## 2 Results and Discussion
### Synthesis of Quinazolin-4(3H)-one: Substrate Scope  
The best optimized conditions obtained in entry 8 of Table 1, were employed to assess the substrate scope, generality and limitations of the present protocol. A reaction of _o_-aminobenzamide and wide range of substituted syrenes were studied under best conditions in hand. As presented in Figure 3, several substituted syrenes showed functional group tolerance under given condition and furnished the desired quinazolin-4(3\(H\))-ones in good to high yields. Styrenes bearing common electron donating functional groups, _tert_-(CH\({}_{3}\))\({}_{3}\) (Figure 3, **3b**), -OCH\({}_{3}\) (Figure 3, **3d**), which are generally sensitive to strong oxidants exhibited very good tolerance under the optimized reaction conditions and were transformed to corresponding quinazolin-4(3\(H\))-ones providing moderate yields 65%, 50% respectively (Figure 3). 54-56% yields were isolated in case of reaction of _o_-aminobenzamide **1**, with _para_-fluoro and _para_-chloro substituted syrenes (Figure 3, **3e, 3f**), whereas _para_ substituted trifluoromethyl (CF\({}_{3}\)) styrene was also tested which smoothly worked and afforded 55% yields on annulation with _o_-aminobenzamide **1** (Figure 3, **3g**). Furthermore, another interesting fused ring syrenes (2-vinylnaphtalene) also worked very well and afforded the anticipated product in 70% (Figure 3, **3h**). Interestingly, another _para_-substituted electron withdrawing group (_p_-NO\({}_{2}\)) afforded corresponding quinazoline in 64% yield (Figure 3, **3c**). In addition a heteroatom containing syrenes (2-vinylpyridine) was also efficiently annulated with _o_-aminobenzamide **1** giving the subsequent quinazolin-4(3\(H\))-one (Figure 3, **3i**) in 62% yield.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Entry** & **Oxidant (Equiv) \({}^{e}\)** & **Additive** & **Temp., Time** & **Solvent** & **Yield \% \({}^{b}\)** \\ \hline
1 & TBHP (5.8) & - & 105 \({}^{\circ}\)C & - & 56 \\ \hline
2 & TBHP (5.8) & - & 105 \({}^{\circ}\)C & H\({}_{2}\)O & 30 \\ \hline
3 & TBHP (5.8) & - & 105 \({}^{\circ}\)C & DMSO & 40 \\ \hline
4 & TBHP (1.5) & - & 80 \({}^{\circ}\)C, 24 h & - & 20 \\ \hline
5 & TBHP (1.5) & - & 120 \({}^{\circ}\)C, 24 h & - & 30 \\ \hline
6 & DTBP (0.54) & - & 110 \({}^{\circ}\)C & DMSO & 35 \\ \hline
7 & DTBP (0.54) & _p_-TSOH & 110 \({}^{\circ}\)C & DMSO & 58 \\ \hline
8 & DTBP (1.09) & _p_-TSOH & 120 \({}^{\circ}\)C & DMSO & 70 \\ \hline
9 & DTBP (0.8) & _p_-TSOH & 105 \({}^{\circ}\)C & DMSO & 45 \\ \hline
10 & DTBP (1.09) & _p_-TSOH & 105 \({}^{\circ}\)C & DMSO & 50 \\ \hline
11 & DTBP (1.4) & _p_-TSOH & 105 \({}^{\circ}\)C & DMSO & 14 \\ \hline
12 & DTBP (1.6) & _p_-TSOH & 105 \({}^{\circ}\)C & DMSO & 23 \\ \hline
13 & DTBP (2.1) & _p_-TSOH & 105 \({}^{\circ}\)C & DMSO & 65 \\ \hline
14 & - & - & 120 \({}^{\circ}\)C & DMSO & 0 \\ \hline
15 & - & _p_-TSOH & 120 \({}^{\circ}\)C & DMSO & 20 \\ \hline
16 \({}^{c}\) & DTBP (1.4) & _p_-TSOH & 120 \({}^{\circ}\)C & CH\({}_{3}\)CN & 60 \\ \hline
17 \({}^{d}\) & DTBP (1.09) & _p_-TSOH & 120 \({}^{\circ}\)C & DMSO & 50 \\ \hline \hline \end{tabular} \({}^{a}\) Reaction conditions: **1** (mmol), **2** (2.0 mmol), additive (0.66 mmol), DMSO (2 mL), \({}^{b}\) Isolated yields, \({}^{c}\) 2 (3 mmol), \({}^{d}\) p-TSOH (1.2 eq), \({}^{e}\) equiv. with respect to **2**.  
\end{table}
Table 1: Model reaction for synthesis of quinazolin-4(3H)-one \({}^{a}\).