## 3 Results and Discussion  
We continue our study to obtain functionalized heterocycles through the development of synthetic strategies. The starting compounds **1** were synthesized by Claisen-Schmidt condensation of 5-chloro-3-methyl-1-phenyl-1_H_-pyrazol-4-carbaldehyde with acetophenones [53, 54]. As part of our ongoing research on the application of ultrasonic irradiation as a clean and useful technique in organic synthesis, we described in this work the synthesis of 5-(pyrazol-4-yl)-4,5-dihydroxyrazole derivatives under ultrasound irradiation (Scheme 1). **Scheme 1. ** Synthesis of 5-(pyrazol-4-yl)-4,5-dihydroxyrazole derivatives. We preliminarily examined the cyclocondensation reaction of (_E_)-3-(5-chloro-3-methyl-1-phenyl-1_H_-pyrazol-4-yl)-1-arylprop-2-en-1-one **1** with hydrazines in the presence of ethanol or methanol and acetic acid as the catalyst under sonication. To achieve suitable reaction conditions in terms of reaction time and catalysis at ambient conditions, we tested different proportions of a mixture of ethanol/methanol and acetic acid. The results are summarized in Table 1.  
The reaction worked out best under sonication conditions in a mixture of ethanol or methanol/acetic acid (5/1) at ambient temperature (35-40 \({}^{\circ}\)C) to provide good yield (65%-80%) in a short time (2-20 min), and the results are summarized in Table 2. To develop the scope of the reaction, we were encouraged to extend this reaction to a variety of (_E_)-3-(5-chloro-3-methyl-1-phenyl-1_H_-pyrazol-4-yl)-1-arylprop-2-en-1-one **1** with different substituents under the determined optimum conditions. We found that the results were excellent compared with 5-pyrazole-4,5-dihidropyrazoline derivatives reported in the literature [55]. Thus, ultrasonic irradiation was found to have a beneficial effect on the synthesis of 1,3-diaryl-5-(1-phenyl-3-methyl-5-chloro-pyrazol)-4,5-dihydropyrazole derivatives, which was superior to the traditional method with respect to yields, reaction times, \begin{table}
\begin{tabular}{c c c c c} \hline
**Compound 3** & **Ar** & **Ar\({}^{\prime}\)** & **Time reaction (min)** & **M.p. °C** & **Yield (\%)** \\ \hline a & 4-H\({}_{3}\)CC\({}_{6}\)H\({}_{4}\) & C\({}_{6}\)H\({}_{5}\) & 20 & 133–135 & 80 \\ b & 4-BrC\({}_{6}\)H\({}_{4}\) & C\({}_{6}\)H\({}_{5}\) & 10 & 163–165 & 75 \\ c & 4-ClC\({}_{6}\)H\({}_{4}\) & C\({}_{6}\)H\({}_{5}\) & 15 & 153–155 & 70 \\ d & 4-O\({}_{2}\)NC\({}_{6}\)H\({}_{4}\) & C\({}_{6}\)H\({}_{5}\) & 20 & 178–180 & 80 \\ e & 4-H\({}_{3}\)COC\({}_{6}\)H\({}_{4}\) & C\({}_{6}\)H\({}_{5}\) & 3 & 130–132 & 80 \\ f & 3,4,5-_tri_-H\({}_{3}\)COC\({}_{6}\)H\({}_{2}\) & C\({}_{6}\)H\({}_{5}\) & 2 & 118–120 & 75 \\ g & 3,4-OCH\({}_{2}\)OC\({}_{6}\)H\({}_{3}\) & C\({}_{6}\)H\({}_{5}\) & 5 & 220–222 & 65 \\ h & 4-H\({}_{3}\)CC\({}_{6}\)H\({}_{4}\) & 4-ClC\({}_{6}\)H\({}_{4}\) & 15 & 158–160 & 80 \\ i & 4-ClC\({}_{6}\)H\({}_{4}\) & 4-ClC\({}_{6}\)H\({}_{4}\) & 10 & 150–152 & 70 \\ j & 4-H\({}_{3}\)COC\({}_{6}\)H\({}_{4}\) & 4-ClC\({}_{6}\)H\({}_{4}\) & 10 & 128–130 & 80 \\ \hline \end{tabular}
\end{table} 
Table 2: The synthesized 1,3-diaryl-5-(1-phenyl-3-methyl-5-chloro-pyrazol)-4,5- dihydropyrazole derivatives under ultrasonic irradiation at ambient conditions (35–40 \({}^{\circ}\)C). \begin{table}
\begin{tabular}{c c c c} \hline
**Entry** & **Conditions** & **Time (min)** & **Yield \({}^{\text{b}}\) (\%)** \\ \hline
1 & Ethanol or Methanol & 35 & 60 \\
2 & Ethanol or Methanol/Acetic acid (10/1) & 20 & 75 \\
3 & Ethanol or Methanol/Acetic acid (5/1) & 20 & 80 \\
4 & Ethanol or Methanol/Acetic acid (10/3) & 20 & 75 \\
5 & Ethanol or Methanol & 20 & 50 \\
6 & Ethanol or Methanol/Acetic acid (10/1) & 15 & 65 \\
7 & Ethanol or Methanol/Acetic acid (5/1) & 15 & 80 \\
8 & Ethanol or Methanol/Acetic acid (10/3) & 15 & 75 \\ \hline \end{tabular} \({}^{\text{b}}\) Isolated yields using ethanol as solvent.  
\end{table} 
Table 1: Effect of reaction conditions. Green factors. simplicity and safety.