69556-74-7Relevant academic research and scientific papers
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
Domino syntheses of five-, six- and seven-membered O-, N- and S-heterocycles from α-, β- and γ-substituted carboxylic esters
Loeffler,Schobert
, p. 2799 - 2802 (2007/10/03)
By a one-pot procedure, tetronic acids, tetronates, coumarins, benzoxepinones and their N- and S-analogues are readily accessible from keteneylidene(triphenyl)phosphorane 2 and carboxylic esters bearing OH, NHR or SH groups in an α-, β- or γ-position by an addition/Wittig olefination/(Claisen rearrangement) sequence. This cascade can be controlled by temperature variation. Extension of this procedure by a further addition step yielding annulated bisheterocycles such as the furoquinolone 28 is possible in some cases.
