Optimisation, Scope and Limitations of Enantioselective Aldol Reactions of an S-Ketene Silyl Acetal with Aliphatic Aldehydes under (R)-BINOL-Titanium(IV) Catalysis Conditions
作者:Reinhold Zimmer、Anke Peritz、Regina Czerwonka、Luise Schefzig、Hans-Ulrich Reißig
DOI:10.1002/1099-0690(200210)2002:20<3419::aid-ejoc3419>3.0.co;2-f
日期:2002.10
1,1′-binaphthyl-derived chiral titanium(IV) complex 4 afforded the corresponding aldol products 6 in good yields and with good to excellent enantioselectivities. The chemical yield could further be enhanced, without loss of stereoselection, by addition of phenol and/or molecular sieves. The presented aldol reactions with aluminium, boron and ytterbium-BINOL catalysts demonstrate that only low chiral
由 1,1'-联萘衍生的手性钛 (IV) 配合物 4 催化的官能化醛 5 和 S-烯酮甲硅烷基缩醛 2 之间的 Mukaiyama 羟醛反应以良好的产率和良好的对映选择性提供了相应的羟醛产物 6。通过添加苯酚和/或分子筛,可以在不损失立体选择的情况下进一步提高化学产率。所提出的铝、硼和镱-BINOL 催化剂的羟醛反应表明,只能实现低手性诱导。羟醛产物 6a 被转化为 α-硫辛酸前体 8,从而提供了这种生物活性化合物的正式合成。(© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)