Question

Question: What product is formed by [3,3] sigmatropic rearrangement of the following compound? Clearly indicate the stereochemistry around all tetrahedral stereogenic centers.

Short answer

Answer

Step-by-step solution

[3,3] sigmatropic rearrangement

The net change in the number of $\mathbf{\sigma }$-bonds is zero. This rearrangement requires little to no heat; no catalyst is required. Along with the change of the position of a -bond, the position of a group is changed.

Ring stability

The driving force for this rearrangement to occur is the instability of the five-membered small ring with a double bond and a hydroxide group in close proximity of the C=C.

Mechanism of the given reaction

The -bond from the -bond is rearranged to change the position of the group. The rearrangement takes place in between the two -bonds and a -bond. The mechanism of the rearrangement is given hereunder

The product of rearrangement has the OH group far from the C=C of the five-membered ring.