Rupe rearrangement

What is Rupe rearrangement?

The Rupe rearrangement, also known as the Rupe reaction, is a process where tertiary α-acetylenic alcohols are transformed into α,β-unsaturated ketones through thermal treatment in the presence of formic acid or other acids. The reaction can also be triggered by the silver carbonate salt. However, it may compete with the Meyer-Schuster rearrangement, which also leads to the formation of α,β-unsaturated ketones or aldehydes.

Rupe rearrangement - general reaction scheme - Rupe reaction
Rupe rearrangement

Although the two reactions share some similarities, they have distinct differences. In the Rupe rearrangement, dehydration produces a vinyl acetylene intermediate that, upon hydration, results in the desired α,β-unsaturated ketone. On the other hand, the Meyer-Schuster rearrangement involves a 1,3- or allylic shift to form an allenic carbonium intermediate that, upon hydration, produces a different α,β-unsaturated ketone or an aldehyde if a terminal acetylene is involved.

The Rupe rearrangement is the only process that occurs in some cases, such as when dealing with phenylethynylcarbinol with a methoxy group at the para-position of the phenyl group.