SYNTHESIS OF 2,3-DIALKENYL DERIVATIVES OF QUINAZOLIN-4-ONE

 In the course of this study, alkylation of two starting thiols — 3-allyl-2-mercaptoquinazolin-4-one and 3-methallyl-2-mercaptoquinazolin-4-one — was carried out using allyl bromide and metallyl chloride in an alcoholic-alkaline medium. As a result of these reactions, new 2,3-dialkenyl derivatives of quinazolin-4-one were obtained, which have not been previously reported in the literature. The structures of the newly synthesized compounds were confirmed by NMR spectroscopy (¹H and ¹³C), as well as elemental analysis. The absence of thioamide proton signals in the ¹H NMR spectra indicates that alkylation occurred at the sulfur atom. In the case of 3-allyl-2-(methallylthio)quinazolin-(3H)-one, characteristic signals of the metallyl fragment were observed, while a chemical shift at 160.30 ppm in the ¹³C NMR spectrum confirmed the formation of the C–S bond. A similar spectral pattern was observed for 3-metallyl-2-(methallylthio)quinazolin-(3H)-one. For 3-methallyl-2-(allylthio)quinazolin-(3H)-one, characteristic signals of the allyl substituent were identified in the ¹H NMR spectrum, confirming the alkylation at position 2 of the quinazoline core. Thus, new potentially bioactive 2,3-dialkenyl quinazolinones were obtained. These compounds contain four nucleophilic centers (two alkenyl fragments, the nitrogen atom at position N1 of the quinazoline ring, and the oxygen atom of the carbonyl group), which makes them promising candidates for studying the regioselectivity of electrophilic heteroannulation reactions. These results provide a solid basis for further research into the synthesis of novel biologically active molecules based on the quinazolin-4-one scaffold.