Propargylation, Allenylation, and Addition of Acetylenes

Notably, unlike with other propargylic and allenic organometallics, no metallo-tropic interconversion of 64 and 66 has been observed, which points to an interesting potential of this methodology [65, 66]. 

An analogous propargylation can be attained with allenyl tributylstannane however, this reaction is catalyzed by SiCk that is activated by a bis-phosphoramide catalyst. Note that, in this case, the role of the Lewis basic phosphoramide is to increase the Lewis acidity of SiCLj rather than to increase the nucleophiUcity of the stannane [66bj. For a discussion of these effects, see Section 15.4.  

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