In this work, a series of thiosemicarbazones with phenol fragments were used as starting compounds for the synthesis of new effective antioxidants containing both a phenol substituent and a heterocyclic fragment: thiazole and thiazolidinone. To determine the most stable conformation of thiosemicarbazone, a potential energy scan was used, along with NOESY NMR spectroscopy data. A number of thiazole derivatives were obtained due the interaction of thiosemicarbazones with several bromoketones: bromoacetophenone, bromodimedone, and bromoacetylcoumarin. The product yields varied from 71 to 94%. Thiazolidinone derivatives were obtained through the reaction between thiosemicarbazones and chloroacetic acid or maleic anhydride with good yields of 82–95%. The antioxidant activities of all the products were determined in vitro: the radical cation scavenging activity was estimated using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate), while the ferric reducing capacity was determined using the ferricyanide/Prussian blue method. It was found that the antioxidant activity of most synthesized substances in both tests exceeds the activity of 4-methyl-2,6-di-tert-butylphenol, while derivatives with a fragment of 2,6-di-tert-butylphenol have the highest activity.

A series of benzotriazole, cyclic amides and pyrimidine derivatives, containing 2,6-di-tert-butyl-phenol fragments, were synthesized. The redox properties of obtained compounds were studied using the cyclic voltammetry on a platinum electrode in acetonitrile. The oxidation potentials of all substances were comparable to those of BHT. The obtained compounds were tested for their antibacterial activity, and N-(2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-oxoethyl)isatin (32 μg/mL) exerted good activity against Staphylococcus aureus.

The Pot, Atom, and Step Economy (PASE) approach is based on the Pot economy principle and unites it with the Atom and Step Economy strategies; it ensures high efficiency, simplicity and low waste formation. The PASE approach is widely used in multicomponent chemistry. This approach was adopted for the synthesis of previously unknown hydroxyquinolinone substituted chromeno[2,3-b]pyridines via reaction of salicylaldehydes, malononitrile dimer and hydroxyquinolinone. It was shown that an ethanol-pyridine combination is more beneficial than other inorganic or organic catalysts. Quantum chemical studies showed that chromeno[2,3-b]pyridines has potential for corrosion inhibition. Real time ¹H NMR monitoring was used for the investigation of reaction mechanism and 2-((2H-chromen-3-yl)methylene)malononitrile was defined as a key intermediate in the reaction.

Six novel lactamomethyl derivatives of 2,5-dimethylphenol and 2,3,5-trimethylphenol were prepared with moderate yields by the reaction of corresponding phenols with 1-(hydroxymethyl)lactams in the presence of an acid catalyst. In all cases, the substitution occurred at position 4 to the phenolic hydroxyl group. The structures of all synthesized compounds were confirmed by FT-IR, ¹H and ¹³C NMR, 2D NMR and elemental analysis. The selectivity and possible pathways of the lactamomethylation reaction were studied by quantum-chemical methods. In silico calculations showed that the substitution at para-position to the hydroxyl group of the corresponding phenols was more preferable due to the higher stability of forming intermediates.