Synthesis of biaryls via palladium-catalyzed [2+2+2] cocyclization of arynes and diynes:: Application to the synthesis of arylnaphthalene lignans

A novel method for construction of biaryls via palladium(0) -catalyzed [2+2+2] cocyclization of diynes and arynes was developed. By this [2+2+2] cocyclization, 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 [2+2+2] cocyclization as a key step, the total syntheses of natural arylnapbthalene lignans, taiwanin C, taiwanin E, and dehydrodesoxypodophyllotoxin were achieved.