Search

An efficient approach is reported for the direct halodecarboxylation of hydroxyaromatic acids by using a readily available N -halosuccinimide (halo = Cl, Br) as the sole promoter in ethanol at room temperature without any other catalyst or additive. This environmentally friendly route tolerates a wide substrate scope with good to excellent yields under convenient conditions. [ABSTRACT FROM AUTHOR]

The ternary strategy proves effective for breakthroughs in organic photovoltaics (OPVs). Elevating three photovoltaic parameters synergistically, especially the proportion‐insensitive third component, is crucial for efficient ternary devices. This work introduces a molecular design strategy by comprehensively analyzing asymmetric end groups, side‐chain engineering, and halogenation to explore the outstanding optoelectronic properties of the proportion‐insensitive third component in efficient ternary systems. Three asymmetric non‐fullerene acceptors (BTP‐SA1, BTP‐SA2, and BTP‐SA3) are synthesized based on the Y6 framework and incorporated as the third component into the D18:Y6 binary system. BTP‐SA3, featuring asymmetric terminal (difluoro‐indone and dichloride‐cyanoindone terminal), with branched alkyl side chains, exhibited high open‐circuit voltage (VOC), balanced crystallinity and compatibility, achieving synergistic enhancements in VOC (0.862 V), short circuit‐current density (JSC, 27.52 mA cm−2), fill fact (FF, 81.01%), and power convert efficiency (PCE, 19.19%). Device based on D18/Y6:BTP‐SA3 (layer‐by‐layer processed) reached a high efficiency of 19.36%, demonstrating a high tolerance for BTP‐SA3 (10–50%). This work provides novel insights into optimizing OPVs performances in multi‐component systems and designing components with enhanced tolerance. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) based on non-fused ring electron acceptors (NFREAs) have shown significant potential for practical application owing to their easily tunable chemical structures and short synthesis routes. The merging of side-chain engineering and terminal-group halogenation has facilitated the optimization of NFREAs properties. Thus, in this study, we developed four NFREAs using a naphthalenediimide (NDI) unit with different alkyl side-chains (–C6C10 or –C8C12) as the building block and two different electron-withdrawing groups 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene) malononitrile (IC) and chlorinated IC (IC-2Cl) as the terminal groups. These NFREAs were designated as NDI610-H, NDI610-Cl, NDI812-H, and NDI812-Cl, respectively. All four NFREAs exhibited similar optical bandgaps and molecular conformations. Under the synergistic effects of side-chain modification and terminal-group halogenation, the NFREAs-based active-layer morphologies were significantly different. The NDI610-Cl-based blended film demonstrated favorable phase-separation morphology, facilitating exciton dissociation and charge transport in the corresponding OSCs. Thus, the PM6:NDI610-Cl-based OSCs achieved a maximum power conversion efficiency (PCE) of 8.35%. Moreover, using D18 as the polymer donor further enhanced the device performance, with the D18:NDI610-Cl-based device yielding a higher PCE of 10.25% due to improved short-circuit current and fill factor. Our findings indicate that selecting an NDI unit as the building block and combining tailored alkyl side-chains with altered terminal groups are promising strategies for constructing highly efficient NFREAs. [ABSTRACT FROM AUTHOR]

By selectively interacting with acceptor components, various typed solid additives achieve boosted power conversion efficiency (PCE) in organic solar cells (OSCs). However, due to the efficient active layer being composed of donor and acceptor materials, it is difficult to obtain the desired morphology by manipulating the acceptor component alone, limiting further improvement of PCEs. Herein, two solid additives with a same backbone of thiophene‐benzene‐thiophene (halogen‐free D1‐H) but different halogen substituents (fluorinated D1‐F and chlorinated D1‐Cl) are developed to probe the working mechanism of halogenated variation of solid additives in OSCs. Unlike D1‐H with continuous charge distributions, D1‐F and D1‐Cl show isolated positive charge distribution in benzene‐core and negative charge distribution in thiophene, offering stronger non‐covalent interactions with both donor (PM6) and acceptor (L8‐BO), especially D1‐Cl. Consequently, D1‐Cl‐treated active layer obtains an optimized phase separation and improved molecular packing, boosting PCE to 18.59% and device stability of OSCs, with 17.62% for D1‐H‐treated counterparts. Moreover, using D18:L8‐BO and D18:BTP‐eC9 as active layers, D1‐Cl‐treated binary OSCs obtain impressive PCEs of 19.29% and 19.39%, respectively. This work indicates that halogenation engineering developed in solid additives can effectively regulate morphology for improving PCE and stability of OSCs, and elucidates the underlying mechanism. [ABSTRACT FROM AUTHOR]

Indigo is a commercially significant dye extensively used in the textile industry for dyeing denim and other fabrics. The synthesis of various colored indigo derivatives necessitates the halogenation of the indole ring in indigo. However, the scarcity of halogenating enzymes, especially those with high positional specificity and commercial availability, limits the biological synthesis of various halogenated indigos. This study presents the discovery of a novel halogenase from Pseudoalteromonas nigrifaciens that is similar to sttH from Streptomyces toxytricini, an enzyme that specifically halogenates the 6th carbon of the indole in indigo. The cloned halogenase gene was validated for halogenation activity and regioselectivity using a recombinant Escherichia coli whole-cell conversion system. The addition of either NaCl or NaBr resulted in the production of 6-chloro indigo or 6-bromo indigo, respectively. Notably, 6-chloro indigo displayed a red coloration, while 6-bromo indigo appeared blue. To optimize the whole-cell conversion system, we evaluated the conversion rate of halogenated indigo production in response to varying concentrations of tryptophan and E. coli cells. The maximum conversion rate (32%) was achieved using 30 mM tryptophan and an E. coli cell density corresponding to an OD50 reading. In conclusion, we have designed a recombinant E. coli whole-cell conversion system capable of producing 6-halogenated indigo by introducing a novel sttH-like halogenase from P. nigrifaciens. This system holds promise for the production of various indigo derivatives. [ABSTRACT FROM AUTHOR]

Choline oxidase from Alcaligenes sp. (ChOx) is used to generate hydrogen peroxide in situ from choline‐based ionic liquids (ILs) to fuel peroxidase‐mediated biocatalysis while mitigating oxidative degradation of the heme‐dependent enzymes. Horseradish peroxidase (HRP) and chloroperoxidase from Caldariomyces fumago (CPO), in combination with the ChOx, are evaluated in enzymatic cascades for the ability of the biocatalytic systems to withstand elevated concentrations of different choline additives in oxidative and halogenative enzymatic assays. The findings are applied in various synthetic scenarios to produce important oxygen‐ and nitrogen‐containing heterocycles, using choline ILs in a dual‐purpose fashion, as a substrate‐solubilizing component in the reaction medium as well as the source for hydrogen peroxide. The ChOx/HRP couple is used to induce intramolecular cyclizations of hydroxamic acids and hydroxycarbamates in a nitroso‐ene‐type pathway with choline dihydrogen phosphate as IL additive. The ChOx/CPO cascade successfully mediates brominative cyclizations of α‐allenic alcohols, while amphiphilic surfactants are employed to turn the aqueous choline propionate IL media into a colloidal suspension. ChOx/CPO partnering is also evaluated in an oxygenative rearrangement of 1‐furylethanol with choline acetate IL. The results show the wide potential of choline oxidase for hydrogen peroxide‐driven biocatalysis with both aqueous and micellar choline ionic liquid solutions. [ABSTRACT FROM AUTHOR]

Efficient and environmentally benign regioselective halogenation protocols have been achieved through the mediation of oxone‐halide, with or without the assistance of aryl iodine. The key to the success of the regioselectivity process is the controlled generation of the active [X]+ or halogen‐substituted hypervalent iodine (III) by manipulating the components of the oxone‐halide‐aryl iodine system. [ABSTRACT FROM AUTHOR]

We disclose a benzylic C−H oxidative coupling reaction with alcohols that proceeds through a synergistic deprotonation, halogenation and substitution sequence. The combination of tert‐butoxide bases with 2‐halothiophene halogen oxidants enables the first general protocol for generating and using benzyl halides through a deprotonative pathway. In contrast to existing radical‐based methods for C−H functionalization, this process is guided by C−H acidity trends. This gives rise to new synthetic capabilities, including the ability to functionalize diverse methyl(hetero)arenes, tolerance of oxidizable and nucleophilic functional groups, precision site‐selectivity for polyalkylarenes and use of a double C−H etherification process to controllably oxidize methylarenes to benzaldehydes. [ABSTRACT FROM AUTHOR]

We disclose a benzylic C−H oxidative coupling reaction with alcohols that proceeds through a synergistic deprotonation, halogenation and substitution sequence. The combination of tert‐butoxide bases with 2‐halothiophene halogen oxidants enables the first general protocol for generating and using benzyl halides through a deprotonative pathway. In contrast to existing radical‐based methods for C−H functionalization, this process is guided by C−H acidity trends. This gives rise to new synthetic capabilities, including the ability to functionalize diverse methyl(hetero)arenes, tolerance of oxidizable and nucleophilic functional groups, precision site‐selectivity for polyalkylarenes and use of a double C−H etherification process to controllably oxidize methylarenes to benzaldehydes. [ABSTRACT FROM AUTHOR]

Organohalogen compounds exhibit wide‐ranging bioactivities and potential applications. Understanding natural biosynthetic pathways and improving the production of halogenated compounds has garnered significant attention. Recently, the biosynthetic pathway of a cyanobacterial neurotoxin, aetokthonotoxin, was reported. It contains two unique enzymes: a single‐component flavin‐dependent halogenase AetF and a new type of nitril synthase AetD. The crystal structures of these enzymes in complex with their cofactors and substrates that were recently reported will be presented here. The AetF structures reveal a tri‐domain architecture, the transfer direction of the hydride ion, a possible path to deliver the hypohalous acid, and the unusual bispecific substrate‐recognition mode. The AetD structures demonstrate that the nitrile formation should occur through the action of a diiron cluster, implying that the enzyme should be capable of catalyzing the nitrile formation of alternative amino acids. This information is of central importance for understanding the mechanism of action as well as the applications of these two the‐first‐of‐its‐kind enzymes. [ABSTRACT FROM AUTHOR]

Benzocyclotrimers (BCTs) like trindane and dodecahydrotriphenylene (DDHTP) have attracted attention as key components for the construction of higher polycyclic aromatic hydrocarbons due to their aesthetic architecture that is useful in developing beautiful carbocycles of higher order. However, there are limited reports on these ring systems since their functionalization is a formidable task. Our personal engagement with these scaffolds prompted us to explore the synthesis of their synthetically useful derivatives. Herein, we report syntheses of a new series of their derivatives by exploiting the α–position of these cycloalkanones using classical Claisen‐Schmidt condensation reaction as well as simple and practical α‐Csp3–H halogenation with suitable halogenating agents. [ABSTRACT FROM AUTHOR]

Chemoselective arylation of 5-aminopyrazoles was performed through oxidative formation of orthoquinones from catechols catalyzed by Myceliophthora thermophila laccase (Novozym 51003), and subsequently nucleophilic attack of 5-aminopyrazole to the catechol intermediates. The C-4 arylated products were obtained under extremely mild conditions without the need for amine protection or halogenation of the substrates. From this method, 10 derivatives with moderate to good efficiency (42–94%) were prepared. [ABSTRACT FROM AUTHOR]

N,N′‐Diarylimidazolium salts containing haloalkyl functional groups that are reactive with various nucleophiles are considered to be promising reagents for the preparation of functionalized N‐heterocyclic carbene (NHC) ligands, which are in demand in catalysis, materials science, and biomedical research. Recently, 4‐chloromethyl‐functionalized N,N′‐diarylimidazolium salts became readily available via the condensation of N,N′‐diaryl‐2‐methyl‐1,4‐diaza‐1,3‐butadienes with ethyl orthoformate and Me3SiCl, but these compounds were found to have insufficient reactivity in reactions with many nucleophiles. These chloromethyl salts were studied as precursors in the synthesis of bromo‐ and iodomethyl‐functionalized imidazolium salts by halide anion exchange. The 4‐ICH2‐functionalized products were found to be unstable, whereas a series of novel 4‐bromomethyl functionalized N,N′‐diarylimidazolium salts were obtained in good yields. These bromomethyl‐functionalized imidazolium salts were found to be significantly more reactive towards various N, O and S nucleophiles than the chloromethyl counterparts and enabled the preparation of previously inaccessible heteroatom‐functionalized imidazolium salts, some of which were successfully used as NHC proligands in the preparation of Pd/NHC and Au/NHC complexes. [ABSTRACT FROM AUTHOR]

The high utility of halogenated organic compounds has prompted the development of numerous transformations that install the carbon‐halogen motif. Halogen functionalities, deemed as "functional and functionalizable" molecules due to their capacity to modulate diverse internal properties, constitute a pivotal strategy in drug discovery and development. Traditional routes to these building blocks have commonly involved multiple steps, harsh reaction conditions, and the use of stoichiometric and/or toxic reagents. With the emergence of solid halogen carriers such as N‐halosuccinimides, and halohydantoins as popular sources of halonium ions, the past decade has witnessed enormous growth in the development of new catalytic strategies for halofunctionalization. This review aims to provide a nuanced perspective on nucleophilic activators and their roles in halogen activation. It will highlight critical discoveries in effecting racemic and asymmetric variants of these reactions, driven by the development of new catalysts, activation modes, and improved understanding of chemical reactivity and reaction kinetics. [ABSTRACT FROM AUTHOR]

Alkenes are valuable feedstocks in organic synthesis. One effective method for synthesizing organic halides with functional groups in close proximity involves the direct difunctionalization of alkenes via three‐component reactions. This approach not only reduces the number of steps involved in the synthesis process, but also minimizes waste generation and enables the formation of complex molecules from simple starting materials. In this review, we mainly discuss decade developments (2013‐2023) in two categories: (1) halogenation via three‐membered ring intermediates, involving haliranium, thiiranium,seleniranium, aziridinium and epoxide species; (2) halogenation via a radical pathway. Reactions with I2, BiI3, NaI, Bu4N+[I(O2CAr)2]−, NIS, NBS, NCS, DBH, BsNMeBr, HBr, HCl, KI, NH4I, I2O5, Et3N ⋅ 3HF, Selectfluor, CuI, CuBr, CuCl, LiCl, KBr, NaCl, SOCl2, Py ⋅ 9HF, NFSI, TBSCl et al have been recorded and how the added reagents work will be discussed. We hope this review will do help for future research in this area. [ABSTRACT FROM AUTHOR]

α‐halo alkylboronic esters, acting as ambiphilic synthons, play a pivotal role as versatile intermediates in fields like pharmaceutical science and organic chemistry. The sequential transformation of carbon–boron and carbon–halogen bonds into a broad range of carbon–X bonds allows for programmable bond formation, facilitating the incorporation of multiple substituents at a single position and streamlining the synthesis of complex molecules. Nevertheless, the synthetic potential of these compounds is constrained by limited reaction patterns. Additionally, the conventional methods often necessitate the use of bulk toxic solvents, exhibit sensitivity to air/moisture, rely on expensive metal catalysts, and involve extended reaction times. In this report, a ball milling technique is introduced that overcomes these limitations, enabling the external catalyst‐free multicomponent coupling of aryl diazonium salts, alkenes, and simple metal halides. This approach offers a general and straightforward method for obtaining a diverse array of α‐halo alkylboronic esters, thereby paving the way for the extensive utilization of these synthons in the synthesis of fine chemicals. [ABSTRACT FROM AUTHOR]

Quinazolines are biologically potent heterocyclic compounds; however, their synthesis poses high challenges. In this present study, we have developed an inexpensive cobalt metal‐catalyzed acceptorless dehydrogenative pathway for the sequential synthesis of alkenylated quinazolines from benzhydrol via dehydrogenation, cyclization, and subsequent dehydrogenative sp3 C−H functionalization. This transformation holds potential owing to its commercially available key starting materials, good functional tolerance, moderate reaction conditions, environmental friendliness, and applicability for gram‐scale synthesis. Furthermore, the synthetic utility of the synthesized derivatives has been explored through various reactions, including reduction, halogenation, methoxylation, Michael addition, and spiro cyclization. Additionally, the photophysical properties indicate that the nitrogen atom of the synthesized derivatives readily undergoes a reversible protonation, leading to significant changes in colour. This characteristic presents an opportunity for the creation of pH sensors with colourimetric capabilities. [ABSTRACT FROM AUTHOR]

Halogenation is one of the most important transformations in organic synthesis. Halogenated compounds are employed in many reactions to prepare useful molecules. Many methods have been developed to introduce halogens into different compounds. Visible light‐mediated reactions are the efficient, low‐toxic, and mild‐condition methods applied for various organic chemistry transformations. Remarkably, there has been an increasing development in the application of visible light‐induced halogenation in recent years. Herein, we present a comprehensive summary of halogenation reactions including chlorination, bromination, and iodination under visible light irradiation since 2020. [ABSTRACT FROM AUTHOR]

Indoles are common motifs in functional agricultural and pharmaceutical molecules. Heteroatom alkylation is the most frequently used chemical reaction in the pharmaceutical field. Developing protocols for the nucleophilic substitution of (indol-2-yl)methyl electrophiles is important for functionalizing indoles. There are few studies on the nucleophilic substitution at the 2′-position of the electrophiles without an electron-withdrawing group at the 1-position or substituents at the 2′- and 3-positions, where the existing approaches require high temperatures and long reaction times. In this study, we demonstrated rapid (7–12 s) and mild (25 °C) microflow nucleophilic substitution at the 2′-position of indole derivatives without an electron-withdrawing group at the 1-position and substituents at the 2′- or 3-positions. Comparable batch conditions resulted in a lower yield. [ABSTRACT FROM AUTHOR]

A practical and efficient synthetic route to construct a variety of 3-halochromones has been realized using Selectfluor reagent as a fluorine source, or Selectfluor-copper(I) halide combination as halogen source under mild conditions. This reaction proceeds via a sequence of electrophilic cation addition, and cyclization leading to a broad range of 3-halochromones in good to excellent yields in a short period of time. Additionally, the utilization of commercially available and cost-effective Selectfluor and copper(I) halide renders this system highly practical. [ABSTRACT FROM AUTHOR]

Nitrogen‐containing compounds are valuable synthetic intermediates and targets in nearly every chemical industry. While methods for nitrogen‐carbon and nitrogen‐heteroatom bond formation have primarily relied on nucleophilic nitrogen atom reactivity, molecules containing nitrogen‐halogen bonds allow for electrophilic or radical reactivity modes at the nitrogen center. Despite the growing synthetic utility of nitrogen‐halogen bond‐containing compounds, selective catalytic strategies for their synthesis are largely underexplored. We recently discovered that the vanadium‐dependent haloperoxidase (VHPO) class of enzymes are a suitable biocatalyst platform for nitrogen‐halogen bond formation. Herein, we show that VHPOs perform selective halogenation of a range of substituted benzamidine hydrochlorides to produce the corresponding N’‐halobenzimidamides. This biocatalytic platform is applied to the synthesis of 1,2,4‐oxadiazoles from the corresponding N‐acylbenzamidines in high yield and with excellent chemoselectivity. Finally, the synthetic applicability of this biotechnology is demonstrated in an extension to nitrogen‐nitrogen bond formation and the chemoenzymatic synthesis of the Duchenne muscular dystrophy drug, ataluren. [ABSTRACT FROM AUTHOR]

We explored the ambiphilic reactivity of SF5‐alkynes, and we proved they can act as both nucleophiles and electrophiles. We selected halogenation reactions as benchmark reactions and developed highly selective stereodivergent hydrohalogenation (I, Br, Cl, F) reactions of SF5‐alkynes. The stereochemistry is finely controlled thanks to the nature of the acids used (strong or soft) in the presence of halide source, while the high regioselectivity is governed by the strong polarization of SF5‐alkynes. Mechanistic studies supported by DFT calculations shed light on two different reaction mechanisms responsible of the excellent stereocontrol. This stereoselectivity was quantitatively rationalized with the ASM and EDA methods. A few dihalogenation reactions are reported and DFT calculations rationalize this cis‐stereoselectivity. Relative configuration of all the SF5‐haloalkenes was unambiguously determined by X‐ray diffraction. Noteworthy, several post‐functionalization reactions such as cross‐couplings, cyanation and reductions are described to strengthen the synthetic potential. [ABSTRACT FROM AUTHOR]

Halogenation of Y‐series small‐molecule acceptors (Y‐SMAs) is identified as an effective strategy to optimize photoelectric properties for achieving improved power‐conversion‐efficiencies (PCEs) in binary organic solar cells (OSCs). However, the effect of different halogenation in the 2D‐structured large π‐fused core of guest Y‐SMAs on ternary OSCs has not yet been systematically studied. Herein, four 2D‐conjugated Y‐SMAs (X‐QTP‐4F, including halogen‐free H‐QTP‐4F, chlorinated Cl‐QTP‐4F, brominated Br‐QTP‐4F, and iodinated I‐QTP‐4F) by attaching different halogens into 2D‐conjugation extended dibenzo[f,h]quinoxaline core are developed. Among these X‐QTP‐4F, Cl‐QTP‐4F has a higher absorption coefficient, optimized molecular crystallinity and packing, suitable cascade energy levels, and complementary absorption with PM6:L8‐BO host. Moreover, among ternary PM6:L8‐BO:X‐QTP‐4F blends, PM6:L8‐BO:Cl‐QTP‐4F obtains a more uniform and size‐suitable fibrillary network morphology, improved molecular crystallinity and packing, as well as optimized vertical phase distribution, thus boosting charge generation, transport, extraction, and suppressing energy loss of OSCs. Consequently, the PM6:L8‐BO:Cl‐QTP‐4F‐based OSCs achieve a 19.0% efficiency, which is among the state‐of‐the‐art OSCs based on 2D‐conjugated Y‐SMAs and superior to these devices based on PM6:L8‐BO host (17.70%) and with guests of H‐QTP‐4F (18.23%), Br‐QTP‐4F (18.39%), and I‐QTP‐4F (17.62%). The work indicates that halogenation in 2D‐structured dibenzo[f,h]quinoxaline core of Y‐SMAs guests is a promising strategy to gain efficient ternary OSCs. [ABSTRACT FROM AUTHOR]

The structure of molecular aggregates is crucial for charge transport and photovoltaic performance in organic solar cells (OSCs). Herein, the intermolecular interactions and aggregated structures of nonfused‐ring electron acceptors (NFREAs) are precisely regulated through a halogen transposition strategy, resulting in a noteworthy transformation from a 2D‐layered structure to a 3D‐interconnected packing network. Based on the 3D electron transport pathway, the binary and ternary devices deliver outstanding power conversion efficiencies (PCEs) of 17.46 % and 18.24 %, respectively, marking the highest value for NFREA‐based OSCs. [ABSTRACT FROM AUTHOR]

The structure of molecular aggregates is crucial for charge transport and photovoltaic performance in organic solar cells (OSCs). Herein, the intermolecular interactions and aggregated structures of nonfused‐ring electron acceptors (NFREAs) are precisely regulated through a halogen transposition strategy, resulting in a noteworthy transformation from a 2D‐layered structure to a 3D‐interconnected packing network. Based on the 3D electron transport pathway, the binary and ternary devices deliver outstanding power conversion efficiencies (PCEs) of 17.46 % and 18.24 %, respectively, marking the highest value for NFREA‐based OSCs. [ABSTRACT FROM AUTHOR]

An efficient and rapid protocol for the oxidative halogenation of tryptamines with 10 % aqueous NaClO has been developed. This reaction is featured by its operational simplicity, metal‐free conditions, no purification, and high yield. Notably, the resulting key intermediates are suitable for further functionalization with various nucleophiles, including amines, N‐aromatic heterocycles, indoles and phenols. The overall transformation exhibits broad functional‐group tolerance and is applicable to the late‐stage functionalization of complex biorelevant molecules. [ABSTRACT FROM AUTHOR]

Due to their high anisotropic behavior, liquid crystals possess strong nonlinear optical properties. The RM734 liquid crystal is famous for having high anisotropic behaviors compared to traditional liquid crystals. The present work focused on the evaluation of electronic, charge-transport, nonlinear optical, electro-optical, and thermochemical properties of the RM734 liquid crystal. Furthermore, the effect of halogenation on the above properties of RM734 was investigated and is discussed in depth as halogen substitution on the liquid crystal molecule can alter the quantum mechanical properties of any liquid crystal molecule. Density functional theory combined with B3LYP and dispersion correction were used to calculate the properties of RM734. The 6-311G** basis set was used for the estimation of these properties, whereas def2-TZVPD was used to evaluate the nonlinear optical parameters. Due to the halogenation of RM734, its electronic properties vary significantly. By halogenation, a better electron-transport molecule can be converted into a hole-transport molecule. The electro-optical properties were calculated with the application of an external electric field for all molecules. With the help of the order parameter, the nematic phase was observed for all reported molecules. The variation in the birefringence with respect to the external electric field was investigated and discussed in detail. Therefore, the present study reveals the significant impact of halogenation in terms of the nonlinear optical and thermochemical properties of RM734. [ABSTRACT FROM AUTHOR]

[Display omitted] Hard carbon as a negative electrode material for sodium-ion batteries (SIBs) has great commercial potential and has been widely studied. The sodium-ion intercalation in graphite domains and the filling of closed pores in the low voltage platform region still remain a subject of controversy. We have successfully constructed hard carbon materials with a pseudo-graphitic structure by using polymerizable p -phenylenediamine and dichloromethane as carbon sources. This was achieved by a halogenated amination reaction and oxidative polymerization. It was found that the capacity of hard carbon materials mainly originates from intercalation into graphite domains. The study found that the prepared hard carbon could store 339.33 mAh g−1 of sodium in a reversible way at a current density of 25 mA g−1, and it had an initial coulomb efficiency of 80.23%. It even maintained a reversible sodium storage capacity of 125.53 mAh g−1 at a high current density of 12.8 A g−1. Based on the analysis of hard carbon structure and electrochemical performance, it was shown that the materials conform with an "adsorption-intercalation" mechanism for sodium storage. [ABSTRACT FROM AUTHOR]

Herein, we disclose a new strategy that rapidly and reliably incorporates bromine atoms at distal, secondary C(sp3)−H sites in aliphatic amines with an excellent and predictable site‐selectivity pattern. The resulting halogenated building blocks serve as versatile linchpins to enable a series of carbon‐carbon and carbon‐heteroatom bond‐formations at remote C(sp3) sites, thus offering a new modular and unified platform that expediates the access to advanced sp3 architectures possessing valuable nitrogen‐containing saturated heterocycles of interest in medicinal chemistry settings. [ABSTRACT FROM AUTHOR]

Herein, we disclose a new strategy that rapidly and reliably incorporates bromine atoms at distal, secondary C(sp3)−H sites in aliphatic amines with an excellent and predictable site‐selectivity pattern. The resulting halogenated building blocks serve as versatile linchpins to enable a series of carbon‐carbon and carbon‐heteroatom bond‐formations at remote C(sp3) sites, thus offering a new modular and unified platform that expediates the access to advanced sp3 architectures possessing valuable nitrogen‐containing saturated heterocycles of interest in medicinal chemistry settings. [ABSTRACT FROM AUTHOR]

Vicinal halohydrins are key building blocks to produce bioactive molecules and drugs, especially if they can be obtained in enantiomerically pure form. In this study, we present a bi‐enzymatic sequence that allows to obtain vic‐halohydrins through a photochemoenzymatic olefin hydroxy halogenation followed by a lipase catalysed kinetic resolution. The absolute configuration of the resulting products was determined using Mosher's method [ABSTRACT FROM AUTHOR]

The halogenation of alkenes is a crucial pathway in forming C-X bonds, with a significant impact on organic synthesis and pharmaceuticals. However, traditional methodologies present potential hazards to both the environment and human health, making the quest for green and efficient halogenation methods paramount. In this study, we introduce a novel iron catalyst based on a polyoxometalate, (NH4)3[FeMo6O18(OH)6], simplified as Fe(III)Mo6. Employing this catalyst, a plethora of styrene derivatives and alcohols were efficiently and successfully converted to the corresponding halogenated products. Also, our catalyst showed excellent performance toward the reaction with various substrates. Moreover, it demonstrates high stability and activity in the cycle test. In addition, we also described the reaction mechanism based on the control experiment. The catalyst exhibits non-toxic, green, and environmentally friendly characteristics that provide future industrialization potential. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Chemodivergent synthesis of benzofurans and 2,3‐dihydrobenzofurans has been realized. Under a reaction system consisting of DBDMH and K2CO3 as promotors, controlled conditions enabled the formation of two sets of valuable heterocycles from the tandem transformation of enaminones and salicylaldehydes. The key to success was the identification of the reaction parameters, in which the imine intermediate which was formed by transient halogenation coupling and substitution processes underwent either aldol condensation/annulation or imine hydrolysis/aldol condensation. The additives NH4Cl or Fe2(SO4)3 controlled the unique selectivity of this reaction. A broad substrate scope of enaminones and salicylaldehydes has been employed in this reaction, demonstrating excellent functional group tolerance and versatility. [ABSTRACT FROM AUTHOR]

The ability of triaryltelluronium salts to interact with N‐halosuccinimides (NXS) through chalcogen bonding (ChB) in the solid state and in solution is demonstrated herein. Cocrystals of the triaryltelluronium bearing two CF3 electron‐withdrawing groups per aryl ring with N‐chloro‐, N‐bromo‐ and N‐iodosuccinimide (respectively NCS, NBS and NIS) were analyzed by X‐ray diffraction, evidencing a ChB between tellurium and the carbonyl group of NXS. This ChB was confirmed in solution by NMR spectroscopy, especially by 125Te NMR titration experiment, which allowed the determination of the association constant (Ka) between the telluronium and NBS. The so‐obtained Ka value of 17.3±0.6 M−1 indicated a moderate interaction in solution because of the competitive role of the solvent. The strength of the Te⋅⋅⋅O ChB was however sufficient enough to promote the catalytic halofunctionalization of aromatics and of alkenes such as the intra‐ and intermolecular haloalkoxylation and haloesterification of alkenes. [ABSTRACT FROM AUTHOR]

Amino acids (AAs) are modular building blocks which nature uses to synthesize both macromolecules, such as proteins, and small molecule natural products, such as alkaloids and non‐ribosomal peptides. While the 20 main proteinogenic AAs display relatively limited side chain diversity, a wide range of non‐canonical amino acids (ncAAs) exist that are not used by the ribosome for protein synthesis, but contain a broad array of structural features and functional groups. In this communication, we report the discovery of the biosynthetic pathway for a new ncAA, pazamine, which contains a cyclopropane ring formed in two steps. In the first step, a chlorine is added onto the C4 position of lysine by a radical halogenase, PazA. The cyclopropane ring is then formed in the next step by a pyridoxal‐5′‐phosphate‐dependent enzyme, PazB, via an SN2‐like attack at C4 to eliminate chloride. Genetic studies of this pathway in the native host, Pseudomonas azotoformans, show that pazamine potentially inhibits ethylene biosynthesis in growing plants based on alterations in the root phenotype of Arabidopsis thaliana seedlings. We further show that PazB can be utilized to make an alternative cyclobutane‐containing AA. These discoveries may lead to advances in biocatalytic production of specialty chemicals and agricultural biotechnology. [ABSTRACT FROM AUTHOR]

Amino acids (AAs) are modular building blocks which nature uses to synthesize both macromolecules, such as proteins, and small molecule natural products, such as alkaloids and non‐ribosomal peptides. While the 20 main proteinogenic AAs display relatively limited side chain diversity, a wide range of non‐canonical amino acids (ncAAs) exist that are not used by the ribosome for protein synthesis, but contain a broad array of structural features and functional groups. In this communication, we report the discovery of the biosynthetic pathway for a new ncAA, pazamine, which contains a cyclopropane ring formed in two steps. In the first step, a chlorine is added onto the C4 position of lysine by a radical halogenase, PazA. The cyclopropane ring is then formed in the next step by a pyridoxal‐5′‐phosphate‐dependent enzyme, PazB, via an SN2‐like attack at C4 to eliminate chloride. Genetic studies of this pathway in the native host, Pseudomonas azotoformans, show that pazamine potentially inhibits ethylene biosynthesis in growing plants based on alterations in the root phenotype of Arabidopsis thaliana seedlings. We further show that PazB can be utilized to make an alternative cyclobutane‐containing AA. These discoveries may lead to advances in biocatalytic production of specialty chemicals and agricultural biotechnology. [ABSTRACT FROM AUTHOR]

A catalytic strategy towards the tribromide‐catalyzed dearomative spirocyclization reaction is described employing tetrabutylammonium bromide (TBAB) and oxone as an oxidising agent. This methodology leads to the exclusive formation of spirofurano dienones without rearomatization or halogenation. Our group has been on trails of tribromide‐catalyzed dearomative transformation during the last decade, and now this exhibits the first report which delivers high functional group tolerance and broad substrate scope with excellent yield (up to 99 %) and good diastereoselectivity (dr up to 14 : 1). The oxidation of naphthols as well as phenols is achieved under this mild conditions. [ABSTRACT FROM AUTHOR]

Unspecific Peroxygenases (UPOs) are increasingly significant enzymes for selective oxygenations as they are stable, highly active and catalyze their reactions at the expense of only hydrogen peroxide as the oxidant. Their structural similarity to chloroperoxidase (CPO) means that UPOs can also catalyze halogenation reactions based upon the generation of hypohalous acids from halide and H2O2. Here we show that the halogenation and oxygenation modes of a UPO can be stimulated at different pH values. Using simple aromatic compounds such as thymol, we show that, at a pH of 3.0 and 6.0, either brominated or oxygenated products respectively are produced. Preparative 100 mg scale transformations of substrates were performed with 60–72 % isolated yields of brominated products obtained. A one‐pot bromination‐oxygenation cascade reaction on 4‐ethylanisole, in which the pH was adjusted from 3.0 to 6.0 at the halfway stage, yielded sequentially brominated and oxygenated products 1‐(3‐bromo‐4‐methoxyphenyl)ethyl alcohol and 3‐bromo‐4‐methoxy acetophenone with 82 % combined conversion. These results identify UPOs as an unusual example of a biocatalyst that is tunable for entirely different chemical reactions, dependent upon the reaction conditions. [ABSTRACT FROM AUTHOR]

Halogen(I) complexes are widely used as halogenation reagents and traditionally feature homoleptic stabilising Lewis bases, though the recent revitalisation of iodine(I) carboxylate chemistry has provided isolable examples of heteroleptic iodine(I) complexes. This work reports iodine(I) pnictogenate complexes stabilised by a Lewis base (L), Ph2P(O)O─I─L, synthesised via cation exchange from the silver(I) precursor, (Ph2P(O)OAg)n. The complexes were characterised in both solution (1H, 1H-15N HMBC, 31P) and the solid state, and supplemented computationally by DFT studies. Interestingly, these iodine(I) pnictogenates demonstrate a range of stabilities, and have been found to excel as iodination reagents in comparison to carbonyl hypoiodites, with comparable reactivity to the eponymous Barluenga's reagent in the iodination of antipyrine. Iodine(I) carboxylates have been explored as iodination reagents, but the role of the carbonyl group in promoting such reactivity remains poorly understood. Here, the authors prepare iodine(I) pnictogenates and find that they excel as iodination reagents in comparison to iodine(I) carboxylates. [ABSTRACT FROM AUTHOR]

Polyphosphamides are normally good flame retardants. Herein a mesoporous polyphosphamide (p‐PPA) with an accessible average pore diameter of <10 nm and a surface area of 1.773 m2/g has been synthesized via condensation of 1,3‐diamino benzene (DAB) and phenyl phosphinic dichloride (PPDC). 31P, 13C CP‐MAS solid‐state NMR, Raman, and X‐ray photoelectron spectroscopic (XPS) characterizations confirm the presence of ‐{PV(O)‐NH}‐ in the repeating unit of the p‐PPA that is further used as a catalytic mediator to perform the Appel reaction i. e., conversion of alcohols to halides with a broad substrate scope and high TON (561). The heterogeneity of p‐PPA allows easy recovery of organic halides and recycling of the catalyst many times. Mesoporous p‐PPA has further given a scope to perform shape‐selective conversion of primary alcohols with linear alkyl chain (1‐dodecanol) while a low conversion for the bulky secondary (cyclo‐hexanol) and tertiary alcohol (tert‐butanol) is observed. Perhaps, the phosphamide units present inside the porous channel are non‐preferable sites for bulkier alcohols, as evident from the competitive experiments. A comparatively less catalytic conversion obtained with an analogous non‐porous n‐PPA, made of tris(2‐aminoethyl)amine (TREN) linker, highlights the role of porosity in p‐PPA to enhance the accessibility of numerous ‐{PV(O)‐NH}‐ reactive units to increase the TON. [ABSTRACT FROM AUTHOR]

An efficiently aerobic dehydrazination of arylhydrazines promoted by potassium tert‐butoxide (tBuOK) is detailed in this study. This method smoothly produces aromatics analogues from arylhydrazines using catalytic amount of tBuOK under practical conditions, exhibiting excellent functional group tolerance and a broad substrate scope. The application potential of this approach is further demonstrated through the preparation of deuterated, iodinated and brominated aromatics. Moreover, it shows that this aerobic base‐mediated dehydrazination could be utilized to prepare unsymmetrical aryl sulfides, selenides and tellurides with high efficiency. [ABSTRACT FROM AUTHOR]

We report the synthesis of two novel halogenated nitro-arylhimachalene derivatives: 2-bromo-3,5,5,9-tetramethyl-1-nitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (bromo-nitro-arylhimachalene) and 2-chloro-3,5,5,9-tetramethyl-1,4-dinitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (chloro-dinitro-arylhimachalene). These compounds were derived from arylhimachalene, an important sesquiterpene component of Atlas cedar essential oil, via a two-step halogenation and nitration process. Characterization was performed using 1H and 13C NMR spectrometry, complemented by X-ray structural analysis. Quantum chemical calculations employing density functional theory (DFT) with the Becke3-Lee-Yang-parr (B3LYP) functional and a 6-31++G(d,p) basis set were conducted. The optimized geometries of the synthesized compounds were consistent with X-ray structure data. Frontier molecular orbitals and molecular electrostatic potential (MEP) profiles were identified and discussed. DFT reactivity indices provided insights into the compounds' behaviors. Moreover, Hirshfeld surface and 2D fingerprint analyses revealed significant intermolecular interactions within the crystal structures, predominantly H–H and H–O contacts. Molecular docking studies demonstrate strong binding affinities of the synthesized compounds to the active site of protein 7B2W, suggesting potential therapeutic applications against various isolated smooth muscles and neurotransmitters. [ABSTRACT FROM AUTHOR]

Enzymatic electrophilic halogenation is a mild tool for functionalization of diverse organic compounds. Only a few groups of native halogenases are capable of catalyzing such a reaction. In this study, we used a mechanism‐guided strategy to discover the electrophilic halogenation activity catalyzed by non‐native halogenases. As the ability to form a hypohalous acid (HOX) is key for halogenation, flavin‐dependent monooxygenases/oxidases capable of forming C4a‐hydroperoxyflavin (FlC4a‐OOH), such as dehalogenase, hydroxylases, luciferase and pyranose‐2‐oxidase (P2O), and flavin reductase capable of forming H2O2 were explored for their abilities to generate HOX in situ. Transient kinetic analyses using stopped‐flow spectrophotometry/fluorometry and product analysis indicate that FlC4a‐OOH in dehalogenases, selected hydroxylases and luciferases, but not in P2O can form HOX; however, the HOX generated from FlC4a‐OOH cannot halogenate their substrates. Remarkably, in situ H2O2 generated by P2O can form HOI and also iodinate various compounds. Because not all enzymes capable of forming FlC4a‐OOH can react with halides to form HOX, QM/MM calculations, site‐directed mutagenesis and structural analysis were carried out to elucidate the mechanism underlying HOX formation and characterize the active site environment. Our findings shed light on identifying new halogenase scaffolds besides the currently known enzymes and have invoked a new mode of chemoenzymatic halogenation. [ABSTRACT FROM AUTHOR]

Enzymatic electrophilic halogenation is a mild tool for functionalization of diverse organic compounds. Only a few groups of native halogenases are capable of catalyzing such a reaction. In this study, we used a mechanism‐guided strategy to discover the electrophilic halogenation activity catalyzed by non‐native halogenases. As the ability to form a hypohalous acid (HOX) is key for halogenation, flavin‐dependent monooxygenases/oxidases capable of forming C4a‐hydroperoxyflavin (FlC4a‐OOH), such as dehalogenase, hydroxylases, luciferase and pyranose‐2‐oxidase (P2O), and flavin reductase capable of forming H2O2 were explored for their abilities to generate HOX in situ. Transient kinetic analyses using stopped‐flow spectrophotometry/fluorometry and product analysis indicate that FlC4a‐OOH in dehalogenases, selected hydroxylases and luciferases, but not in P2O can form HOX; however, the HOX generated from FlC4a‐OOH cannot halogenate their substrates. Remarkably, in situ H2O2 generated by P2O can form HOI and also iodinate various compounds. Because not all enzymes capable of forming FlC4a‐OOH can react with halides to form HOX, QM/MM calculations, site‐directed mutagenesis and structural analysis were carried out to elucidate the mechanism underlying HOX formation and characterize the active site environment. Our findings shed light on identifying new halogenase scaffolds besides the currently known enzymes and have invoked a new mode of chemoenzymatic halogenation. [ABSTRACT FROM AUTHOR]

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is responsible for outbreaks of hemorrhagic colitis worldwide, but no effective therapy exists for EHEC infections. EHEC readily forms antimicrobial-tolerant biofilms on various biotic and abiotic surfaces. Here, we investigated the antimicrobial and antibiofilm abilities of 16 halogenated (fluoro-, chloro-, bromo-, or iodo-) indoles and indole against a pathogenic EHEC strain. Antibiofilm activities followed the order chloroindoles > bromoindoles > indole > fluoroindoles. For example, the minimum inhibitory concentrations (MICs) of 4-bromoindole and 5-bromoindole were 100 and 200 μg/mL, respectively, and at 20 μg/mL, they both inhibited EHEC biofilm formation by more than 61% without affecting planktonic cell growth. However, at concentrations greater than their MICs, both showed bactericidal activity. Antibiofilm effects were confirmed by scanning electron microscopy. Both 4-bromoindole and 5-bromoindole reduced swimming and swarming motility and curli formation, which are important factors for EHEC biofilm formation. Furthermore, quantitative structure–activity relationship analysis demonstrated that halogenation of indole with chlorine, bromine, or iodine at positions C-4 or C-5 promotes antimicrobial activity but that substitution at C-7 is detrimental. The study shows that halogenated indoles, particularly bromoindoles, have potential use as antimicrobial and antibiofilm therapies against EHEC. [ABSTRACT FROM AUTHOR]

Dihydrogen bond (DHB) interaction that exists in ammoniated metal borohydride systems is recognized as an effective intermediate step involved in the evolution of H2 molecules. Mechanism of DHB formation and its electronic properties upon halogenations were explored for Mg(BH4)2·2NH3⋯M(BH3X) (where M = Li, Na, K, and X = H, F, Cl, and Br) systems using ab initio (MP2) and DFT (ωB97XD) calculations. The influence of halogens in varying the nature of the DHB that forms in Mg(BH4)2·2NH3⋯M(BH3X) complexes was explored with the Quantum Theory of Atoms In Molecule (QTAIM) analysis. Further, Energy decomposition analysis (EDA) was made to understand the strength of DHB interaction through the calculation of the Edisp term in interaction energy. The results obtained from EDA and QTAIM were found to correlate well with the structural parameter and the interaction energy values. This study reveals the influence of halogenations on tuning the electronic properties of DHB interaction in all the complexes. Our results suggest that the effective substitution of halogens in BH4 molecule enhances DHB interaction, and the impact of halogenations on DHB has been revealed through QTAIM, EDA, Natural Bond Order (NBO), Non-covalent Interaction (NCI), and Bader charge analyses. Dihydrogen bonds in ammine metal borohydride systems are responsible for its large hydrogen storage capacity. This study reveals the DHB interaction found in the chosen Mg(BH4)2.2NH3⋯M(BH3X) systems and their property enhancement upon introducing halogens through QTAIM parameters. [ABSTRACT FROM AUTHOR]

Azetidines are valuable nitrogenous heterocycles. Herein, we disclose a strategy for the modular assembly of 3‐azetidines and related spirocyclic congeners featuring all‐carbon quaternary centers. This approach leverages titanacyclobutanes generated from ketones or alkenes. Halogenation of these organotitanium species gives rise to functionalized alkyl dihalides that can be subsequently captured by amines to afford azetidine building blocks. This strategy facilitated the synthesis of a small molecule anti‐tuberculosis drug. It also enabled access to carbon‐13 isotopologs of diazaspiro[3.3]heptane fragments that are challenging to prepare by any other means. [ABSTRACT FROM AUTHOR]

As simple and versatile tools, additives have been widely used to refine active layer morphology and have played a crucial role in boosting the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, three novel solvent additives named Th‐FSi, Th‐ClSi, and Th‐BrSi with the same backbone of 2,5‐bis(trimethylsilyl)thiophene are designed and synthesized by substituting different halogens of fluorine, chlorine, and bromine, respectively. Notably, Th‐ClSi exhibits the more significant dipole moment and engages in non‐covalent interactions with a small‐molecule acceptor (SMA) L8‐BO, which slight adjustments in intermolecular interaction, crystallinity, and molecular packing in the PM6:L8‐BO active layer. Consequently, the OSCs incorporating Th‐ClSi outperform their Th‐FSi and Th‐BrSi counterparts in photo‐capturing, reduced energy loss, superior exciton dissociation, and charge transfer properties, out‐coming yields in an enhanced PCE of 18.29%. Moreover, by integrating a near‐infrared absorbing SMA (BTP‐eC9) guest into the PM6:L8‐BO matrix, the absorption spectrum to span 880–930 nm, and the resultant ternary OSCs achieve a commendable PCE of 19.17%, ranking among the highest efficiencies reported to date is expanded. These findings underscore the promise of halogenated thiophene‐based solvent additives as a potent avenue for morphological fine‐tuning and consequent PCE enhancement in OSCs. [ABSTRACT FROM AUTHOR]

We have developed a straightforward and cost-effective construction of continuous-flow electrochemical reactors using readily available metal wires and carbon fibers as electrodes. Teflon tubing, known for its chemical resistance and temperature tolerance, served as the flow channels. The flow length and material of the electrodes can be easily adjusted. Moreover, precise control of the reaction temperature is possible. As a proof of concept, environmentally benign halogenations of alkenes, alkynes, and aromatics were developed using easy-to-handle halide salts such as LiBr and LiCl as the halogen sources. [ABSTRACT FROM AUTHOR]

Tris(hydroxymethyl)phosphine oxide, (HOCH2)3PO (THPO), is recognized as an efficient flame-retardant polyol and a derivative of PH3 – an environment-friendly, halogen-free source for phosphorus compounds and polymers. Synthesis and industrial production of THPO are based on straightforward oxidation of tris(hydroxymethyl)phosphine, (HOCH2)3P (THP), or neutralized tetrakis(hydroxymethyl)phosphonium chloride (THPC), or sulfate (THPS), by air/O2 or H2O2. In alkaline aqueous media, THP is oxidized by water with liberation of H2. As an alcohol, THPO readily reacts with isocyanates, epoxides, aziridines, and carboxylic acid derivatives, and is widely used as crosslinker or chain-extender to produce flame-retardant polyurethanes, polyethers, polyesters, and composite materials. Similarly, with compounds containing E–Cl bonds (E = P, Si, and S), THPO forms a variety of flame-retardant P/E-compounds or polymers. Condensation of THPO with phenols proceeds via cleavage of a P–C bond of THPO and liberation of CH2O that leads to flame-retardant THPO-phenol resins. With functionalized alkyl halides, THPO forms tris(alkoxymethyl)phosphine oxide monomers containing, for example, pendant allyl, propargyl, or silane groups. Halogenation of THPO leads to tris(chloromethyl)phosphine oxide, (ClCH2)3PO, or tris(bromomethyl)phosphine oxide, (BrCH2)3PO, useful for syntheses of multifunctional organophosphorus compounds, for example, tris(aminomethyl)phosphine oxide, (NH2CH2)3PO, and phosphorus-containing podands. Similar to THPO, tris(hydroxymethyl)phosphine sulfide, (HOCH2)3PS, is used in preparation of flame-retardant components for polymers, and, in synthesis of asymmetric phosphorus compounds. [ABSTRACT FROM AUTHOR]