DEVELOPMENT OF ENVIRONMENTALLY FRIENDLY ACTIVATION PROCESS OF UNREACTIVE OLEFINS AND ITS APPLICATION TO NATURAL PRODUCT SYNTHESIS

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Recently, the author has developed a palladium-catalyzed cycloalkenylation process as a catalytic activation method of unreactive olefins. It has become clear that an intramolecular coupling reaction of unreactive olefins with silyl enolates proceeds in the presence of catalytic amount of palladium acetate under one atmosphere of oxygen. In this research, the author has examined total synthesis of aphidicolin by use of palladium-catalyzed cycloalkenylation. In addition, the author has next investigated the construction of blcyclo[3.3.0]octane compounds and bicycio[4.3.0]nonane derivatives by means of the palladium-catalyzed cycloalkenylation.(1)Total Synthesis of AphidicolinA diastereoselective total synthesis of aphidicolin has been achieved by exploiting a unique characteristic of a bicyclo[3.2.1]octane prepared by employing a palladium-catalyzed cycloalkenyaltion process. In this sequence, highly diastereoselective oxirane formation was employed to install C-16 functionality. The strategy used in this aphidicolin synthesis, relying on the combined use of palladium-catalyzed cyclolakenylation and intramolecular Diels-Alder reactions for diastereoselective polycyclic ring system formation, should be broadly applicable to the preparation of targets with related structural features.(2)Simple Construction of Bicyclo[4.3.0]nonane, Blcyclo[3.3.0]octane, and Related Benzo Derivatives by Palladium-Catalyzed CycloalkenylationBicyclo[4.3.0]nonanes (hydrindanes) and blcyclo[3.3.0]octanes (octahydropentarenes) have been easily synthesized by palladium-catalyzed cycloalkenylation. Additionally, benzo-fuzed bicyclo[3.3.0]octanes have been prepared for the first time through coupling between silyl enolates and aromatic rings in the presence of catalytic palladium acetate. It is notable that reaction between sp2 carbons of silyl enol ether and an aromatic ring was observed under neutral reaction conditions.