25. Condensation Chemistry

Show how the following products might be synthesized from suitable Michael donors and acceptors.

(f)

Determine the product in the following conjugated addition reaction.

What reagents should be used to prepare the following compounds?

a.

Predict the products of the following reactions.

(i)

Determine the product in the following conjugated addition reaction

Show how you would accomplish each conversion using an enamine synthesis with pyrrolidine as the secondary amine.

(a) cyclopentanone → 2-allylcyclopentanone

(b) pentan-3-one → 2-methyl-1-phenylpentan-3-one

Which of the following pairs of starting materials can be used to synthesize ${\mathrm{CH}}_3\mathrm{COCH}{2}_2\mathrm{CH}{2}_1\mathrm{COOEt}$ via a Michael addition reaction?

Show how the following products might be synthesized from suitable Michael donors and acceptors.

(e)

Show reaction sequences (not detailed mechanisms) that explain these transformations:

(a)

A compound known as Hagemann's ester can be prepared by treating a mixture of formaldehyde and ethyl acetoacetate first with base and then with acid and heat. Write the structure for the product of each of the steps.

b. The second step is a Michael addition.

In Solved Problem 22-9, the target molecule was synthesized using a Michael addition to form the bond that is β,γ to the upper carbonyl group. Another approach is to use a Michael addition to form the bond that is β,γ to the other (lower) carbonyl group. Show how you would accomplish this alternative synthesis.

Predict the products from this sequence of reactions.

Many of the condensations we have studied are reversible. The reverse reactions are often given the prefix retro-, the Latin word meaning “backward.” Propose mechanisms to account for the following reactions.

(c)

Draw the products of the following reactions:

a.

Determine the product in the following conjugated addition reaction.