ABSTRACT N-(2-(4-chlorophenyl)-1-(4-oxo-4H-benzo[d][1,3]oxazin-2-yl)vinyl)-2-(1,3-dioxoisoindolin-2-yl)acetamide 2 has been synthesized by treatment of anthranilic acid with (Z)-2-((4-(4-chlorobenzylidene)-5-oxo-4,5-dihydrooxazol-2-yl)methyl)isoindoline-1,3-dione 1 in boiling butanol. The reaction of 2 with nitrogen and carbon nucleophiles and with carbon electrophiles have been investigated. INTRODUCTION 4H-3,1-benzoxazin-4-ones have been known for more than a century [‎1]. Several of these compounds have been used as linking-units in thermally stable polymer [‎‎2] and have been shown to possess biological activity. They are potent inhibitors of human leukocyte elastase [3], HSV-1 protease [‎4] and inactivators of Clr serine protease[‎‎5]. Moreover, 2-substituted 4H-3,1-benzoxazin-4-ones are the most frequently used precursors in the preparation of biologically active heterocyclic compounds such as quinazolinones [‎6]. As a result of these attractive features and in continuation of our investigation on biologically active derivatives among six-membered heterocycles [‎‎7,‎8].