Metal-based Lewis acid catalysts for conversion of a variety of aldehydes with acetic anhydride to gem 1,1-diacetates

Abstract

Selective protection of carbonyl groups such as oxathioacetals, acylals, acetals and dithioacetals is the vital steps in organic chemistry. Among these groups, protection of aldehydes such as diacetates (acylals) has attracted more attention in the organic chemistry due to its superior applications such as commodity chemical in various fields of chemistry, their ease of preparation and their stability toward basic and neutral conditions. Beyond their protecting role, 1,1-diacetates are important precursors for the synthesis of acetoxydienes, starting materials as valuable intermediates for Diels–Alder cycloaddition reactions and neutral and basic media. Also acylals have been used as intermediates in industry as cross-linking agents for cellulose in cotton. Protection of carbonyl group of aldehydes by acetic anhydride in the presence of acid catalyst is the most convenient way. This review precises chemoselective procedure for the preparation of acylals by using the metal-based Lewis acid catalysts, magnetic nanocatalysts, ionic liquids, strong protic acid and solid acids.