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1-phenyl-2H,6H-imidazo[1,5-c]quinazoline-3,5-dione reacts with ethyl bromoacetate under mild conditions to give 2-(ethoxycarbonylmethyl)-1-phenyl-6H-imidazo[1,5-c]quinazoline-3,5-dione (MEPIQ) and next 2,6-bis(ethoxycarbonylmethyl)-1-phenylimidazo[1,5-c]quinazoline-3,5-dione (BEPIQ). The products were isolated at high yield and identified on the basis of IR, 1H- and 13C-NMR, UV spectroscopy, and X-ray crystallography. Diester (BEPIQ) can be presented by 16 possible pair of enantiomers. Only one pair of them is the most stable and crystallizes which is shown crystallographic research. Based on quantum-mechanical modeling, with the use of DFT method, which conformers of mono- and diester and why they were formed was explained. It was calculated that 99.93% of the monoester (MEPIQ) is formed at position No. 2 and one pair of the monoester conformers, from six possible, has the largest share (51.63%). These results afforded to limit the number of diester conformers to eight. Unfortunately, the quantum-mechanical calculations performed that their shares are similar. Further quantum-mechanical modeling showed that conformers are able to undergo mutual transformations. As a result only one pair of diester conformers forms crystals. These conformers have substituents in trans position and these substituents are located parallel to imidazoquinazoline ring. This allows for the denser packing of the molecules in the unit cell.Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-017-3284-1) contains supplementary material, which is available to authorized users.

In this work, research concerning the synthesis and properties of linear polyurethanes (PUs) with the imidazoquinazoline rings was represented. Reaction conditions of 2,6-bis(2-hydroxyethyl)-1-phenylimida-zo[1,5-c]quinazoline-3,5-dione (BHPIQ) with 1,6-hexamethylene diisocyanate were determined and optimized. These conditions are adapted to reaction of BHPIQ with 4,4′-diphenylmethane diisocyanate and 2,4-toluene diisocyanate. New PUs with imidazoquinazoline rings were characterized by spectral methods (1 H-NMR and IR spectroscopies), which confirm their structures. Their molar masses and dispersity index were measured by size exclusion chromatography method. The wide-angle X-ray scattering and differential scanning calorimetry (DSC) studies have shown that all PUs based on BHPIQ are amorphous. Moreover, thermal properties of PUs were investigated by thermogravimetry analysis, standard DSC, and temperature-modulated DSC methods. During thermogravimetric measurements, the exhaust gases were analyzed by FTIR method. Incorporation of imidazoquinazoline ring into the PU chains escalates their glass transition temperature; thus, their heat resistance was enhanced. Furthermore, their degradation rate and the amount of released degradation products were

The reaction of 1-phenyl-2H,6H-imidazo[1,5-c]quinazolino-3,5-dione (4) with 3-molar excess ethylene oxide was described. The resulting product was characterized by spectroscopic techniques (1 H-, 13 C-NMR, IR, and UV) and by X-ray crystallography. It was expected to produce a product of the subsequent reaction in the hydroxyl groups of the initially formed diol-1-phenyl-2,6-bis(2-hydroxyethyl)imidazo[1,5-c]quinazoline-3,5-dione (7) with ethylene oxide (5). However, crystallographic studies revealed that the proper and only product of the reaction is 3-{2-[1,3-bis(2hydroxyethyl)-2-oxo-4-phenylimidazolidin-5-yl]phenyl}-1,3-oxazolidin-2-one (8). This product was formed by quinazoline ring opening which occurred in the presence of more than 2-molar excess ethylene oxide. In the work, the exemplary reaction mechanism explaining the formation of the unexpected product was proposed. In order to understand the reasons of quinazoline ring opening, the quantum mechanical modeling was performed. Energy of transition states indicated that the reaction with the third mole of ethylene oxide was controlled by kinetics.