# Aldol Reaction on an intermediate

I was given the following reaction to prove a mechanism for:

and I managed to prove the first step with ease.

The second step, forming the "base-catalysed aldol" is the part that's rather confusing me.

Consider the mechanism of a base-catalysed aldol reaction below.

For this reaction to take place, I need a second carbonyl molecule, but the $$\ce{CO2Me}$$ on the right hand side ring appears untouched, and likewise so does the carbonyl group on the left hand side too.

I tried the reaction a second way (giving the mechanism below) but am unsure if this is correct.
Is this the correct mechanism?

• Looks mostly reasonable to me. There’s an alkene missing from your final product though. Also, in the final elimination you’ve drawn an E2 reaction, but OH typically isn’t a good enough leaving group to do this. Can you think of an alternative elimination pathway? – PCK Jun 12 at 21:04