Theoretical Elucidation on the Regio-, Diastereo-, and Enantio-Selectivities of Chiral Primary鈥揟ertiary Diamine Catalyst for Asymmetric Direct Aldol Reactions of Aliphatic Ketones

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• 作者：Xiangting Sun ; Rongxiu Zhu ; Jun Gao ; Dongju Zhang ; Dacheng Feng
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：July 5, 2012
• 年：2012
• 卷：116
• 期：26
• 页码：7082-7088
• 全文大小：561K
• 年卷期：v.116,no.26(July 5, 2012)
• ISSN：1520-5215

文摘

The asymmetric direct aldol reactions of aliphatic ketones (acetone, butanone, and cyclohexanone) with 4-nitrobenzaldehyde catalyzed by a chiral primary鈥搕ertiary diamine catalyst (trans-N,N-dimethyl diaminocyclohexane) have been investigated by performing density functional theory calculations to rationalize the experimentally observed stereoselectivities. Focused on the crucial C鈥揅 bond-forming steps, we located several low-lying transition states and predicted their relative stabilities. The calculated results demonstrate that the catalytic direct aldol reactions of acetone favors the (S)-enantiomer and that butanone prefers the branched syn-selective product, while cyclohexanone yields predominantly the opposite anti-selective product. The theoretical results are in good agreement with the experimental findings and provide a reasonable explanation for the high enantioselectivity and diastereoselectivity, as well as regioselectivity, of the aldol reactions under consideration.