Isobutyl Nitrite-Mediated Synthesis of Quinoxalines through Double C-H Bond Amination of N-Aryl Enamines

An efficient and metal-free double C-H bond amination of N-aryl enamines using isobutyl nitrite (IBN) has been developed. This method enables the preparation of functionalized quinoxalines in good to excellent yields and tolerates a variety of N-aryl enamines with diverse functional substituents. Mechanistic studies revealed the presence of a key beta-imino oxime ester intermediate. A quinoxaline derivative could be prepared from beta-carbonyl ester in one-pot sequence on a gram scale. Finally, two important quinoxaline scaffolds were easily prepared in moderate yields over two steps.