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9 pages, 2059 KB

Open AccessCommunication

High-Performance Photochromic Diarylethene with a Boron–Nitrogen Heterocyclic Ethene Bridge

by Chen Zhang, Yuping Dai, Yilin Chen, Shaoqiang Dong and Jiaxing Wang

Molecules 2026, 31(7), 1115; https://doi.org/10.3390/molecules31071115 - 28 Mar 2026

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Photochromic diarylethene molecules are promising candidates for applications in optical data storage devices. However, many reported diarylethene compounds suffer from inefficiencies due to low photocyclization quantum yields or poor fatigue resistance. To address this issue, we have developed a highly efficient boron–nitrogen heterocycle-bridged diarylethene. The bulky boron–nitrogen heterocyclic ethene bridge blocks interconversion between parallel and anti-parallel conformations, yielding two separated rotamers. Evaluation of their photochromic properties demonstrated that the anti-parallel conformer exhibits a high photocyclization quantum yield (Φ_o-c, 89.2%), excellent thermodynamic stability at 298 K and moderate fatigue resistance in hexane. Furthermore, direct comparison with its isosteric carbonaceous analog revealed that incorporating the azaborine moiety into the diarylethene scaffold significantly enhances its photochromic performance. This work presents a strategy that employs azaborine chemistry for the development of potential diarylethene-based photoswitchable materials. Full article

(This article belongs to the Section Materials Chemistry)

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15 pages, 4026 KB

Open AccessArticle

Novel Azaborine-Based Inhibitors of Histone Deacetylases (HDACs)

by Martin Behringer, Markus Schweipert, Enna E. Peters, Aleksandra Kopranovic and Franz-Josef Meyer-Almes

Molecules 2025, 30(19), 4017; https://doi.org/10.3390/molecules30194017 - 8 Oct 2025

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Abstract

Aromatic ring systems appear ubiquitously in active pharmaceutical substances, such as FDA-approved histone deacetylase inhibitors. However, these rings reduce the water solubility of the molecules, which is a disadvantage during application. To address this problem, azaborine rings may be substituted for conventional aromatic ring systems. These are obtained by replacing two adjacent carbon atoms with boron and nitrogen. Incorporating B–N analogs in place of aromatic rings not only enhances structural diversity but also provides a strategy to navigate around patent-protected scaffolds. We synthesized azaborines, which are isosteric to naphthalene and indole, and utilized them as capping units for HDAC inhibitors. These molecules were attached to various aliphatic and aromatic linkers with different zinc-binding units, used in established active compounds. Nearly half of the twenty-four molecules tested exhibited inhibitory activity against at least one of the enzymes HDAC1, HDAC4, or HDAC8, with three compounds displaying IC₅₀ values in the nanomolar range. We have therefore demonstrated that azaborine building blocks can be successfully incorporated into HDACis, resulting in a highly active profile. Consequently, it should be feasible to develop active substances containing azaborine rings against other targets. Full article

(This article belongs to the Special Issue Design, Synthesis and Biological Evaluation of Novel Small Molecules Inhibitors, 2nd Edition)

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17 pages, 3723 KB

Open AccessFeature PaperEditor’s ChoiceReview

Synthesis of Axially Chiral Boron Compounds

by Ana Maria Faisca Phillips and Armando J. L. Pombeiro

Symmetry 2024, 16(1), 11; https://doi.org/10.3390/sym16010011 - 21 Dec 2023

Cited by 6 | Viewed by 5042

Abstract

Boron-doped organic compounds display unique properties as a result of the presence of an empty p orbital on boron and the ability to switch between a trigonal planar and a tetrahedral geometry. In recent years, they have found several applications not only as synthetic reagents, e.g., in the Suzuki–Miyaura reaction, but also as pharmaceuticals and as specialized materials due to their optical and electronic properties. Some boron compounds may exist as atropisomers, and these rotamers may have different properties according to their sense of rotation. Synthetic strategies to separate them and, more recently, to obtain them in an asymmetric manner are becoming popular. In this review, we survey the literature on this emerging field of research. Full article

(This article belongs to the Special Issue Chemistry and Symmetry/Asymmetry: Feature Papers 2023)

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14 pages, 5486 KB

Open AccessArticle

Synthesis and Theoretical Studies of Aromatic Azaborines

by Pipsa Hirva, Petri Turhanen and Juri M. Timonen

Organics 2022, 3(3), 196-209; https://doi.org/10.3390/org3030016 - 11 Jul 2022

Cited by 4 | Viewed by 3855

Abstract

Organoboron compounds are well known for their use as synthetic building blocks in several significant reactions, e.g., palladium-catalyzed Suzuki-Miyaura cross-coupling. As an element, boron is fascinating; as part of a molecule it structurally resembles a three-valent atom, but if there is a lone pair of electrons nearby, the boron atom’s empty p-orbital may capture the lone pair and form a covalent bond. This is the main aspect that is challenging chemistry during the synthesis of boron containing molecules and may lead into unexpected reactions and products. To study this, we synthesized and studied novel aromatic azaborines for better understanding of their structures and reactions. Here, we report a one-pot method for the synthesis of substituted aromatic azaborines and computational studies of their structure to explain their observed chemical properties. Full article

(This article belongs to the Collection Advanced Research Papers in Organics)

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9 pages, 3306 KB

Open AccessCommunication

Mono- and Dinitro-BN-Naphthalenes: Formation and Characterization

by Mao-Xi Zhang, Nathaniel B. Zuckerman, Philip F. Pagoria, Bradley A. Steele, I-Feng Kuo, Gregory H. Imler and Damon Parrish

Molecules 2021, 26(14), 4209; https://doi.org/10.3390/molecules26144209 - 11 Jul 2021

Cited by 4 | Viewed by 3795

Abstract

Mono- and dinitro-BN-naphthalenes, i.e., 1-nitro-, 3-nitro-, 1,6-dinitro-, 3,6-dinitro-, and 1,8-dinitro-BNN, were generated in the nitration of 9,10-BN-naphthalene (BNN), a boron–nitrogen (BN) bond-embedded naphthalene, with AcONO₂ and NO₂BF₄ in acetonitrile. The nitrated products were isolated and characterized by NMR, GC-MS, IR, and X-ray single crystallography. The effects of the nitration on the electron density and aromaticity of BNN were evaluated by B-11 NMR analysis and HOMA calculations. Full article

(This article belongs to the Special Issue The Chemistry of Nitrocompounds)

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