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.
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
What is the product of the following reaction?
Show how you would synthesize the following product from the starting material using any reagents necessary.
What product is expected in this reaction sequence?
Provide a mechanism for the following reaction.
Draw the structural formula, including stereochemistry when necessary, of the organic product(s) for the following reaction.