| 1. |
- Belda, O., et al.
(författare)
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Highly stereo- and regioselective allylations catalyzed by Mo-pyridylamide complexes : Electronic and steric effects of the ligand
- 2000
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Ingår i: Journal of Organic Chemistry. - Uppsala Univ, Uppsala Biomed Ctr, Dept Organ Pharmaceut Chem, SE-75123 Uppsala, Sweden. Royal Inst Technol, Dept Chem, SE-10044 Stockholm, Sweden. : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 65:18, s. 5868-5870
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Bengtson, A, et al.
(författare)
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Protected indanones by a Heck-Aldol annulation reaction
- 2002
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Ingår i: Journal of Organic Chemistry. - Uppsala Univ, Dept Organ Pharmaceut Chem, SE-75123 Uppsala, Sweden. : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 67:16, s. 5854-5856
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Tidskriftsartikel (refereegranskat)abstract
- Monoprotected 3-hydroxyindan-1-ones have been prepared in moderate to good yields by a new tandem reaction involving salicylaldehyde triflates and commercially available 2-hydroxyethyl vinyl ether. This one-pot annulation reaction proceeds in the presence of a palladium bidentate catalyst and results in the formation of two new ring systems.
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| 3. |
- Blid, Jan, et al.
(författare)
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Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic alpha-Amino Amides
- 2004
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:9, s. 3043-3049
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Tidskriftsartikel (refereegranskat)abstract
- Boron trifluoride and BBr3 mediated [2,3]-sigmatropic rearrangements of allylic alpha-amino amides have been developed affording secondary amines in good yields. (E)-Crotyl and (E)-cinnamyl alpha-amino amides 2b and 2c exhibit excellent syn-diastereoselectivity upon rearrangement with either Lewis acid. The allylic amine 2a forms upon treatment with BF3 or BBr3 a five-membered heterocylic complex in which a single halide anion has been displaced by the carbonyl oxygen atom. The structures of the Lewis acid-amine complexes were elucidated using NMR spectroscopy. A plausible reaction mechanism, based on DFT calculations, is presented. Thus, BF3- or BBr3-complexed allylic amines 2 are shown to preferentially proceed, after deprotonation, via an endo transition state.
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| 4. |
- Blomberg, David, et al.
(författare)
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Synthesis and conformational studies of a β-turn mimetic incorporated in Leu-enkephalin
- 2004
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:10, s. 3500-3508
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Tidskriftsartikel (refereegranskat)abstract
- A β-turn mimetic in which the four amino acids of a β-turn have been replaced by a 10-membered ring has been designed, synthesized, and subjected to conformational studies. In the mimetic, the intramolecular COi − HNi+3 hydrogen bond that is often found in β-turns has been replaced by an ethylene bridge. In addition, the amide bond between residues i and i + 1 was exchanged for a methylene ether isoster. Such a β-turn mimetic, based on the first four residues of Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu), was prepared in 15 steps. The synthesis relied on a β-azido alcohol prepared in five steps from Cbz-Tyr(tBu)-OH as a key, i-position building block. tert-Butyl bromoacetate, glycine, and a Phe-Leu dipetide were then used as building blocks for positions i + 1, i + 2, and i + 3, respectively. Conformational studies based on 1H NMR data showed that the β-turn mimetic was flexible, but that it resembled a type-II β-turn at low temperature. This low energy conformer closely resembled the structure determined for crystalline Leu-enkephalin.
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| 5. |
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| 6. |
- Buskas, T., et al.
(författare)
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Use of n-pentenyl glycosides as precursors to various spacer functionalities
- 2000
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 65:4, s. 958-963
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Tidskriftsartikel (refereegranskat)abstract
- Pent-4-enyl ß-D-glucopyranoside and its peracetylated and perbenzylated derivatives are shown to be excellent substrates for preparation of a wide variety of spacer functionalities. The spacer derivatives so obtained are promising substrates for preparing agents such as neo-glycoconjugates, micelies, and liquid crystalline phases, which are of interest for studying various biological and physiological phenomena of carbohydrates.
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| 7. |
- Carlqvist, P., et al.
(författare)
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A theoretical study of the uncatalyzed and BF3-assisted Baeyer-Villiger reactions
- 2001
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 66:4, s. 1193-1199
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms for the uncatalyzed and boron trifluoride (BF3) assisted Baeyer-Villiger reactions between acetone and hydrogen peroxide have been investigated using high level ab initio [MP2 and CCSD(T)] and density functional theory (B3LYP) methods. Both steps in the uncatalyzed reaction are found to have very high transition state energies. It is clear that detectable amounts of the Crieege intermediate or the products cannot be formed without the aid of a catalyst. The main function of BF3 in both the addition step and the rearrangement (migration) step is to facilitate proton transfer. In the addition step the complexation of hydrogen peroxide with BF3 leads to an increased acidity of the attacking OH group, while in the rearrangement step BF3 takes active part in the proton-transfer process. This latter step is found to be rate determining with an activation free energy of 17.7 kcal/mol in organic solution. The products of the reaction are BF2OH, hydrogen fluoride, and methyl acetate. Thus, BF3 is not directly regenerated from the reaction.
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| 8. |
- Carlqvist, Peter, et al.
(författare)
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Computational study of the amination of halobenzenes and phenylpentazole. A viable route to isolate the pentazolate anion?
- 2004
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:9, s. 3222-3225
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Tidskriftsartikel (refereegranskat)abstract
- Amination of halobenzenes, which proceeds via the benzyne intermediate (1), has been studied using quantum chemical methods. The computational data are in agreement with experimentally observed trends in reactivity and provide a qualitative explanation for the observed hydrogen isotope effects. To investigate if this is a viable way to isolate the pentazolate anion (2), the reactivities of the halobenzenes have been compared to phenylpentazole (3). The reaction energetics for phenylpentazole become favorable after complexation with Zn2+.
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| 9. |
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| 10. |
- Ek, Fredrik, et al.
(författare)
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Aromatic allylation via diazotization: Metal-free C-C bond formation
- 2002
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 67:18, s. 6376-6381
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Tidskriftsartikel (refereegranskat)abstract
- A new method for the synthesis of allyl aromatic compounds not involving any metal-containing reagent or catalyst has been developed. Arylamines substituted with a large number of different substituents were converted via diazotizative deamination with tert-butyl nitrite in allyl bromide and acetonitrile to the corresponding allyl aromatic compounds. The allylation reaction was found to be suitable for larger scale synthesis due to short reaction times, a nonextractive workup, and robustness toward moisture, air, and type of solvent.
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