °C, addition of 0.10–0.30 wt.% of certain organotellurium compounds to polypropylene caused a notable protection against oxidation of the material. The best stabilizers (diaryl telluride 3 and alkyl aryl telluride 4), offered a similar degree of protection as commercial stabilizer formulations comprising a mixture of Irganox® 1010 and Irgafos® 168 (0.1 wt.% of each). The protective effect of the organotelluriums was substantially improved in combinations with sterically hindered phenols or thiols. The protection was often much better than the added effects of the individual components and, thus, can be considered as synergistic. Evaluation of a series of stabilizers where tellurium had been exchanged for selenium and sulfur (compounds 2) showed that the synergistic protective effect was unique for tellurium.

  • 18.
    Trifonova, Anna
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Synthesis of Novel Chiral Bicyclic Ligands and their Application in Iridium-Catalyzed Reactions2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The synthesis of 2-aza-norborane derivatives is presented. The use of these compounds in preparation of Ir catalysts for asymmetric hydrogenations is described. The evaluation and optimization of the catalysts as well as the mechanistic aspects of the catalytic process are discussed.

    The use of non-activated iminodieniphiles in stereoselective aza-Diels-Alder reaction has expanded the scope of the reaction and provided a convenient root for preparation of 2-aza-norboranes, analogues of which were developed into novel bicyclic 2-aza-norbornyl-oxazoline ligands for Ir-catalyzed asymmetric transfer hydrogenations. Using ths Ir complexes acetophenone was hydrogenated in 79% ee.

    2-Aza-norbornyl-oxazolines were also developed into novel N,P-ligands. Resulting phosphine-oxazolines were evaluated in Ir-catalyzed asymmetric hydrogenation of structurally diverse imines and olefins.

    Optimization of ligands was performed through: 1) Alteration of the stereoconfiguration at the 5’-position as well as variation of the size and geometry of the substituents at this position; 2) Screening through various phosphine substituents of the ligand. Both directions of optimization reflect on the influence of the ligands’ sterik bulk on stereoselectivity of catalytic process. High performance catalysts were developed for both transformations allowing asymmetric hydrogenation of imines with 92% ee and asymmetric hydrogenation of olefins with 99% ee.

    Possible mechanisms for these transformations were suggested based on computational studies. Selectivity model for rationalization of results of Ir-catalyzed olefin hydrogenation also was designed.

    List of papers
    1. The use of nonactivated iminodienophiles in the stereoselective aza-Diels-Alder reaction
    Open this publication in new window or tab >>The use of nonactivated iminodienophiles in the stereoselective aza-Diels-Alder reaction
    2004 In: Tetrahedron: Asymmetry, ISSN 0957-4166, Vol. 15, no 3, p. 445-452Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93021 (URN)
    Available from: 2005-05-04 Created: 2005-05-04Bibliographically approved
    2. Development of a new class of (1S,3R,4R)-2-azabicyclo[2.2.1]heptane-oxazoline ligands and their application in asymmetric transfer hydrogenation
    Open this publication in new window or tab >>Development of a new class of (1S,3R,4R)-2-azabicyclo[2.2.1]heptane-oxazoline ligands and their application in asymmetric transfer hydrogenation
    2004 In: Tetrahedron, ISSN 0040-4020, Vol. 60, no 15, p. 3393-3403Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93022 (URN)
    Available from: 2005-05-04 Created: 2005-05-04Bibliographically approved
    3. Application of Phosphine-Oxazoline Ligands in Ir-Catalyzed Asymmetric Hydrogenation of Acyclic Aromatic N-Arylimines
    Open this publication in new window or tab >>Application of Phosphine-Oxazoline Ligands in Ir-Catalyzed Asymmetric Hydrogenation of Acyclic Aromatic N-Arylimines
    2004 In: Organic Letters, ISSN 1523-7060, Vol. 6, no 21, p. 3825-3837Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-93023 (URN)
    Available from: 2005-05-04 Created: 2005-05-04Bibliographically approved
    4. Asymmetric Hydrogenation of Imines and Olefins Using Phosphine-oxazoline Iridium Complexes as Catalysts
    Open this publication in new window or tab >>Asymmetric Hydrogenation of Imines and Olefins Using Phosphine-oxazoline Iridium Complexes as Catalysts
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-93024 (URN)
    Available from: 2005-05-04 Created: 2005-05-04 Last updated: 2010-01-13Bibliographically approved
  • 19.
    Trifonova, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Andersson, Pher G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    The use of nonactivated iminodienophiles in the stereoselective aza-Diels-Alder reaction2004In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 15, no 3, p. 445-452Article in journal (Refereed)
    Abstract [en]

    This paper describes the preparation of nitrogen-containing bicycles by the aza-Diels–Alderreaction ofnonactivatediminodienophiles and cyclopentadiene. Readily available starting materials such as (S)-(−)-lactate and l-amino acids were used for the preparation of chiral aldehydes with high enantiomeric excess. The improved oxidation procedure by Dess–Martin periodinane was employed for the synthesis of l-alanine derived phthalimide protected aldehyde 14, which was difficult to obtain in high enantiomeric excess by other methods. The influence of different Lewis acids on the stereoselectivity of the aza-Diels–Alderreactionwas also investigated: It was found that the use of a combination of BF3·Et2O and TFA in the cycloaddition leads to complete racemization of the imine prepared from 14 whereas the use of TiCl4 gives the cycloaddition products 17a and 17b with high enantioselectivity (90%).

  • 20.
    Trifonova, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Diesen, Jarle S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Chapman, Christopher J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Andersson, Pher G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Application of Phosphine-Oxazoline Ligands in Ir-Catalyzed Asymmetric Hydrogenation of Acyclic Aromatic N-Arylimines2004In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 6, no 21, p. 3825-3827Article in journal (Refereed)
  • 21.
    Trifonova, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Källström, Klas E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Andersson, Pher G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Development of a new class of (1S,3R,4R)-2-azabicyclo[2.2.1]heptane-oxazoline ligands and their application in asymmetric transfer hydrogenation2004In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 60, no 15, p. 3393-3403Article in journal (Refereed)
  • 22.
    Zeng, Xiaofeng
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Mechanisms for Solvolytic Elimination and Substitution Reactions Involving Short-lived Carbocation Intermediates2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Solvolysis reactions of a range of tertiary substrates in largely aqueous solvents were studied in such respects as β-deuterium kinetic isotope effects, linear free energy relationships and stereochemistry.

    Solvolysis of the fluorene derivatives 9-methyl–9-(2´-X-2´-propyl)fluorene (1-X, X = Cl, Br, OOCCF3) involves a very short-lived carbocation intermediate. The fraction of alkene is increased by addition of general bases, which can be expressed by a Brφnsted parameter β = 0.07. The kinetic deuterium isotope effects vary with solvent composition in a way which is not consistent with a common carbocation intermediate which has time to choose between dehydronation and addition of a solvent water molecule.

    In the absence of bases, the reaction of 4-chloro-4-(4´-nitrophenyl)pentan-2-one (2-Cl) proceeds through a short-lived carbocation intermediate yielding 4-(4´-nitrophenyl)-2-oxopent-4-ene (2-t-ne)as the main elimination product. Addition of acetate ion and other weak bases results in the base-promoted E2 (or E1cb) reaction to give (E)-4-(4´-nitrophenyl)-2-oxopent-3-ene (2-E-ne) and (Z)-4-(4´-nitrophenyl)-2-oxopent-3-ene(2-Z-ne). There is no evidence for a water-promoted E2 (or E1cb) reaction.

    The stereochemistry studies of elimination from (R,S and S,R)-[1-(3´-fluoro)phenyl-2-methyl]cyclopentyl-p-nitrobenzoate (3-PNB) and its (R,R and S,S)isomer 3´-PNB and (R,S and S,R)-[1´-(3´´-fluoro)phenyl-2´-methylcyclopentyl]-2,2,2-trifluoroacetate(3-OOCCF3) exclude the concerted pericyclic elimination mechanism for formation of the alkene 1-(3´-fluoro)phenyl-2-methylcyclopentene(3-m-ne). The effects of added thiocyanate ion and halide ions on the solvolysis reaction are discussed.

    Mass spectrometry analysis showed complete incorporation of the labeled oxygen from solvent water into the product 2-hydroxy-2-phenyl-3-butene (4-OH), confirming that it is the tertiary carbon-oxygen bond that is broken in the acid-catalyzed solvolysis of 2-methoxy-2-phenyl-3-butene (4-OMe). The mechanism for the dominant formation of the less stable 4-OH is discussed.

1 - 22 of 22
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