Direct Catalytic Asymmetric Aldol Additions of Methyl Ynones. Spontaneous Reversal in the Sense of Enantioinduction

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• 作者：Barry M. Trost ; Alec Fettes ; and Brock T. Shireman
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：March 10, 2004
• 年：2004
• 卷：126
• 期：9
• 页码：2660 - 2661
• 全文大小：76K
• 年卷期：v.126,no.9(March 10, 2004)
• ISSN：1520-5126

文摘

In this Communication, we report the direct, catalytic, asymmetric aldol addition of methyl ynones using our dinuclear zinc catalyst. A spontaneous reversal in the sense of enantioinduction was observed for these reactions; formation of the (S)-enantiomer is favored in the early stages (69% ee after 5 min), whereas the (R)-enantiomer is isolated as the major product after prolonged reaction times (97% ee after 22 h). It could be shown that this reversal in enantioselectivity is due to formation of a new catalytic species which incorporates the aldol product.