Question

Question: Alkene A can be isomerized to isocomene, a natural product isolated from goldenrod, by treatment with TsOH. Draw a stepwise mechanism for this conversion. (Hint: Look for a carbocation rearrangement.)

Short answer

Answer

Step-by-step solution

Isomerization of alkene

The isomerization alkene occurs by the formation of a carbocation intermediate.

This intermediate carbocation leads to 1,2-bond shift (driving force is the relaxation of the strained molecule), which forms another isomer of the alkene.

Explanation

The given alkene compound is acidified by TsOH to form a tertiary carbocation intermediate. Further, the 1,2-bond shift occurs from the highly strained four-membered ring to give another alkene isomer.

Isomerization of the alkene