THE PHOTOCHEMICAL REACTION AND THE ABSOLUTE ASYMMETRIC SYNTHESIS IN THE CHIRAL CRYSTALLINE ENVIRONMENT

从非手性试剂开始，在没有任何外部手性试剂的情况下实现不对称合成一直是化学家们的一个有趣的挑战，也是自然界旋光性起源问题的核心。由非手性材料形成的手性晶体的立体定向固体板岩化学反应被定义为“绝对”不对称合成。这种不对称合成包括两个方面：产生手性晶体和进行拓扑化学控制的固体反应，从而产生手性产物。我们证明了立体控制的光化学苯基迁移也可以发生在固态中。由邻苯甲酰苯甲酰氯和邻甲基噻吩制备的硫酯在P2_12_12_1的手性空间基上结晶。给出了两种对映异构体在KBr中的圆二色性（CD）光谱。当硫酯的对映晶体被照射成白色粉末时，分离出一种光学活性的邻苯酞。苯酞的形成可以用芳基硫迁移过程和苯基迁移过程来解释。通过对产物和受手性晶格影响的非手性分子的绝对构型相关性研究，确定了苯基迁移机理。部分邻苯甲酰苯甲酸酯也在手性空间基上结晶，固相光解通过C(=O)-O键裂解生成邻苯二甲酸衍生物，其机理与硫酯不同。用N，N-二取代邻苯甲酰苯酰胺进行了绝对不对称合成。该领域的未来与有机固态化学的总体进展以及对晶体分子堆积模式的深入理解密切相关。

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-slate chemical reactions of chiral crystals formed by achiral materials are defined as "absolute" asymmetric synthesis. This asymmetric synthesis involves two aspects : generating chiral crystals and performing topochemically controlled solid-state reactions, which yield chiral products.We demonstrated that the stereo-controlled photochemical phenyl migration could also occur in the solid state. Thioester prepared from o-benzoylbenzoylchloride and o-methylthiophenol crystallized in a chiral space group P2_12_12_1. The circular dichroism (CD) spectra of the two enantiomorphs in KBr were presented. When the enantiomorphic crystals of the thioester was irradiated as white powders, an optically active phthalide was isolated. The formation of phthalide is explained in terms of either arylthio-migration of phenyl-migration process. The phenyl-migration mechanism was confirmed on the basis of the absolute-to-absolute configuration correlation studies of both product and an achiral molecule influenced by chiral crystal lattice.Some of o-benzoylbenzoic acid esters also crystallized in chiral space group, and the photolysis in solid-state gave phthalide derivatives via a cleavage of C(=O)-O bond, which involved the different mechanism from that of thioesters. The absolute asymmetric synthesis was also performed by the photoreaction of N,N-disubstituted o-benzoylbenzamides.The future of this field is intimately connected with progress in the general area of organic solid-state chemistry as well as with deeper understanding of the molecular packing modes of crystals.