Rearrangement: 1,2-Shift
1,2-Rearrangement involves a functional group transferring from one atom to an adjacent atom. The process may be concerted or it may proceed via a tricyclic intermediate. Either way, 1,2-rearrangement processes are usually strongly stereoselective.

For more information look in the Chemogenesis webbook sections on rearrangement reactions and pericyclic reactions.