The study of 5,7-dihydroxycoumarins as nucleophilic agents in the S reaction with pyrimidines showed that the reaction does not stop at the stage of σ-adduct formation as the intermediate in the S mechanism, but proceeds further with annulation of the 1,3,5-oxadiazazine ring in moderate to excellent yields. The structures of the obtained compounds were confirmed using NMR and X-ray diffraction. A primary in vitro assessment of antitumor activity was performed.
R.F. Fatykhov (Wed,) studied this question.