Synthesis, characterization, and catalytic activity of palladium(II) complexes containing tridentate N-(pyridin-2yl)-1,2-azol-3-carboxamide ligands with various length amide linkers [CONH(CH2)n, n = 0,1,2] is reported. Complexation of previously undescribed mixed pyridin-azol-carboxamide ligands with PdCl2 occurs unusually by deprotonation of the amide group and elimination of HCl affording the palladium(II) pincer complexes [(k3NNN)PdCl]n (n = 1, 2), which was proven by single crystal X-ray diffraction. The first time synthesized complexes are high-turnover catalysts, as was shown during the evaluation in Suzuki reaction between aryl halides and arylboronic acids: substituted biaryls, including practically significant, were obtained with up to quantitative yields under Green Chemistry conditions.

Based on magnetic ferrites of iron (magnetite), cobalt, and nickel, modified with 3-aminopropyltriethoxysilane (APTES), Pd–Fe–Co–Ni/MFe2O4@Si–NH2@Pd (M = Fe, Co, Ni) hybrid materials with a protective palladium coating were synthesized. Due to the synergistic effect, the new Pd-polymetallic composites exhibit high catalytic activity in the Suzuki reaction in an aqueous solution of an ionic liquid. The developed catalysts are easily separable from the reaction mixture by magnetic decantation and can be reused several times without loss of catalytic activity.

5-Arylisoxazolyl- and 4,5-dichloroisothiazolyl-3-carboxamides were synthesized based on trichlorethylene and its dimer. The prepared carboxamides were used for the synthesis of azanediylbisisoxazolyl(isothiazolyl)carboxamides and bis(azolyl)carboxamides. The new polynitrogen ligands form palladium complexes LPdCl 2 , which exhibit high catalytic activity in cross-coupling reactions in water media in organic solvent-free conditions.

Based on magnetite modified with 3-aminopropyltriethoxysilane (APTES) hybrid materials Pd-Fe-Co-Ni/Fe3O4@Si-NH2 and Pd-Fe-Co-Ni/Fe3O4@Si-NH2@Pd were synthesized. Due to the synergistic effect, new magnetic polymetallic composites exhibit high catalytic activity in the Sonogashira reaction in an ionic liquid medium, which makes it possible to perform catalysis efficiently in the presence of 0.5 mol% of palladium. The new catalysts are easily removed from the reaction mixture using an external magnet and can be used up to 5-6 times without any visible loss of activity.

A convenient one-step method for the synthesis of new bisacridine derivatives, containing fragments of 5-arylisoxazoles, 4,5-dichloroisothiazole, as well as isonicotinic acid residues covalently attached by ester groups to various positions of the aromatic core, was developed. A three-component cascade condensation of 1,5-naphthalenediamine, aldehydes, and cyclic β-dicarbonyl compounds was carried out by refluxing in butanol. Quaternary ammonium salts of synthesized bisacridine derivatives were obtained. It was shown that the synthesized bisacridine compounds form complexes with palladium LPdCl2, which exhibit high catalytic activity in the model Suzuki reaction in water in the absence of organic co-solvent.

A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan, which are highly efficient catalysts for the Heck reaction in aqueous media in the presence of an ionic liquid and can be readily extracted with an external magnet for reuse in catalysis.

A method for the synthesis of 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carboxylic acids derivatives based on 4-acetyl- and 4-benzoylpyridine has been developed. Esters and amides were prepared by acylation of (pyridin-4-yl)methanols and (pyridin-4-yl)methanamines with acid chlorides of substituted 1,2-azole-3-carboxylic acids in ether or methylene chloride in the presence of triethylamine. Quaternary ammonium salts of synthesized pyridine derivatives were also obtained.

Bimetallic proline-containing composites Pd–Ni(Co, Cu, Fe)–Pro/Al2O3, due to the synergistic effect, exhibit high catalytic activity in the Suzuki reaction in aqueous media, which makes it possible to reduce the amount of expensive Pd to 10–2 mol %. New catalysts are easily regenerated from the reaction mixture and can be reused up to 5 times without losing activity.

Hybrid materials based on Pd- and Cu-doped Raney nickel appeared to be highly efficient catalysts for the Heck reaction in aqueous media in the absence of organic cosolvents. The catalysts can be easily removed by an external magnet and reused without losing catalytic activity.

Based on esters of nicotinic and isonicotinic acids with hydroxybenzaldehydes, a series of functionally substituted derivatives containing isoxazole and isothiazole heterocycles in the molecule have been synthesized. Azomethines were obtained by condensation of nicotinates and isonicotinates with p-bromoaniline and m-aminophenol, which have been reduced with sodium triacetoxyborohydride to give the corresponding amines. Acylation of amino derivatives of nicotinates and isonicotinates with 5-arylisoxazole- and 4,5-dichloroisothiazolecarbonyl chlorides leads to the esters and amides with isoxazole and isothiazole residues.

A mechanochemical method for the synthesis of Pd-Fe-Co-Ni ferromagnetic composites was developed. The composites are highly efficient catalysts for the Suzuki reaction in aqueous media. They can be easily removed with an external magnet and reused without losing catalytic activity.

New methylamine derivatives with 1,2-azole fragments (phenylisoxazole, p-tolylisoxazole, 2,5-dimethylphenylisoxazole and 4,5-dichloroisothiazole) and their palladium complexes were synthesized. It was shown that palladium complexes with the obtained N-methyl-1-(1,2-azol-3-yl)methylamine exhibit high catalytic activity in the Suzuki reaction in aqueous medium.

Natural and synthetic derivatives of acridine and pyrimidoquinoline series are of considerable interest for study as antiviral, antitumor, antibacterial, antiparasitic agents; they are also useful in the treatment of Alzheimer’s disease. The combination of acridine and pyrimidoquinoline cycles with other pharmacophore groups can lead to a synergistic effect of their properties, the appearance of new types of biological activity, as well as a reducing of the severity of side effects. The synthesis of new derivatives of 8,9,10,12-tetrahydrobenzo[a]acridin-11(7H)-one and 10,12-dihydrobenzo[ f ] pyrimido [4,5- b ] quinoline-9,11 (7H, 8H)-dione containing isoxazole, isothiazole heterocycles, ferrocene fragment, as well as nicotinic and isonicotinic acid residues covalently attached via ester groups to different positions of the aromatic nucleus, is described. A three-component cascade condensation of aromatic amines, aldehydes and cyclic β —dicarbonyl compounds was carried out by refluxing in butanol. The heat effects of the cyclization reaction have been determined using the DFT / B3LYP1 / MIDI method. The cytotoxic activity of the synthesized compounds was assessed on four different cancer cell lines (RKO, COLO320, LS174T, SW480).

A convenient one-pot approach was proposed for the synthesis of new derivatives of 8,9,10,12tetrahydrobenzo[a]acridin-11(7H)-one and 10,12-dihydrobenzo[f]pyrimido[4,5-b]quinoline-9,11(7H,8H)-dione containing residues of nicotinic and isonicotinic acids covalently attached via ester groups in different positions of the aromatic core. Quaternary ammonium salts of the synthesized acridine derivatives as well as a metal complex with palladium PdLCl2 were obtained. These compounds contain a number of pharmacophore groups so going to be promising potential drugs with antimicrobial, antiviral, and antitumor activity.

The chemistry of isothiazoles is being intensively developed, which is evidenced by the wide range of selective transformations involving the isothiazole heterocycle and the high biological activity of its derivatives that can be used as effective new drugs and plant protection chemicals. Some representatives of isothiazoles have proven to be synergists of bioactive substances, which opens the way to lower the doses of drugs used and is especially important in cancer chemotherapy. In the framework of the present review, the accomplishments in the chemistry of isothiazoles over the past 18 years are examined, whilst current strategies for the synthesis of isothiazole-containing molecules and key directions of studies in this field of heterocyclic chemistry are discussed. Considerable attention is paid to chlorinated isothiazoles and strategies for their use in the synthesis of biologically active substances. In addition, a comprehensive review of existing literature in the field of metal complexes of isothiazoles is given, including the results and prospects for the practical use of isothiazole-metal complexes as catalysts for cross-coupling reactions in aqueous and aqueous-alcoholic media ('green chemistry'). 1 Introduction 2 Synthesis by Ring-Forming Reactions 2.1 Intramolecular Cyclization 2.2 (4+1)-Heterocyclization 2.3 (3+2)-Heterocyclization 2.4 Syntheses by Ring Transformations 3 Isothiazoles by Ring Functionalization Reactions: Nucleophilic Substitution, Cross-Coupling and Side-Chain Functionalization 4 Selected Syntheses of Biologically Active Isothiazole Derivatives 5 Isothiazoles in the Synthesis of Transition-Metal Complexes and in Metal-Complex Catalysis 6 Conclusion

We report for the first time cyclic phosphine-free "head to tail" N,N,N pincer-like (pincer complexes mimicking) N-(pyrimidin-2-yl)-1,2-azole-3-carboxamide Pd(II) complexes with deprotonated amide groups as high-turnover catalysts (TON up to 106, TOF up to 1.2 × 107 h-1) for cross-coupling reactions on the background of up to quantitative yields under Green Chemistry conditions. The potency of the described catalyst family representatives was demonstrated in Suzuki-Miyaura, Mizoroki-Heck, and Sonogashira reactions on industrially practical examples. Corresponding ligands could be synthesized based on readily available reagents through simple chemical transformations. Within the complex structures, a highly unusual 1,3,5,7-tetraza-2,6-dipalladocane frame could be observed.

N-(4,6-Dimethylpyrimidin-2-yl)-5-phenylisoxazole-3-carboxamide was used as a ligand for obtaining bimetallic boron-containing heterogeneous catalysts Pd–Ni(Co)–B–L (Ni(Co):Pd = 9:1). The obtained composites were highly active as catalysts of Suzuki reaction in aqueous media, allowing to develop convenient methods for the synthesis of heterobiaryls containing furyl and thienyl rings.

Acylation of vanillin with isonicotinoyl chloride gave 4-formyl-2-methoxyphenyl pyridine-4-carboxylate which was converted into a number of functional derivatives, including those containing isoxazole and isothiazole heterocycles. In particular, the condensation of the title compound with primary amines afforded the corresponding Schiff bases. 4-Formyl-2-methoxyphenyl pyridine-4-carboxylate and one of the Schiff bases derived therefrom were reduced with sodium triacetoxohydridoborate to the corresponding alcohol and amine which were acylated with 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carbonyl chlorides to obtain esters and amides having isoxazole and isothiazole fragments. The synthesized compounds readily formed complexes with palladium(II) chloride, which showed a high catalytic activity in the Suzuki reaction of 3-bromobenzoic acid with 4-methoxyphenylboronic acid in water in the absence of an organic solvent.