Development of Novel Cyclizations via Rhodacycle Intermediate and Its Application to Synthetic Organic Chemistry.

Novel Rh(I)-catalyzed cyclizations through a different type of rhodacycle intermediate which is formed by hydroacylation of 4,6-dienal or oxidative addition of diene and alkene are described. Hydroacylation of 4,6-dienal afforded various 7-membered rings in good to high yields, while cycloisomerization of diene and alkene provided 5- or 6-membered rings in good yields. On the basis of these studies, we have also succeeded in developing the sequential reaction of hydroacylation followed by cycloisomerization to produce bicyclic compounds in a stereoselective manner and thus this reaction was expanded to the synthesis of epiglobulol. Furthermore, both Rh(I)-catalyzed hydroacylation and cycloisomerization using ionic liquid (IL) as a solvent were investigated and it was found that the IL recovered after the reaction, which contains the Rh(I) catalyst, could be recycled several times without loss of catalytic activity.