165337-03-1Relevant articles and documents
Gold(I)-catalyzed tandem alkoxylation/lactonization of γ-hydroxy- α,β-acetylenic esters
Ramon, Ruben S.,Pottier, Christophe,Gomez-Suarez, Adrian,Nolan, Steven P.
, p. 1575 - 1583 (2011/08/04)
The formation of 4-alkoxy-2(5H)-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)(NTf2)]. 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)(NTf2)], reactions with cationic complexes such as [2,6-bis(diisopropylphenyl)imidazol-2-ylidine] (acetonitrile)gold tetrafluoroborate [Au(IPr)(CH3CN)][BF4] or (μ-hydroxy)bis{[2,6-bis(diisopropylphenyl)imidazol-2-ylidine]gold} tetrafluoroborate or bis(trifluoromethanesulfonyl)imidate - [{Au(IPr)} 2(μ-OH)][X] (X=BF4, NTf2) - mostly stop after the alkoxylation. Analysis of the intermediate proved the exclusive formation of the E-isomer which allows for the subsequent lactonization. Copyright
