Direct Catalytic Asymmetric Aldol Additions of Methyl Ynones. Spontaneous Reversal in the Sense of Enantioinduction
作者:Barry M. Trost、Alec Fettes、Brock T. Shireman
DOI:10.1021/ja038666r
日期:2004.3.1
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.