Nataliya P. Belskaya

Synthesis of 2H-1,2,3-Triazoles

This chapter gives an overview of methods for the synthesis of NH- and N(2)-substituted 1,2,3-triazoles, their advantages, lacks, scope, and limitations. Moreover, it will give some insights on the reaction mechanisms and will explain how different conditions and structure substrates can influence the direction for reactions. An extensive analysis for the last 20 years (starting at 1990) of NH-1,2,3-triazoles chemistry is presented. Some older data with high importance are also included.

Reaction of Enamines and Azaenamines Containing a Thioamide Group with Dimethyl Acetylenedicarboxylate

The reaction between enamines and azaenamines containing a thioamide group and dimethyl acetylenedicarboxylate was studied under various conditions. It was shown that exchanging one of the carbon atoms in the structure of the investigated compounds for a nitrogen atom significantly affected the reactivity. Functionalized thiopyrans and thiazolidinones were obtained during this investigation.

Synthesis of 1,2,3-Thiadiazole and Thiazole-Based Strobilurins as Potent Fungicide Candidates

Strobilurin fungicides play a crucial role in protecting plants against different pathogens and securing food supplies. A series of 1,2,3-thiadiazole and thiazole-based strobilurins were rationally designed, synthesized, characterized, and tested against various fungi. Introduction of 1,2,3-thiadiazole greatly improved the fungicidal activity of the target molecules. Compounds 8a, 8c, 8d, and 10i exhibited a relatively broad spectrum of fungicidal activity. Compound 8a showed excellent activities against Gibberella zeae, Sclerotinia sclerotiorum, and Rhizoctonia cerealis with median effective concentrations (EC50) of 2.68, 0.44, and 0.01 μg/mL, respectively; it was much more active than positive controls enestroburin, kresoxim-methyl, and azoxystrobin with EC50 between 0.06 and 15.12 μg/mL. Comparable or better fungicidal efficacy of compound 8a compared with azoxystrobin and trifloxystrobin against Sphaerotheca fuliginea and Pseudoperonspera cubensis was validated in cucumber fields at the same application dosages. Therefore, compound 8a is a promising fungicidal candidate worthy of further development.

Synthesis and (3+2) cycloaddition reactions of N , N ʹ - and C , N -cyclic azomethine imines

This review considers new methods for the synthesis of N,Nʹ- and C,N-cyclic azomethine imines, as well as the most characteristic of their transformations – (3+2)-dipolar cycloaddition reactions. Particular attention was focused on the issues of regio- and stereoselectivity, the effects of the structure of starting materials, solvents, and catalysts on the reaction direction and yields of cycloadducts. The review covers literature data about the chemistry of cyclic azomethine imines published over the previous 10 years. There are 71 references given.

Synthesis of 5‐Acyl‐2‐Amino‐3‐Cyanothiophenes: Chemistry and Fluorescent Properties

Independent of the substrate structure and reaction conditions, 3-amino-2-cyanothioacrylamides, which contain two active electrophilic centers, were shown to interact with various active halo methylene compounds under mild conditions to afford 5-acyl-2-amino-3-cyanothiophenes as the only products. A series of new polyfunctional thiophene derivatives with a rare combination of functionalities were synthesized, and their photophysical properties were experimentally and computationally investigated. The calculated electronic characteristics of the ground and excited states were compared to the experimental results, which provided a good understanding of the relationship between the optoelectronic properties and the molecular structures. After absorption of light quanta, the systems populate an intramolecular charge-transfer (ICT) Franck-Condon state, and emission occurs from a twisted ICT minimum.

The new facile and straightforward method for the synthesis of 4H-1,2,3-thiadiazolo[5,4-b]indoles and determination of their antiproliferative activity.

A series of 4H-1,2,3-thiadiazolo[5,4-b]indoles were synthesized by novel tandem of oxidative cyclization of 3-alkoxycarbonylhydrazonoindoline-2-thiones, 1,5-H-shift and elimination of tert-butoxy(ethoxy)carbonyl group. The simple method for their modifications by the reactions with electrophilic agents were elaborated and as a result of the synthetic investigation a number of N-alkyl-, N-acyl- and N-sulfonyl-4H-1,2,3-thiadiazolo[5,4-b]indoles were prepared in good yields. Preliminary biological tests for the three examples of synthesized compounds with different substituents at the nitrogen atom indole ring have shown that the biological behavior of the investigated 1,2,3-thiadiazolo[5,4-b]indoles is substantially directed by this structural fragment.

Highlights on the Road towards Highly Emitting Solid-State Luminophores: Two Classes of Thiazole-Based Organoboron Fluorophores with the AIEE/AIE Effect

Developing a novel, small-sized molecular building block that may be capable of emitting light in the solid state is a challenging task and has rarely been reported in the literature. BF2 -containing dyes seem to be promising candidates towards this aim. Two series of new N^NBF2 complexes showing aggregation-induced emission (AIE) and aggregation-induced emission enhancement (AIEE) were designed and synthesized by means of a new protocol, which improved on the traditional method by employing microwave irradiation. The optical and photophysical properties of the BF2 complexes were investigated in depth. The synthesized complexes showed fluorescence in both solution and the solid state and, in a mixture of tetrahydrofuran/water, may aggregate into fluorescent nanoparticles. The experimental investigation was supported by quantum mechanical calculations. Their availability, stability, large Stokes shifts, and aggregation capabilities, along with their solid-state emission capability, render this new class of BF2 complexes promising AIEE/AIE fluorophores for further applications in the fields of fluorescence imaging and materials science.

Synthesis and Fluorescent Behaviour of 2-Aryl-4,5-dihydro-1H-1,2,4-triazoles

A series of new 4,5-dihydro-1H-1,2,4-triazoles was synthesized from amidrazones and acetylenedicarboxylic acid esters in the presence of pyridine in toluene. The synthesized compounds were characterized by 1H, 13C NMR, FT-IR spectral analyses and XRD data. Optical studies revealed that most of the compounds reported here exhibited emission of blue or green-yellow light upon irradiation in acetone and showed Stokes shifts in the region of 70-96 nm and quantum yields of up to 45%. The interpretation of the experimental findings was supported by state-of-the-art quantum mechanical calculations.

Synthesis and fungicidal activity of 3,4-dichloroisothiazole based strobilurins as potent fungicide candidates

A series of 3,4-dichloroisothiazole based novel strobilurin analogs were designed and synthesized, and their structures were elucidated by NMR and HRMS, and the typical crystal structure was determined by X-ray diffraction for validation. Results from different biological assays suggested that most target compounds displayed very good fungicidal activity against one or multiple plant pathogens in vitro and in vivo. Among them, compounds 6d, 6g and 8d showed a broad spectrum of fungicidal activity. Further field experiments indicated that compound 8d displayed better efficacy against Sphaerotheca fuliginea than commercial standards azoxystrobin and trifloxystrobin, and better efficacy against Pseudoperonospora cubensis than trifloxystrobin. Overall, a new fungicidal candidate for plant disease management was discovered in this study.

Reaction of arylhydrazonoacetamidines with carbonyl compounds. Novel synthetic route to 2,3-dihydro-1,2,4-triazines

Cyclization of arylhydrazonoacetamidines with acetals resulted in 2-aryl-5-amino-2,3-dihydro-1,2,4-triazines in the yields from moderate to good. This is a novel synthetic approach to access 1,2,4-triazine cycle proceeding apparently via tandem condensation and electro-cyclization reaction.