A new bicyclic oxazaborines with a bridged nitrogen atom, their thermic rearrangement and fluorescence properties

Recent Advances in the Synthesis of Borinic Acid Derivatives

Borinic acids [R2B(OH)] and their chelate derivatives are a subclass of organoborane compounds used in cross-coupling reactions, catalysis, medicinal chemistry, polymer or optoelectronics materials. In this paper, we review the recent advances in the synthesis of diarylborinic acids and their four-coordinated analogs. The main strategies to build up borinic acids rely either on the addition of organometallic reagents to boranes (B(OR)3, BX3, aminoborane, arylboronic esters) or the reaction of triarylboranes with a ligand (diol, amino alcohol, etc.). After general practical considerations of borinic acids, an overview of the main synthetic methods, their scope and limitations is provided. We also discuss some mechanistic aspects.

Synthesis and Characterization of New Boron Compounds Using Reaction of Diazonium Tetraphenylborate with Enaminoamides

A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with 4-methylbenzenediazonium tetraphenylborates. The reaction conditions (stirring in CH₂Cl₂ at room temperature (Method A) or stirring with CH₃COONa in CH₂Cl₂ at room temperature (Method B) or refluxing in the CH₂Cl₂/toluene mixture (Method C)) controlled the formation and relative content of these compounds in the reaction mixtures from one to three products. Substituted oxazaborines gradually rearranged into diazaborinones at 250 °C. The prepared compounds were characterized by ¹H NMR, ¹³C NMR, IR, and UV–Vis spectroscopy, HRMS, or microanalysis. The structure of individual compounds was confirmed by ¹¹B NMR, ¹⁵N NMR, 1D NOESY, and X-ray analysis. The mechanism of reaction of enaminoamides with 4-methylbenzenediazonium tetraphenylborate was proposed.

Progress in the medicinal chemistry of organoboron compounds

The review aims to draw attention to the latest advances in the organoboron chemistry and therapeutic use of organoboron compounds. The synthetic strategies towards boron-containing compounds with proven in vitro and/or in vivo biological activities, including derivatives of boronic acids, benzoxaboroles, benzoxaborines and benzodiazaborines, are summarized. Approaches to the synthesis of hybrid structures containing an organoboron moiety as one of the pharmacophores are considered, and the effect of this modification on the pharmacological activity of the initial molecules is analyzed. On the basis of analysis of the published data, the most promising areas of research in the field of organoboron compounds are identified, including the latest methods of synthesis, modification and design of effective therapeutic agents.

The bibliography includes 246 references.

Novel Alkyl(aryl)-Substituted 2,2-Difluoro-6-(trichloromethyl)-2H-1,3,2-oxazaborinin-3-ium-2-uides: Synthesis, Antimicrobial Activity, and CT-DNA Binding Evaluations

The synthesis, antimicrobial activity evaluations, biomolecule-binding properties (DNA), and absorption and emission properties of a new series of (Z)-1,1,1-trichloro-4-alkyl(aryl)amino-4-arylbut-3-en-2-ones (4, 5) and 2,2-difluoro-3-alkyl(aryl)amino-4-aryl-6-(trichloromethyl)-2H-1,3,2-oxazaborinin-3-ium-2-uides (6, 7) in which 3(4)-alkyl(aryl) = H, Me, iso-propyl, n-butyl, C6H5, 4-CH3C6H4, 4-CH3OC6H4, 4-NO2C6H4, 4-FC6H4, 4-BrC6H4, 2-naphthyl, is reported. A series of β-enaminoketones (4, 5) is synthesized from the O,N-exchange reaction of some amines (3) with (Z)-1,1,1-trichloro-4-methoxy-4-aryl-but-3-en-2-ones (1, 2) at 61-90% yields. Subsequently, reactions of the resulting β-enaminoketones with an appropriate source of boron (BF3.OEt2) gave the corresponding oxazaborinine derivatives (6, 7) at 50-91% yields. UV-Vis and emission properties of biomolecule-binding properties for the DNA of these new BF2-β-enamino containing CCl3 units were also evaluated. Some compounds from the present series also exhibited potent antimicrobial effects on various pathogenic microorganisms at concentrations below those that showed cytotoxic effects. Compounds 4d, 4e, 6e, and 6f showed the best results and are very significant against P. zopfii, which causes diseases in humans and animals.

From synthetic control to natural products: a focus on N-heterocycles

Natural products containing a N-heterocycle motif are widespread in nature and medicinal plants, in particular, have proved to be a source of almost unlimited N-derived structures with high molecular diversity. Because of their intrinsic potential for use in both biomedical and agricultural applications, there is a general need for new compounds and for the synthesis of 'natural-inspired' analogues. Importantly, transition of a natural product from discovery to a 'market lead' is associated with an increasingly challenging demand for more of the compound, which cannot be met by isolation from natural plant sources, often due to low extraction yields and uneven availability of the plant source itself. Synthesis remains the most reliable approach to provide valuable products for the market. In this review, a comprehensive overview of our contribution to synthetic access to N-derived natural products is given. Major strengths of the proposed methodologies are discussed critically. © 2019 Society of Chemical Industry.

Boron-Based Inhibitors of the NLRP3 Inflammasome

NLRP3 is a receptor important for host responses to infection, yet is also known to contribute to devastating diseases such as Alzheimer's disease, diabetes, atherosclerosis, and others, making inhibitors for NLRP3 sought after. One of the inhibitors currently in use is 2-aminoethoxy diphenylborinate (2APB). Unfortunately, in addition to inhibiting NLRP3, 2APB also displays non-selective effects on cellular Ca²⁺ homeostasis. Here, we use 2APB as a chemical scaffold to build a series of inhibitors, the NBC series, which inhibit the NLRP3 inflammasome in vitro and in vivo without affecting Ca²⁺ homeostasis. The core chemical insight of this work is that the oxazaborine ring is a critical feature of the NBC series, and the main biological insight the use of NBC inhibitors led to was that NLRP3 inflammasome activation was independent of Ca²⁺. The NBC compounds represent useful tools to dissect NLRP3 function, and may lead to oxazaborine ring-containing therapeutics.

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

Easily obtainable cyclic enaminones (piperidin-2-ylidenealkanones) can be transformed into substituted bicyclic pyridazinium tetrafluoroborates upon treatment with corresponding diazonium salts. The transformation can be performed either in a one-pot way or in a two-step process with the isolation of single azo-coupled enaminone as the intermediate. The former method is superior. Under the optimized conditions, a number of pyridazinium salts substituted with both electron-donating and electron-withdrawing substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by using a more reactive diazonium salt before a less reactive one.