Ändra sökning
Avgränsa sökresultatet
1 - 29 av 29
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1. Bourguignon, J.
    et al.
    Bremberg, U.
    Dupas, G.
    Hallman, K.
    Hagberg, L.
    Hortala, L.
    Levacher, V.
    Lutsenko, S.
    Macedo, E.
    Moberg, Christina
    KTH, Tidigare Institutioner                               , Kemi.
    Queguiner, G.
    Rahm, F.
    Chiral ditopic receptors. Application to palladium-catalyzed allylic alkylation2003Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 59, nr 48, s. 9583-9589Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chiral pyridinooxazoline, quinolinooxazoline, bis(oxazolino)pyridine (pybox), and bisoxazoline (box) derivatives containing crown ether residues were prepared. Some of the ligands were assessed in substrate binding studies and in palladium catalyzed allylic alkylations.

  • 2. Cai, Shengyun
    et al.
    Hu, Xiaohao
    Tian, Guojian
    Zhou, Haitao
    Chen, Wei
    Huang, Jinhai
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Su, Jianhua
    Photo-stable substituted dihydroindolo[2,3-b]carbazole-based organic dyes: tuning the photovoltaic properties by optimizing the pi structure for panchromatic DSSCs2014Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, nr 43, s. 8122-8128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three dihydroindolo[2,3-b]carbazole (DDC) donor based organic dyes (DDC6-DDC8) with long conjugated systems were successfully synthesized and characterized by optical, electrochemical, computational analysis, and photovoltaic methods. It was found that the elongated pi system as well as the high molar extinction coefficients (4.2-5.3 M-1 cm(-1)) sufficiently reinforced the light harvesting ability with the IPCE response of one dye DDC8 extended to 850 nm, which resulted in large J(sc) of these dyes based devices (high as 16.41 mA cm(-2)). The attached alkyl chains suppress the dark current to some extent, resulting the DDC6 and DDC7 devices in high V-oc, while DDC8 displayed low V-oc, because BTD in DDC8 could attract the iodine ion, which could accelerate the charge recombination. Among the three dyes, DDC7 displayed the best performance with an eta value 6.53% under 4 mu m thick scattering layer (condition 1+1), which was boosted to 7.49% under 8 mu m thick scattering layer (condition 1+2). The photo-stability measurements indicated that all the three dyes are fairly photo-stable.

  • 3. Engstrom, Karin
    et al.
    Vallin, Michaela
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Backvall, Jan-E.
    Kinetic resolution of diarylmethanols using a mutated variant of lipase CALB2012Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr 37, s. 7613-7618Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An enzymatic kinetic resolution of diarylmethanols via acylation has been developed. This was achieved by the use of a mutated variant of CALB that accepts larger substrates compared to the wild type. By the use of diarylmethanols with two differently sized aryl groups, enantioselective transformations were achieved. A larger size-difference led to a higher enantioselectivity. In addition, substrates with electronically different aryl groups, such as phenyl and pyridyl, also gave an enantioselective reaction. The highest E value was observed with a substrate where steric and electronic effects were combined.

  • 4. Gao, Yan
    et al.
    Liu, Jianhui
    Wang, Mei
    Na, Yong
    Akermark, Bjorn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Synthesis and characterization of manganese and copper corrole xanthene complexes as catalysts for water oxidation2007Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 63, nr 9, s. 1987-1994Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two corrole xanthene ligands and four corresponding Mn-IV and Cu-III complexes have been synthesized and spectroscopically characterized. This kind of complexes, comprising of xanthene and corrole linked by an amide bond, were designed as bio-inspired models for the oxygen evolving complex (OEC) in Photosystem II. We find that both manganese complexes 4a and 5a have efficiency on catalyzing oxygen evolution at low potential (about 0.80 V) by electrochemical method, which is a significant progress in the study of dioxygen formation.

  • 5. Hammer, Stephan C.
    et al.
    Dominicus, Joerg M.
    Syren, Per-Olof
    Universitaet Stuttgart, Germany.
    Nestl, Bettina M.
    Hauer, Bernhard
    Stereoselective Friedel-Crafts alkylation catalyzed by squalene hopene cyclases2012Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr Copyright (C) 2013 American Chemical Society (ACS). All Rights Reserved., s. 7624-7629Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In org. synthesis the Friedel-Crafts alkylation is of eminent importance, as it is a key reaction in many synthetic routes. A general access to enzymic Friedel-Crafts alkylations would be very beneficial due to the high selectivity of biocatalysts. We used designed polyprenyl Ph ethers to specifically address this reaction by using squalene hopene cyclases as catalysts. Polycyclic products with arom. rings constituting important biol. active compds. were obtained. Our results demonstrate that squalene hopene cyclases can be utilized for Friedel-Crafts alkylations and reveal the potential of these enzymes for chiral Bronsted acid catalysis.

  • 6. Hao, Yan
    et al.
    Yang, Xichuan
    Cong, Jiayan
    Hagfeldt, Anders
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD. Dalian Univ Technol, China.
    Engineering of highly efficient tetrahydroquinoline sensitizers for dye-sensitized solar cells2012Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr 2, s. 552-558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four novel tetrahydroquinoline dyes by inserting isophorone and/or thiophene moieties as pi bridge between the electron donating unit of substituted tetrahydroquinoline and the electron withdrawing unit of cyano carboxylic acid have been synthesized and successfully applied to dye-sensitized solar cells. Among them, DSCs sensitized by HYTIC, which shows the simplest molecular structure, exhibit improved efficiency of 7.0%. This by now is the highest efficiency for the reported tetrahydroquinoline sensitizers and comparable to the performance of N719-sensitized solar cells under the conditions employed here. (C) 2011 Elsevier Ltd. All rights reserved.

  • 7.
    Hellberg, Jonas
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Dahlstedt, Emma
    KTH, Tidigare Institutioner, Kemi.
    Pelcman, Margit
    KTH, Tidigare Institutioner, Kemi.
    Synthesis of annulated dioxins as electron-rich donors for cation radical salts2004Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 60, nr 40, s. 8899-8912Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The synthesis of a series of new alkoxylated linearly annulated dioxins is described together with their cyclic voltammetric behavior and some preliminary result on their ability to form cation radical salts. Of these dioxins, seven (8, 12, 19, 21, 27, 33, 34) are the first representatives of entirely new heterocyclic systems. Dioxins 8, 21, 22 and 27 gave good quality cation radical salts upon electrocrystallization.

  • 8.
    Hertzberg, Robin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Widyan, Khalid
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Heid, Berenice
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Enantioenriched ω-bromocyanohydrin derivatives. Improved selectivity by combination of two chiral catalysts2012Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr 37, s. 7680-7684Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Highly enantioenriched (R)-4-bromo-1-cyanobutyl acetate and (R)-5-bromo-1-cyanopentyl acetate were prepared by acetylcyanation of 4-bromobutanal and 5-bromopentanal, respectively, catalyzed by (S,S)-[(4,6-bis(t-butyl)salen)Ti(Ό-O)] 2 and triethylamine followed by enzymatic hydrolysis of the minor enantiomer. A cyclic procedure employing the same two chiral catalysts provided inferior results due to a slowly reached steady state and, in reactions with the former substrate, to ring-closure of the free cyanohydrin formed as an intermediate in the reaction. Hydrolysis of the acylated cyanohydrins followed by AgClO 4-promoted cyclization provided (R)-2-cyanotetrahydrofuran and (R)-2-cyanotetrahydropyran in essentially enantiopure form.

  • 9.
    Jönsson, Christina
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Lundgren, Stina
    KTH, Tidigare Institutioner, Kemi.
    Haswell, S. J.
    Department of Chemistry, University of Hull.
    Moberg, Christina
    KTH, Tidigare Institutioner, Kemi.
    Asymmetric Catalysis in a Micro Reactor: Ce, Yb and Lu Catalysed Enantioselective Addition of Trimethylsilyl Cyanide to Benzaldehyde2004Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 60, nr 46, s. 10515-10520Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A T-shaped micro reactor was used for the optimisation of reaction conditions for the enantioselective silyleyanation of benzaldehyde catalysed by lanthanide-pybox complexes. Compared to a conventional batch procedure, higher conversion was observed within shorter reaction time. The micro reactor process involving Lu(III) afforded essentially the same enantioselectivity as the batch process (73 vs 76% ee), whereas the enantioselectivity was lower in the micro reactor for catalysts containing Yb(III) (53 compared to 72%). Ce(III) provided very low selectivity in both types of processes (1 and 11 % ee, respectively). A study of the effect of additives showed that the enantioselectivity in the Yb catalysed reaction performed in the micro reactor could be increased to 66%, whereas only a minor improvement, to 78% ee, was observed in the reaction with Lu.

  • 10.
    Laglet, Abraham
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Wellmar, Ulf
    Bemm, Ulf
    Latypov, Nikolaj V.
    Bergman, Jan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Synthesis and Reactions of 1,1-dinitro-2,2-dinitroethylene1998Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Tetrahedron, Vol. 54, nr 38, s. 11525-11536Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low temperature nitrations of 2-methylimidazole gave in addition to the known 2-methyl-5(4)-nitroimidazole (1), 2-(dinitromethylene)-5,5-dinitro-4-imidazolidinone (3) and parabanic acid (2). The tetranitro compound 3 was also obtained by nitration of 2-methyl-4,5-dihydro-(1H)-5-imidazolone (8). Thermal decomposition of 3 gave 2-(dinitromethylene)-4,5-imidazolidinedione (4) which also was the product from nitration of the new compound 2-methoxy-2-methyl-4,5-imidazolidinedione. Treatment of 4 with aqueous ammonia gave the previously unknown 1,1-diamino-2,2-dinitroethylene (5). The physical properties and chemical behaviour of (5) are described.

  • 11.
    Larsson, Michael
    et al.
    Mittuniversitetet.
    Galandrin, Elodie
    Mittuniversitetet.
    Högberg, Hans-Erik
    Mittuniversitetet.
    Diastereoselective addition of organozinc reagents to 2-alkyl-3-(arylsulfanyl)propanals2004Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 60, nr 47, s. 10659-10669Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The preparation of compounds incorporating the 3-hydroxy-2-methyl-1-alkyl moiety of high diastereomeric purity is described. Such compounds can serve as potential building blocks for the preparation of several kinds of natural products. Diastereoselective synthesis of two potential pine sawfly pheromone components, one the pure racemic threo-isomer of 3-methylpentadecan-2-ol and the other the racemic erythro-isomer of 3-methyltridecan-2-ol are described. The diastereoselective addition of R2Zn (R = Me, Et and n-Bu) to several 2-alkyl-3-(arylsulfanyl)propanals in the presence of a Lewis acid and CH2Cl2 as solvent was studied. An excellent diastereomeric ratio (95/5 anti-Cram/Cram) was obtained with 2-[(phenylsulfanyl)methyl]pentanal, 2-[(phenylsulfanyl)methyl]decanal and 2-[(phenylsulfanyl)methyl]dodecanal and Me2Zn in the presence of TiCl4.

  • 12.
    Larsson, Michael
    et al.
    Mittuniversitetet i Sundsvall.
    Högberg, Hans-Erik
    Mittuniversitetet.
    Diastereoselective addition of methylmetal reagents to 2-methylaldehydes.2001Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 57, nr 35, s. 7541-7548Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The preparation of compounds incorporating the 3-hydroxy-2-methyl-1-butyl moiety of high diastereomeric purity is described. These compounds can serve as potential building blocks for the preparation of several kinds of natural products. The diastereoselective addition of a number of methylmetal derivatives to three 3-substituted 2-methylaldehydes in various solvents was studied. An excellent diastereomeric. ratio (95:5 anti-Cram/Crain) was obtained with 2-methyl-3-(phenylsulfanyl)propanal (5) and Me2Zn in the presence of TiCl4.

  • 13.
    Lega, Matteo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH Sch Chem Sci & Engn, Dept Chem, SE-10044 Stockholm, Sweden..
    Figliolia, Rosario
    Univ Naples Federico II, Dipartimento Sci Chim, I-80126 Naples, Italy..
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH Sch Chem Sci & Engn, Dept Chem, SE-10044 Stockholm, Sweden..
    Ruffo, Francesco
    Univ Naples Federico II, Dipartimento Sci Chim, I-80126 Naples, Italy..
    Erratum to: Expanding the scope of the elpaN-type library: glucose-derived bis(pyridine-2-carboxamide) ligands (elpaN-Py) for molybdenum-catalyzed asymmetric allylic alkylations2013Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 69, nr 25, s. 5259-5259Artikel i tidskrift (Refereegranskat)
  • 14.
    Lega, Matteo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Figliolia, Rosario
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Ruffo, Francesco
    Expanding the scope of the elpaN-type library: glucose-derived bis(pyridine-2-carboxamide) ligands (elpaN-Py) for molybdenum-catalyzed asymmetric allylic alkylations2013Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 69, nr 20, s. 4061-4065Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The elpaN-Py family of ligands, which represents a subset of the elpaN-type library based on a-glucose, is described. The ligands are structural analogs of the privileged bis(pyridine-2-carboxamides) derived from trans-1,2-diaminocyclohexane, and differ for the type of substitution in the coordinating functions present in positions 1 and 2. Their ability to induce high enantioselectivity in asymmetric allylic alkylations promoted by molybdenum under microwave irradiation has been successfully demonstrated, starting from both a linear (ee up to 99%) and a branched substrate (ee up to 96%). The multifunctional nature of the sugar scaffold was exploited for the preparation of a polar ligand, through deprotection of the hydroxyl groups in positions 3, 4 and 6. In this version, it was possible to verify the performance in catalysis in alternative solvents, such as ionic liquids and water.

  • 15. Lindquist, C.
    et al.
    Ersoy, O.
    Somfai, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Parallel synthesis of an indole-based library via an iterative Mannich reaction sequence2006Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 62, nr 14, s. 3439-3445Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A library of 1,3-disubstituted indoles has been prepared via an iterative Mannich reaction sequence. The first Mannich reaction with secondary amines and formaldehyde preferentially yields 3-aminomethyl indoles, while the second Mannich reaction introduces an additional aminomethyl group at the N1-position of the indole ring. A library of 25 substituted indoles has thus been prepared in moderate to good yields with purity.

  • 16. Liu, X. E.
    et al.
    Liu, J. H.
    Pan, J. X.
    Chen, R. K.
    Na, Y.
    Gao, W. M.
    Sun, Licheng C.
    A novel ruthenium(II) tris(bipyridine)-zinc porphyrin-rhenium carbonyl triad: synthesis and optical properties2006Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 62, nr 15, s. 3674-3680Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel ruthenium(II) tris(bipyridine)-zinc porphyrin-rhenium carbonyl triads and its free base porphyrin derivative were synthesized and characterized by H-1, C-13 NMR, UV-vis, mass-spectrometry and elemental analysis. The redox potentials of the two Compounds were measured and compared to their corresponding reference complexes. The fluorescence and transient absorption spectra of the two complexes revealed the features of two different pathways for possible photoinduced intramolectular electron transfer or energy transfer in the triads.

  • 17. Liu, X.
    et al.
    Liu, J. H.
    Jin, K.
    Yang, X. C.
    Peng, Q. J.
    Sun, Licheng C.
    Synthesis, characterization and some properties of amide-linked porphyrin-ruthenium(II) tris(bipyridine) complexes2005Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 61, nr 23, s. 5655-5662Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new molecular dyad, comprised of a zinc-porphyrin and a ruthenium(II) tris(bipyridine) complex linked through an amide bond has been synthesized and characterized by H-1, C-13 NMR, UV-vis, mass-spectrometry and elemental analysis. The electrochemistry as well as the steady-state emission properties were investigated. The redox behavior of the dyad exhibits a favorable reversible characteristic. Substantial quenching of porphyrin emission was found when the Q hand of 5 and 5-Zn was selectively photoexcited. This observation suggests a quenching mechanism with possible intramolecular electron transfer or energy transfer between the Ru(bpy)(3) moiety and the porphyrin free-base or Zn porphyrin moieties.

  • 18. Liu, Xien
    et al.
    Liu, Jianhui
    Pan, Jingxi
    Andersson, Samir
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Synthesis, electrochemical, and photophysical studies of multicomponent systems based on porphyrin and ruthenium(II) polypyridine complexes2007Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 63, nr 37, s. 9195-9205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two ruthenium tris-bipyridine functionalized porphyrins 4, 8 and their Zn derivatives 4-Zn, 8-Zn were designed, synthesized, and characterized. The redox potentials of these complexes as well as their corresponding monomeric reference porphyrin and ruthenium bipyridine complexes were also measured for comparison. Primary dynamic studies on the electron injection and backing recombination between these complexes and TiO2 nanoparticles were carried out by means of transient absorption spectroscopy. The results indicate that a long-lived charge separation state was obtained in these assemblies.

  • 19. Mesas-Sanchez, Laura
    et al.
    Diaz-Alvarez, Alba E.
    Koukal, Peter
    Dinér, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Uppsala University.
    Kinetic resolution of 2-hydroxy-2-aryl-ethylphosphonates by a non-enzymatic acylation catalyst2014Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, nr 24, s. 3807-3811Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optically pure hydroxyphosphonates are widely used as derivatizable compounds that can be incorporated into a variety of synthetic strategies for the preparation of other high value organic products. A non-enzymatic kinetic resolution procedure to obtain chiral 2-hydroxy-2-arylethylphosphonates from the easily available racemic counterparts is described. A range of 2-hydroxy-2-arylethylphosphonates was efficiently resolved employing a planar-chiral DMAP derived catalyst with good selectivities (up to S=68). The chiral hydroxyphosphonates were isolated in good yields and high enantiomeric excess (>94% ee).

  • 20. Mesas-Sánchez, Laura
    et al.
    Díaz-Álvarez, Alba Estrella
    Dinér, Peter
    Uppsala University.
    Non-enzymatic kinetic resolution of 1,2-azidoalcohols using a planar-chiral DMAP derivative catalyst2013Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 69, nr 2, s. 753-757Artikel i tidskrift (Refereegranskat)
  • 21. Olofsson, B.
    et al.
    Wijtmans, R.
    Somfai, Peter
    KTH, Tidigare Institutioner                               , Kemi.
    Synthesis of N-H vinylaziridines: a comparative study2002Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 58, nr 30, s. 5979-5982Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vinylaziridines are useful and versatile synthetic intermediates, as the relief of ring-strain provides a driving force for efficient ring-opening or ring-expansion reactions. Furthermore, the vinyl group can be derivatized into interesting functionalities. The ring-closure of vicinal amino alcohols constitutes a straightforward route to aziridines. Several methods exist for this transformation, although many cannot be applied to vinylaziridines due to their acid lability. This comparative study describes the most effective sequences for the formation of N-H vinylaziridines.

  • 22. Pettersson, Birgitta
    et al.
    Bergman, Jan
    Svensson, Per H.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Synthetic studies towards 1,5-benzodiazocines2013Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 69, nr 12, s. 2647-2654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anthranilonitrile reacted with phenylmagnesium bromide to yield a dianion, which when heated (similar to 120 degrees C) yielded the condensation product 2-(2-aminophenyl)-2,4-dipheny1-1,2-dihydroquinazoline 8. This heterocycle, when treated with palladium acetate, was converted into 6,12-diphenyldibenzo[b,f][1,5] diazocine 9. Methylmagnesium bromide and anthranilonitrile, under similar conditions directly gave a nitrogen-bridged diazocine, whose structure was determined by X-ray crystallography and also proven to be an analogue of Troger's base. Acid-induced condensation of 2-amino-3-methoxybenzaldehyde gave the trimeric product 45 rather than a dibenzo[b,f][1,5]diazocine.

  • 23. Ray, C. A.
    et al.
    Risberg, E.
    Somfai, Peter
    KTH, Tidigare Institutioner                               , Kemi.
    Diastereoselective Lewis acid-catalysed 4+2 cycloadditions of 3-alkyl-, 3-aryl- and 3-carboxyl-2H-azirines: a route to aziridine containing azabicyclo 4.1.0 heptanes and azatricyclo 2.2.1.0 nonanes2002Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 58, nr 30, s. 5983-5987Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    3-Substituted-2H-azirines have been employed as 2pi components in Lewis acid-catalysed hetero Diels-Alder reactions with a variety of diene systems. A series of Lewis acids were screened for catalytic behaviour in the reaction between Danishefsky's diene and 3-phenyl-2H-azirine to give the cycloaddition adduct, and in most cases elevated temperature were required to effect cycloaddition. A noteworthy exception was a BF3.Et2O-catalysed cycloaddition which proceeded in less than I h between -70degreesC and -60degreesC. The cycloadditions were found to proceed with endo selectivity providing a single diastereoisomeric product. Benzyl 2H-azirine-3-carboxylates were found to be activated by Lewis acids and participate in endo selective cycloadditions at -20degreesC.

  • 24. Risberg, E.
    et al.
    Fischer, A.
    Somfai, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Lewis acid-catalyzed asymmetric radical additions of trialkyl-boranes to (1R,2S,5R)-2-(1-methyl-1-phenylethyl)-5-methylcyclohexyl-2H-azirine-3-carboxylate2005Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 61, nr 35, s. 8443-8450Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The asymmetric addition of alkyl radicals to (IR,2S,5R)-2-(l-methyl-l-phenylethyl)-5-methylcyclohexyl-2H-azirine-3-carboxylate (1) yielding the corresponding 2-alkylaziridine-2-carboxylates has been investigated. High diastereoselectivities and good yields were obtained in the addition of primary alkyl radicals to azirine 1, while secondary radicals gave a lower dr. The influence of Lewis acids was also investigated, 10 mol% of CuCl were found to increase the dr.

  • 25.
    Slätt, Johnny
    et al.
    Unit for Organic Chemistry, Department of Biosciences, Karolinska Institute and Södertörn University College, Novum Research Park.
    Bergman, Jan.
    Unit for Organic Chemistry, Department of Biosciences, Karolinska Institute and Södertörn University College, Novum Research Park.
    Oxygenation of 2,3-dihydroindoles.2002Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 58, nr 45, s. 9187-9191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Indolines (2,3-dihydroindoles) and isatogens (3-oxo-3H-indole 1-oxides) have been prepd. in an efficient route starting from indoles substituted in position 2. Redn. of the 2-substituted indoles was performed with tin and hydrochloric acid to give racemic indolines, which were converted to isatogens by 3-chloroperoxybenzoic acid (m-CPBA). [on SciFinder(R)]

  • 26.
    Somfai, Peter
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Marchand, P.
    Torsell, S.
    Lindström, U. M.
    Asymmetric synthesis of (+)-1-deoxynojirimycin and (+)-castanospermine2003Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 59, nr 8, s. 1293-1299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Asymmetric total syntheses of (+)-1-deoxynojirimycin (1) and (+)-castanospermine (2) are described. Starting from diene 3, the required absolute stereochemistry is introduced by an asymmetric hydroxylation followed by epoxidation. An intramolecular cyclization of amine 17 gives access to the corresponding tetrasubstituted piperidine 18, which is a precursor to compounds 1 and 2. (+)-Deoxynojirimicyn (1) was obtained in 36% yield over 11 steps from diene 3, while (+)-castanospermine (2) was achieved in 13% after 19 steps from the same starting material.

  • 27. Ying, Weijiang
    et al.
    Zhang, Xiaoyu
    Li, Xin
    Wu, Wenjun
    Guo, Fuling
    Li, Jing
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Hua, Jianli
    Synthesis and photovoltaic properties of new [1,2,5]thiadiazolo[3,4-c]pyridine-based organic Broadly absorbing sensitizers for dye-sensitized solar cells2014Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, nr 25, s. 3901-3908Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, by introducing [1,2,5]thiadiazolo[3,4-c]pyridine (PT) as an auxiliary acceptor into the molecular design of organic sensitizers, we have synthesized four new dyes (PT1 -P14) for dye-sensitized solar cells (DSSCs) with triphenylamine or N,N-diphenylthiophen-2-amine as the donor units and thiophene or benzene as the pi-bridges, respectively. All the structures, optical and electrochemical properties were fully characterized. Nanocrystalline TiO2 dye-sensitized solar cells were also fabricated using these dyes. Among them, PT2-based DSSCs showed the highest overall conversion efficiency of 6.11% with V-oc=668 mV, J(sc)=12.61 mA cm(-2) and a fill factor (FF)=0.74 after a chenodeoxycholic acid (CDCA) treatment under standard illumination condition (100 mW cm(-2) simulated AM 1.5 solar light).

  • 28.
    Zhang, Yan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Schaufelberger, Fredrik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Sakulsombat, Morakot
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Liu, Chelsea
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through dynamic covalent kinetic resolution2014Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, nr 24, s. 3826-3831Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through an enzyme-catalyzed, dynamic covalent kinetic resolution strategy is presented. Dynamic hemithioacetal formation combined with intramolecular, lipase-catalyzed lactonization resulted in good conversions with moderate to good enantiomeric excess (ee) for the final products. The process was evaluated for different lipase preparations, solvents, bases, and reaction temperatures, where lipase B from Candida antarctica (CAL-B) proved most efficient. The substrate scope was furthermore explored for a range of aldehyde structures, together with the potential access to nucleoside analog inhibitor core structures.

  • 29. Zhou, Haitao
    et al.
    Huang, Wei
    Ding, Li
    Cai, Shengyun
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Li, Bo
    Su, Jianhua
    New cyano-substituted organic dyes containing different electrophilic groups: aggregation-induced emission and large two-photon absorption cross section2014Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, nr 39, s. 7050-7056Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three aggregation-induced emission active dyes (3a-c) were synthesized and their one- and two-photon absorption properties have been investigated. They were all found to be weakly fluorescent in THF solution, while they exhibited dramatic fluorescence enhancement in water/THF mixtures. The solid fluorescence of 3a-c was recorded and their fluorescence quantum efficiency (Phi(F)) values were determined to be 8.0%, 8.1%, and 16.4%, respectively. Moreover, the two-photon absorption (2PA) cross-sections (sigma) of 3a-c were measured and 3a showed the highest value of 702 GM. The excellent aggregation-induced emission and 2PA properties provide a promising alternative for biophotonic materials.

1 - 29 av 29
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf