Synthesis and physico-chemical properties of six 5-arylidène-3-benzyl-1-methyl-2-thioxoimidazolidin-4-ones and three 2-arylidene-6-nitro-2H-1,4-benzothiazin-3(4H)-ones have been described. These new compounds were synthetised by Knoevenagel condensation reaction from aromatic aldehydes. The N-alkylation reaction of arylidenebenzothiazines by methyl iodide give the N-methylarylidenebenzothiazines.