title: Direct Access to π-Extended Phosphindolium Salts by Simple Proton-Induced Cyclization of (o-Alkynylphenyl)phosphanes.
abstract: A detailed synthetic and mechanistic study for the synthesis of phosphindolium salts from easy accessible (o-alkynylphenyl)phosphanes is reported. Mechanistic investigation indicates a fast protonation at phosphorus as evidenced by the isolation of the phosphonium intermediate, followed by a protophosphonylation reaction across the alkyne moiety. DFT calculations support our mechanistic proposal and indicate a reaction highly exergonic compared to our recently reported phosphinoauration. Photophysical measurements recorded fluorescence quantum yields up to 97 % in solution for the phosphindolium core and fluorescence was observed in the solid state.
authors.affiliation: Organisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Arndt
authors.affiliation: Organisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
authors.forename: Max M
authors.initials: MM
authors.lastname: Hansmann
authors.affiliation: Organisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Rominger
authors.affiliation: Organisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Rudolph
authors.affiliation: Organisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.|Chemistry Department, Faculty of Science, King Abdulaziz University (KAU), Jeddah, 21589, Saudi Arabia.
authors.forename: A Stephen K
authors.identifier: http://orcid.org/0000-0002-6720-8602
authors.initials: ASK
authors.lastname: Hashmi
keywords: Brønsted acid; phospholes; phosphorus compounds; pi-extended systems; rearrangement