PECULIARITES OF INTERACTION BETWEEN 3-(2-AMINOPHENYL)-6-R-1,2,4-TRIAZIN-5(2 H )-ONES AND CYCLIC ANHYDRIDES OF NON-SYMMETRIC DICARBOXYLIC ACIDS

The peculiarities of the reaction between 3-(2-aminophenyl)-6-R-1,2,4-triazin-5(2H)-ones and cyclic anhydrides of non-symmetric (2-methylsuccinic, 2-phenylsuccinic and camphoric) acids have been described in the present article. The influence of electronic and steric effects of substituents in the anhydride molecule on cyclisation pro- cesses has been discussed. The results have shown that the interaction of 3-(2-aminophenyl)-6-R-1,2,4-triazin-5(2H)-ones mentioned above with 2-methylsuccinic and 2-phenylsuccinic acid anhydrides proceeded non-se- lectively and yielded the mixtures of 2-R 1 -3-(2-oxo-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-6-yl)propanoic acids and 1-(2-(5-oxo-6-R-2,5-dihydro-1,2,4-triazin-3-yl)phenyl)-3-R 1 -pyrrolidine-2,5-diones. It has been found that low regioselectivity of the acylation process may be explained by insignificant electronic effects of substituents (of the methyl and phenyl fragment) in position 2 of the anhydride molecule on the electrophilic reaction centre. It has been also determined that the reaction between 3-(2-aminophenyl)-6-R-1,2,4-triazin-5(2H)-ones and camphoric anhydride proceeds regioselectively and yielded 1,2,2-trimethyl-3-(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazolin-6-yl)cyclopentan-1-carboxylic acids. Regioselectivity of the interaction mentioned above may be explained by the steric effect of the methyl group. Identity of compounds has been proven by LC-MS, the structure has been determined via a set of characteristic signals in 1 Н NMR, 13 С NMR spectra and position of cross peaks in the correlation HSQC-experiment. Mass spectra of the compounds synthesized have been also studied, the princi- pal directions of the molecule fragmentation have been described. The structure of 1,2,2-trimethyl-3-(3-methyl-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazolin-6-yl)cyclopentane-1-carboxylic acid has been proven by X-ray analysis.

The study of the biological action of the compounds mentioned above and their salts has shown that they reveal a high actoprotective and cerebroprotective activities, and may be characterized as promising objects of research aimed at creating new medicines. Taking into consideration the abovementioned fact we decided to extend the potential of the reaction between 3-(2-aminophenyl)-6-R-1,2,4-triazin-5(2H)-ones and cyclic anhydrides of dicarboxilic acids as the method for preparation of carboxyl-con-taining derivatives of [1,2,4]triazino [2,3-c]quinazoline as possible bioactive compounds. Anhydrides of 2-methylsuccinic, 2-phenylsuccinic and camphoric acids have been used as the research objects. It is important to mention that structural features of the last described, in particular electronic and steric effects of substituents, may cause the ambiguous course of the reaction.

Results and Discussion
As initial compounds we used 1.1-1.6, reactions were carried out in conditions similar to the described earlier [6], namely by boiling of the starting substances in acetic acid for 6 hours. The results obtained were quite unexpected, so, according to LC-MS data the interaction between 3-(2-aminophenyl)-6-R-1,2, 4-triazin-5(2H)-ones 1.1-1.6 and 2-methylsuccinic anhydride occurred ambiguously and led to the formation of the mixture of 2-methyl-3-(2-oxo-3-R-2H- [1,2,4]triazino[2,3-c]quinazoline-6-yl)propanoic acid as a major product and 3-methyl-1-(2-(6-R-5-oxo-2,5-dihydro-1,2,4-triazino-3-yl)phenyl)pyrrolidin-2,5diones (3.1-3.6) as the minor one (Scheme 1). A low regioselectivity of the acylation process may be explained by -an insignificant inductive effect of the methyl group on the electrophilic reaction centre. Target compounds 2.1-2.6 were isolated by crystallization from methanol, and to confirm the structure of compound 3.1 it was isolated from the reaction mixture.  Identity of compounds 2.1-2.6 was proven by LC-MS, the structure was determined via a set of characteristic signals in 1 Н NMR, 13 С NMR spectra and position of cross peaks in the correlation HSQC-experiment. In 1 Н NMR-spectra of the compounds mentioned the signals of the carboxylic group proton at 12.10-12.36 ppm are characteristic. Location of the ABCD-system of the benzene fragment of the quinazoline system in a comparatively low field additionally confirms formation of the electron deficient tricyclic system. Mutual location of signals of the carboxyalkyl fragment, in particular signals of stereotopic protons of the methylene fragment in the aliphatic part at 3.74-3.79 and 3.10-3.40 ppm, allows to suggest that the methyl group is located at α-position relative to the carboxylic group. Location of other signals in 1 Н NMR and 13 C NMR-spectra, аs well as location of cross peaks in correlation of the HSQC-experiment also confirm the structures proposed. 1 Н NMR-spectra of compounds 3.1 substantially differ from the spectra of compounds 2.1-2.6. Thus, in the spectra of compound 3.1 instead of the carboxylic group signal the abnormally deshielded NHproton signal at 13.19 ppm was detected. The protons of the benzene cycle of the quinazoline fragment were located in quite higher field comparing to the spectra of compounds 2.1-2.6 indicating the absence of the electron deficient triazinoquinazoline system.
The unexpected results were also obtained while studying the interaction of 3-(2-aminophenyl)-6-phenyl-1,2,4-triazine-5(2H)-ones with 2-phenylsuccinic anhydride. According to LC-MS data boiling of the compounds mentioned above in acetic acid yielded the mixture of two compounds with the equivalent value of m/z corresponding to the molecular weight Formation of the products mentioned, as we consider, may be explained by the fact that the electronic effect of the phenyl moiety cannot be characterized as an obvious donor or acceptor. Thus, reactivity of carbonyl groups is approximately equal, which, in turn, causes nonselective acylation of the amino group. Intermediates A and B formed undergo further dehydration. Dehydration of intermediate A leads to formation of the triazinoquinazoline system, at the same time such direction of dehydration is impossible for intermediate B in consequence of steric restrictions. In this case, there was the alternative direction of cyclisation followed by formation of the correspond- quinazoline-6-yl)-2-phenylpropanoic acid (4.1) was isolated from the mixture of the products and characterized as an individual compound. The 1 Н NMR spectral pattern of the compound mentioned was similar to the spectra of compounds 2.1-2.5. Thus, signals of the carboxylic group at 12.59 ppm, the ABCD system of triazinoquinazoline protons and the carboxyalkyl fragment were present in 1 Н NMR-spectra of 4.1. The signals being characteristic for the phenyl moiety in position 3 were also observed.
The interaction of 3-(2-aminophenyl)-6-R-1,2,4triazin-5(2H)-ones with camphoric anhydride was also studied. The reaction given above was especially interesting considering that among products of condensation of camphoric anhydride with diamines the ISSN 2308-8303 potent hypoglycemic agents were found [9]. According to the data of physicochemical methods the interaction of the compound mentioned occurred regioselectively and yielded 1, To confirm the structure of compounds 6.1-6.3 the complex of physicochemical methods such as LC-MS, 1 H NMR-, 13 C NMR-and mass-spectrometry was used. The molecular weight of compounds, signals of the carboxylic group (11.91-11.97 ppm) and protons of the quinazoline fragment in 1 H NMR spectra and 13 С NMR spectral pattern indicated formation of the triazinoquinazoline system, but we could not differentiate the product out of two alternative structures. The mass spectral (EI) pattern of compound 6.1 was characterized by the complex structure, but also did not allow definitely evaluating direction of the reaction. Primary fragmentation was caused by the decar-boxylation process (the signal with m/z = 321, I rel = 29.0% (F 2 )) and degradation of triazine fragments on bonds С2-C3 and N4-N5 (signals with m/z = 325, I rel = 16.8% (F 2 )). The subsequent elimination of CO from the fragment ion F 2 yielded the fragmental ion F 3 (the signal with m/z = 297, I rel = 30.4%). Degradation of the cyclopentane moiety of fragments F 1 and F 2 caused the presence of signal series, including the most intensive with m/z = 198. Elimination of the cycloalkyl fragment from F 2 yielded an ion with m/z = 171 and the intensity of 28.4% being typical for the triazinoquinazoline system and fragmentation was undergone according to the directions described [10]. Considering that the complex of spectral methods did not allow to identify the structure of the products formed the X-ray structural study was used; it showed that we obtained 1,2,2-trimethyl-3-(3-R-2-oxo-2H- [1,2,4]triazino[2,3-c]quinazoln-6-yl)cyclopentan-1-carboxylic acids.
The tricyclic fragment of molecule 6.1 is planar within 0.03 Å. The saturated five-membered substituent adopts an envelope conformation where deviation of the C16 atom from the mean plane of the remaining atoms of the ring is -0.65 Å. The five-membered ring is turned in such way that its planar part is slightly non-coplanar to the N2-C8 endocyclic double bond (the N2-C8-C12-C13 torsion angle is 32.5(3)°). It can be assumed that C12-H…N4 (H…N 2.31 Å C-H…N 104°) and C13-H13b…N2 (H…N 2.43 Å C-H…N 107°) weak intramolecular hydrogen bonds promote such location of the saturated ring. The methyl group at the C15 atom is located in the axial position (the C13-C14-C15-C19 torsion angle is 91.3(3)°) and the carboxyl group has equatorial orientation and is almost coplanar to the C14-C15 endocyclic bond (the C13-C14-C15-C20 and C14-C15-C20-O2 torsion angles are 147.8(2)° and -12.1(3)°, respectively). The presence of the geminal substituents at the neighbouring atoms of the pentane ring leads to the appearance of the significant steric repulsion (the shor-   In the crystal phase molecules 6.1 form the zigzag chains along the [0 1 0] crystallographic direction due to formation of the O3-H…O1' (1.

Experimental Part
Melting points were determined in open capillary tubes and were uncorrected. The elemental analyses (C, H, N, S) were performed using an ELEMENTAR vario EL Cube analyzer (USA). Analyses were indicated by the symbols of the elements or functions within ±0.3% of the theoretical values. IR spectra (4000-600 cm -1 ) were recorded on a Bruker ALPHA FT-IR spectrometer (Bruker Bioscience, Germany) using a module for measuring attenuated total reflection (ATR). 1 H NMR spectra (400 MHz) and 13 C NMR spectra (100 MHz): were recorded on Varian-Mercury 400 (Varian Inc., Palo Alto, CA, USA) spectrometers with TMS as an internal standard in DMSO-d6 solution. LC-MS were recorded using the chromatography/mass spectrometric system consisting of a "Agilent 1100 Series" high performance liquid chromatograph (Agilent, Palo Alto, CA, USA) equipped with a diode-matrix and a "Agilent LC/MSD SL" mass-selective detector (atmospheric pressure chemical ionization -APCI). Electron impact mass spectra (EI-MS) were recorded on a Varian 1200 L instrument at 70 eV (Varian, USA). The purity of all the compounds obtained was checked by 1H-NMR and LC-MS. Compounds 1.1-1.6 were obtained according to the synthetic protocols described [1].