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Gold(I)‐Catalyzed Tandem Alkoxylation/Lactonization of γ‐Hydroxy‐α,β‐Acetylenic Esters
Author(s) -
Ramón Rubén S.,
Pottier Christophe,
GómezSuárez Adrián,
Nolan Steven P.
Publication year - 2011
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201100115
Subject(s) - chemistry , tetrafluoroborate , acetonitrile , tandem , catalysis , medicinal chemistry , cationic polymerization , dichloroethane , alkoxy group , organic chemistry , alkyl , ionic liquid , materials science , composite material
The formation of 4‐alkoxy‐2(5 H )‐furanones was achieved via tandem alkoxylation/lactonization of γ‐hydroxy‐α,β‐acetylenic esters catalyzed by 2 mol% of [2,6‐bis(diisopropylphenyl)imidazol‐2‐ylidine]gold bis(trifluoromethanesulfonyl)imidate [Au(IPr)(NTf 2 )]. The economic and simple procedure was applied to a series of various secondary propargylic alcohols allowing for yields of desired product of up to 95%. In addition, tertiary propargylic alcohols bearing mostly cyclic substituents were converted into the corresponding spiro derivatives. Both primary and secondary alcohols reacted with propargylic alcohols at moderate temperatures (65–80 °C) in either neat reactions or using 1,2‐dichloroethane as a reaction medium allowing for yields of 23–95%. In contrast to [Au(IPr)(NTf 2 )], reactions with cationic complexes such as [2,6‐bis(diisopropylphenyl)imidazol‐2‐ylidine](acetonitrile)gold tetrafluoroborate [Au(IPr)(CH 3 CN)][BF 4 ] or (μ‐hydroxy)bis{[2,6‐bis(diisopropylphenyl)imidazol‐2‐ylidine]gold} tetrafluoroborate or bis(trifluoromethanesulfonyl)imidate – [{Au(IPr)} 2 (μ‐OH)][X] (X=BF 4 , NTf 2 ) – mostly stop after the alkoxylation. Analysis of the intermediate proved the exclusive formation of the E ‐isomer which allows for the subsequent lactonization.