The first step of this reaction is a simple nucleophilic attack on the carbonyl group of the ketone.
In the migration step of this reaction, the group with the highest
migratory aptitude
undergoes migration.
This reaction can also be
intramolecular
.
References:
Fukuda O.; Sakaguchi S.; Ishii Y.;
Tetrahedron Lett
., 2001, Volume 42, Issue 20, 3479
Kobayashi S.; Tanaka H.; Amii H.; Uneyama K.;
Tetrahedron
, 2003, Volume 59, Issue 9, 1547