[spidermclovin]

Really stuck on this one. I'm fairly sure you have to use grubbs catalyst to form a new 5 membered ring but I can't get the mechanism straight.

Suggest a suitable reagent for this transformation and propose a mechanism that accounts for
the formation of compound D.

[Enthalpy]

Maybe you need no additional reagent. Try the metathesis within the given reactant, opening one cycle and closing a new one at the proper side of the old double bond.

Err, I didn't heck every single atom.