title: Gold catalysis: catalyst oxidation state dependent dichotomy in the cyclization of furan-yne systems with aromatic tethers.
abstract: Four different synthetic strategies led to a variety of furan-yne systems that contained an aryl system in the tether. Due to the short routes to these systems (four steps or less), a small library of substrates could easily be prepared. These were treated with AuCl(3) or with the Gagosz's catalyst Ph(3)PAuNTf(2) complex. The AuCl(3)-catalyzed reactions delivered highly substituted fluorene derivatives, a class of compounds of great importance as precursors for luminophores with extraordinary abilities. Conversely, a different mechanistic pathway was observed with the cationic gold(I) catalyst. In the latter case, a mechanistically interesting reaction cascade initiated a formal alkyne insertion into the furyl-sp(3)-C bond, which gave indene derivatives as the final products. This new reaction pathway depends on the aromatic moiety in the tether, which stabilizes a crucial cationic intermediate as a benzylic cation.
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany. hashmi@hashmi.de
authors.forename: A Stephen K
authors.initials: AS
authors.lastname: Hashmi
authors.forename: Julia
authors.initials: J
authors.lastname: Hofmann
authors.forename: Shuai
authors.initials: S
authors.lastname: Shi
authors.forename: Alexander
authors.initials: A
authors.lastname: Schütz
authors.forename: Matthias
authors.initials: M
authors.lastname: Rudolph
authors.forename: Christian
authors.initials: C
authors.lastname: Lothschütz
authors.forename: Marcel
authors.initials: M
authors.lastname: Wieteck
authors.forename: Miriam
authors.initials: M
authors.lastname: Bührle
authors.forename: Michael
authors.initials: M
authors.lastname: Wölfle
authors.forename: Frank
authors.initials: F
authors.lastname: Rominger