Question

p-Dimethoxytrityl (DMT) ethers are easily cleaved by mild acid treatment. Show the mechanism of the cleavage reaction.

Short answer

The mechanism of the cleavage reaction can be shown:

Step-by-step solution

Definition of detritylation

The detritylation can be denoted as a p-Dimethoxtrityl protective group that can be taken out of acid Cl₃COOH and its process. The reaction will take place by the S_N1 mechanism. The support of the silica bounded mechanism has a 5’- DMT protecting group. The main function is to protect the polymerization during the formation of resin.

Steps of the cleavage reaction mechanism

In step 1, the attack of oxygen lone pairs with trichloroacetic acid in dichloromethane and forms tertiary carbocation. The tertiary carbocation will increase the reaction rate and highly stable.

In step 2, the attack of the nucleophile on benzylic dimethoxytrityl cation will give the final product.

Overall reaction 

The overall reaction will occur by the stable carbocation formation by the S_N1 mechanism. The overall reaction can be,