Answer:
See explanation below
Explanation:
You are missing the initial structure, but in picture 1 you have the structure which I found on another place.
Now, as you can see in picture 1, you have a diene, which are two rings with 4 doubles bonds, however, only two of them, in the second ring are conjugated, therefore, the reaction will take place there. This is a Diels Alder reaction, so the mechanism is pretty easy. Picture 2, shows the product obtained after the reaction.
