Vinylidene Rearrangement of Internal Alkynes: Development, Basic Properties and Control

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 have found that even alkyl or aryl substituted internal alkynes can take part in this reaction to give the corresponding disubstituted vinylidenes. In this seminar I would like to show the vinylidene rearrangement of internal alkynes is a potentially general reaction in organometallic chemistry, to introduce its basic properties and mechanism, and finally to report how we can control the competition between vinylidene rearrangement and 1,2- insertion reaction.