Polymer- and Dendrimer-Bound Ti-TADDOLates in Catalytic (and Stoichiometric) Enantioselective Reactions: Are pentacoordinate cationic Ti complexes the catalytically active species?
作者:Dieter Seebach、Roger E. Marti、Tobias Hintermann
DOI:10.1002/hlca.19960790621
日期:1996.9.18
studied with these new chiral auxiliaries are: enantioselective nucleophilic additions to aldehydes (of R2Zn and RTi(OCHMe2)3; Scheme 5, Table 1) and to ketones (of LiAlH4, Table 2); enantioselective ring opening of meso-anhydrides (Scheme 6); [4+2] and [3+2] cycloadditions of 3-crotonyl-1,3-oxazolidin-2-one to cyclopentadiene and to (Z)-N-benzylidenephenylamine N-oxide ( 48, 49, Scheme 7, Tables 3, 4
α,α,α',α'- Ť ETRA一个RYL -1,3- d ioxolane -4,5- d imethan醇S中的杂环的,或在(TADDOLs),含苯乙烯基基团或者在C(2)用通常的方法(18-22、24、25)准备α位。这些化合物与苯乙烯和二乙烯基苯在悬浮液中共聚,生成呈颗粒状分布的聚合物(33–40,方案3),粒径分布相当均匀(150–45μm),在普通有机溶剂中可溶胀。还制备了HOCH 2-和BrCH 2取代的TADDOL,并用于连接到Merrifield树脂或树状分子上(23,26–32)。这些材料中的TADDOL部分易于形成Ti(和Al)络合物(方案4),可用作聚合物或树状聚合物结合的试剂(化学计量)或路易斯酸(催化)。用这些新的手性助剂研究的反应是:对醛(R 2 Zn和RTi(OCHMe 2)3;方案5,表1)和酮(LiAlH 4,表2)的对映选择性亲核加成;内消旋酸酐的对