Gold-catalyzed cyclization of diynes

• Verfasst von: Hansmann, Max M. [VerfasserIn]
• Verfasst von: Tšupova, Svetlana [VerfasserIn]
• Verfasst von: Rudolph, Matthias [VerfasserIn]
• Verfasst von: Rominger, Frank [VerfasserIn]
• Verfasst von: Hashmi, A. Stephen K. [VerfasserIn]
• Titel: Gold-catalyzed cyclization of diynes
• Titelzusatz: controlling the mode of 5-​endo versus 6-​endo cyclization$d​an experimental and theoretical study by utilizing diethynylthiophenes
• Verf.angabe: Max M. Hansmann, Svetlana Tšupova, Matthias Rudolph, Frank Rominger, A. Stephen K. Hashmi
• E-Jahr: 2014
• Jahr: 16 January 2014
• Umfang: 9 S.
• Fussnoten: Gesehen am 24.09.2020
• Titel Quelle: Enthalten in: Chemistry - a European journal
• Ort Quelle: Weinheim : Wiley-VCH, 1995
• Jahr Quelle: 2014
• Band/Heft Quelle: 20(2014), 8, Seite 2215-2223
• ISSN Quelle: 1521-3765
• DOI: doi:10.1002/chem.201302967
• Datenträger: Online-Ressource
• Sprache: eng
• Bibliogr. Hinweis: Erscheint auch als : druck-Ausgabe: Gold-catalyzed cyclization of diynes. - 2014
• Sach-SW: alkynes
• Sach-SW: bifurcation
• Sach-SW: CH activation
• Sach-SW: density functional calculations
• Sach-SW: gold
• K10plus-PPN: 1733675914

Abstract

Herein, a dual-gold catalyzed cyclization of 3,4-diethynylthiophenes generating pentaleno[c]thiophenes through gold-vinylidenes and CH bond activation is disclosed. Various new heteroaromatic compounds—substrate classes unexplored to date—exhibiting three five-membered annulated ring systems could be synthesized in moderate to high yields. By comparison of the solid-state structures of the corresponding gold-acetylides, it could be demonstrated that the cyclization mode (5-endo versus 6-endo) is controlled by the electronic and not steric nature of the diyne backbone. Depending on different backbones, we calculated thermodynamic stabilities and full potential-energy surfaces giving insight into the crucial dual-activation cyclization step. In the case of the 3,4-thiophene backbone, in which the initial cyclization is rate and selectivity determining, two energetically distinct transition states could be localized explaining the observed 5-endo cyclization mode by classical transition-state theory. In the case of vinyl and 2,3-thiophene backbones, the theoretical analysis of the cyclization mode in the bifurcated cyclization area demonstrated that classical transition-state theory is no longer valid to explain the high experimentally observed selectivity. Herein, for the first time, the influence of the backbone and the aromatic stabilization effect of the 6-endo product in the crucial cyclization step could be visualized and quantified by calculating and comparing the full potential-energy surfaces.