Memory of Chirality Generated by Spontaneous Crystallization and Absolute Asymmetric Synthesis Using the Frozen Chirality

长期以来，在没有任何外部手性试剂的情况下，从非手性试剂开始实现不对称合成一直是化学家们感兴趣的挑战，也是自然界光学活性起源问题的核心。非手性材料形成的手性晶体的立体定向固相化学反应被定义为绝对的不对称合成。这种不对称合成包含了绝对不对称合成的新概念，利用手性结晶的冻结手性记忆，我们发现立体可控的光化学反应可以在固态发生。此外，还展示了在均相条件下使用手性手性晶状体进行绝对不对称合成的新方法。我们发现氮原子上含有大量取代基的非手性无环酰亚胺在手性空间群中结晶，并且在低温下溶解在THF中时保持了手性构象。在-80~20℃范围内与正丁基锂反应生成光学活性的丁基加合物和氢化产物。该反应提供了在均相条件下利用手性晶体进行绝对不对称合成的第一个例子。

The achievement of an asymmetric synthesis starting from an achiral reagent and in the absence of any external chiral agent has long been an intriguing challenge to chemists and is also central to the problem of the origin of optically activity in nature. Stereospecific solid-state chemical reactions of chiral crystals formed by achiral materials are defined as "absolute" asymmetric synthesis. This asymmetric synthesis involves new concept of absolute asymmetric synthesis using the frozen Chirality memoried by chiral crystallization.We found that the stereo-controlled photochemical reaction could occur in the solid state. Furthermore, new absolute asymmetric synthesis in homogeneous conditions using chiral christals were also demonstrated. We found achiral acyclic imides with bulky substituents on the nitrogen atom crystallized in chiral space group, and maintain the chiral conformation when the crystals dissolved in THF at low-temperature. The reaction with n-butyllithium at a range of-80-20℃ gave optically active butyl adduct and hydrogenated product. This reaction provides the first example of absolute asymmetric synthesis using chiral crystals in homogeneous conditions.