Acetoacetic ester synthesis substituted acetones

Related and equally important reactions are the acetoacetic ester synthesis and the eyanoaeetie ester synthesis Here too the initial substituted product can be hydrolyzed and decarboxylated, to yield a ketone 11 (i.e. a substituted acetone) from acetoacetic ester 10, and a substituted acetonitrile 14 from eyanoaeetie ester 13 respectively. Furthermore a substituted acetoacetic ester can be cleaved into a substituted acetic ester 12 and acetate by treatment with strong alkali ... 

Acetoacetic ester synthesis is the preparation of substituted acetones, and it s an important method for creating a variety of products. It begins with the reaction of acetoacetic ester (a dicarbonyl) or a similar compound with a strong base to produce a carbanion, which then reacts with alkyl halide, RX. The structure of acetoacetic ester is in Figure 15-10. Figure 15-11 illustrates an example of an acetoacetic ester synthesis and two possible outcomes. Figure 15-12 shows the preparation of 2-heptanone with a 65 percent yield via the acetoacetic ester synthesis. Figure 15-13 presents the preparation of 2-benzylcyclohexanone with a 77 percent yield. 

Acetoacetic Ester Synthesis The formation of a substituted acetone through the base-catalyzed alkylation or arylation of a (3-keto ester. 

The acetoacetic ester synthesis is similar to the malonic ester synthesis, but the final products are ketones specifically, substituted derivatives of acetone. In the acetoacetic ester synthesis, substituents are added to the enolate ion of ethyl acetoacetate (acetoacetic ester), followed by hydrolysis and decarboxylation to produce an alkylated derivative of acetone. 

Show how the malonic ester synthesis makes substituted acetic acids, and how the acetoacetic ester synthesis makes substituted acetones. Give mechanisms for these reactions. 

As in the malonic ester synthesis, you should identify the structural fragments of the target compound. The acetoacetic ester synthesis converts an alkyl halide to a methyl ketone ("substituted acetone"). The methyl ketone component comes from acetoacetic ester the other component comes from a halide. 

The single bond to this substituted acetone can be made by the acetoacetic ester synthesis. How can we make the a,p double bond Aldol condensation ... 

Acetoacetic ester synthesis—a ky atm followed by hydrolysis and decarboxylation gives substituted acetones ... 

We have already seen the chemistry of the individual steps in this synthesis, but we have not put them together in this particular sequence. Let us illustrate the acetoacetic ester synthesis by choosing 5-hexen-2-one as a target molecule. The three carbons shown in color are provided by ethyl acetoacetate. The remaining three carbons represent the —R group of a substituted acetone. 

In this reaction sequence, ethyl acetoacetate is alkylated twice, each time with a different alkyl group. Then, hydrolysis followed by decarboxylation produces a derivative of acetone in which two alkyl groups are positioned at the a position. Why is it necessary to use an acetoacetic ester synthesis instead of simply treating the enolate of acetone with an alkyl halide Wouldn t that be a more direct method for preparing substituted acetones There are two answers to this question (1) Direct alkylation ofenolates is often difficult to achieve in good yields and (2) enolates are not only strong nucleophiles, but they are also strong bases, and as a result, enolates can react with alkyl halides to produce elimination products. 

Two specific j8-dicarbonyl compounds have had broad use in organic synthesis. These are acetoacetic ester (ethyl acetoacetate, ethyl 3-oxobutanoate), which can be used to make substituted acetone derivatives, and diethyl malonate (diethyl 1,3-propanedicarboxylic acid), which can be used to make substituted acetic acid derivatives. We shall consider syntheses involving ethyl acetoacetate and diethyl malonate in the upcoming sections of this chapter. 

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