Homo-Favorskii rearrangement

E1cb will occur if α-carbon adjacent to the halogen atom has hydrogens on it.

The reaction proceeds in an analogous manner to that of the Favorskii rearrangement.

[1] The selectivity is similar to the Favorskii rearrangement in that the most stable carbanion is formed.

The homo-Favorskii rearrangement is a key step in the synthesis of Kelsoene, constructing its four-membered ring.

Therefore, the cyclobutanone intermediate can be isolated and is further reacted to yield the product.