Two similar rearrangements involving radical pair mechanisms.

The radicals in the radical pair are held in close proximity by the solvent 'cage' that will surround the charged species.

Wittig

Compared to a benzylic radical, an oxygen radical is not particularly favourable, so the left hand of the two resonance species will be the prevalent one.

There is more detail on the Wittig reaction in the Organic > Heteroatom > Phosphorus chapter.

Stevens