The effect of hydrogen bond donors in asymmetric organocatalytic conjugate additions |
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Authors: | Jin-hua Lao Xue-jing Zhang Jin-jia Wang Xue-ming Li Ming Yan Hai-bin Luo |
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Institution: | Industrial Institute of Fine Chemicals and Synthetic Drugs, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China |
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Abstract: | A series of primary amine organocatalysts with various hydrogen bond donors were prepared and examined in the conjugate addition of isobutyraldehyde and acetone to trans-β-nitrostyrene and (E)-methyl 2-oxo-4-phenylbut-3-enoate. The effect of N–H acidity and hydrogen-bonding modes of the catalysts on the catalytic activity and enantioselectivity was studied. The experimental results did not support a general correlation of N–H acidity and hydrogen-bonding modes with catalytic activity and enantioselectivity. The catalysts with double hydrogen-bonding interactions provided better catalytic activities and enantioselectivities than the catalysts with single hydrogen-bonding interactions for the reaction of trans-β-nitrostyrene. The catalyst with the most acidic N–H bond showed the best catalytic activity and enantioselectivity for the reaction of (E)-methyl 2-oxo-4-phenylbut-3-enoate. These results suggest that the effect of hydrogen bond donors in organocatalytic reactions may be highly dependent on the substrates and the reaction conditions. |
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