New synthetic methodology for construction of the 3,4-dihydroquinolin-2-one skeleton

We hereby report a new method for preparation of 3,4-dihydroquinolin-2(2H)-one starting from the methyl 2-(2-carboxyethyl)benzoic acid. The acid functionality, adjacent to the methylene, was regiospecifically converted to the desired methyl ester and the remaining acid functionality was transferred into acyl azide. Curtius rearrangement of acyl azide followed by trapping with aniline and alcohols provided the corresponding urea and urethane derivatives. Hydrolysis of methyl ester groups gave the acids. Ring closure in the presence of thionyl chloride resulted in the formation of the 3,4-dihydroquinolin-2(2H)-one skeleton.