Knoevenagel condensation of several aromatic aldehydes 1 with different active methylene compounds 2 under conventional heat condition was efficiently mediated by TRIZMA as a benign catalyst to afford the corresponding arylidenes 3 in excellent yield. In the same reaction the yield has dramatically reduced when microwave irradiation was employed under nitrogen while when the irradiation has carried out in presence of oxygen air TRIZMA showed an extraordinary reactivity and N1-(1,1-diethylpropyl)-N2-(1-ethyl-1-hydroxymethylpropyl) ethanediamide 4 was obtained instead.