Achiral additives dramatically enhance enantioselectivities in the BINOL–Ti(IV) complex catalyzed aldol condensations of aldehydes with Chan’s diene
摘要:
Achiral additives can dramatically enhance the enantioselectivities in the BINOL-Ti(IV) complex catalyzed aldol condensations of aldehydes with Chan's diene. The best results were obtained by using 2.0 equiv of LiCl with respect to (S)-BINOL/Ti(Oi-Pr)(4) as the additive. In the presence of 4.0 mol % of LiCl and 2.0 mol % of BINOL/Ti(Oi-Pr)(4), all aldehydes tested gave delta-hydroxy-beta-ketoesters as almost pure single enantiomers. Moreover, the present catalyst system was highly effective on reducing the catalyst loadings to 0.1 mol %. Published by Elsevier Ltd.
Achiral additives dramatically enhance enantioselectivities in the BINOL–Ti(IV) complex catalyzed aldol condensations of aldehydes with Chan’s diene
作者:Qinyao Xu、Jianghui Yu、Fengyan Han、Juan Hu、Weiping Chen、Liping Yang
DOI:10.1016/j.tetasy.2010.01.008
日期:2010.2
Achiral additives can dramatically enhance the enantioselectivities in the BINOL-Ti(IV) complex catalyzed aldol condensations of aldehydes with Chan's diene. The best results were obtained by using 2.0 equiv of LiCl with respect to (S)-BINOL/Ti(Oi-Pr)(4) as the additive. In the presence of 4.0 mol % of LiCl and 2.0 mol % of BINOL/Ti(Oi-Pr)(4), all aldehydes tested gave delta-hydroxy-beta-ketoesters as almost pure single enantiomers. Moreover, the present catalyst system was highly effective on reducing the catalyst loadings to 0.1 mol %. Published by Elsevier Ltd.