The paper is devoted to the synthesis of arylidene malonic acid monoanilides and cinnamoyl anilines by condensation of malonic acid monoanilides with aromatic aldehydes. The presented synthetic route applies simple, cheap, and commercially available aromatic aldehydes and amines, thus overcoming traditional schemes, which involve derivatives of hydroxycinnamic acids. Besides, a mild and effective pyridine-mediated decarboxylation of carboxylic group at Csp2 in arylidene malonic acid monoanilides leading to cinnamoyl anilines is presented. The structures of obtained selected arylidene derivatives were approved additionally by X-ray analysis. The antiradical properties (2,2-diphenyl-1-picrylhydrazyl and galvinoxyl tests) and structure–activity relationships of the synthesized compounds were studied. Graphical abstract: [Figure not available: see fulltext.].