A Comprehensive Overview of Cyclodextrins Catalyzed Diels-Alder Reactions

Abstract

Diels-Alder (DA) reactions typically yield heterocyclic six-membered ring compounds via a [\(4\Pi\)+\(2\Pi\)] cycloaddition of a diene (such as furan or cyclopentadiene) and a dienophile. The choice of solvent and catalyst is critical in affecting the yield and stereoselectivity of the reaction. Cyclodextrins, particularly beta-cyclodextrin (\(\beta\)-CD) and its derivatives, are commonly used as catalysts in aqueous medium due to their ability to form a favorable ternary complex with both the diene and dienophile. As a result, this paper summarizes several experimental studies on the catalytic effects of CDs on DA reactions, with an emphasis on yields, reaction durations, quantities, and selectivity. The first phase, reported by Ronald Breslow and colleagues in 1980, looked at the effect of inner cavity size on catalytic and inhibitory effects on DA processes. The following phase investigated the effect of cyclodextrin catalysts on endo- and stereoselectivity. Numerous studies have examined the potential of \(\beta\)-CD's interior size, derivatives, amounts, organic and aqueous media, and compatibility with the two reagents. In contrast, some research has concentrated on employing cyclodextrins as catalysts in Diels-Alder processes to generate large yields of bioactive chemicals and polymer synthesis under mild conditions, generally in aqueous solutions.