Selective preparation of benzene derivatives from three different alkynes and pyridine derivatives from two different alkynes and a nitrile*

Since the first zirconacyclopentadiene was prepared by coupling of 2 equiv of diphenylacetylene on zirconocene in 1970 [1], many groups have reported the formation of zirconacyclopentadienes [1]. Surprisingly, for more than 20 years almost no carbon–carbon bond formation reactions have been reported for zirconacyclopentadienes. Only one paper appeared in 1983 to show the insertion reaction of the third alkyne into a zirconacyclopentadiene to form a zirconacycloheptatriene [2]. However, unfortunately, the zirconacyclopentadienes we prepared did not show such insertion reactions. Therefore, we decided to develop general carbon–carbon bond formation of zirconacyclopentadienes, since various zirconacyclopentadienes could be conveniently prepared.