Innovative Green synthesis of Schiff bases and their Antimicrobial Activity

Objective: To optimize microwave assisted solvent free synthesis of Schiff bases of substituted benzaldehydes and aromatic amines (3-amino-6-bromo/Iodo-2-phenylquinazoline-4(3H) one) by using wetting reagent 000-ethoxyethanol. The goal of this study was to investigate the % yields and time required for the completion of reaction for Schiff bases by microwave and conventional conditions. Methods: Schiff bases have been synthesized by condensation of substituted various aromatic substituted benzaldehydes (0.001mol) with 3-amino-6-bromo/Iodo-2-phenylquinazoline-4(3H) one (0.001mol) by two different methods as by conventional method (Heating) & Microwave accelerated synthesis by using wetting reagent 000-ethoxyethanol. The reaction time for conventional method and microwave method is in the range of 4-7 hr. and 3-5 min. respectively. The % yield for conventional method and microwave method is in the range of 56-77%. and 77-90% respectively. All synthesized compounds were characterized by elemental analyses, IR spectroscopy, mass spectroscopy, 1H NMR and 13C NMR spectroscopy. Results: The simple microwave assisted solvent-free method for the synthesis of Schiff bases using a wetting reagent (-ethoxyethanol) led to improvement in the yield of all the target compounds with reduction in their reaction byproducts & substantially reduced the overall process time as expected as compare to traditional method. Excellent isolated yields (up to 90%) were attained within short reaction times (typically, 3 min.) when the reaction was performed under microwaves irradiation. Conclusion: Compared with traditional methods, these methods are more convenient and reaction can be carried out in higher yield, short reactions time and milder conditions, without generation of pollution, elimination of side products and safer to analyst. From these features present methods can be correlated for safer and efficient synthesis of other products.