16. Conjugated Systems

Predict the product of the Claisen reactions shown.

(c)

Predict the product of the Claisen reactions shown.

(b)

Propose a mechanism for the following reaction:

If the terminal sp² carbon of the substituent attached to the benzene ring is labeled with ¹⁴C, where will the label be in the product?

Draw the product of the following reaction:

The Claisen rearrangement can be used to attach allyl groups to benzene via initial alkylation of a phenol.

(a) Predict the identity of A and B

(b) provide an arrow-pushing mechanism for each step. [The phenol alkylation is simply a Williamson ether synthesis reaction.]

The Ireland–Claisen reaction is a variant of the Claisen reaction studied in this chapter.

(a) Suggest a mechanism for the first step.

(b) Predict the product (B) that would result from heating intermediate A.

(c) Hydrolysis of B gives a carboxylic acid.

Suggest a mechanism for this reaction.

Only after working Assessment 22.53, predict the product of the following reactions.

(a)

Only after working Assessment 22.53, predict the product of the following reactions.

(b)

The Johnson–Claisen reaction is a variant of the Claisen reaction studied in this chapter. (a) Suggest a mechanism for the first step. (b) Predict the product (B) that would result from heating intermediate A.

The Eschenmoser–Claisen reaction is a variant of the Claisen reaction studied in this chapter. Based on your answers to Assessments 22.53–22.55, predict a product of this reaction.