25. Condensation Chemistry

Which product is the most likely intramolecular aldol addition product formed when $O_2$-hexanedione is treated with base and then acid workup?

What is the major product formed when ${\mathrm{CH}}_2\mathrm{COCH}{2}_{\mathrm{CO}}\mathrm{CH}{2}_{\mathrm{CO}}\mathrm{CH}{2}_{\mathrm{CO}}\mathrm{CH}{2}_{\mathrm{CO}}\mathrm{CH}{2}_{\mathrm{CO}}$ (hexane-2,6-dione) undergoes intramolecular aldol condensation under basic conditions?

Consider the following reaction. Provide a stepwise mechanism to explain the given transformation.

Draw the product of the reaction of each of the following compounds with a base:

c.

Can 2,4-pentanedione undergo an intramolecular aldol addition? If so, why? If not, why not?

Draw the product of the reaction of each of the following compounds with a base:

d.

The following compound results from base-catalyzed aldol cyclization of a 2-substituted cyclohexanone.

(b) Propose a mechanism for the cyclization.

The following compound results from base-catalyzed aldol cyclization of a 2-substituted cyclohexanone.

(a) Show the diketone that would cyclize to give this product.

When cyclodecane-1,6-dione is treated with sodium carbonate, the product gives a UV spectrum similar to that of 1-acetyl-2-methylcyclopentene. Propose a structure for the product, and give a mechanism for its formation.

Show how octane-2,7-dione might cyclize to a cycloheptenone. Explain why ring closure to the cycloheptenone is not favored.

Draw the product of the reaction of each of the following compounds with a base:

a.

Draw the product of the reaction of each of the following compounds with a base:

b.

Propose mechanisms for the two Dieckmann condensations just shown.