Studies on asymmetric reaction catalized by optically active metallocenes

高立体选择性和催化反应的发展促进了天然产物、药物和其他有用材料的合成。茂金属如二氯化二茂钛和二氯化二茂锆已被用作聚合（齐格勒-纳塔催化剂）、碳环丁烷和氢化的催化剂。由于间茂具有两个空间上需要的环戊二烯基配体，在茂金属催化的反应中，对间茂手性的引入可能带来高的不对称诱导。通过光学拆分，已经制备出了一些取代基与亚烷基链相连的光学活性间二茂化合物。然而，将手性引入到异戊二烯的亚烷基链中似乎消除了麻烦的拆分步骤，并为合成各种光学活性的间茂提供了机会。 ...更多信息 （S）-乳酸乙酯、（S）-1，3-丁二醇、（2S，3S）-2，3-丁二醇、（2S，4S）-2，4-戊二醇。另一方面，茚基由于其比普通的烷基环戊二烯更高的化学稳定性而被用作取代的环戊二烯部分。然后，通过偶联反应合成了几种具有光学活性的二茚基配体。接下来，发现配体与四氯化钛或四氯化锆的络合是困难的，并且几乎在每种情况下都获得络合物分解产物。在大量实验之后，通过用（R）-1，3-二（1-茚基）丁烷或（2R，4R）-2，4-二（1-茚基）戊烷处理四氯化钛并随后氢化以9 - 11%产率制备两种结晶二茂钛。结构分析表明，产物为取代基同向排列的重叠配合物。令人惊讶的是，高度不对称诱导不能预期在黯然失色的配合物催化反应。最近，R。L. Halterman等人报道了在亚烷基链上具有联萘轴向不对称性的光学活性二茂钛的合成[Organometallics，10，2998（1991）]。由于我们的结果与Halterman的结果之间的差异的原因目前还不清楚，需要进一步的实验。少

The development of highly stereoselective and catalytic reactions has syntheses of natural products, pharmaceuticals, and other useful materials. Metallocenes such as titanocene dichloride and zirconocene dichloride have been used as a catalyst for polymerization (Zieglar-Natta catalyst), carbonetallation, and hydrogenation. Since metaflocenes have two sterically demanded ligands of cyclopentadenyl group, inmkuction of chirality on metahocenes may bring high asymmetric induction in the metallocene catalyzed reactions. Some optically active metahocenes whose substituted cyclopentadienyl groups were connected with alkylene chain had already been prepared by optical resolution. However, prior introduction of chirality into the alkylene chain of metallocenes seemed to eliminate the troublesome resolution step and to open an opportunity for the synthesis of various Kinds of optically active metahocenes.The chiral alkylene chains were prepared from easily available (2S, 3S)-diethyl tartrate, … More (S)-ethyl lactate, (S)-1, 3-butanediol, (2S, 3S)-2, 3-butanediol, (2S, 4S)-2, 4-pentanediol. On the other hand, indenyl group was employed as the substituted cyclopentadienyl part due to its higher chemical stability than ordinary'alkylcyclopentadienes. Then, several o]fftically active diindenyl ligands were synthesized by coupling of the two parts. Next complexation of the ligands with titanium or zirconium tetrachloride was found to be difficult and complex decomposition products were obtained in almost every case. After numerous experimentations, two crystalline titanocenes were produced by a treatment of titanium tetrachloride with (R)-1, 3-di(1 -indenyl) butane or (2R, 4R)-2, 4-di(l-indenyl) pentane and subsequent hydrogenation in 9-1 1% yield. The structure elucidation revealed that the crystalline products were eclipsed complex whose substituent arranged to same direction. Disappointingly, highly asymmetric induction could not be expected in the eclipsed complex catalyzed reaction. Quite recently, R. L. Halterman et al. reported a synthesis of optically active titanocene having binaphthyl axial asymmetry on the alkylene chain [Organometallics, 10, 2998(1991)]. Since it is not clear a reason for the difference between our result and Halterman's result at present, further experimentations are required. Less