Dramatic acceleration of the Diels-Alder reaction by adsorption on chromatography adsorbents

Phthalate plasticizers covalently linked to PVC via copper-free or copper catalyzed azide-alkyne cycloadditions

“…The first approach (Scheme 1) involved Diels-Alder reaction of isoprene and dimethylacetylene dicarboxylate catalyzed by anhydrous silica gel [30] to give cyclohexadiene dicarboxylate 11 in 96% yield. Oxidation using Dess-Martin periodinane gave dimethyl-4-methylphthalate in 68% yield.…”

A Study of the Diastereoselectivity of Diels-Alder Reactions on the Ce-SiO2as Support

“…23 Cerium (IV) is a strong Lewis acid than Zn(II), thus the frequency shift of C=O for cerium ion will shift to the lower wave number region than zinc ion. However, the width of this band is attributed to the several kinds of carbonyl groups coordination and also possibility of hydrogen bonding with the Si-OH of silica surface.…”

“…23 Vesselovskii and coworker have proposed that the adsorption of reactants on the surface of silica particles may facilitate the formation and stabilization of pre-reaction complexes by bringing the reacting moieties within each reactant into closer proximity. 24 A related theory has been advanced by Menger who suggested that the rigid anchoring of functional groups can fix reactants in proximity to each other less than the critical bonding distance, thus leading to significant rate enhancements.…”

Environmentally Benign Solvent Systems: Toward a Greener [4+2] Cycloaddition Process

“…30 The starting materials were simple (e.g. butadiene and acrolein), and by applying the reactants to the solid support they prepared a variety of adducts in good to excellent yields.…”