O-Alkyl hydrazinecarbothioates, which are potential building blocks in the synthesis of heterocycles and antimicrobial agents, were obtained from primary alcohols in 38–89% yields by a one-pot method. The obtained compounds are characterized by thione-thiol tautomerism in a solution. An experimental screening for antibacterial and antifungal activity of hydrazinecarbothioates was performed, the highest activity was found against B. cereus and St. aureus strains.

The reaction of carboxylic acid amides with malonyl chloride in acetonitrile or tetrahydrofuran without heating leads to the formation of previously unknown 2-substituted 5-hydroxypyrano[2,3-d][1,3]oxazines. The structure of the obtained compounds was established by high resolution mass spectrometry, NMR spectroscopy, and X-ray analysis.

The aim of the research was investigation of the antimicrobial and antifungal activity of the reaction products of 2,5-substituted 4-hydroxy-6H-1,3-oxazin-6-ones with N-nucleophiles. The activity of the obtained substances was tested on the test-cultures Staphylococcus aureus, Escherichia coli и Candida albicans, respectively. The significant antifungal effect of the studied compounds was revealed.

Methods for synthesizing new heterocyclic compounds based on 1,3,4-thiadiazoles were developed. It was shown that these compounds possessed pronounced antifungal activity and could be recommended for further investigation as potential antimicrobial agents with fungicidal activity.

Получены новые 4-гидрокси-6H-оксазин-6-оны, содержащие в положении 2 нитрофурильный и нитротиофеновый фрагменты. Взаимодействием этих оксазинов с моно- (этанол) и бинуклеофильными (фенилгидразин) реагентами синтезированы новые производные нитрофурана и тиофена. Показано, что синтезированные соединения обладают выраженным бактерицидным эффектом в отношении золотистого стафилококка и, в ряде случаев, кишечной палочки.

A series of new 4-hydroxy-6H-oxazin-6-ones containing 2-(5-nitrofuranyl) and 2-(5-nitrothienyl) moieties were obtained. New nitrofuran and thiophene derivatives were synthesized by reacting these oxazines with mono- (EtOH) and dinucleophiles (phenylhydrazine). It was established that the synthesized compounds possessed pronounced bactericidal activity against Staphylococcus aureus and, in some cases, Escherichia coli strains.

4-Hydroxy-6H-1,3-oxazin-6-ones containing a 3-vinylchromone fragment in the 2-position were synthesized. The direction of their reactions with hydrazine hydrate was found to depend on the solvent nature. The reaction in protic solvents (methanol, acetic acid) resulted in recyclization of both oxazine ring to 1,2,4-triazole and pyranone ring to pyrazole. Aprotic acetonitrile favored attack of hydrazine exclusively on the oxazine ring, while the 3-vinylchromone fragment remained intact.

2-(2-Furyl)- and 2-(2-thienyl)-5-alkyl-4-hydroxy-6 H -1,3-oxazin-6-ones react with guanidine in methanol in the presence of an equimolar amount of sodium methoxide to give previously unknown sodium 4-amino-6-hetaryl-1,3,5-triazin-2-ylacetates. The reactions of 2-(2-furyl)- and 2-(2-thienyl)-5-phenyl-4-hydroxy-6 H -1,3-oxazin-6-ones with guanidine under analogous conditions are accompanied by decarboxylation, yielding 4-benzyl-6-hetaryl-1,3,5-triazin-2-amines. The corresponding decarboxylation products are also obtained by treatment of sodium 2-(4-amino-6-hetaryl-1,3,5-triazin-2-yl)propionates with aqueous HCl.

Reactions of 2-alkylsulfanyl- and 2-alkoxy-4-hydroxy-6H-1,3-oxazin-6-ones with oxygen-centered nucleophiles were studied. 2-Alkoxy-4-hydroxy-6H-1,3-oxazin-6-ones reacted with water and alcohols to give the corresponding alkyl 3-amino-3-oxopropanoates as a result of opening of the oxazine ring at the C6-O bond, whereas their 2-alkylsulfanyl analogs turned out to be stable toward O-nucleophiles. The different reactivities of the title compounds were interpreted in terms of quantum-chemical calculations of their electronic structure.