&. II as 11, regardless of how unsymmetrical the bridge might be, were involved, ring expansion may accompany opening of the bridged ion to give stereochemical control. A protonated epoxide would be such a case. Indeed, treatment of 1 with tert-butyl hydroperoxide in the presence of a vanadium catalyst"[VO (a~ ac)~ or (Ph3Si0) 3V0]'2 in toluene at-10 OC to room temperature leads to a unique cyclobutanone 5, which has also ...