No abstract

A diastereoselective three-component cascade reaction, catalyzed by p-sulfonic acid calix[4]arene, provides a unique method to access diverse julolidine derivatives in high yields. Additionally, the reaction was also monitored by mass spectrometry and the mechanistic pathway uncovered.

An efficient method is proposed for obtaining tetrahydrobenzo[a]xanthene-11-ones and tetrahydro-[1,3]-dioxolo[4,5-b]xanthen-9-ones. The method is based on the use of p-sulfonic acid calix[n]arenes as catalysts under solvent-free conditions. The antiproliferative activity of fifty-nine xanthenones against six human cancer cells was studied. The capacity of all compounds to inhibit cancer cell growth was dependent on the histological origin of the cells. QSAR studies indicate that among compounds derived from β-naphthol the most efficient compounds against glioma (U251) and renal (NCI-H460) cancer cells are those having higher hydrogen bonding donor ability.

The use of calix[n]arenes as organocatalysts has increasingly been considered a prime focus due to their adjustable three‐dimensional molecular structure, easy synthesis, and versatile structural modification at the upper and lower edges. For instance, these macromolecules have been described as efficient catalysts for asymmetric aldol reactions, asymmetric Michael addition, esterification and transesterification, dehydration, nucleophilic aromatic substitution, and multicomponent reactions. Furthermore, calix[n]arenes also tolerate aqueous or solvent‐free reaction systems and can be supported on solid and/or magnetic particles, showing cost, time and energy savings, easier experimental procedures, and chemical waste reduction.