How to synthesize from the malonic ester the dialkylated intermediate required for the synthesis of aprobarbitol is to be shown. Further a mechanism for the reaction of the intermediate with urea to give aprobarbitol is to be proposed. Concept introduction: Removal of both the hydrogens of the active methylene group in malonic ester by treating with LDA and then treating the enolate ions with alkyl halides will yield the dialkylated product. The steps involved in the reaction of the dialkylated product with urea are i) Nucleophilic attack of nitrogen of urea on the carbonyl carbon of the dialkylated ester ii) Elimination of the ethanol iii) Another nucleophilic attack by second nitrogen of urea on the carbonyl of the other ester group iv) Elimination of another ethanol. To state: How to synthesize from the malonic ester the dialkylated intermediate required for the synthesis of aprobarbitol. Further to propose a mechanism for the reaction of the intermediate with urea to give aprobarbitol

Question

A variation of the acetamidomalonate synthesis can be used to synthesize threonine. The process involves the following steps: Ethoxide ion deprotonates diethyl acetamidomalonate, forming enolate anion 1; Enolate anion 1 makes a nucleophilic attack on acetaldehyde, forming tetrahedral intermediate 2; Protonation of the oxyanion forms alcohol 3; Acid hydrolysis yields dicarboxyamino alcohol 4; Decarboxylation leads to the final amino acid. Write out the mechanism on a separate sheet of paper, and then draw the structure of enolate anion 1.

Answer 1

Question

Chapter 22.SE, Problem 49AP

Interpretation Introduction

Interpretation:

How to synthesize from the malonic ester the dialkylated intermediate required for the synthesis of aprobarbitol is to be shown. Further a mechanism for the reaction of the intermediate with urea to give aprobarbitol is to be proposed.

Concept introduction:

Removal of both the hydrogens of the active methylene group in malonic ester by treating with LDA and then treating the enolate ions with alkyl halides will yield the dialkylated product.

The steps involved in the reaction of the dialkylated product with urea are i) Nucleophilic attack of nitrogen of urea on the carbonyl carbon of the dialkylated ester ii) Elimination of the ethanol iii) Another nucleophilic attack by second nitrogen of urea on the carbonyl of the other ester group iv) Elimination of another ethanol.

To state:

How to synthesize from the malonic ester the dialkylated intermediate required for the synthesis of aprobarbitol. Further to propose a mechanism for the reaction of the intermediate with urea to give aprobarbitol

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