## 3 Results and Discussion
### Chemistry
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Compound 4** & **R** & **Ar** & **Time (min)** & **Yield \({}^{*}\) (\%)** & **mp (\({}^{\circ}\)C)** \\ \hline
**a** & & C\({}_{6}\)H\({}_{5}\) & 5 & 80 & \textgreater{}300 \\
**b\({}^{a}\)** & & _p_-CH\({}_{3}\)-C\({}_{6}\)H\({}_{4}\) & 5 & 80 & \textgreater{}300 \({}^{a}\) \\
**c\({}^{a}\)** & & _p_-OCH\({}_{3}\)-C\({}_{6}\)H\({}_{4}\) & 5 & 80 & \textgreater{}300 \({}^{a}\) \\
**d** & & \(3\),4_,5_-tri_-OCH\({}_{3}\)-C\({}_{6}\)H\({}_{2}\) & 5 & 80 & 265 \\
**e** & & 2-Thienyl & 5 & 70 & \textgreater{}300 \\
**f** & & _p_-F-C\({}_{6}\)H\({}_{4}\) & 5 & 70 & \textgreater{}300 \\
**g** & & _p_-Cl-C\({}_{6}\)H\({}_{4}\) & 5 & 80 & \textgreater{}300 \\
**h** & & _p_-Br-C\({}_{6}\)H\({}_{4}\) & 5 & 80 & \textgreater{}300 \\ \hline
**i** & & C\({}_{6}\)H\({}_{5}\) & 6 & 81 & 277 \\
**j** & & _p_-CH\({}_{3}\)-C\({}_{6}\)H\({}_{4}\) & 8 & 75 & 280 \\
**k** & & _p_-OCH\({}_{3}\)-C\({}_{6}\)H\({}_{4}\) & 9 & 70 & 282 \\
**l** & & \(3\),4_-tri_-OCH\({}_{3}\)-C\({}_{6}\)H\({}_{2}\) & 6 & 80 & 263 \\
**m** & CH\({}_{3}\) & _p_-CH\({}_{3}\)-C\({}_{6}\)H\({}_{4}\) & 6 & 75 & \textgreater{}300 \\
**n** & & 3_,4_-(OCH\({}_{2}\)O)-C\({}_{6}\)H\({}_{3}\) & 8 & 75 & 254 \\
**o** & & 4-F-C\({}_{6}\)H\({}_{4}\) & 9 & 74 & 276 \\
**p** & & 4-Cl-C\({}_{6}\)H\({}_{4}\) & 6 & 71 & 283 \\
**q** & & 4-Br-C\({}_{6}\)H\({}_{4}\) & 6 & 76 & 264 \\ \hline \end{tabular} \({}^{a}\) Compounds which showed decomposition. \({}^{*}\) Isolated yield.  
\end{table} 
Table 2: Results of microwave (MW)-assisted synthesis of **4a–q** compounds, in solvent/catalyst-free conditions. yields. As shown in Table 2, the difference between the yields of the compounds obtained are not significant, results suggest that the electronic nature of the substituent on aromatic aldehydes and the pyrimidin-4-ones have no significant effect on rate, yields and the course to lead to aromatization of pyridinic ring. This protocol is a like a Mannich-type reaction, which compared with conventional methods, does not require long reaction times, and the use of flammable solvents, or expensive and toxic catalysts (ionic liquids, superacid, Bronsted acids), to obtain regioselectivity the reaction products [40; 41; 43; 44]. The structures of 5-aryl-2-methylthio-5,12-dihydrobenzo[g]pyrimido[4,5-_b_]quinoline-4,6,11(3_H_) -trione **4a-q** derivatives were elucidated from the standart spectroscopic and analytical methods (\({}^{1}\)H, \({}^{13}\)C NMR, IR, mass spectra and Elemental Analysis (EA). The naphtoquinone system formed by the two non-equivalent nucleophilic center of 6-aminopyrimidinone **1** (-NH\({}_{2}\) group and C-5), is evidenced from \({}^{1}\)H NMR spectra. All derivatives **4a-q** showed a singlet between 5.17-5.53 ppm assigned to methine proton (stereogenic centre) and other single between 9.21-9.89 ppm corresponding to NH of the pyridine ring. All protons exhibit chemical shift signals in their respective expected region. In this reaction, two possible regioisomer could be formed depending on the carbonyl group of naphthalene-1,2,4(3_H_)-trione **2** involved in the cyclocondensation with the amino group (Figure 1). NOESY (Nuclear Overhauser Effect Spectroscopy) experiments show no correlation between the NH from dihydropyridine (DHP) ring and aromatic protons of the naphtoquinone system as expected for the non-linear derivatives **5**. It is clear that the lack of correlation is not sufficient to rule out a structure, but this is confirmed with the rest of spectroscopic analysis. In similar work, we have changed the amino-heterocyclic component (5-amino-1-NH-pyrazole by 6-amino-pyrimidinone), both bearing two non-equivalent nucleophilic center (-NH\({}_{2}\) group and C-4 in pyrazole or C-5 in pyrimidinone). In order to obtain pyrazolo[3,4-_b_]quinolioniones derivatives, the reaction with (1-NH)-5-aminopyrazole, which has an additional nucleophilic center lead regioselectivity to the formation of non-linear tetracyclidihydrocompounds.