4,6-Dihydroxysalicylic Acid-Catalyzed Oxidative Olefination of Methyl N-Heteroarenes with Benzyl Amines

Benzyl amines were deaminated for the olefination of methyl N-heteroarenes such as quinolines, benzothiazoles, and quinoxalines catalyzed by 4,6-dihydroxysalicylic acid with only 1 mol % catalyst loading. A wide range of N-heteroaryl stilbenoids were synthesized in yields of 42 to 96 % using oxygen (1 atm) as the sole oxidant. 4,6-dihydroxysalicylic acid not only behaves as an organocatalyst for the oxidation of benzyl amines to the imine intermediates, but also provides an acidic reaction condition for the olefinations. Gram scale reaction and the synthesis of two pharmaceutically relevant conjugated olefins were also successful using this methodology.