Concept: Concept: General Reactions2m
Now we’re going to take a look at the other form of beta-carbonyl ester reactions, which is malonic ester synthesis. If you see this chart and you’re thinking, “Oh my gosh, another set of reagents that I need to memorize.” You’re probably getting depressed, but don’t. This is the same exact thing as acetoacetic ester. Notice that every single reagent here hasn't changed. Nothing has changed. The only difference is that because I'm starting off with malonic ester, I have an extra OEt group over here.
What that means is that after I hydrolyze, not just this one turns into carboxylic acid. They both do. That means that the only difference between acetoacetic ester and malonic ester synthesis is that my products have carboxylic acids at the end. That’s it. Everything else stays the same. You could literally take everything you learned from acetoacetic acid, and when you see malonic, just draw the same thing as the acetoacetic acid and add the carboxylic acid at the end.
I’m not even going to go over every reaction here because this is the same as acetoacetic ester. Let's go through this practice problem. Go ahead and try to solve it yourself, and then I’ll step in and help.
Concept: Example: Predict the Products5m
Hey guys. So, one word of caution here, if you feel like you couldn't get this question right, Because you're having a hard time interpreting this content structure, you probably need to go back and review condemned structures, just saying, because we're pretty late in orgo 2 and they could show up anywhere, condensed structures I do have videos about them, okay? So, if you need extra help, I got you, but anyway the way you interpret this was it's a carbon with these two esters coming off of it, so it would be CO-OEt, so that would be like that and like that and then obviously it's CH2. So, I'm just going to put this H, cool. So, again, this is just and this is just another way to write malonic ester, okay? So, the first step was my base, do you think that this base was a good choice for this ester? sure the R group is the same, I don't worry about transesterification, the negative is going to grab one of the H's and make an enolate. So, I'm going to make something look like this, okay? Now, that enolate is going to be exposed to the following alkyl halide, something like this. So, Cl carbon, carbon, just make sure I'm getting this right, CH3 to, let's just make sure. So, CH3 to then CH, then CH2 yes, that's, right? okay? So, then we're going to do a backside attack, what that's going to give us is now malonic ester that is substituted and what's attached now is, I have my new bond? Well, I want to use a different color, I have my new bond and then I have the thing that I attached so, 1, 2, I believe that's right. Wait making sure, I think I'm actually off, yes, it should actually, that is that and then that is that, okay perfect, okay. Cool. Just making sure it's not a bad idea to slow it down and make sure that you're counting a carbons right, cool. So, there we have it, we just did an alkylation, the next step is what? hydrolysis.
Now, guys what's important about hydrolysis here is that you're going to hydrolyze both of your esters, right? So, that means that you're going to get carboxylic acid on one side and carboxylic acid on the other, you can't stop it plus your R group, right? Then finally, we have decarboxylation, and guys you might be wondering how do I know which ones did decarboxylate, because we said that carboxylic acid can decarboxylate. Well, it doesn't matter which one, you could either take off the green one or you could take off the red one but you can't take off both. So, pick one make a go away the other one stays. So, let's just say the red one leaves, that's going to give me a final compound that looks like this OH, carbon what's that attached to? carbon, carbon 1, 2, 3, 1, 2, 3, something like that, okay? Plus my CO2 guys, cool right? So notice that once again guys I just did an alpha alkylation but I used malonic ester to do it and notice that I have a carboxylic acid as the end product cuz I started off with malonic ester. Alright guys. So, I hope that made sense, it's not as scary as it looks, it's actually really fun, it's actually one of my favorite reactions to teach, most of my students like it, okay? So, that being said let's move on to the next videos.
Problem: Provide the major product for the following reaction7m
Problem: Provide the major product for the following reaction4m
Concept: Practice 3: Malonic Ester Retrosynthesis4m
Okay guys, let's take a look at the following retrosynthesis question. So, here I say beginning from diethyl malonate and using any other necessary reagents show the necessary compounds needed to form the following compound. So, remember diethyl malonate is the beginning compound that we use in malonic ester synthesis and what's the whole point of malonic ester synthesis, it's to change an alkyl halide into a carboxylic acid. So, all we do here is we replace that halogen with two carbons with the end carbon being a carboxylic acid. So, we have to think here is, okay? So, the last two carbons are part of the diethyl malonate that I used. So, here's your diaphragm malonate that we had here. So, those two carbons that we have came from diethyl malonate. So, all we got to do here is look at this molecule, here are my last two carbons that were part of my diethyl malonate that help to make the carboxylic acid. So, what does that mean the rest of this was? Well, the rest of this must have been my alkyl halide.
So, what must have happened with this, we had diethyl malonate, we used NaOEt. So, Na positive OEt minus, this shout out ripped off an alpha hydrogen, so that carbon is now negative because it has a lone pair, remember, we're saying that this portion here was the alkyl halide. So, my alkyl halide look like this, same exact compound with this carbon here connected to a halogen. So, then when I used SN2 this got kicked out and kicked this out, then what we had next was this, so that CH2 group is still connected to the ring and then what did I do? I could have used acid base hydrolysis or just acid hydrolysis to change my derivatives back into the parent of carboxylic acids and then what did I do? I used heat to undergo decarboxylation. So, they go decarboxylation. So, you lose CO2. So, then that's how we got this structure here. So, this was one and two part of the diethyl malonate, this carbon three here it's part of this ring here. So, remember focus on what malonic ester synthesis does, it adds two carbons, here;re my two carbons, those are part of diethyl malonate, the rest of it must have been part of the alkyl halide, so the carbon here had to have the halogen and knowing that is key to knowing what you started with in order to obtain this final product.