Development of Stereoselective Reactions by Using Newly Prepared Optically Active Pyrazole Derivatives

本研究始于1997年，主要关注杂原子在立体选择性反应中的作用。首先，我们研究了由薄荷酮衍生的光学活性二醇的不对称Diels-Alder反应。仅通过将溶剂从THF切换为二氯甲烷，观察到对映体选择性反转。另一方面，薄荷酮衍生的光学活性吡唑衍生物被发现可以作为轴向配体调节非手性（salen）锰配合物的构象。这种构象调控首次实现了非手性催化剂的不对称环氧化反应，但不对称诱导程度较低。实验结果有力地支持了（salen）锰配合物的阶梯配体构象在salen配合物对映体选择中起重要作用的假设。基于这一考虑，本文合成了乙二胺上带有羧酸根的新型（salen）锰配合物，并将其用于色烯衍生物的不对称环氧化反应。除了定量的产率和98%ee的优异的不对称性外，还实现了约10000的高转化数。另一方面，我们发展了使用二氮杂环丙烷的α，β-不饱和酰胺的顺式选择性和非立体特异性的氮杂环丙烷化。使用光学活性的二氮杂环丙烷使得不对称的氮杂环丙烷化反应虽然化学产率很低，但仍有很好的ee值。

This research was started from 1997 by focusing on the feature of heteroatoms for setereoselective reactions. At the beginnings, we examined asymmetric Diels-Alder reaction by using optically active diol derived from menthone. Only by switching the solvent from THF to dicholoromethane, reversal of enantioface selectively was observed. On the other hand, optically active pyrazole derivatives derived from menthone was found to regulate the conformation of achiral (salen)manganese complex as axial ligand. This conformational regulation for the first time realized asymmetric epoxidation with achiral catalyst, though the asymmetric induction was low. The hypothesis that the stepped ligand conformation of (salen)manganese complex plays an important role in the enantioface selection by the salen complex is strongly supported by the present experimental results. Basing in this consideration, new type of (salen)manganese complex bearing carboxylate group on its ethylene diamine moiety was prepared and used as a catalyst for asymmetric epoxidation of chromene derivatives. In addition to the quantitative yield and excellent asymmetric of 98% ee, high turn over number of about 10000 was achieved.On the other hand, we developed cis-selective and non-stereospecific aziridination of α, β-unsaturated amide by using a diaziridine. Employment of optically active daiziridine made asymmetric aziridination possible in excellent % ee though the chemical yield was only modest.