Boron-Containing Enamine and Enamide Linchpins in the Synthesis of Nitrogen Heterocycles

The use of alpha-boryl enamine and enamide linchpins in the synthesis of nitrogen heterocycles has been demonstrated. Boryl enamines provide ready access to the corresponding alpha-halo aldehydes, which undergo regioselective annulation to form borylated thiazoles. A condensation/amidation sequence converts alpha-boryl aldehydes into stable alpha-boryl enamides without concomitant C -> N migration. We also show that palladium-catalyzed cyclization of alpha-boryl enamides leads to synthetically versatile isoindolones. These molecules can be subsequently used to access polycyclic scaffolds.