Try to use "Green Reagents" and use less protecting groups etc.minimize number of steps, try to use Flow or Click Chemistry

See attached files

Thank you sir...but we dont have flash chromatography at our college, so any alternative way to get chalcones easily

Have you tried crystallization?

For Flash chromatography see attachment.

do you have Prep TLC for purification of smaller quantities?

Possibly you receive halkon in the alkaline environment. Coumarines in the alkaline environment are unstable and can form salts of oxycinnamon acids. Replace alkali with secondary amines and use an azeotropic removal of water.

Dear Sir, ( V. S. Talismanov ) can u tel me hw to set up this reaction, any paper or method?

I recommend Jürgen's answer

Best Regards