Eco-Friendly Synthesis of 2-Styryl-benzo[d][1,3]oxazin-4-ones from N-Cinnamoyl-Anthranilic Acids

N-cinnamoyl anthranilic acids are synthesized in a single, eco-friendly step by condensing various cinnamic acids with free 2-aminobenzoic acid derivatives using the mixed carbonic anhydride method. Subsequently, converting the resulting N-cinnamoyl anthranilic acids into their corresponding mixed carbonic anhydrides rapidly and efficiently affords 2-styryl-benzo[d][1,3]oxazin-4-ones. The method employs green solvents, such as acetone and 2-methyltetrahydrofuran; does not require metal catalysts or reflux conditions; and yields the desired final products without chromatographic purification.