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Catalytic Asymmetric Synthesis of Allenoates by Isomerization of Alkynoates
H. Liu, D. Leow, K.-W. Huang*, C.-H. Tan*
National University of Singapore, Singapore
22 June 2009 (online)
The authors report an enantioselective isomerization of various alkynoates to the corresponding allenoates catalyzed by a chiral Brønsted base. The products were obtained in moderate to high yields and good enantioselectivities at relatively low catalyst loadings. Although most of the products were inseparable from unreacted starting material, the obtained mixtures were successfully used in further transformations, such as cycloadditions or lactonizations. These reactions proceeded with good chirality transfer and allowed the reisolation of the unreacted alkyne.