: A series of 4-(benzyloxy)-N-(3-chloro-2-(substituted phenyl)-4-oxoazetidin-1-yl) benzamide 6a-j were synthesized in good yield from Schiff bases by cyclo-condensation with chloro acetyl chloride in the presence of catalyst tri ethylamine and solvent DMF by using ultra-sonication as one of the green chemistry tool. Synthesis of these derivatives by a conventional method like stirring at room temperature required 20–28 hr and by refluxing nearly takes 8–10 hr whereas using ultra-sonication it requires only 2h for completion of reaction. The use of ultrasound to promote chemical reactions is called sono-chemistry, it is complementary technique for promoting chemical reactions by ecofriendly green synthetic protocol. Ultrasound assisted synthesis are used to reduce the amount of undesired hazardous chemicals and solvents, reduce energy consumption and increase the selectivity towards the given product. Schiff bases are the compounds carrying imine or azomethine (–C=N–) functional group in which the electrophilic carbon and nucleophilic nitrogen confers the Schiff bases possibility to interact with several biological targets and have gained importance in medicinal and pharmaceutical fields exhibiting broad spectrum of biological activities. These key compounds 4-(benzyloxy)-N'-(substituted benzylidene) benzo hydrazide i.e Schiff bases 5a-j were obtained by condensation 4-(benzyloxy)benzo hydrazide with various aromatic aldehydes. The four-membered cyclic amides commonly known as 2-azetidinones or β-lactam occupy an eminent place in organic and medicinal chemistry since the structure of penicillin showed the presence of β-lactam ring in it and various potent activities of penicillin are due to the presence of β-lactam ring.  Azetidinones are known to exhibit various biological activities like anti-tubercular, antibacterial and antifungal with β-lactam ring. Hence we are introducing the eco-friendly protocol for the synthesis of substituted azetidinone derivatives. All the synthesized compounds were characterized by FTIR, ¹HNMR, ¹³CNMR and mass spectral analysis.