TADDOLs, Their Derivatives, and TADDOL Analogues: Versatile Chiral Auxiliaries.
TADDOLs, Their Derivatives, and TADDOL Analogues: Versatile Chiral Auxiliaries.
复制标题
DOI：
10.1002/1521-3773(20010105)40:1
复制
发表时间：
2001-01
影响因子：
--
通讯作者：
D. Seebach;A. Beck;A. Heckel
中科院分区：
文献类型：
--
作者：
D. Seebach;A. Beck;A. Heckel
TADDOL在1，3-二氧戊环上含有两个呈反式关系的相邻二芳基羟甲基，可以由酒石酸酯的缩醛或缩酮通过后者与芳香族格利雅试剂反应来制备。它们是非常通用的手性助剂。在这里，一个历史回顾的主题，其次是讨论的准备TADDOLs和类似的系统，包括TADDOLs与N-，P-，O-，和S-杂原子配体适合金属。晶体结构分析表明，二芳基甲基基团上的杂原子几乎总是彼此非常接近，通过氢键连接在一起，并倾向于形成螯合物，其中金属中心位于螺旋桨状手性环境中。TADDOL衍生物在对映选择性合成中的应用从用作化学计量的手性试剂或在刘易斯酸介导的反应中扩展到在催化氢化和有规立构易位聚合中的作用。迄今为止已经研究了基于以下金属的衍生物和络合物：Li、B、Mg、Al、Si、Cu、Zn、Ce、Ti、Zr、Mo、Rh、Ir、Pd、Pt。已经用TADDOL完成的立体选择性反应的数量相应地很大。也容易制备易于聚合和接枝的TADDOL衍生物，并将其转化为固定化固相催化剂。结果是催化剂简单或树枝状固定在聚苯乙烯或硅胶上，即使在钛TADDOLate介导的反应中多次使用后，其特征也具有意想不到的稳定性。TADDOLs显示出进一步的不寻常的特性，使它们在材料科学和超分子化学中的应用非常有用：它们是已知的用于将非手性（手性）液晶相转变为手性（手性）液晶的最有效的掺杂剂。不参与分子内氢键的TADDOL OH基团显示出与氢键受体分子间缔合的强烈倾向。在结晶过程中，这导致对映选择性地形成包合化合物，其本身有助于分离外消旋混合物，否则不适合通过非对映异构体盐结晶的经典方法。TADDOLs的高熔点甚至可以通过蒸馏拆分外消旋体！TADDOLs和非手性配体之间形成的主-客体化合物可以作为对映选择性光反应的平台。似乎可以肯定地预测，TADDOLs及其衍生物将被发现更多的应用。本文的支持信息可以在http://www.angewandte.com下的WWW上获得，也可以从作者那里获得。
TADDOLs, which contain two adjacent diarylhydroxymethyl groups in a trans relationship on a 1,3-dioxolane ring, can be prepared from acetals or ketals of tartrate esters by reaction of the latter with aromatic Grignard reagents. They are extraordinarily versatile chiral auxiliaries. Here, a historical review of the subject is followed by discussion of the preparation of TADDOLs and analogous systems, including TADDOLs with N-, P-, O-, and S-heteroatom ligands appropriate for metals. Crystal structure analysis reveals that the heteroatoms on the diarylmethyl groups are almost always in close proximity to each other, joined together by H-bonds, and predisposed to form chelate complexes in which the metallic centers reside in propeller-like chiral environments. Applications of TADDOL derivatives in enantioselective synthesis extend from utilization as stoichiometric chiral reagents or in Lewis acid mediated reactions, to roles in catalytic hydrogenation and stereoregular metathesis polymerization. Derivatives and complexes based on the following metals have so far been investigated: Li, B, Mg, Al, Si, Cu, Zn, Ce, Ti, Zr, Mo, Rh, Ir, Pd, Pt. The number of stereoselective reactions already accomplished with TADDOLs is correspondingly large. It is also easy to prepare TADDOL derivatives that are readily polymerizable and graftable, and to transform them into immobilized solid-phase catalysts. The result is catalysts, simply or dendritically immobilized in polystyrene or on silica gel and characterized by unexpected stability even after multiple use in titanium TADDOLate mediated reactions. TADDOLs show further unusual characteristics that make them useful for applications in material science and supramolecular chemistry: they are the most effective doping agents known for phase transformations of achiral (nematic) into chiral (cholesteric) liquid crystals. The TADDOL OH group that is not involved in intramolecular H-bonding shows a strong tendency to associate intermolecularly with H-bond acceptors. In the process of crystallization this leads, enantioselectively, to the formation of inclusion compounds that lend themselves to the separation of racemic mixtures not otherwise suited to the classical method of crystallization through diastereomeric salts. The high melting points of TADDOLs even make possible the resolution of racemates by distillation! Host-guest compounds formed between TADDOLs and achiral partners can serve as platforms for enantioselective photoreactions. It seems safe to predict that many more applications will be discovered for the TADDOLs and their derivatives. Supporting information for this article is available on the WWW under http://www.angewandte.com or from the author.