Enantioselective aldol condensation of 1,3-bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene promoted by chiral Ti(IV)/BINOL complex
摘要:
Enantiomerically enriched delta-hydroxy-beta-ketoesters are easily available by aldol condensation of 1,3-bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene in the presence of Ti(O-iPr)(4)/(S)-(-)-BINOL system. All reaction mixtures were separated by column chromatography and mostly isolated in moderate to good yields and all in high enantiomeric excesses. (C) 2000 Elsevier Science Ltd. All rights reserved.
A new organocatalytic system was tested as a promoter for the asymmetric addition of Chan’s diene to aldehydes under solvent-free conditions. This new organocatalyst generated in situ by mixing 1-naphthyl-TADDOL derivative and Emim BF4 was able to give enantioenriched vinylogous aldols and hetero-Diels-Alder cycloadducts. A mechanistic investigation through the detection of nonlinear effects confirmed
An efficient asymmetric aldol reaction of Chan's diene promoted by chiral Ti(IV)–BINOL complex
作者:Annunziata Soriente、Margherita De Rosa、Marina Stanzione、Rosaria Villano、Arrigo Scettri
DOI:10.1016/s0957-4166(01)00150-1
日期:2001.4
1.3-Bis-(trimethylsilyloxy)-1-methoxy-buta-1,3-diene (Chan's diene) can be conveniently used in asymmetric aldol reaction with aromatic, heteroaromatic, alpha,beta -unsaturated and aliphatic aldehydes in the presence of catalytic amounts (2-8% mol) of chiral Ti(IV)/(R)-BINOL complex. (C) 2001 Elsevier Science Ltd. All rights reserved.
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.
Solvent-free asymmetric vinylogous aldol reaction of Chan's diene with aromatic aldehydes catalyzed by hydrogen bonding
Chan's diene proved to react with aromatic aldehydes under organocatalytic conditions in presence of a chiral naphthyl-TADDOL derivative to give vinylogous aldols (up to 65% ee) with complete gamma-selectivity. A further process of hetero-Diels-Alder cycloaddition, leading to chiral pyran-4-one derivatives (up to 60% ee), was favoured by electron-withdrawing substituents on the aromatic ring. (C) 2009 Elsevier Ltd. All rights reserved.