(untitled) - Baldwin, J E; Kruse, L I (J. Chem. Soc., Chem. Commun., 1977)
Baldwin noted that when endocyclic alkylation of ketone enolates constructs five-membered rings, O-cyclization would be preferable because of an in-plane approach to enolates. The chemoselectivity in our case could be partially explained by a similar reasoning, albeit with the sp2-CF2 electrophile instead of sp3-C electrophiles. See: