Claisen Rearrangement
Claisen rearrangement involves the shift of a group from oxygen to carbon. The first reported Claisen rearrangement is the [3,3]-sigmatropic rearrangement of an allyl phenyl ether to 2-allylphenol.
Generally, group migrates to ortho position but Shifting (or migrating) of group to the the para position is also observed. When both the ortho positions are occupied, the group migrates to the para position. When both the ortho and para positions are occupied, there is no reaction.
During the ortho migration, the allyl group undergoes allylic shift. However, in the para migration there is no change.
In this rearrangement, there is no need of catalyst.
Migration to the para position
Generally, group migrates to ortho position but Shifting (or migrating) of group to the the para position is also observed. When both the ortho positions are occupied, the group migrates to the para position. When both the ortho and para positions are occupied, there is no reaction.
During the ortho migration, the allyl group undergoes allylic shift. However, in the para migration there is no change.
In this rearrangement, there is no need of catalyst.
Mechanism of Claisen rearrangement
The possible mechanism is given below-Migration to the para position