Newly Designed Asymmetric Reaction Sites Induced by Rotational Barrier around the Carbon-Sulfur Bond Axis and their Reactions

考察了1-亚磺基萘甲苯2-位上的甲醛或亚氨基的亲核加成反应。所考察的反应如下：格氏反应、与烷基锂的烷基化反应、用LiAlH_4或二异丁基氢化铝还原以及Mukaiyama Aldol反应。立体选择性依赖于亚磺基上的取代基。在含有2，4，6-三异丙基苯基的全氢萘甲醛的反应中，可以获得高的立体选择性(&gt；98：2)。另一方面，叔丁基亚磺酸基萘甲醛或-萘甲亚胺具有较低的立体选择性，这与核磁共振分析所证明的碳-硫键轴旋转势垒引起的非对映异构体的比例很好地一致。我们的结论是，1-(2，4，6-triisopropylphenyl)sulfinyl-2-naphthaldehyde或-萘甲亚胺反应的高立体选择性是由高旋转势垒…引起的更多的是围绕碳-硫键轴进行的，因为上面显示的所有反应都具有高的立体选择性，而无论是螯合还是非螯合过渡态。此外，假设1-对甲苯基亚磺基苯甲醛或-苯基甲亚胺绕碳-硫键轴自由旋转，仅在反应中通过络合过渡态表现出高的立体选择性。亚磺基可以从产物中去除。例如，可以非常高效地制备光学活性醇，特别是具有两个芳基的光学活性醇。因此，本反应提供了一种新的高效的制备光学活性甲醇的方法，该方法具有两个不同的芳香基，具有相似的体积，如苯基-对甲苯基甲醇，这是很难通过不对称还原制备的。β-酮基磺酸盐与Dibal的还原显示出完全的立体选择性，该选择性受β-位的硅基控制。在本研究中，还成功地设计了一种具有旋转势垒的新型手性配体，用于对映体选择性反应。因此，一种在1-和1‘-位含有亚磺基和二苯基膦基团的二茂铁化合物被发现是丙二酸酯与钯催化剂进行烯丙化反应的有效手性配体。通过这些研究，我们可以开发由旋转势垒引起的新的立体选择反应，其中包括一个新的概念，即使用围绕碳-硫键轴的旋转势垒来进行立体选择反应。较少

Nucleophilic addition reactions to the carbaldehyde or imino groups at the 2-position of 1-sullinylnaplithalene have been examined. The reactions examined are as follows : Grignard reactions, alkylation reactions with alkyllithiums, reductions with LiAlH_4 or diisobutylaluminum hydride and Mukaiyama aldol reactions. Stereoselectivity was found dependent on the substituents on the sulfinyl group. High stereoselectivity (>98:2) could be achieved in the reactions of suffinylnaphthaldehyde having a 2,4,6-triisopropylphenyl group. On the other hand, tert-butylsulfinyl-naphthaldehyde or -naphthylmethanimine showed lower stereoselectivities which, however, were in good accord to the ratio of the diastereomers caused by the rotational barrier around the carbon-sulfur bond axis evidenced by the nmr analyses. We have concluded that the high stereoselectivity in the reactions of 1-(2,4,6-triisopropylphenyl)sulfinyl-2-naphthaldehyde or -naphthylmethanimine is caused by the high rotational barrier … More around the carbon-sulfur bond axis, because all the reactions shown above proceeded with high stereoselectivities irrespective of the chelating or non-chelating transition states. Furthermore, 1-p-tolylsulfinyl-benzaldehyde or -phenylmethanimine, in which a free rotation around the carbon-sulfur bond axis is assumed, showed high stereoselectivity only in the reaction through chelating transition states. The sulfinyl group can be removed from the products. For example, optically active alcohols especially having two aromatic groups can be prepared very efficiently. Thus, the present reaction provides a new efficient preparative method for optically active methanol having two different aromatic groups, with a similar bulkiness such as phenyl-p-tolylmethanol which is mostly difficult to prepare by the asymmetric reduction.Reduction of β-ketosuklfoxides with Dibal was found to show complete stereoselectivity which was controlled by the silyl group at the β-position. In this study a new chiral ligand having a rotational barrier for enantioselective reactions was also successfully designed. Thus, a ferrocenyl compound having sulfinyl and diphenylphosfinyl groups at 1-and 1'-positions was found to be an afficient chiral ligand for the allylation of malonate with a Pd catalyst.Through these studies, we could develop new stereoselective reactions caused by rotational barriers which includes a new concept of stereoselective reactions using a rotational barrier around the carbon-sulfur bond axis. Less