| 1. |
- Allared, Fredrik, 1974-
(författare)
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Synthesis of new building blocks for conjugated oligomers
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the synthesis of new organicmaterials for electronic applications. Several new ring-formingmethods are employed to construct sulphur heterocycles: Tandemelectrophilic aromatic substitution and acid-catalyzedtransetherification of methoxythiophene, double electrophilicaromatic substitutions with ethane-1, 2-disulphenyl chloride,and also, the reaction of dienes with sulphur dichloride. Twonew condensed thiophenes have been incorporated in end-cappedoligothiophenes. An improvement of the synthesis of [3,2-b:2’, 3-d]thiophene is reported, with some attempts toincorporate it in oligomers. A synthesis of substitutednaphthalenes is also described. A new method of producingdisubstituted thiophenes from substituted butadienes anssulphur dichloride is employed in a new route to 3, 4-ethylenedioxythiophene, a very important monomer for conductingpolymers. Keywords :Organic Semiconductors, Thiophenes,Heterocyclic Synthesis, Dithienothiophene, Naphthalene,Ethylenedioxythiophene
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| 2. |
- Andersson, Fredrik
(författare)
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1. Asymmetric aldol and alkylation reactions using pyrrolidine-based chiral auxiliaries 2. Syntheses of pine sawfly pheromone precursors and structurally related compounds
- 2002
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the syntheses of the 1-propionylatedauxiliaries (S)-(− )-2-(pyrrolidin-2-yl)propan-2-ol and (S)-(− )-2-(1-methoxy-1-methylethyl)pyrrolidine andtheir use in asymmetric aldol and alkylation reactions. Thesynthesis of 1-propionylated (2S,4R) 2-{4-[(tert-butyldimethylsilyl)oxy]pyrrolidin-2-yl}propan-2-olis also described. The effects on the stereoselectivity, byvariations of solvent, temperature, Lewis acids as additive aswell as the amount of additive are studied. None of thepropionylated auxiliaries exhibited remarkable selectivity foreither diastereomer in aldol reactions with benzaldehyde. Bestresults were obtained with SnCl2as additive giving asyn:antiratio up to 73:27, and Cp2ZrCl2and Cp2TiCl2giving a reversedsyn:antiratio up to 27:73 for the former auxiliary. Highselectivity for onesynand oneantidiastereomer were obtained with TMS-Cl as anadditive. The latter propionylated auxiliary was less selectivethan the former. Reversal insyn/antiselectivity was observed when Cp2ZrCl2and Cp2TiCl2was used with asyn:antiratio = 68:32 and 33:67. In alkylation reactions,the former propionylated auxiliary showed lower and similarselectivity with benzyl bromide andn-butyl iodide, compared with the literature. Enhancedselectivity was obtained in the benzylation reactions (78% and84% diastereomeric excess), with LiCl and Cp2ZrCl2as additives. Cp2ZrCl2and Cp2TiCl2resulted in lower selectivity in butylationreactions. High selectivity was obtained for the latterpropionylated auxiliary and with a reversal in selectivity,compared with the former. Benzylation reactions resulted in82-98% diastereomeric excess, with the highest selectivity ofCp2ZrCl2as additive. In butylation reactions the use ofLiCl resulted in highest diastereomeric excess (94%).The second part of the thesis describes the syntheses ofcompounds related to sex pheromones of pine sawflies. (2S,6R)-(− )-2,6-Dimethyl-1-octanol, a building blockin the synthesis of the sex pheromone of the pine sawflyMicrodiprion pallipesin high stereoisomeric purity wasprepared from the optically pure (S)-citronellal. Lipase-catalysed (Amano PS and Im-CRL)kinetic separations, based on selective acylation andesterification of (2R/S,6R)-2,6-dimethyl-1-octanol and the corresponding acidwere the key steps in this sequence. The alcohol precursors tosex pheromones ofDiprion nipponica,Macrodiprion nemoralisandMicrodiprion pallipeswere synthesised as racemicmixtures in moderate yields. Stereoisomeric mixtures of severalmethyl-branched long-chain 2-alkanols, structurally related tosex pheromone alcohol precursors of pine sawfly species, werealso synthesised in moderate yields. The key reaction in thesyntheses was the ring opening ofγ-butyrolactonesusing different alkyl lithiums as nucleophiles.Keywords: Chiral auxiliary, Stereoselectivity, Lewisacid, Aldol, Alkylation, Sex pheromone, Pine sawfly, Lipase,Synthesis, Diprion nipponica, Macrodiprion nemoralis,Microdiprion pallipes
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| 3. |
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| 4. |
- Belda de Lama, Oscar, 1976-
(författare)
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Bispyridylamides as ligands in asymmetric catalysis
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the preparation and use of chiralbispyridylamides as ligands in metal-catalyzed asymmetricreactions. The compounds were prepared by amide formation usingdifferent coupling reagents. Bispyridylamides havingsubstituents in the 4- or 6- positions of the pyridine ringswere prepared by functional group interconversion of the 4- or6- halopyridine derivatives. These synthetic approaches provedto be useful for various types of chiral backbones. Pseudo C2-symmetric bispyridylamides were also synthesizedby means of stepwise amide formation. The compounds were used as ligands in themicrowave-accelerated Mocatalyzed asymmetric allylic alkylationreaction. Ligands having ð-donating substituents in the4-positions of the pyridine rings gave rise to products withhigher branched to linear ratio. The catalytic reaction, whichproved to be rather general for allylic carbonates with anaromatic substituent, was used as the key step in thepreparation of (R)-baclofen. The Mo-bispyridylamide catalystprecursor was studied by NMR spectroscopy. Bispyridylamide complexes of metal alkoxides were alsoevaluated in the asymmetric addition of cyanide to aldehydesand the metal complexes involved were studied by NMRspectroscopy and X-ray crystallography. Chiral diamines wereused as additives to study the ring opening of cyclohexeneoxide with azide, catalyzed by Zr(IV)-bispyridylamidecomplexes. Various bispyridylamides were attached to solid supports oforganic or inorganic nature. The solid-supported ligands wereused in Mo-catalyzed asymmetric allylic alkylation reactionsand in the asymmetric addition of cyanide to benzaldehyde. Keywords:asymmetric catalysis, chiral ligand, pyridine,amide, allylic alkylation, enantioselective, cyanation,ring-opening, chiral Lewis acid.
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| 6. |
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| 7. |
- Blid, Jan, 1970-
(författare)
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Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis describes the realization of an asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines. It is divided into two parts; the first part deals with the development of a Lewis acid-mediated [2,3]-sigmatropic rearrangement and the second the asymmetric version thereof. Quaternization of an -amino amide with various Lewis acids established BBr3 and BF3 to be the most appropriate ones. Various allylic amines were subsequently rearranged into the corresponding homoallylic amines in good to excellent syn-diastereoselectivities, revealing the endo-transition state to be the preferred pathway. The structures of the intermediate Lewis acid-amine complexes were confirmed by NMR spectroscopy studies and DFT calculations. Based on this investigation a chiral diazaborolidine was chosen as Lewis acid and was shown to efficiently promote the asymmetric [2,3]-sigmatropic rearrangement furnishing homoallylic amines in good yields and excellent enantiomeric excesses. In contrast to the achiral rearrangement mediated by BBr3 and BF3, the asymmetric version gave the opposite major diastereomer, revealing a preference for the exo-transition state in the asymmetric rearrangement. To account for the observed selectivities, a kinetic and thermodynamic pathway was presented. On the basis of a deuterium exchange experiment on a rearranged Lewis acid-amine complex and an NMR spectroscopic investigation, the kinetic pathway was shown to be favored.
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| 8. |
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| 9. |
- Bremberg, Ulf
(författare)
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Asymmetric catalysis : ligand design and microwave acceleration
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals partly with the design and synthesis ofligands for use in asymmetric catalysis, and partly with theapplication of microwave heating on metal-based asymmetriccatalytic reactions.Enantiomerically pure pyridyl alcohols and bipyridylalcohols were synthesized from the chiral pool for future usein asymmetric catalysis. Lithiated pyridines were reacted withseveral chiral electrophiles, yielding diastereomeric mixturesthat could be separated without the use of resolutiontechniques.New pyridino- and quinolinooxazolines were synthesized andtested in palladium-catalyzed asymmetric allylation using1,3-diphenyl-2-propenyl acetate and dimethyl malonate. Theconformational preferences of the ligands in palladiumcomplexes were studied with crystallography, 2D-NMR techniquesand DFT calculations. Conclusions about how the chirality wastransferred from the ligand to the substrate could be drawnfrom the conformational analysis.The effect of heating Pd- and Mo-catalyzed asymmetricallylic substitution reactions was investigated with oil bathheating and microwave irradiation. With a few exceptions,ligands with high room temperature selectivity were shown toretain their selectivity on heating. Reaction rates, catalyststability and product selectivities of microwave-heatedreactions were compared with those of reactions performed inoil bath.Palladium-catalyzed asymmetric allylation was studied withseveral ligand types, allylic substrates and nucleophiles. Someof the experimental procedures had to be adapted to microwaveheating conditions.The procedure for asymmetric allylation catalyzed bybispyridylamide molybdenum complexes was developed into aone-pot microwave-mediated reaction. With microwaves, Mo(CO)6could be used as an easily-handled metal sourceand inert conditions could be omitted. Derivatives of thebispyridylamide ligandswere synthesized and tested withmolybdenum as catalysts to investigate the effects ofsubstituents on the pyridine ring.Keywords: ligand, asymmetric catalysis, pyridylalcohols, oxazolines, conformational study, Pd-allyl, fastchemistry, microwave chemistry, Mo-allyl, bispyridylamides.
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| 10. |
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