The reaction of 5,6-diamino-l,3-dimethyluracil with 1,3-diaryl-2,3-dibromopropan-l-ones gave {3-(5-amino-6imino-l,3-dimethyluracil)chalcones, and conditions for their cyclocondensation to pyrimidinodiazepines were found. For substantiation of the reaction mechanism, the reaction of the diamine with other halogen derivatives of chalcones was studied. The IR, UV, and mass spectra of the synthesized compounds and their condensation products are discussed.
o-Phenylenediamine and its substituted derivatives react with 1,3-diaryl-2,3-dibromopropan-l-ones (c~,/3-chalcone dibromides) with formation of photochromic azirinoquinoxalines [1, 2]. In other communications [3, 4], the formation of 1,5diazepine structures was noted in a study of similar reactions. The purpose of the present paper was an investigation of the reactions of 5,6-diamino-1,3-dimethyluracil (I) with o~,/3-chalcone dibromides Ila-s and other halogen derivatives of chalcones VIIa, Vile, Villa, ViIIe, and X.
The reaction of diamine I with compounds IIa-k was carried out by boiling (2-2.5 h) methanol solutions of equimolecular amounts of I and IIa-k in the presence of triethylamine. Compounds llIa-k precipitated (their purity was confirmed by thin-layer chromatography); their yield was 20-40% (Table 1). Under the same experimental conditions, diamine I and 4'-nitrochalcone dibromide (II/) formed 4'-nitrochalcone (XIs in 67% yield as the only product. The reaction of 4nitrochalcone dibromide (lie) with diamine I occurred similarly if the process was carried out in ethanol (the yield of 4nitrochalcone was 60%).
Subsequent heating of the reaction mixtures and also boiling of ethanolic and methanolic solutions of IIIa-k in the presence of catalytic amounts of triethylamine or acetic acid resulted in a mixture of substances in which the main component was compound IV. Theophylline V was a side component (from trace amounts in methanol to 25-30% in ethanol). Theophyllines Va-g were the main products of thermolysis of compounds IIIa-k and boiling of Ilia-k, IVa-e, and IVi-k in dimethylformamide (DMFA). It is of interest that only 8-(4-R-phenyl)theophyllines (and not Rl-substituted derivatives) were formed in these reactions. The structure of theophyllines Va-g was confirmed by back synthesis from diamine I and the corresponding substituted benzaldehyde with subsequent oxidation of intermediate azomethines by N-bromosuccinimide. With respect to their characteristics, theophyllines Va-g were identical to the compounds described in [5].
Compounds Ilia and IIIe were also obtained in reactions of diamine I with 1,3-diphenylpropyn-3-one (VI) and 1-phenyl-3-(4-nitrophenyl)-2-bromo-3-chloropropan-l-one (Vile), respectively. In the reaction of diamine I with t~-bromochalcone (Villa), compound Ilia was formed together with the main product, compound IX, which was also the only product of the reaction of compounds I and ViIa.
In all cases, product XII, with intense green fluorescence, was formed in trace amounts. Its yield increased when methanol was replaced by ethanol. It should be noted that in a control experiment, i.e., during boiling of methanolic solutions of diamine I with triethylamine in the absence of dibromide, the product was virtually not formed. (See scheme on following pages.)