Cascade resulting in the reductive ethynylation of aldehydes: dissection of its components.

A mild and efficient two-carbon homologation of aldehydes exploiting multiple modes of KOt-Bu was developed. This process involves a sequential Peterson allenylation/allene-alkyne isomerization/protodesilylation in a single-flask operation. The differential roles played by the various elements of the process were demonstrated through dissection experiments.