Efficient Syntheses of Pharmacologically Active Compounds Using Multiple Cascade Reactions

级联反应是有机合成中最理想的方法之一，它通过一个步骤以立体选择性和区域选择性的方式形成多个键。我们在四种不同的条件下，利用级联反应研究了多环体系的结构，即离子反应、自由基反应、过渡金属催化反应和周环反应。我们已经建立了两种类型的级联反应，这对天然产物的合成是有用的。因此，分子内双迈克尔反应提供稠合到具有五个立体中心的六元环的多环化合物。另一方面，分子内的Michael-aldol反应构建了稠合到具有多个立体中心的四元环的多环体系。这些级联反应的催化不对称反应进行了广泛的研究。此外，还进行了相应的分子间反应，发展了一种新型的钯催化级联反应：在催化量的零价钯存在下，碳酸炔丙酯与苯酚反应生成环状碳酸酯。该反应具有很高的对映选择性，可用于（S）-BINAP的不对称合成。使用催化量的Pd（II）实现环烯基化反应。对乙烯基自由基的级联加成反应也进行了广泛的研究。利用这些特征反应，发现了一种新的神经保护剂的先导化合物。

Cascade reactions forming multiple bonds in a stereo-and regio-selective manner by one procedure is one of the most ideal processes in organic synthesis. We have been studying constructions of polycyclic ring systems by using cascade reaction under four different conditions, ionic reaction, radical reaction, transition metal catalyzed reaction and pericyclic reaction. we have already established two types of cascade reactions, which are useful for natural products synthesis. Thus, intramolecular double Michael reaction provides a ploycyclic compound fused to six membered ring possessing five stereogenic centers. On the other hand, the intramolecular Michael-aldol reaction constructs polycyclic ring systems fused to four membered ring having multiple stereogenic centers. Catalytic asymmetric reactions of these cascade reactions were extensively studied. Furthermore, the corresponding intermolecular reactions were performed.We have developed a new type of palladium-catalyzed cascade reaction; treatment of propalgyl carbonate with phenol in the presence of catalytic amount of zero valence palladium producing a cyclic carbonate. The reaction has been easily extended to asymmetric synthesis using (S)-BINAP with high enantio selectivity. Cycloalkenylation reaction using catalytic amount of Pd(II) was achieved. Cascade addition reaction of vinyl radical was also extensively studied. Using these characteristic reactions, a novel lead compound for neuroprotective agent has been found.