Claisen Rearrangement

Claisen Rearrangement

Figure 1:) Claisen Rearrangement Reaction Scheme

     NOTE:  After the [3,3]-rearrangement occurs, the created ketone tautomerizes into a phenol in order to restore aromaticity to the system in form of a phenol.  This reaction follows an ortho-Claisen since the alcohol and alkenyl groups are ortho to one another.  However, take notice that if the other ortho-position to the alcohol is avaliable, if this position were blocked, by a methyl group for example, the reaction in Figure 2 would occur.

Figure 2 :) Para-Claisen Rearrangement

     Because both ortho-positions are blocked by the methyl groups, a [3,3] rearrangement will occur to yield an ortho-ortho-para-substituted ring.  This happens because the ether group activates the ring towards ortho and para substitution, however since the other locations are blocked by methyls, the para-position is attacked.