Cadmium iodide-mediated allenylation of terminal alkynes with ketones.

Allenes are important building blocks in organic synthesis and have attracted much attention from researchers worldwide. So far, mono- and 1,3-disubstituted allenes can be prepared easily by applying the allenylation of terminal alkynes reaction of aldehydes. However, trisubstituted allenes have never been reported using this reaction due to the extremely low reactivity of ketones.