Kuan-Jen Su

University of Vienna, Vienna, Vienna, Austria

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Publications (5)19.15 Total impact

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    ABSTRACT: Foiled carbene structures comprising strong stabilizing interactions between the divalent carbon and the intramolecular double bond have been located by DFT calculations. These tetracyclic species bearing fused five-membered rings impeding intramolecular rearrangements are theoretically predicted to lie in a deep potential energy well. A suitable dibromocyclopropane precursor for this type of foiled carbene has been prepared in 12 steps. Its treatment with methyllithium led to the isolation of a product of a formal carbene dimerization, a bicyclopropylidene.
    The Journal of Organic Chemistry 08/2011; 76(18):7491-6. · 4.56 Impact Factor
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    ABSTRACT: Tetravinylbenzene 4 was prepared in nearly quantitative yield from commercially available tetrabromobenzene; the improved, one-step procedure now employs Suzuki-Miyaura cross-coupling conditions. Intermolecular cyclopropanation of 4 with dibromocarbene gave a series of gem-dibromide adducts. Intramolecular cyclopropanation of monoadduct 5, putatively by its methyllithium-generated cyclopropylidene(oid), produced compound 11, which features a highly distorted spiropentane having a C-C-C bond angle of 163.5°. The stability of the reported spiropentanes was investigated using DFT calculations.
    The Journal of Organic Chemistry 10/2010; 75(21):7494-7. · 4.56 Impact Factor
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    ABSTRACT: Two achiral diazirines 1a and 1b have been encapsulated in the inherently chiral cavity of α-cyclodextrin (6-Cy), β-cyclodextrin (7-Cy) and permethylated β-cyclodextrin (TRIMEB) and photolyzed. Because of supramolecular photochirogenesis the generated carbenes afford intramolecular C–H insertion products not as a racemate but one enantiomer is slightly favored. With 1a@(6-Cy)2 the ee of product 7a is doubled. To the best of our knowledge for the first time for carbene Introduction It is often useful to perform a reaction in a constrained system.[1] For example, zeolites are employed on a large scale to force the isomerization of hydrocarbons in stereotype patterns, amongst others.[2] Indeed, the use of a host molecule as a reaction vessel opens up the possibility to synthesize products that would be difficult to obtain in solution[3] or to modify the course of a reaction.[4] This technique can also be applied to the generation of reactive molecules which might get bottleable if they are incarcerated in a host molecule.[5] It is particularly meaningful to perform carbene reactions in a molecular reactor because of the high reactivity of the divalent carbon atom. In fact, methylene has been described as the most indiscriminating reagent in chemistry.[6] Even if all other carbenes are partly stabilized and therefore more selective,[7] they still tend to generate product mixtures. This is especially true for C–H insertion reactions by which only stabilized carbenes like the nucleophilic foiled carbenes[8] or the electrophilic dihalocarbenes[ 9] give synthetically useful results. For more reactive carbenes, encapsulation in a cavitand permits to reduce the mobility of the intermediate, therefore lessening the number of accessible bonds or lone-pairs that may act as reaction partners and consequently, reducing the amount of side-products. Moreover, the equilibrium conformation of a guest molecule can also be modified.[10] This may permit to [‡] Carbene Rearrangements, 77. Part 76: J.-L. Mieusset, A. Schrems, M. Abraham, V. B. Arion, U. H. Brinker, Tetrahedron 2009, 65, 765–770. [a] Lehrstuhl für Physikalisch-Organische Chemie und Strukturchemie, Institut für Organische Chemie, Universität Wien, Währinger Straße 38, 1090 Wien, Austria Fax: +43-1-4277-52140 E-mail: udo.brinker@unive.ac.at Eur. J. Org. Chem. 2009, 5907–5912 © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 5907 reactions, products are imprinted, though modestly, with handedness derived from Cys. The reaction of 1b is highly dependent on the molecular reactor used for inclusion. Whereas 7-Cy is very efficient for favoring dimerization through azine formation, the use of TRIMEB permits exclusive formation of intramolecular insertion product 7b. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
    Annalen der Chemie und Pharmacie 10/2009; 2009(34):5907 - 5912. · 3.10 Impact Factor
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    ABSTRACT: The molecule of the title compound, C(10)H(6)N(24), lies on a crystallographic inversion centre located in the middle of the benzene ring. Steric overcrowding by the bulky N(3) groups is avoided by the tendency of four azide entities to be arranged parallel to the benzene ring and the other four azide groups to be arranged alternately above and below the benzene plane in a skeletal C(i) symmetry. The compound is of interest for high-energy research and as a precursor for the synthesis of carbon nanotubes, nanospheres or high-nitrogen carbon nitrides with great potential for biological and technological applications.
    Acta Crystallographica Section C Crystal Structure Communications 06/2009; 65(Pt 5):o240-2. · 0.78 Impact Factor
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    ABSTRACT: [reaction: see text] A reinvestigation of the thermolysis of 4,4-dibromotetracyclo[6.2.1.0(2,7).0(3,5)]undec-9-ene (2) affords diene 8 with a completely rearranged hydrocarbon skeleton via the isolable intermediate 4, along with cyclopentadiene and bromobenzene. DFT calculations show that the novel tandem retro-Diels-Alder-Diels-Alder reaction with role reversal is slightly less favored than the overall single-step Cope rearrangement.
    Organic Letters 02/2007; 9(1):113-5. · 6.14 Impact Factor