Boroxine template for macrocyclization and postfunctionalization

Ono, Kosuke; Onodera, Satoru; Kawai, Hidetoshi

doi:10.1039/d2cc04691a

Cited by 9 publications

(6 citation statements)

References 28 publications

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“…The preorganization of the three boronic acid units in the macrocycle is also the key factor of the favorable intramolecular boroxine formation from 1 , as opposed to the network structure formation reported in a previous study on boroxine formation from triboronic acids with tripodal flexible linkers (Figure 1b). [5c] Actually, macrocyclic triboronic acid 1 was synthesized from a thermodynamic cyclization product [8,13] …”

Section: Resultsmentioning

confidence: 99%

“…[5c] Actually, macrocyclic triboronic acid 1 was synthesized from a thermodynamic cyclization product. [8,13] The Lewis acidities of boroxines 2 and 4 were compared to evaluate the linker effect of 2. Boroxines are known to form 1 : 1 adducts with Lewis bases, [1,4] and adduct formations of boroxines 2 and 4 with N,N-dimethylaminopyridine (DMAP) were examined (Figure 4).…”

Section: Chemistry-a European Journalmentioning

confidence: 99%

“…[7] Recently, we reported a boroxine-templated method for synthesizing large macrocyclic compounds. [8] Using a simple one-pot procedure, 39-, 45-, and 51-membered macrocycles with three pinacol boronic esters were synthesized using 3,5bis(alkenyloxy)phenylboronic acids. Herein, we report a unique structural interconversion between 45-membered macrocyclic triboronic acid 1 and tricyclic boroxine 2 with three 21membered rings based on the intramolecular boroxine formation using water and temperature as external stimuli.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, we reported a boroxine‐templated method for synthesizing large macrocyclic compounds [8] . Using a simple one‐pot procedure, 39‐, 45‐, and 51‐membered macrocycles with three pinacol boronic esters were synthesized using 3,5‐bis(alkenyloxy)phenylboronic acids.…”

Section: Introductionmentioning

confidence: 99%

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Structural Interconversion Based on Intramolecular Boroxine Formation

Ono

Sawanaga

Onodera

et al. 2023

Chemistry A European J

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A novel structural interconversion unit based on intramolecular boroxine formation has been developed. A macrocyclic triboronic acid consisting of three phenylboronic acid units linked by covalent linkers preferentially underwent intramolecular rather than intermolecular boroxine formation, resulting in a quantitative formation of tricyclic boroxine. This structural transformation was accompanied by changes in the polarity, flexibility, and size of the molecule. Dynamic interconversion between the macrocyclic triboronic acid and the tricyclic boroxine was achieved by simple heating/cooling, whereas no boroxine formation occurred upon heating when three boronic acid units were not connected by linkers. Thermodynamic analysis revealed that the entropic advantage of the intramolecular boroxine formation process resulted in these unique features. The entropically stabilized tricyclic boroxine also shows high stability with respect to hydrolysis.

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Section: Resultsmentioning

confidence: 99%

Section: Chemistry-a European Journalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural Interconversion Based on Intramolecular Boroxine Formation

Ono

Sawanaga

Onodera

et al. 2023

Chemistry A European J

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“…Boroxine formation from the respective boronic acid is a dynamic and reversible process that is high-yielding under dehydrating conditions, [27] or by ligand-assisted synthesis [28][29][30][31] in bulk and solution. Furthermore, boronic acids play a central role in organic synthesis, [32][33][34][35] and in the construction of COFs, [36] macrocycles, [37,38] cages, [39,40] and dynamic covalent polymer networks, [28,41,42] giving a wide range of commercially accessible boronic acid precursors. As a result, the combination of chemical addressability, orthogonality to supramolecular interactions, [43,44] C 3 -symmetrical architecture, and commercial availability of precursors, the boroxine scaffold offers new opportunities to explore boroxine-based monomers as reactive motifs in supramolecular polymers.…”

Section: Introductionmentioning

confidence: 99%

Functionalization of Supramolecular Polymers by Dynamic Covalent Boroxine Chemistry

Preuss,

Schnitzer,

Jansen

et al. 2024

Angew Chem Int Ed

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Molecular scaffolds that enable the combinatorial synthesis of new supramolecular building blocks are promising targets for the construction of functional molecular systems. Here, we report a supramolecular scaffold based on boroxine that enables the formation of chiral and ordered 1D supramolecular polymers, which can be easily functionalized for circularly polarized luminescence. The boroxine monomers are quantitatively synthesized in situ, both in bulk and in solution, from boronic acid precursors and cooperatively polymerize into 1D helical aggregates stabilized by threefold hydrogen‐bonding and π–π stacking. We then demonstrate amplification of asymmetry in the co‐assembly of chiral/achiral monomers and the co‐condensation of chiral/achiral precursors in classical and in situ sergeant‐and‐soldiers experiments, respectively, showing fast boronic acid exchange reactions occurring in the system. Remarkably, co‐condensation of pyrene boronic acid with a hydrogen‐bonding chiral boronic acid results in chiral pyrene aggregation with circularly polarized excimer emission and g‐values in the order of 10−3. Yet, the electron deficiency of boron in boroxine makes them chemically addressable by nucleophiles, but also sensitive to hydrolysis. With this sensitivity in mind, we provide first insights into the prospects offered by boroxine‐based supramolecular polymers to make chemically addressable, functional, and adaptive systems.

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Covalent Template‐Directed Synthesis of a Spoked 18‐Porphyrin Nanoring**

et al. 2023

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Rings of porphyrins mimic natural light‐harvesting chlorophyll arrays and offer insights into electronic delocalization, providing a motivation for creating larger nanorings with closely spaced porphyrin units. Here, we demonstrate the first synthesis of a macrocycle consisting entirely of 5,15‐linked porphyrins. This porphyrin octadecamer was constructed using a covalent six‐armed template, made by cobalt‐catalyzed cyclotrimerization of an H‐shaped tolan with porphyrin trimer ends. The porphyrins around the circumference of the nanoring were linked together by intramolecular oxidative meso‐meso coupling and partial β‐β fusion, to give a nanoring consisting of six edge‐fused zinc(II) porphyrin dimer units and six un‐fused nickel(II) porphyrins. STM imaging on a gold surface confirms the size and shape of the spoked 18‐porphyrin nanoring (calculated diameter: 4.7 nm).

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Boroxine template for macrocyclization and postfunctionalization

Abstract: A novel synthetic strategy for large macrocyclic molecules using boroxine formation was developed. For this, the threefold intramolecular olefin metathesis of 3,5-bis(alkenyloxy)phenylboroxines with various lengths of alkenyl chains, formed by...

Cited by 9 publications

References 28 publications

Structural Interconversion Based on Intramolecular Boroxine Formation

Structural Interconversion Based on Intramolecular Boroxine Formation

Functionalization of Supramolecular Polymers by Dynamic Covalent Boroxine Chemistry

Covalent Template‐Directed Synthesis of a Spoked 18‐Porphyrin Nanoring**

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