Primary Amine Confinement at the Interface of Grafted Calixarenes and Silica

Abstract

A general approach for functional group confinement is demonstrated for primary amines and relies on the formation of a pocket in the shape of an inverted wedge at the interface between grafted monosubstituted calix-[4]-arenes and silica surface. Shape-selective binding of salicylaldehyde to the confined amine materials is demonstrated.

Coumarin–Calix[4]arene Conjugate-Anchored SiO2 Nanoparticles as an Ultrasensor Material for Fe3+ to Work in Water, in Serum, and in Biological Cells

“… 11 − 19 Calixarenes have also been coated onto different solid surfaces and were explored for ion selectivity. 20 − 30 Reports are scant in the literature where calixarenes are covalently attached on to the solid support like silica nanoparticles 30 − 35 and are further scarce in that these exhibit enhanced sensitivity and greater selectivity.…”

“…Among several compounds, silica (SiO 2 ) is an important inorganic component of the hybrid material that has been used more frequently because of its non-toxic nature and easy adaptation into porous nanoforms, besides its high thermal and mechanical stability. − Among various macrocyclic compounds, calix[4]­arene with a cone conformation provides an interesting supramolecular platform because of its ease of organic derivatization both at its lower and upper rims in order to decorate it by using a variety of different functional moieties. Calixarenes have been well explored in the literature for their host–guest interactions, sensing, and catalysis. − Calixarenes have also been coated onto different solid surfaces and were explored for ion selectivity. − Reports are scant in the literature where calixarenes are covalently attached on to the solid support like silica nanoparticles − and are further scarce in that these exhibit enhanced sensitivity and greater selectivity.…”

Iodine-Catalyzed Functionalization of Primary Aliphatic Amines to Oxazoles, 1,4-Oxazines, and Oxazinones

“…Aliphatic primary amines are represented in a wide range of chemical feedstock and display great biological, pharmaceutical, agricultural, materials, and synthetic applications. − Of late, functionalization of C­(sp 3 )-H has emerged as a promising synthetic tool. − The C­(sp 3 )-H activated functionalization of secondary and tertiary aliphatic amines is well investigated employing transition-metal catalysts. − However, site-selective functionalization of inactivated C­(sp 3 )-H bonds of primary aliphatic amines is more challenging because of their strong nucleophilic, reducing, chelation, and deactivating properties, which may hamper or deactivate catalytic power of the possible metal catalysts. Thus, use of prefunctionalized amines, directing group (DGs), and/or transient DG, their removal after the desired transformation, and intramolecular annulation are frequently exercised in the metal catalysis processes. − A limited number of approaches were devoted for the site-selective C­(sp 3 )-H functionalization of primary aliphatic amines, such as Zr IV /Ni II -catalyzed α-selective cyclization, , Pd II -tuned β-arylation, Pd II -Ag I guided γ-substitution, ,− and Pd II -activated δ-arylation. , However, a metal-free C­(sp 3 )-H functionalization is always a more appealing strategy to be developed for minimizing the harmful impact on nature. − …”

pH and redox-operated nanovalve for size-selective cargo delivery on hollow mesoporous silica spheres

“…The responsive controlled release of cargos from mesoporous silica nanoparticles (MSNs) has become a hot spot for drug delivery systems due to their biocompatibility, insignificant toxicity, uniform-ordered mesoporous, large surface area and abundant surface hydroxyl groups [2][3][4][5]. As a result, supramolecular nanovalves, such as calixarenes [6], cyclodextrins [7,8], and cucurbiturils [9] macrocyclic molecules need be introduced on the surface of MSNs to realize the controlled release. These macrocyclic molecules are decorated as a moving component on the nanoparticle surface, which thread with a stalk-like molecule by supramolecular forces.…”