Q26E - Organic Chemistry (Mcmurry)

Question

Nitriles can be converted directly to esters by the Pinner reaction, which first produces an iminoester salt that is isolated and then treated with water to give the final product. Propose a mechanism for the Pinner reaction using curved arrows to show the flow of electrons at each step.

Step-by-Step Solution

Answer

The mechanism for the Pinner reaction  and its product formation is shown below

Step 1: Definition of Pinner reaction

 The acid catalyzed reaction of a nitrile with an alcohol to form an imino ester salt is referred as Pinner reaction

Step 2: Mechanism for Pinner reaction

The benzonitrile is protonated by HCl. The nucleophilic attack of methanol on the protonated nitrile and the subsequent proton transfer yields iminoester.

In the next step, the nucleophilic attack of water on the protonated iminoester  accompanying deprotonation yields aminomethoxyphenylmethanol.

In the last step, the elimination of ammonia leads to the formation of methyl benzoate

The mechanism for the Pinner reaction is elucidated as follows