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Gold Catalysis: Catalyst Oxidation State Dependent Dichotomy in the Cyclization of Furan–Yne Systems with Aromatic Tethers
Author(s) -
Hashmi A. Stephen K.,
Hofmann Julia,
Shi Shuai,
Schütz Alexander,
Rudolph Matthias,
Lothschütz Christian,
Wieteck Marcel,
Bührle Miriam,
Wölfle Michael,
Rominger Frank
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201202004
Subject(s) - cationic polymerization , furan , alkyne , catalysis , chemistry , moiety , indene , cycloisomerization , fluorene , aryl , combinatorial chemistry , organic chemistry , alkyl , polymer
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.