Vinylidene Rearrangement of Internal Alkynes

In spite of a long and successful history of the vinylidene rearrangement of terminal alkynes, internal alkynes have been believed incorrectly not to undergo this rearrangement.Some time ago, however, with an adequate metal center as the reaction site, we havefound that even alkyl or aryl substituted internal alkynes can take part in this reaction togive the corresponding disubstituted vinylidenes. In this seminar I would like to show thevinylidene rearrangement of internal alkynes is a potentially general reaction inorganometallic chemistry, to introduce its basic properties and mechanism, and finally toreport how we can control the competition between vinylidene rearrangement and 1,2-insertion reaction.