Efficient Syntheses of Pharmacologically Active Compounds Using Multiple Cascade Reactions

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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.