Base-catalyzed highly stereoselective conversion of gamma-hydroxy-alpha,beta-acetylenic esters to gamma-acetoxy dienoates.
Gamma-hydroxy-alpha,beta-acetylenic esters can be conveniently prepared from the reaction of methyl propiolate with aldehydes in the presence of ZnEt(2) and N-methylimidazole at room temperature. It is discovered that the gamma-hydroxy-alpha,beta-acetylenic esters can be catalyzed by p-N,N-dimethylaminopyridine (DMAP) in acetic anhydride to generate the gamma-acetoxy dienoates with high stereo control. The mechanism of this conversion is investigated by NMR analyses and isotope labeling experiments. An intramolecular Diels-Alder reaction of a gamma-acetoxy dienoate is conducted to show the synthetic potential of these compounds.
Yue
Yang
Y
Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.
Yu
Xiao-Qi
XQ
Pu
Lin
L