A facile green chemistry approaches towards the synthesis of bis-Schiff bases using ultrasound versus microwave and conventional method without catalyst

A sonochemistry-based method was used to synthesize a novel series of bis-Schiff bases using
aromatic aldehydes and diamines (trans-1,4-diaminocyclohexane, p-xylylenediamine and
ethylenediamine dihydrochloride) without catalyst. Yields and reaction times needed for reaction
completion using conventional heating, microwave (MW) and ultrasound (US) irradiation are
compared. The environmentally friendly sonochemical waves, in the presence of electron
withdrawing and electron donating groups, afford the desired products in high yields and short
time. The structures of the products were proven by elemental analyses, IR, MS, 1H, 19F, and 13C
NMR spectroscopy. 1H NMR spectral data revealed that some derivatives have stronger
intramolecular hydrogen bonding than others.