**2.1 Solution synthesis method of PENQ**

For the solution method synthesis ortho-phthalaldehyde and cyclohexanedione were mixed thoroughly in an appropriate quantity of ethanol. To this mixture KOH is added dropwise and all the reaction mixture was refluxed till the reddish yellow precipitate get formed. After further purification and drying 40-45% of yield is recorded. In this method elevated temperature is used with organic solvents which is not in accordance to the green chemistry principles and not acceptable.

## **2.2 Solid-state method synthesis of PENQ**

In a typical solid-state synthesis process, phthalaldehyde and cyclohexanedione were ground neatly in a clean mortar and pestle till gel like mass seen. Dropwise addition of KOH is done. During the addition, the brownish solution alters in yellow ppt. After the complete synthesis it was washed with water followed by acetone to remove unwanted products. The formation of PENQ was confirmed by NMR.

## **2.3 High pressure method synthesis of PENQ**

Above aldehyde and ketone were mixed and heated at high pressure using a special autoclave type of reactor. In this method there were no need of any solvent as the reaction products tends to aromaticity and high stability of five membered ring system. As compared to above two methods this present method is found to be more economical and safe.
