Which of the following best describes a Claisen rearrangement?
◦ [2,3] sigmatropic rearrangement with all atoms of the cyclic transition step are carbon atoms
◦ [2,3] sigmatropic rearrangement with heteroatoms
◦ [2,2] sigmatropic rearrangement with all atoms of the cyclic transition step are carbon atoms
◦ [3,3] sigmatropic rearrangement with heteroatoms
◦ [3,3] sigmatropic rearrangement with all atoms of the cyclic transition step are carbon atoms