When a diester cyclizes and self-condenses, the product is going to be a cyclic beta-ketoester. This just makes sense because a beta-ketoester is always the product of a Claisen. But now it's going to be a ring because it's intramolecular. Chemists just had to make this overly complicated and, apparently, the person who discovered this specific cyclization was called Deichmann. This is also called a condensation. But don't get too hung up on the name because really all it is is an intramolecular Claisen. Intramolecular Claisen and Deichmann are the same thing. Once again, we're going to determine where to form enolates based on whether we should, based on if we can make a 5- or 6-membered ring. Esters are a little bit more straightforward because I don't have possibilities on both sides. I only have really 1. Would that enolate make sense? Would that give me a 5- or 6-membered ring if it attacked the other ester like this? Let's see. That's perfect. A 6-membered ring, we know that that's going to be favored.

What I'm going to do is draw the rest of the mechanism which would be O facing up. Once again, since I have a 6-membered ring, I'm going to draw my six numbers. I'm going to start at this corner and I'm going to move my way around counterclockwise. Really, you can start wherever you want but this is just the way that I like to do it. Now I'm wondering what's missing in the different places. Let's even just do the whole mechanism. At this point of the mechanism, what's missing? It looks like ₁ is missing an ester. Let's add that. ₁ is missing this whole ester thing. What else? ₆ is missing two things. ₆ is missing an O-negative and it's missing an O₁₈. Perfect. Now that looks like it's correctly drawn. I'm going to erase the numbers because we know we did it right.

Now, the next step of this mechanism is? What's the next step? The next step is that I have to kick out the leaving group. I would reform the ketone and kick out the OET. What that's going to give me is a compound that now looks like OET and then ketone. Now, I'm wondering, guys, did I get the right compound? Because remember that whenever you get a Dieckmann, a Dieckmann should always yield a cyclic beta-ketoester. Is this a cyclic compound? Yes. Is it a beta-ketoester? Well, I still have an ester and I have a ketone at the beta. So yes, this is correct. Cool, right? So intramolecular. Got to get used to it in this chapter. This isn't the last time it's going to come up. It's going to come up again. I'm warning you. Get good at it now. Let's move on to the next topic.