| 1. |
- Henry, Jeffrey L., et al.
(författare)
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Highly Selective Olefin-Assisted Pd-II-Catalyzed Oxidative Alkynylation of Enallenes
- 2017
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 23:33, s. 7896-7899
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Tidskriftsartikel (refereegranskat)abstract
- An olefin-assisted, palladium-catalyzed oxidative alkynylation of enallenes for regio- and stereoselective synthesis of substituted trienynes has been developed. The reaction shows a broad substrate scope and good tolerance for various functional groups on the allene moiety, including carboxylic acid esters, free hydroxyls, imides, and alkyl groups. Also, a wide range of terminal alkynes with electron-donating and electron-withdrawing aryls, heteroaryls, alkyls, trimethylsilyl, and free hydroxyl groups are tolerated.
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| 2. |
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| 3. |
- Li, Man-Bo, et al.
(författare)
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Diastereoselective Cyclobutenol Synthesis : A Heterogeneous Palladium-Catalyzed Oxidative Carbocyclization-Borylation of Enallenols
- 2019
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 25:1, s. 210-215
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Tidskriftsartikel (refereegranskat)abstract
- A highly selective and efficient oxidative carbocyclization/borylation of enallenols catalyzed by palladium immobilized on amino-functionalized siliceous mesocellular foam (Pd-AmP-MCF) was developed for diastereoselective cyclobutenol synthesis. The heterogeneous palladium catalyst can be recovered and recycled without any observed loss of activity or selectivity. The high diastereoselectivity of the reaction is proposed to originate from a directing effect of the enallenol hydroxyl group. Optically pure cyclobutenol synthesis was achieved by the heterogeneous strategy by using chiral enallenol obtained from kinetic resolution.
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| 4. |
- Posevins, Daniels, et al.
(författare)
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Highly Diastereoselective Palladium-Catalyzed Oxidative Carbocyclization of Enallenes Assisted by a Weakly Coordinating Hydroxyl Group
- 2018
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 140:9, s. 3210-3214
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Tidskriftsartikel (refereegranskat)abstract
- A highly diastereoselective palladium-catalyzed oxidative carbocyclization-borylation of enallenes assisted by a weakly coordinating hydroxyl group was developed. The reaction afforded functionalized cyclo-hexenol derivatives, in which the 1,3-relative stereo chemistry is controlled (d.r. > 50:1). Other weakly coordinating oxygen-containing groups (ketone, alkoxide, acetate) also assisted the carbocyclization toward cyclo-hexenes. The reaction proceeds via a ligand exchange on Pd of the weakly coordinating group with a distant olefin group. The high diastereoselectivity of the hydroxyl directed reaction could be rationalized by a face-selective coordination of the distant olefin. It was demonstrated that the primary coordination of the close-by oxygen containing functionality was necessary for the reaction to occur and removal of this functionality shut down the reaction.
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| 5. |
- Posevins, Daniels, et al.
(författare)
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Highly Diastereoselective Palladium-Catalyzed Oxidative Cascade Carbonylative Carbocyclization of Enallenols
- 2020
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 22:2, s. 417-421
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Tidskriftsartikel (refereegranskat)abstract
- A palladium-catalyzed oxidative cascade carbonylative carbocyclization of enallenols was developed. Under mild reaction conditions, a range of cis-fused [5,5] bicyclic gamma-lactones and gamma-lactams with a 1,3-diene motif were obtained in good yields with high diastereoselectivity. The obtained lactone/lactam products are viable substrates for a stereoselective Diels-Alder reaction with N-phenylmaleimide, providing polycyclic compounds with increased molecular complexity.
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| 6. |
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| 7. |
- Qiu, Youai, et al.
(författare)
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Highly selective olefin-assisted palladium-catalyzed oxidative carbocyclization via remote olefin insertion
- 2017
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 8:1, s. 616-620
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Tidskriftsartikel (refereegranskat)abstract
- A highly selective olefin-assisted palladium-catalyzed oxidative carbocyclization via remote olefin insertion to afford cyclohexenes has been developed. It was shown that the assisting olefin moiety was indispensable for the formation of the cyclohexene product. Furthermore, preliminary studies on chiral anion-induced asymmetrical carbocyclization-borylation of enallenes have been carried out.
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| 8. |
- Qiu, Youai, et al.
(författare)
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Mechanistic Insight into Enantioselective Palladium-Catalyzed Oxidative Carbocyclization-Borylation of Enallenes
- 2018
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 24:10, s. 2433-2439
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Tidskriftsartikel (refereegranskat)abstract
- The asymmetric palladium-catalyzed oxidative carbocyclization-borylation of enallenes, employing a chiral phosphoric acid as co-catalyst, constitutes an efficient and convenient entry into functionalized building blocks with cyclopentene scaffolds in high enantiopurity. Up till now there has been a lack of knowledge concerning the origin of enantioselectivity of this reaction as well as the absolute configuration of the product. Herein, we report the crystal structure of one of the compounds generated via this carbocyclization, providing the link between the configuration of the products and the configuration of the chiral phosphoric acid used in the reaction. Furthermore, the origin of the enantioselectivity is thoroughly investigated with density functional theory (DFT) calculations. By careful examination of different possible coordination modes, it is shown that the chiral phosphoric acid and the corresponding phosphate anion serve as ligands for palladium during the key stereoselectivity-determining cyclization step. In addition, we examine reactions wherein an extra chiral reagent, a p-benzoquinone containing a chiral sulfoxide, is used. The combined experimental and theoretical studies provide insight into the details of complexation of palladium with various species present in the reaction mixture, furnishing a general understanding of the factors governing the stereoselectivity of this and related catalytic reactions.
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| 9. |
- Qiu, Youai, et al.
(författare)
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Palladium-Catalyzed Oxidative Carbocyclization–Borylation of Enallenes to Cyclobutenes
- 2016
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Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 55:22, s. 6520-6524
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Tidskriftsartikel (refereegranskat)abstract
- A highly efficient palladium-catalyzed oxidative borylation of enallenes was developed for the selective formation of cyclobutene derivatives and fully-substituted alkenylboron compounds. Cyclobutenes are formed as the exclusive products in MeOH in the presence of H2O and Et3N, whereas the use of AcOH leads to alkenylboron compounds. Both reactions showed a broad substrate scope and good tolerance for various functional groups, including carboxylic acid ester, free hydroxy, imide, and alkyl groups. Furthermore, transformations of the borylated products were conducted to show their potential applications.
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| 10. |
- Qiu, Youai, et al.
(författare)
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Palladium-Catalyzed Oxidative Cascade Carbonylative Spirolactonization of Enallenols
- 2017
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Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 56:12, s. 3221-3225
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Tidskriftsartikel (refereegranskat)abstract
- A highly selective palladium-catalyzed oxidative carbonylation/carbocyclization/alkoxycarbonylation of enallenols to afford spirolactones bearing an all-carbon quaternary center was developed. This transformation involves the overall formation of three C-C bonds and one C-O bond through a cascade insertion of carbon monoxide (CO), an olefin, and CO. Preliminary experiments on chiral anion-induced enantioselective carbonylation/carbocyclization of enallenols afforded spirolactones with moderate enantioselectivity.
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