TMSCl Promoted Direct Conversion of Cyclic Anhydrides to (Un)Symmetric-Diesters/Amide Esters.

Abstract

We present a mild, efficient, and one-pot method for the silyl-promoted transformation of cyclic anhydrides into homo- and hetero-dicarboxylic acid diesters and amide esters. This versatile reaction operates under ambient conditions, on a gram scale, and accommodates a wide range of alcohols, amines, and cyclic anhydrides. The one-pot process involves a two-step sequence, starting with the nucleophilic opening of anhydride by an amine or alcohol, followed by esterification. TMSCl serves a dual role, acting as a sacrificial reagent to remove in situ water and as a Lewis acid to promote the anhydride opening. The reaction proceeds successfully in the absence and presence of a base, as confirmed by NMR and crossover experiments, which validated the formation of dicarboxylic acid monoester and alkyl silyl mixed diester respectively. Controlled experiments have shown that the one-pot process yields higher efficiencies when compared to the same reaction conducted using a two-step process. This is the first comprehensive study demonstrating a broad substrate scope for the conversion of cyclic anhydride into diesters and amide esters. The method finds application in the synthesis of various commercial plasticizers.