16. Conjugated Systems

While attempting to recrystallize maleic anhydride, a student dissolved it in freshly distilled cyclopentadiene rather than in freshly distilled cyclopentane. Was her recrystallization successful?

What are the products of the following reactions?

a.

What are the products of the following reactions?

b.

Predict the products of the following proposed Diels–Alder reactions.

(e)

Predict the products of the following proposed Diels–Alder reactions.

(d)

Predict the products of the following proposed Diels–Alder reactions.

(c)

Predict the products of the following reactions.

(i)

Predict the products of the following reactions.

(d) furan + trans-1,2-dicyanoethylene

Predict the major product for each proposed Diels–Alder reaction. Include stereochemistry where appropriate.

(a)

Predict the products of the following Diels–Alder reactions.

(a)

(b)

Predict the products of the following proposed Diels–Alder reactions. Include stereochemistry where appropriate.

(a)

(b)

(c)

Give the structures of the products represented by letters in this synthesis.

Part 3:

The diene lactone shown in part (a) has one electron-donating group (-OR) and one electron-withdrawing group (C=O). This diene lactone is sufficiently electron-rich to serve as the diene in a Diels–Alder reaction.

b. The Diels–Alder product A is not very stable. Upon mild heating, it reacts to produce CO₂ gas and methyl benzoate (PhCOOCH₃), a very stable product. Explain how this strongly exothermic decarboxylation takes place. (Hint: Under the right conditions, the Diels–Alder reaction can be reversible.)

Predict the products of the following reactions.

(h) cyclopentadiene + methyl acrylate, CH₂=CH–COOCH₃