4H-3,1-Benzoxazin-4-ones are valuable starting materials for the synthesis of a variety of heterocycles.1 Also, they are used directly or indirectly in many clinical applications.2 Contrary to the parent compounds 4H-3,1-benzoxazin-4-ones,3 very few synthetic routes have ever been reported for bis-1,2-dihydro-(4H)-3,1-benzoxazin-4-ones.4 Here, a convenient synthesis of bis-N-acetyl-1,2-dihydro-(4H)-3,1-benzoxazin-4-ones 4 are reported by first, a condensation reaction of anthranilic acid derivatives 1 with glyoxal 2 at room temperature and then, cyclization reaction of the produced Schiff-bases 3 with acetic anhydride under reflux conditions (Scheme 1). High yields of the desired products are obtained in high purity and simple work-up.
