C(sp2) – H functionalization of aldimines and related compounds: advances and prospects

This is the first systematic review of the most relevant approaches to direct C(sp2)–H bond functionalization of azomethine derivatives. The scope of the applicability of various transformations is analyzed. The review assesses prospects of the application of this functionalization strategy in the multistep synthesis of valuable compounds for use in medicinal chemistry, materials science and related areas.

The bibliography includes 124 references.

Meso-functionalization of calix[4]arene with 1,3,7-triazapyrene in the design of novel fluorophores with the dual target detection of Al3+ and Fe3+ cations

A meso-functionalization strategy has successfully been applied to the synthesis of novel 1,3,7-triazapyrene derivatives of calixarenes. The key synthetic step in these transformations providing the direct C-C bond formation is nucleophilic substitution of hydrogen (SN H) in 1,3,7-triazapyrene. General photophysical characteristics for these macrocyclic compounds, as well as features in emission properties upon addition of various metal cations have been elaborated. Studies using NMR spectroscopy have also shown a mutual effect of both calix[4]arene and 1,3,7-triazapyrene moieties on the coordination process. The complex stoichiometry and binding constants for Al3+ and Fe3+ guests have been explored with titration experiments.

C(sp2)-H functionalization in non-aromatic azomethine-based heterocycles

Direct C(sp2)-H functionalization of the endocyclic azomethine and aldonitrone moieties in non-aromatic azaheterocycles has established itself as a promising methodology over the last decade. Transition metal-catalyzed cross-coupling reactions, α-metalation-electrophile quenching protocols, and (metal-free) nucleophilic substitution of hydrogen reactions (SNH) are the major routes applied on cyclic imines and their derivatives. In this overview, we show the tangible progress made in this area during the period from 2008 to 2020.

Recent advances in the functionalization of polyfluoro(aza)aromatics via C-C coupling strategies

Polyfluoro(aza)aromatic compounds are of interest in various fields of practical applications, such as medicinal and agrochemistry, materials science and advanced technologies. The C-C coupling reactions are known to be a promising synthetic tool to create challenging fluorinated molecules of diverse architectures. In this review, we have summarized the recent advances in the functionalization of polyfluoro(aza)aromatics via both transition metal-catalyzed and metal-free C-C coupling reactions for the period from 2006 to the beginning of 2021. Also, mechanistic features for chemical transformations of fluoroarene scaffolds and new opportunities for practical applications of the designed fluorinated molecules have been highlighted.

1,2,4,5-Tetrazine derivatives as components and precursors of photo- and electroactive materials

Synthetic approaches to 3,6-disubstituted-1,2,4,5-tetrazine systems are analyzed, and their properties attractive to practical applications in photo- and electroactive materials are overviewed.

Azapyrene-based fluorophores: synthesis and photophysical properties

The latest methods for the preparation/functionalization of azapyrenes, and their photophysical/electrochemical properties and possible applications are overviewed.

Computer vision vs. spectrofluorometer-assisted detection of common nitro-explosive components with bola-type PAH-based chemosensors

Computer vision (CV) algorithms are widely utilized in imaging processing for medical and personal electronics applications. In sensorics CV can provide a great potential to quantitate chemosensors' signals. Here we wish to describe a method for the CV-assisted spectrofluorometer-free detection of common nitro-explosive components, e.g. 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), by using polyaromatic hydrocarbon (PAH, PAH = 1-pyrenyl or 9-anthracenyl) – based bola-type chemosensors. The PAH components of these chemical bolas are able to form stable, bright emissive in a visual wavelength region excimers, which allows their use as extended matrices of the RGB colors after imaging and digital processing. In non-polar solvents, the excimers have poor chemosensing properties, while in aqueous solutions, due to the possible micellar formation, these excimers provide “turn-off” fluorescence detection of DNT and TNT in the sub-nanomolar concentrations. A combination of these PAH-based fluorescent chemosensors with the proposed CV-assisted algorithm offers a fast and convenient approach for on-site, real-time, multi-thread analyte detection without the use of fluorometers. Although we focus on the analysis of nitro-explosives, the presented method is a conceptual work describing a general use of CV for quantitative fluorescence detection of various analytes as a simpler alternative to spectrofluorometer-assisted methods.

Simplified computer vision-assisted algorithm for the excimer fluorescence "turn-off" detection of nitro-analytes in aqueous media is described.

Biodegradability of hydroxylated derivatives of commercial polychlorobiphenyls mixtures by Rhodococcus-strains

For the first time, investigations are is carried out for the interactions of hydroxylated polychlorobiphenyls (HO-PCBs) mixtures, which were obtained from PCBs commercially available under the trade name Sovol, with the Rhodococcus (R.) strains. It is established that the HO-PCBs mixtures containing basic products within the range of 83.2-95.8% cause a toxic effect on the growth of R. wratislaviensis KT112-7, R. wratislaviensis CH628, R. ruber P25 strains. The inhibitory concentration (IC50) was varied within the range of 30-490 mg/l. For the first time, it is found that the bacterial strains can use HO-PCBs as a source of carbon with no co-substrate added. The strains are shown to degrade 95.5-100% of the HO-PCBs mixtures at a concentration of 0.1 g/l during 14 days. It is demonstrated that HO-PCBs degrading occurs following the classical bacterial pathway of transforming biphenyl/PCB. However, the HO-PCBs metabolites, which are substituted benzoic acids, are not the final products of the transformation and are subjected to further degrading by the strains. Therefore, the R. wratislaviensis KT112-7, R. wratislaviensis CH628, and R. ruber P25 strains are shown to degrade the HO-PCBs mixtures efficiently and are found to be stable to their toxic action.

Indolyl- and Pyrrolylazine Derivatives Cause the Accumulation of Heat Shock Protein Hsp70 in Sh-Sy5Y Human Neuroblastoma Cells

The heat shock protein Hsp70 is involved in cell defense from various types of stress, including the proteotoxic stress, which occurs during the development of many neurodegenerative diseases. This work presents data on the detection of small molecules, derivatives of indolyl- and pyrrolylazines, which can activate the synthesis of Hsp70 and cause its accumulation in the cell. The toxicity level of the new Hsp70 synthesis inducers was evaluated, and the safety of these compounds was demonstrated in experiments on SH-SY5Y neuroblastoma cell line. Derivatives of indolyl- and pyrrolylazines presented in this work can be potential therapeutic agents in models of neurodegenerative diseases that should be studied in more detail.