| Research Abstract |
This project focused on the development of new reactions of highly strained alkynes such as arynes and heteroarynes using a transition metal catalyst. A novel method for construction of biaryls via palladium-catalyzed [2+2+2] cocyclization of diynes and arynes was developed. By this methodology, various arylnaphthalene derivatives, including a sterically hindered 2,2'-disubstituted-1,1'-binaphthyl, can be constructed by virtue of a variety of combinations of diynes and aryne precursors. Using this reaction as a key step, the total syntheses of taiwanins C, E, and dehydrodesoxypodophyllotoxin were achieved. Furthermore, a [2+2+2] cocyclization of diynes and heteroarynes was also investigated. As the result, a nickel-catalyzed [2+2+2] cocyclization of diynes and 3,4-pyridynes was developed for the first time, affording isoquinoline derivatives in good yields. In this reaction, an electron-donating substituent on the pyridine ring of the 3,4-pyridyne precursor was tolerated, giving various substituted isoquinolines in good yields, respectively. On the other hand, it was found that an electron-withdrawing substituent on the pyridine ring of the precursor retarded the [2+2+2] cocyclization.
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