[Robsh9]

Epoxies are a three membered ether ring. THF is a five membered ether ring. Oxetane is the four membered equivalent. Ring strain causes the epoxides to react and THF does not react because the ring strain is not large enough. Does the four membered ring react or not? Does it favor reaction with the harder or softer nucleophile perhaps - thus only reacting with some Grignard reagents?

[OrgXemProf]

Grignard reagents react slowly with oxetanes to afford primary alcohols after acidic workup. Application of heat accelerates this reaction.

Better way: Reactions of Grignard reagents with oxetanes when performed in the presence of copper catalysts proceed under mild conditions and afford the corresponding primary alcohol in good yield. Reference: Huynh, C.; Derguini-Boumechal, F.; Linstrumelle, G. Tetrahedron Lett. 1979, 20, 1503-1506.

Enantioselective opening of oxetanes has been achieved by the combination of a chiral ether and phenyllithium in the presence of boron trifluoride to give the corresponding alcohol in 47% ee. Reference: Mizuno, M.; Kanai, M.; Iida, A.; Tomioka, K. Tetrahedron Asymmetry 1996, 7, 2483-2484.