Boron Macrocycles Based on Multicomponent Assemblies using (3‐Aminophenyl)boronic Acid and Pentaerythritol as Common Reagents; Molecular Receptors toward Lewis Bases

Abstract

Four cyclic boronate esters were synthesized by using a multicomponent reaction from (3‐aminophenyl)boronic acid, pentaerythritol, and aldehyde derivatives [isophthalaldehyde (1), dialdehyde A (2), (3‐formylphenyl)boronic acid (3), and (2,4‐difluoro‐3‐formylphenyl)boronic acid (4)]. All four reactions lead to the formation of macrocyclic compounds in good yields of more than 70 %. The cavities of the compounds consist of 29‐, 30‐ and 40‐membered rings, and the macrocyclic structures contain two (2) and four (1 and 3–4) boron atoms as Lewis acids. Additionally, the molecules contain eight (1) and six (2–4) donor atoms (N,O) within the macrocyclic structure, thus constituting a ditopic cavity. X‐ray analysis of 2 and 3 revealed the whole conformation within the trigonal planar geometry for the boron atoms and the inclusion of neutral guest molecules, chloroform for 2 and benzene for 3. Titration of the receptors with triethylamine, pyridine, and tetrabutylammonium fluoride show that the Lewis acids are available for interaction with Lewis bases. The interaction was follow by 11B NMR and UV/Vis spectroscopy.

Bis‐Imine Boronic Esters Obtained by One‐Step Multicomponent Reactions. Synthesis and X‐Ray Diffraction Structural Analysis

“…For the same group, a single signal was observed for the initial aminoalcohol used as starting material. On the other hand, at 13 C NMR spectra, signals for the carbon of imine group were observed between δ = 156.5 and δ = 164.4 ppm, which are comparable whit those of compounds already reported . The 11 B NMR spectra were determinant to stablish the environment of the boron atom.…”

Synthesis and inclusion properties of boroncalix[3]arene compounds obtained by self‐assembly of 3‐aminophenylboronic acid and salicylaldehyde derivatives

“…It is well known that boronate esters can act as Lewis acids, being able to form donor‐acceptor complexes. Using N‐donor ligands, coordinative or dative N–B bonds can be formed, given place to self‐assembled systems like macrocycles, polymeric, or cage compounds . Previously, we have described that boron macrocycles including boron‐nitrogen coordinative bonds are easily formed by reaction of salicylaldehyde derivatives with 3‐aminophenylboronic acid monohydrate .…”

Arylboronic Acids and their Myriad of Applications Beyond Organic Synthesis

“…Due to their stability, boronate esters of pentaerythritol are currently used in the synthesis of macrocycles. Barbas' group has prepared B‐containing macrocycles via multicomponent reactions between (3‐aminophenyl)boronic acid, aldehydes and pentaerythritol with yields greater than 70 % (Scheme ) . Other macrocycles derived from aldehydes and their respective imines have also been reported (Scheme ) .…”