Green chemistry is defined as environmentally chemical synthesis of esterification reaction Microwave assisted synthesis in that micro wave is a general-purpose green chemistry for performing organic synthesis reaction the method is faster reaction synthesis of esterification reaction esterification reaction in microwave 7 mint, better yield and higher purity, Uniform and selective heating and also rate of reaction is fast by using dehydrating reagent (H2S04), acts as catalyst in this reaction and removing water molecule [1-3].

in this research molecular docking is one of the most frequently and methods [1-4] in structure-based drug design, drug design, due to its ability to predict the binding – conformation of small molecule ligand to the appropriate target binding site, characterization of binding behavior plays as important role in rational design of drug as well as to elucidate fundamental bio chemical [3,5-8] processes, the esters biological activity Antimicrobial, anti Fungil, antimalarial, anticancer and anti- inflammatory. disappears added sulphuric acid and refluxed (30min) was filtered and recrystallized from ethanol [10-13]     

Figure 1: Biological Activity

Synthesis of esters by microwave mixed thoroughly alcohols and carboxylic acid of pyrazine by using sulphuric acid catalyst in this reaction use microwave irradiation 120w 10 min.

Esterification reaction microwave synthesis six esters is green synthesis and docking studies as shown in Figure 2.

R = H, COOH, Br, Cl, CH₃–CH₃, N, N₁₂

The compounds characterization by spectral FT-IR: disappearance of 3500 cm⁻¹ for (OH) group and appearance of carbonyl stretch (C=O) 1750–1735 cm⁻¹ and C–O stretch from 1300–1000 cm⁻¹.
And this compound's characterization was done using ¹H NMR and ¹³C NMR.

• A1: 2,3,5-Tetramethyl benzoate pyrazine

¹H NMR (DMSO-d₆, ppm):
3.7 (CH₃–O), 7.32–7.59 (aromatic ring)
¹³C NMR (DMSO-d₆, ppm):
51 (CH₃–O), 127–136 (C=C aromatic ring), 150 (C=N of pyrazine), 165 (C=O)

• A3: 2,5-Dimethyl benzoate-3,6-dichloro pyrazine

¹H NMR (DMSO-d₆, ppm):
3.6 (CH₃), 7.35–7.62 (aromatic ring)
¹³C NMR (DMSO-d₆, ppm):
53 (CH₃–O), 127–135 (C=C aromatic ring), 134 (C–Cl), 155 (C=N), 162 (C=O)

• A4: 2,5-Dimethyl benzoate-3,6-di-p-bromophenyl pyrazine

¹H NMR (DMSO-d₆, ppm):
3.6 (CH₃–O), 7.4–7.8 (aromatic ring)
¹³C NMR (DMSO-d₆, ppm):
58 (CH₃–O), 117 (C–Br), 125–132 (C=C aromatic ring), 152 (C=N), 165 (C=O)

• A5: 2,5-Dimethyl benzoate-3,6-di-p-dimethylamine pyrazine

¹H NMR (DMSO-d₆, ppm):
3.7 (CH₃–O), 2.13 N(CH₃)₂, 7.3–7.6 (aromatic ring)
¹³C NMR (DMSO-d₆, ppm):
52 [N(CH₃)₂], 56 (CH₃–O), 127–135 (C=C aromatic ring), 155 (C=N), 167 (C=O)

• A6: 2,5-Dimethyl benzoate-3,6-di-p-nitrophenyl pyrazine

¹H NMR (DMSO-d₆, ppm):
3.5 (CH₃–O), 7.4–7.8 (aromatic ring)
¹³C NMR (DMSO-d₆, ppm):
55 (CH₃–O), 127–135 (C=C aromatic), 148 (C–NO₂), 153 (C=N), 165 (C=O)

In the second part, the study of molecular docking plays an increasingly important role in the targeted drug discovery and development process, since it saves time. The new esters showed intermolecular bonding forces with amino acids through ionic bonds, hydrogen bonds, and Van der Waals interactions, and were found to have good anticancer skin activity.

The antibacterial properties of the prepared compounds were examined using the disk diffusion method with Escherichia coli and Staphylococcus aureus, and exhibited good antibacterial activity when compared to ciprofloxacin.

Table 1: Antibacterial activity of synthesized esters (A1–A6) against Escherichia coli (G. coli) and Staphylococcus aureus (Staph), compared to ciprofloxacin (Cipro) as a standard reference. Data represent inhibition zones in millimeters (mm).

Figure 2: Microwave-assisted esterification reaction scheme used for the synthesis of six esters (A1–A6).

Using microwave synthesis of near esters from methanol and carboxylic acids of pyrazine and study molecular doing active sit of DNA binding and study biological activities agonists staphylococcus and Escherichia coli comparing with ciprohboxacine.

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