Using Aldol Reactions in Synthesis

Problem 23.3 What enone product would you expect from aldol condensation of each of the following compounds  

Problem 23.4 Aldol condensation of 3-mcthylcyclohexanone leads to a mixture of two enone products, not counting double-bond isomers. Draw them. 

The aldol condensation reaction yields either a jS-hydroxy aldehyde/ketone or an a,jS-unsaturated aldehyde/ketone, depending on the reactant and on the experimental conditions. By learning how to think backward, it s possible to predict when the aldol reaction might be useful in synthesis. Any time the target molecule contains either a -hydroxy aldehyde/ketone or a conjugated enone functional group, it might come from an aldol reaction. 

Problem 23. S Which of the following compounds are aldol condensation products What is the 

Problem 23.6 1-Butanol is prepared commercially by a route that begins with an aldol reaction. Show the steps that are likely to be involved. 

ThomsonNOV Click Organic Interactive to use a web-based palette to design syntheses utilizing aldol-type reactions. 

We can extend this kind of reasoning even further by imagining that subsequent transformations might be carried out on the aldol products. For example, a saturated ketone might be prepared by catalytic hydrogenation of the enone product. A good example can be found in the industrial preparation of 2-ethyl- 

1- hexanol, an alcohol used in the synthesis of plasticizers for polymers. Although 2-ethyl-l-hexanol bears little resemblance to an aldol product at finst glance, it is in fact prepared commercially from butanal by an aldol reaction. Working backward, we can reason that 2-ethyl-l-hexanol might come from 

2- ethylhexanal by a reduction. 2-Ethylhexanal, in turn, might be prepared by catalytic reduction of 2-ethyl-2-hexenal, which is the aldol condensation product of butanal. The reactions that follow show the sequence in reverse order. 

Show how you would synthesize the following compound using an aldol reaction  

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Use of Enzymatic Aldol Reactions in Synthesis Table 1 (continued)... 

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