KCS

Recently a variety of aerobic oxidative protocols to generate nitriles from alcohol or aldehyde have been developed. Not only heterogeneous catalyst system such as Ru(OH)_X/Al₂O₃ and MnO₂ but also homogeneous catalyst system such as Cu/TEMPO and Fe/TEMPO efficiently facilitated aerobic oxidative nitrile synthesis. However, a nitroxyl radical/NO_X catalytic system, which has been widely used in aerobic alcohol oxidation, has never been investigated in aerobic oxidative nitrile synthesis from alcohol or aldehyde. Herein, we would like to describe our efforts to achieve transition-metal-free aerobic oxidative conversion of benzaldehydes to benzonitriles using a nitroxyl radical/NO_X catalysis. In the presence of a catalytic amount of 4-AcNH-TEMPO (4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl), NaNO₂, and HNO₃, benzaldehydes containing a variety of functional groups underwent condensation with NH₄OAc followed by aerobic oxidation to produce nitriles selectively under an O₂ balloon. Aerobic oxidative conversion of a primary alcohol instead of aldehyde was also achieved by a one-pot sequential reaction as well.