Pd(II)-Catalyzed Aerobic Intermolecular 1,2-Diamination of Conjugated Dienes: A Regio- and Chemoselective [4 + 2] Annulation for the Synthesis of Tetrahydroquinoxalines

A Pd(II)-catalyzed aerobic intermolecular 1,2-diamination of conjugated dienes was developed for the regio- and chemoselective preparation of a variety of functionalized tetrahydroquinoxalines, using simple sulfonyl protected o-phenylendiamines as a nitrogen source. This methodology provides a direct and efficient synthesis of tetrahydroquinoxalines. O2 was used as the stoichiometric oxidant, and reaction conditions were applied to a series of o-phenylendiamines and conjugated dienes. 35 examples are described, and good yields and selectivities are obtained for the majority of the products.