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The mechanism for each reaction should be proposed.
The product is a b-keto ester.
The Dieckmann condensation has a name.
It is just an internal Claisen condensation.
There is a mechanism for the Dieckmann condensation.
A piece of paper is needed to record your answer.
Let's see what we can do with b-keto esters.
There are some very useful synthetic techniques.
In order to see how they work, we need to remind ourselves of a reaction we saw in the previous chapter.
When we looked at the chemistry of carboxylic acid derivatives, we saw that esters can be used to give carboxylic acids.
The b-keto acid will have a unique reaction when heated.
This is the basis for the synthetic techniques we will learn in this section, so let's make sure we understand how a decarboxylation occurs.
A ring of electrons moving around in a circle is a pericyclic reaction.
The Diels-Alder reaction is an important pericyclic reaction that we will cover in Chapter 10.
Many textbooks do not devote an entire chapter to pericyclic reactions, and this is because they are just scattered throughout the various chapters.
It is possible that your instructor will spend some time on pericyclic reactions.
We need to continue with the topic at hand, so we won't cover them right now.
The carboxyl group is expelled when CO gas is liberated.
The carboxyl group is expelled when a b-keto acid is heated.
The product is a ketone.
We need to add one more step at the beginning of the process to see why this is so useful.
This kind of reaction has been seen before.
It's just an alkylation.
We used an alkoxide ion to produce a stable enolate that attacks the alkyl halide in an S 2 reaction.
Look closely at the product.
A wide variety of substituted derivatives of acetone can be made using this method.
The desired product would be produced with many other products.
We have learned a way to make substitute derivatives of acetone.
Primary alkyl halides will be more efficient if you remember that the alkylation step is an S 2 process.
It would have required an alkylation step involving a tertiary alkyl halide, which can't function in an S 2 process.
ethyl acetoacetate is a compound.
This compound is part of a class of compounds called acetoacetic esters.
The acetoacetic ester synthesis has three main steps: alkylate, hydrolyze and decarboxylate.
The acetoacetic synthesis ester has four steps: alkylate, hydrolyze, and decarboxylate.
R groups don't have to be the same.
The alkyl groups may be different in this sequence.
For the following transformation, propose a synthesis.
The acetoacetic synthesis is a common synthetic strategy.
Let's focus on this other strategy now.
We follow the same three steps as before: alkylate, hydrolyze, and decarboxylate.
Our product will be slightly different because we start with a slightly different starting material.
The structure of our end product can be seen through the three steps: alkylate, hydrolyze, and then decarboxylate.
Remember how a decarboxylation works.
After the first carboxyl group is expelled, there is no longer a bond between the two groups.
You should find that you can't draw a mechanism for the second carboxyl group leaving.
The product is now a substitute for carboxylic acid.
The power of the synthesis is shown here.
The process is most efficient for primary R groups because alkylation is an S 2 process.
It would be difficult to alkylate a carboxylic acid directly.
You can't form an enolate in the presence of an acidic protons.
The synthesis gives us a way around the obstacle.
There is a method for making substitute carboxylic acids.
The malonic synthesis is made up of alkylate, hydrolyze, and then decarboxylate.
We need to identify the alkyl group that should be installed in order to solve this problem.
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